**2.3 "Growth of particles of phase-forming substance" stage**

Each nucleated particle, being in supersaturated media, attaches to itself the molecules of the medium more often than their separation from the particles. In order to join a particle, the molecule moves from the volume of the medium to the surface of the particle, is adsorbed on it, and then, migrating along the surface, takes the place where its connection with the particle becomes energetically favorable and in this sense strong enough to fix on its place. The probability of fixing a molecule depends on its size, shape, and electronic structure. In fact, controlled molecular selection occurs on the surface of the growing particle.

Considering the decrease in the free energy of the system, a phenomenon of *molecular selection*, which develops in it, results in the following process: nuclei become clusters of molecules containing only slightly different in structure and size of the molecule.

From a nanotechnological point of view, it is possible to keep in mind the tasks of changing the concentration conditions of crystallization as well as the use of nano-additives with a crystal-chemical structure similar to the germ of the phase and providing targeted acceleration of the particles' growth processes of the phase-forming substance [4–6] and their morphological structure—finification. In connection with the three global transitions indicated by us during the evolution of a solid substance, it is expedient to refine the classification of additives, dividing them according to the size attribute into nanoscale, ultrafine, and microdisperse (**Table 2**). In the general case, the structure-forming participation and the modifying influence of nanoscale modifiers can be the result of interrelated mechanisms.


**1.6 Research directions**

In recent years, research has been aimed at further reducing the operating temperature of the cell, leading to the development of a new class of planar SOFC, the intermediate temperature (IT-SOFC). This configuration provides an even greater reduction in operation temperature, allowing a large-scale use of metal interconnects. However, the ionic conductivity of the electrolyte is greatly affected by reducing the temperature. In this context, there are two ways to develop electrolytes for IT-SOFC: by changing the electrolyte to a material that has a high conductivity; or by reducing of the electrolyte thickness. In IT-SOFC cells, the electrolyte thickness should be as thin as possible (less than 10 µm has been suggested). In this case, the cell can operate at temperatures between 600 °C and 800 °C (Cooper et al., 2008).

In recent years, research has been aimed at further reducing the operating temperature of the cell, leading to the development of a new class of planar SOFC, the intermediate temperature (IT-SOFC). This configuration provides an even greater reduction in operation temperature, allowing a large-scale use of metal interconnects. However, the ionic conductivity of the electrolyte is greatly affected by reducing the temperature. In this context, there are two ways to develop electrolytes for IT-SOFC: by changing the electrolyte to a material that has a high conductivity; or by reducing the electrolyte thickness. In IT-SOFC cells, the electrolyte thickness should be as thin as possible (less than 10 µm has been suggested). In this case, the cell can operate at temperatures between 600 °C and 800 °C.

For the case of electrolyte change, materials with better ionic conductivity than YSZ have been studied to replace it. LSGM has been successful when applied with a metallic Ni anode, presenting ionic conductivity in temperatures around 400 °C (Sasaki et al., 2008; Tuker, 2010). The problem with such material is its low chemical stability. Another exhaustly studied material for SOFC electrolyte is gadolinium-doped ceria (CGO). This material has better ionic conductivity than YSZ and can be used in lower temperatures. However, at 600 °C the Ce reduction occurs. This reduction confers electric conduction to the material and the cell can suffer a short circuit (Tuker, 2010; Yuan et al., 2010).

The greatest challenge nowadays is to reach fuel cells operating around 700 °C without efficiency losses. The operation temperature can be lowered when the electrolyte thickness is reduced and the densification optimized. Several researches aim the obtaining of thin and dense electrolytes (Gaudon et al., 2006).

In the present study, some results about the elaboration of the YSZ thin film by spray pyrolysis process will be presented.


*4.7. Histochemical Staining*

On days 7, 14 and 21 of osteogenic, chondrogenic and adipogenic differentiation, the cells were washed with PBS and fixed with 4% paraformaldehyde (POCH, Avantor Performance Materials Poland S.A., Gliwice, Poland) for 30 min at RT.

To evaluate calcium phosphate deposition in the cells differentiated into osteoblasts, the cells were rinsed twice with distilled water following fixation and stained with 2% Alizarin Red S solution with pH 4.2 (Sigma-Aldrich) for 3 min.

To visualize sulphated proteoglycans that are characteristic for chondrogenic differentiation, fixed cells were rinsed with PBS and stained with 1% Alcian Blue solution (Sigma-Aldrichprepared in 0.1 N HCl (POCH, Avantor Performance Materials Poland S.A) for 30 min. The wells were rinsed thrice with 0.1 N HCl (POCH) and then distilled water was added to neutralize the acidity.

To visualize the presence of oil droplets during adipogenic differentiation, the cells were rinsed with distilled water and incubated with 60% isopropanol (POCH, Avantor Performance Materials Poland S.A) for 5 min. After the removal of isopropanol, the cells were stained with 1% Oil Red O solution (Sigma-Aldrich) for 5 min.

After histochemical staining, the cells were rinsed with distilled water and visualized using an Olympus IX81 microscope equipped with MicroPublisher 3.3 RTV camera (Olympus, Tokyo, Japan).


Since the background is Minkowskian, the perturbed Ricci tensor is given by *δRµν* = 1 2 (*∂σ∂µh σ ν* + *∂σ∂νh σ µ* − *∂µ∂νh* − *hµν*) ≈ − 1 2 ∆*hµν* and *∂* 2*h ∂t* 2 ≈ 0, *∂* 2*ψ ∂t* 2 ≈ 0 (slow motion) [87,101]. Using the following gauge conditions: *∂λ* e*h λ µ* − 1 1 + *φ*0 *∂µψ* = 0, where e*h λ ν* ≡ *h λ ν* − 1 2 *δ λ ν h α α* [87], Equation (A13) becomes: − 1 ∆*hµν*(1 + *φ*0) = *κ*(*Tµν* − 1 *ηµνT*) + 1 *ηµν*(*V*(*φ*) + ∆*φ*), (A19)

2

2

and from this, we obtain:

$$
\Delta h\_{00} = -\frac{2\kappa}{1+\phi\_0}(T\_{00} - \frac{1}{2}\eta\_{00}T) + \frac{-2\eta\_{00}}{2(1+\phi\_0)}(V\_0 + \Delta\psi),
\tag{A20}
$$

where *V*0 is the minimum of potential *V* [71], and then

$$h\_{00} = -\frac{\kappa Mc^2}{1+\phi\_0} \frac{1}{4\pi r} + \frac{V\_0}{1+\phi\_0} \frac{r^2}{6l\_c^2} + \frac{\psi}{1+\phi\_0},\tag{A21}$$

where *lc* is a characteristic length scale, corresponding to the cosmological background. By equating 2Φ(*r*)/*c* 2 = *h*00, we have:

$$\begin{array}{rcl} \mathfrak{L}\Phi(r)/c^2 &=& -\frac{2GM}{1+\phi\_0}\frac{1}{c^2r} + \frac{V\_0}{1+\phi\_0}\frac{r^2}{6l\_c^2} + \frac{2G\phi\_0M}{3(1+\phi\_0)c^2}\frac{e^{-m\_\phi r}}{r} \\ &=& -\frac{2G\_{eff}M}{c^2r} + \frac{V\_0}{1+\phi\_0}\frac{r^2}{6l\_c^2} \end{array} \tag{A22}$$

with an effective potential introduced *Ge f f* = *G* 1 + *φ*0 1 − *φ*0 3 *e* −*mφr* . The term in

Equation (A22) proportional to *r* 2 corresponds to the cosmological background, and it can be neglected on a galactic level [87].

The modified gravitation potential of the Newtonian limit is:

$$\Phi(r) \approx -\frac{G\_{eff}M}{r} = -\frac{G}{1+\phi\_0} \left(1 - \frac{\phi\_0}{3}e^{-m\varphi r}\right) \frac{M}{r}.\tag{A23}$$

#### **References**

MDPI St. Alban-Anlage 66 4052 Basel Switzerland Tel. +41 61 683 77 34 Fax +41 61 302 89 18 www.mdpi.com

*Universe* Editorial Office E-mail<EMAIL_ADDRESS>www.mdpi.com/journal/universe

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www.mdpi.com

ISBN 978-3-0365-5830-1


**1. Introduction**

The increase in the frequency of flooding in urban areas related to the increase of impermeable surfaces highlights the inadequacy of traditional urban drainage systems. According to Min et al. [1], it is expected that the frequency of high intensity and short duration rainfall events will increase in the coming decades as a consequence of climate change. Wasko and Sharma [2] identified a strong correlation between peak precipitation intensity and high temperatures, and concluded that global warming may lead to an increase of floods of short duration. In addition, Luo et al. [3] report that flash floods have occurred more frequently in Asian cities, with recent increases in urbanization and extreme rainfall, causing significant damage to infrastructure, communities and the environment. This increase in the number of floods shows that it is necessary to use sustainable urban drainage systems capable of restoring the natural hydrological cycle in urban areas and allowing an increase in evapotranspiration and infiltration capacity. Permeable pavements are examples of systems that fulfill this function [4].

According to Scholz and Grabowiecki [5], the management of stormwater in urban areas was observed in a more ecological way due to the emergence of sustainable drainage systems that collect, store, treat and redistribute or recycle water. Compared to the traditional drainage system, stormwater retention and infiltration is a sustainable and cost-effective process, which is suitable for urban areas. In addition, these systems have benefits such as the reduction of runoff, groundwater recharge, saving water through recycling, and preventing pollution.

Permeable pavements are considered sustainable drainage systems because they are pavements that support the demands of mechanical efforts and at the same time allow the percolation and temporary accumulation of water, reducing surface runoff without causing damage to their structures [6]. Several studies have shown the advantages of using this type of pavement. In comparison to conventional pavements, permeable pavements provide runoff reductions of up to 42% [5]. According to Pagotto et al. [7], the quality of stormwater is improved by the use of permeable pavements for most pollutants. Heavy metals are reduced by up to 74%, solids are retained at a rate of 87% and hydrocarbons are intercepted at an even higher rate (90%).

Brattebo and Booth [8] examined the long-term efficacy of four permeable pavement systems in the United States. The study showed a significantly better performance for permeable pavements, both for water quality, which had lower toxic levels, and for stormwater infiltration. In the four systems, practically all of the precipitation was infiltrated. The levels of copper and zinc obtained in the water samples collected from the conventional asphalt concrete runoff were alarming: toxic concentrations were reached in 97% of the samples. However, in 31 out of 36 water samples infiltrated in permeable pavements, the concentrations were below the detectable toxic level.

According to Maiolo et al. [9], there is a need to have a methodology capable of providing an accurate estimate of the sustainability of drainage systems. In fact, this assessment may not only be tied to environmental benefits related to lifespan, but assessments are necessary in the steps that precede and follow the lifespan. A valid criterion for the verification of the sustainability of a product or system is the life cycle assessment (LCA). LCA presents an opportunity to evaluate and compare projects and choose the most appropriate drainage systems, quantifying a variety of environmental impacts and benefits. LCA has been effectively applied to assess the environmental performance of the water infrastructure, including the environmental impacts associated with the construction, maintenance and disposal of various green infrastructure technologies, such as permeable pavements [10]. This assessment is based primarily on the amount of greenhouse gas emissions, as well as the consumption of energy and natural resources. Some parameters significantly affect the evaluation, such as local climatic patterns, regulatory requirements, quality of infiltrated stormwater, lifespan and treatment efficiency of the systems [11].

As stated by the Electric Power Research Institute [12], at a national scale, the transport and treatment of water and wastewater accounts for nearly 4% of the US electricity demand. Such dependency of water infrastructure on electric utility infrastructure leads to serious environmental impacts. In this way, decentralized water management brings benefits not only as a means of reducing stresses on the water treatment infrastructure but also as a strategy to reduce the demand that water companies impose on the regional energy system, and on reducing the carbon footprint [13]. As a point of reference, the City of New York [14] estimates that systems of water treatment, supply, and sewage along with the methane escaping into the atmosphere (generated by the sewage treatment process) add up to 17% of New York's greenhouse gas emissions.

De Sousa et al. [15] evaluated the environmental performance of green infrastructures (permeable pavements and bioretention basins) by comparing them to water storage and treatment scenarios using traditional drainage systems (grey infrastructure). The results showed that green infrastructures emitted 75% to 95% less greenhouse gases, mainly due to the lower use of electricity during the life cycle. Wang et al. [11] showed by means of a case study in China that 73.48% of energy consumption, 46.70% of greenhouse gas emissions, 98.33% of lead emissions and 99.70% of zinc emissions could be avoided by using permeable pavement instead of conventional pavement.

While understanding the life cycle implications of sustainable drainage systems is only in its early stages, LCA studies are important in guiding planning and decision-making when considering multiple objectives such as increased water resources and reduction of natural disasters and environmental impacts [16]. Thus, the objective of this paper is to present an overview of permeable pavements and show studies of LCA that compare the environmental performance of permeable pavements with traditional drainage systems, in order to provide scientific instructions for the choice of more

sustainable drainage systems and thus improve the sustainable management of stormwater in urban areas.


**5. Discussion of findings**

### **5.1 Teachers' feelings and attitudes on teaching writing using technology in the FP**

Feelings and attitudes about teaching writing with technology are characterized in this study as informal training that affected teachers' willingness to adopt and use technology for teaching writing in the FP. To fulfill the demand of living in the twenty first century, new information and abilities are necessary, and our teachers and students will be asked to learn in creative ways. In view of the foregoing, the Action Plan for 2019 [2] emphasizes the importance of well-designed government initiatives to address the digital gap in South Africa by taking charge of technological advancement. On the other hand, this policy structure does not serve the FP and, worse, does not explain the pedagogical components of employing technology in teaching and learning. Nyambane et al. [14] say that "when technology is used, content and pedagogy, the two core aspects of teaching and learning, must be integrated." As a result, role players must recognize that employing a given technology can change how learners grasp concepts in that content area in order to deliver the required sustenance for choosing the real technology as well as the associated information for the technology. This suggests that teachers need to be taught in using technology to teach writing in the FP.

### **5.2 Teachers' experience of teaching writing using technology**

When applied effectively, the data showed that technology can help pedagogy. When it came to teaching writing while incorporating technology in the FP classroom, participants highlighted several ideas and techniques. It is widely acknowledged that FP learners differ from previous generations, and as a result, the manner they are taught should be different as well. Despite the fact that these learners have a unique learning style that needs a child-centered, play-based curriculum, technology can help in the construction of a plan that is accessible and flexible outside of the classroom. Teachers were unanimous in their assessment of the platform's effectiveness in the FP classroom. Teachers also felt that technology is useful in a variety of ways, particularly in assisting learners in learning to write in an enjoyable, dynamic, and meaningful way. In addition, our findings are consistent with many studies on infusing technology in teaching and learning which agree that technology has a vital role to play in teaching at all levels [30]. Moreover, findings indicated that one area

where technology integration has the potential to increase learners learning is in the area of teaching writing. Shams-Abadi et al. [34] back up the claims, stating that writing in blended learning produces good writing and reactions from students.

### **5.3 Learners' experience of learning writing skills using technology**

The findings revealed that learners were enthusiastic about using technology to improve their writing skills. Affectively, the learners expressed a desire to use technology because of its novelty, novelty, and appeal. Learning to write with technology was easy and uncomplicated for the learners, and it encouraged them to write. The overall learner experience of learners was excellent, learners confirmed that technology helped them to learn better about the writing. Much research [30, 33, 34] have come to similar conclusions. In this study, the participants had access to a smartphone and a computer or laptop at home, as well as a positive attitude toward technology use. Prensky et al. [15] highlights this point by arguing that learners have changed as a result of the introduction and quick spread of digital technology in the later eras of the twentieth century, as well as its progression into the twenty first century. This conclusion applies to all language learning situations, both national and international, and allows teachers to better address the requirements of their own learners, especially when learners come from a variety of educational backgrounds and have varying technological skills.

## **6. Conclusion**

This study is significant because it paves the way for a technology-based pedagogical investigation of teaching writing in the FP. Today's learners are socialized in a fundamentally different way than earlier generations because we now all live in a "wired" and connected global information society. The impact of technology at the dawn of the information era was largely focused on information access or transmission, but it should now be extended to encompass how teachers teach (i.e., pedagogy) and how learners learn. It is necessary to integrate technology with knowledge content.

## **7. Recommendations**

This study's recommendations are made from the top-down manner. Starting with the suggestion that the government provides technological assistance to FP teachers. Following that, it is proposed that FP teachers adjust the way they organize their classes in order to respond to the benefits of technology-assisted instruction. Finally, it is advocated that FP learners have access to the most appropriate technology-based information. Therefore, it is advised that schools provide the essential infrastructure for our young learners to take advantage of technology instruments for learning. Because technology allows for the adaptation of classroom procedures as well as the ability to teach and learn in exciting, new ways, its proper deployment still requires assistance. It is, therefore, suggested that a set of recommendations for an emergent curriculum centered on the interests of this generation of learners be produced to aid teachers and learners in successfully integrating teaching and technology in the FP. Teachers' attitudes about technology must be modified, and teachers must have the proper training in how to use technology to teach writing in the FP. Any policy governing the use of technology in the classroom must be simple to understand.

*Technology Integration on Teaching Writing in the Foundation Phase Classrooms in the Eastern… DOI: http://dx.doi.org/10.5772/intechopen.103666*


**TITANIUM ALLOYS - ADVANCES IN PROPERTIES CONTROL**

Edited by **Jan Sieniawski** and **Waldemar Ziaja**

#### **Titanium Alloys - Advances in Properties Control**

http://dx.doi.org/10.5772/49999 Edited by Jan Sieniawski and Waldemar Ziaja

#### **Contributors**

James Wang, Farid Umarov, Yaroslav Matychak, Iryna Pohrelyuk, Viktor Fedirko, Oleh Tkachuk, Faramarz Djavanroodi, Wilson Wang, Poh Chye Khoon, Jan Sieniawski, Maciej Motyka

#### **© The Editor(s) and the Author(s) 2013**

The moral rights of the and the author(s) have been asserted.

All rights to the book as a whole are reserved by INTECH. The book as a whole (compilation) cannot be reproduced, distributed or used for commercial or non-commercial purposes without INTECH's written permission. Enquiries concerning the use of the book should be directed to INTECH rights and permissions department (permissions@intechopen.com).

Violations are liable to prosecution under the governing Copyright Law.

Individual chapters of this publication are distributed under the terms of the Creative Commons Attribution 3.0 Unported License which permits commercial use, distribution and reproduction of the individual chapters, provided the original author(s) and source publication are appropriately acknowledged. If so indicated, certain images may not be included under the Creative Commons license. In such cases users will need to obtain permission from the license holder to reproduce the material. More details and guidelines concerning content reuse and adaptation can be foundat http://www.intechopen.com/copyright-policy.html.

#### **Notice**

Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book.

First published in Croatia, 2013 by INTECH d.o.o. eBook (PDF) Published by IN TECH d.o.o. Place and year of publication of eBook (PDF): Rijeka, 2019. IntechOpen is the global imprint of IN TECH d.o.o. Printed in Croatia

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Titanium Alloys - Advances in Properties Control Edited by Jan Sieniawski and Waldemar Ziaja p. cm. ISBN 978-953-51-1110-8 eBook (PDF) ISBN 978-953-51-6340-4


**6. Antimicrobial and antifouling activity**

**Figure 4.** Cryo-scanning electron micrograph of crosslinked alginate synthesized with a minuscule amount of GO and 18 wt.% of calcium chloride (with respect to the mass of sodium alginate) in the swollen state after 2 minutes of immersion in water at 24 ± 0.5°C (a). Apparent diffusion coefficients of liquid water (mean ± standard deviation) in calcium alginate hydrogels with different crosslinker contents with (black columns) and without (gray columns)

0.1 wt.% of GO (b). *Reprinted with permission from Ref* [48].

100 Hydrogels

Microbial infections can lead to implant failure, which may cause major economic losses and suffering among patients despite the use of preoperative antibiotic prophylaxis and the aseptic processing of materials. Therefore, novel antimicrobial materials are urgently in need for medical uses [96]. For that reason, much effort is being done in the development of advanced hydrogels with inherent antimicrobial properties. Thus, syringe-injectable bioadhesive hydrogels prepared from mixing polydextran aldehyde and branched polyethylenimine, able to kill both Gram-negative and Gram-positive bacteria, while sparing human erythrocytes [97] and injectable conductive self-healed hydrogels based on quaternized chitosan-g-polyaniline (QCSP) and benzaldehyde group functionalized poly(ethylene glycol)-co-poly(glycerol sebacate) (PEGS-FA) with antibacterial, anti-oxidant and electroactive dressing for cutaneous wound healing have been developed [98].

Antibacterial properties can also be imparted to a hydrogel by doping in an exogenous antibiotic for eventual release [107]. In these delivery systems, the active agent is released from the polymer matrix over time. However, the material's antibiotic activity is eventually exhausted with the remaining matrix being left inactive and the remaining vehicle may become a substrate for colonization by bacterial biofilms once the payload is depleted, which can become life threatening. For this reason, secondary surgeries are typically performed to remove these empty depots as a means of preventing this type of infection. To avoid this second surgery, a hydrogel drug delivery system in which the drug release rate of vancomycin and degradation rate of the hydrogel are linked via covalent incorporation of vancomycin in the hydrogel

Enhancement of Hydrogels' Properties for Biomedical Applications: Latest Achievements

http://dx.doi.org/10.5772/intechopen.71671

103

However, many hydrogels themselves do not have any antimicrobial activity and therefore some fillers, and antimicrobial agents need to be incorporated by physical blending in order to produce antimicrobial materials [109]. Thus, graphene has emerged as a novel green broad-spectrum antimicrobial nanomaterial, with little bacterial resistance and tolerable cytotoxic effect on mammalian cells. It exerts its antibacterial action via physical damages through direct contact of its sharp edges with bacterial membranes and destructive extraction of lipid molecules. The antimicrobial activity of GO against two bacterial pathogens (*Pseudomonas syringae* and *Xanthomonas campestris pv. undulosa*) and two fungal pathogens (*Fusarium graminearum* and *Fusarium oxysporum*) showed that GO had a powerful effect on the reproduction of all these four pathogens because it killed nearly 90% of the bacteria and repressed 80% macroconidia germination along with partial cell swelling and lysis at 500 μgmL−1. The graphene-based nanocomposites have a wide range of biomedical applications, such as wound dressing due to its superior antimicrobial properties and good

Another strategy to design hydrogels with desired antimicrobial performance consists of adding silver nanoparticles (Ag NPs). Hence, silver nanoparticles have emerged up with diverse medical applications ranging from silver based dressings, silver coated medicinal devices,

Infections are also frequent and highly undesired occurrences after orthopedic procedures. Thus, for example, medicated hydrogels of hyaluronic acid derivatives have been developed [112] to address this problem. However, the growing concern caused by the rise in antibiotic resistance is progressively dwindling the efficacy of such drugs and the integration of silver

The combination of both previous strategies (graphene and Ag NPs) to design antimicrobial hydrogels with good water maintaining ability is of particular significance to promote the development of wound dressing. Thus, a series of hydrogels were synthesized by crosslinking of Ag/graphene composites with acrylic acid and N,N′-methylene bisacrylamide at different mass ratios. In this study, prepared hydrogel with an optimal Ag to graphene mass ratio of 5:1 exhibited much stronger antibacterial abilities than other hydrogels and showed excellent biocompatibility, high swelling ratio, and good extensibility at the same time. Besides, *in vivo* experiments indicated that this nanocomposite hydrogel could significantly accelerate the healing rate of artificial wounds in rats, and it helped to successfully reconstruct intact and

nanoparticles in hydrogels has become a very promising alternative [113].

backbone was successfully developed [108].

biocompatibility [110].

such as nanogels, nanolotions, etc. [111].

Other hydrogels such as chitosan and its derivatives has been widely used as implant coatings for its intrinsic properties such as non-toxic, osteoconductive, pH responsive, anti-microbial, biocompatible and cell adhesive [99, 100]. Nevertheless, the development of new chitosan derivatives or composites with superior antimicrobial activity is still under research. Thus, for example, a novel hydrogel coating produced by electrophoretic co-deposition of chitosan/alkynyl chitosan showed high antibacterial effect against *Escherichia coli* and *Staphylococcus aureus* [101] by disk diffusion method [102] (see **Figure 5**). Antibacterial polymer coating adhered on the surface of medical implants and devices have attracted great interests in the last decades for its ability to reduce implantassociated infections [103, 104].

Antimicrobial hydrogels formed by crosslinking polyallylamine with aldaric acid derivatives exhibited complete kill within 4 hours against *Pseudomonas aeruginosa*, *Escherichia coli*, *Staphylococcus aureus* and *Candida albicans* suspended in culture medium [105] and a facile strategy to fabricate antibacterial ultrathin hydrogel films via a layer-by-layer (LbL) technique and "click" chemistry was reported by Wang et al. [106]. This hydrogels consisted of poly[oligo(ethylene glycol)fumarate]-co-poly[dodecyl bis(2-hydroxyethyl)methylammonium fumarate] (POEGDMAM) containing multi-enes and poly[oligo(ethylene glycol)mercaptosuccinate] (POEGMS). These ultrathin films exhibited excellent antibacterial activity against both *Staphylococcus aureus* and *Escherichia coli* due to the presence of ammonium groups with long alkyl chains in the POEGDMAM.

**Figure 5.** Antimicrobial results of chitosan and alkynyl chitosan against *E. coli* and *S. aureus* by using disk diffusion method. Images (a–e) are paper disks containing 1 wt. % chitosan, 1 wt. % alkynyl chitosan (ACS1, ACS2, ACS3 and ACS4), respectively against *E. coli*; images (f–j) correspond to paper disks containing 1 wt. % chitosan, 1 wt. % alkynyl chitosan (ACS1, ACS2, ACS3 and ACS4), respectively against *S. aureus*. Alkynyl chitosan coded as ACS1, ACS2, ACS3 and ACS4 were prepared by changing the molar ratio of chitosan 0 unit to 3-bromopropyne monomer as 1:0.5, 1:1, 1:1.5 and 1:2. *Reprinted with permission from Ref* [101].

Antibacterial properties can also be imparted to a hydrogel by doping in an exogenous antibiotic for eventual release [107]. In these delivery systems, the active agent is released from the polymer matrix over time. However, the material's antibiotic activity is eventually exhausted with the remaining matrix being left inactive and the remaining vehicle may become a substrate for colonization by bacterial biofilms once the payload is depleted, which can become life threatening. For this reason, secondary surgeries are typically performed to remove these empty depots as a means of preventing this type of infection. To avoid this second surgery, a hydrogel drug delivery system in which the drug release rate of vancomycin and degradation rate of the hydrogel are linked via covalent incorporation of vancomycin in the hydrogel backbone was successfully developed [108].

to kill both Gram-negative and Gram-positive bacteria, while sparing human erythrocytes [97] and injectable conductive self-healed hydrogels based on quaternized chitosan-g-polyaniline (QCSP) and benzaldehyde group functionalized poly(ethylene glycol)-co-poly(glycerol sebacate) (PEGS-FA) with antibacterial, anti-oxidant and electroactive dressing for cutaneous

Other hydrogels such as chitosan and its derivatives has been widely used as implant coatings for its intrinsic properties such as non-toxic, osteoconductive, pH responsive, anti-microbial, biocompatible and cell adhesive [99, 100]. Nevertheless, the development of new chitosan derivatives or composites with superior antimicrobial activity is still under research. Thus, for example, a novel hydrogel coating produced by electrophoretic co-deposition of chitosan/alkynyl chitosan showed high antibacterial effect against *Escherichia coli* and *Staphylococcus aureus* [101] by disk diffusion method [102] (see **Figure 5**). Antibacterial polymer coating adhered on the surface of medical implants and devices have attracted great interests in the last decades for its ability to reduce implant-

Antimicrobial hydrogels formed by crosslinking polyallylamine with aldaric acid derivatives exhibited complete kill within 4 hours against *Pseudomonas aeruginosa*, *Escherichia coli*, *Staphylococcus aureus* and *Candida albicans* suspended in culture medium [105] and a facile strategy to fabricate antibacterial ultrathin hydrogel films via a layer-by-layer (LbL) technique and "click" chemistry was reported by Wang et al. [106]. This hydrogels consisted of poly[oligo(ethylene glycol)fumarate]-co-poly[dodecyl bis(2-hydroxyethyl)methylammonium fumarate] (POEGDMAM) containing multi-enes and poly[oligo(ethylene glycol)mercaptosuccinate] (POEGMS). These ultrathin films exhibited excellent antibacterial activity against both *Staphylococcus aureus* and *Escherichia coli* due to the presence of ammonium groups with

**Figure 5.** Antimicrobial results of chitosan and alkynyl chitosan against *E. coli* and *S. aureus* by using disk diffusion method. Images (a–e) are paper disks containing 1 wt. % chitosan, 1 wt. % alkynyl chitosan (ACS1, ACS2, ACS3 and ACS4), respectively against *E. coli*; images (f–j) correspond to paper disks containing 1 wt. % chitosan, 1 wt. % alkynyl chitosan (ACS1, ACS2, ACS3 and ACS4), respectively against *S. aureus*. Alkynyl chitosan coded as ACS1, ACS2, ACS3 and ACS4 were prepared by changing the molar ratio of chitosan 0 unit to 3-bromopropyne monomer as 1:0.5, 1:1, 1:1.5

wound healing have been developed [98].

102 Hydrogels

associated infections [103, 104].

long alkyl chains in the POEGDMAM.

and 1:2. *Reprinted with permission from Ref* [101].

However, many hydrogels themselves do not have any antimicrobial activity and therefore some fillers, and antimicrobial agents need to be incorporated by physical blending in order to produce antimicrobial materials [109]. Thus, graphene has emerged as a novel green broad-spectrum antimicrobial nanomaterial, with little bacterial resistance and tolerable cytotoxic effect on mammalian cells. It exerts its antibacterial action via physical damages through direct contact of its sharp edges with bacterial membranes and destructive extraction of lipid molecules. The antimicrobial activity of GO against two bacterial pathogens (*Pseudomonas syringae* and *Xanthomonas campestris pv. undulosa*) and two fungal pathogens (*Fusarium graminearum* and *Fusarium oxysporum*) showed that GO had a powerful effect on the reproduction of all these four pathogens because it killed nearly 90% of the bacteria and repressed 80% macroconidia germination along with partial cell swelling and lysis at 500 μgmL−1. The graphene-based nanocomposites have a wide range of biomedical applications, such as wound dressing due to its superior antimicrobial properties and good biocompatibility [110].

Another strategy to design hydrogels with desired antimicrobial performance consists of adding silver nanoparticles (Ag NPs). Hence, silver nanoparticles have emerged up with diverse medical applications ranging from silver based dressings, silver coated medicinal devices, such as nanogels, nanolotions, etc. [111].

Infections are also frequent and highly undesired occurrences after orthopedic procedures. Thus, for example, medicated hydrogels of hyaluronic acid derivatives have been developed [112] to address this problem. However, the growing concern caused by the rise in antibiotic resistance is progressively dwindling the efficacy of such drugs and the integration of silver nanoparticles in hydrogels has become a very promising alternative [113].

The combination of both previous strategies (graphene and Ag NPs) to design antimicrobial hydrogels with good water maintaining ability is of particular significance to promote the development of wound dressing. Thus, a series of hydrogels were synthesized by crosslinking of Ag/graphene composites with acrylic acid and N,N′-methylene bisacrylamide at different mass ratios. In this study, prepared hydrogel with an optimal Ag to graphene mass ratio of 5:1 exhibited much stronger antibacterial abilities than other hydrogels and showed excellent biocompatibility, high swelling ratio, and good extensibility at the same time. Besides, *in vivo* experiments indicated that this nanocomposite hydrogel could significantly accelerate the healing rate of artificial wounds in rats, and it helped to successfully reconstruct intact and thickened epidermis during 15 day of healing of impaired wounds [114]. In the same way, acrylic acid (AA) grafted onto poly(ethylene terephthalate) (PET) film through gamma-ray induced graft copolymerization with silver nanoparticles on the surface showed strong and stable antibacterial activity [115].

**7. Porosity**

last decades (see **Figure 6**).

Porous polymers have received an increased level of research interest because of their potential to merge the properties of both porous materials and polymers [119]. Porous polymers have potential applications in many fields such as gas storage and separation materials [120, 121], drug delivery [122], catalysts [123], supports for electrochemical sensing [124], low-dielectric constant materials [125], packing materials in chromatography [126], scaffolds or three-dimensional porous matrices for tissue engineering in regenerative medicine [5, 41, 127, 128] and many others. These high value applications have driven much emphasis on development of reliable methods for preparation of porous polymers with designed pore architectures in the

Enhancement of Hydrogels' Properties for Biomedical Applications: Latest Achievements

http://dx.doi.org/10.5772/intechopen.71671

105

Tissue engineering holds great promise for regeneration and repair of diseased tissues, making the development of new porous supports as scaffolds for tissue regeneration a topic of great interest in biomedical research. Hydrogels have emerged as leading candidates for engineered tissue scaffolds due to their good biocompatibility and similarities to native extracellular

**Figure 6.** Different porous polymers prepared by different preparation methods to obtain diverse pore architectures.

Reprinted with permission from Ref [12, 41, 48, 128–130].

It is highly desired to have a hydrogel material bearing the excellent antifouling property/biocompataiblity to prolong the lifetime of implanted materials, switchable antimicrobial property to eliminate infection and inflammation, and good mechanical properties to avoid the failure of the implanted material. We hypothesize derivatives of zwitterionic carboxybetaine with hydroxyl group(s) can switch between the lactone form (anti-microbial) and the zwitterionic form (anti-fouling) and the intramolecular hydrogen bonds will enhance the mechanical property of the zwitterionic hydrogel. It is highly desired to have a hydrogel material bearing the excellent antifouling property/biocompataiblity to prolong the lifetime of implanted materials, switchable antimicrobial property to eliminate infection and inflammation, and good mechanical properties to avoid the failure of the implanted material. We hypothesize derivatives of zwitterionic carboxybetaine with hydroxyl group(s) can switch between the lactone form (antimicrobial) and the zwitterionic form (anti-fouling) and the intramolecular hydrogen bonds will enhance the mechanical property of the zwitterionic hydrogel.

On the other hand, the surface of hydrogels must be modified to make it resistant to protein adsorption and cell adhesion to avoid fouling. Thus, there is a need for coatings with antifouling properties that are able to improve the performances of implanted biomedical devices. Thus, the antifouling properties of poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) hydrogels were improved by the surface grafting of a brush of poly(oligoethylene glycol methyl ether acrylate) [poly(OEGA)] [116]. Novel antifouling highly wettable hydrogels with superior mechanical and self-healing properties have also been developed by UV-initiated copolymerization of non-fouling zwitterionic carboxybetaine methacrylamide (CBMAA-3) and 2-hydroxyethyl methacrylate (HEMA) in the presence of uniformly dispersed clay nanoparticles (Laponite XLG) in water [117].

Therefore, it would be highly desired to have a hydrogel material bearing the excellent antifouling property/biocompataiblity to prolong the lifetime of implanted materials, switchable antimicrobial property to eliminate infection and inflammation, and good mechanical properties to avoid the failure of the implanted material. Thus, derivatives of zwitterionic carboxybetaine have been developed with hydroxyl group(s), which can switch between the lactone form (antimicrobial) and the zwitterionic form (anti-fouling) [118]. Besides, the intramolecular hydrogen bonds enhance the mechanical property of the zwitterionic hydrogel.

Nevertheless, the rapid emergence of antibiotic resistance in pathogenic microbes is becoming an imminent global public health problem because they are highly prone to develop resistance through mutation and the treatment with conventional antibiotics often leads to resistance development leaving the bacterial morphology intact. Therefore, much research is currently being done in the development of new antimicrobial hydrogels because they have been demonstrated to be very effective in preventing and treating multidrug-resistant infections.


**1. Introduction**

414 Chronic Kidney Disease

Rush D, Nickerson P, Gough J et al. (1998). Beneficial effects of treatment of early subclinical rejection: a randomized study. *J Am SocNephrol*; Vol. 9, pp. 2129–2134 Safinia N, Afzali B, Atalar K, Lombardi G, Lechler RI. (2010). T-cell alloimmunity and chronic allograft dysfunction. *Kidney Int;* Vol. 78 (Suppl 119) pp. S2–S12 Salama AD, Delikouras A, Pusey CD et al. (2001). Transplantaccommodation in highly

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sensitized patients: a potential role for Bcl-xL and alloantibody. *Am J Transplant*;

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simultaneous pancreas-kidney transplantation, despite immunosuppression, is associated with autoantibodies and pathogenic autoreactive CD4 T-cells.

findings of subclinical kidney allograft rejection and its association with graft

Chronic kidney disease (CKD) is a disease which is characterized by the presence of renal damage or decreased GFR for at least 3 months. The prevalence of CKD in the US has been reported to be 3.3% (stage 1), 3.0% (stage 2), 4.3% (stage 3), 0.2% (stage 4), and 0.1% (stage 5) (Levey et al., 2003; 2002). Because of the increasing elderly population in industrial countries, the development of new strategies for the prevention and regression of CKD is important.

Clinical studies have suggested that renin-angiotensin system (RAS) inhibitors can exert a renoprotective effect independent of blood pressure, and attenuate the progression of renal dysfunction (Bakris, 2010; Berl, 2009; Stojiljkovic et al., 2007). Recent studies have suggested that the use of RAS inhibitors, when combined with other treatment modalities such as aggressive blood pressure control, lowering of blood lipids, tight glucose control for diabetics, and lifestyle changes may cause remission of albuminuria, and stablization or even reversal of the decline in GFR, i.e. regression of CKD in some patients (Aros et al., 2002; Macconi, ; Ruggenenti et al., 2008).

These early clinical findings are important, because they suggest that appropriate interventions may be effective for causing an improvement in renal function, which raises the hope that a 'cure' for CKD may eventually be found in the future. In our laboratory, we have been examining the molecular mechanisms involved in the pathogenesis of CKD and hypertension. Our underlying concept is that both these diseases are highly related, and share common pathophysiological mechanisms, including the abnormal accumulation of extracellular matrix proteins in the kidney. The result is glomerulosclerosis, when the matrix accumulates in the renal glomeruli, and renal arteriolosclerosis, when the matrix is deposited in the renal arterioles and small vessels. In this chapter, we will review the evidence from our and other laboratories that these processes may be reversed in animal models, and possibly in humans.

#### **2.1 Studies on CKD prevention**

Regardless of the initial injury, most causes of CKD (including diabetic nephropathy, and chronic glomerulonephritis) share several common pathological features, one of which is the development of glomerular scarring or glomerulosclerosis.

Prevention and Regression of Chronic Kidney Disease and Hypertension 417

Although it has been widely accepted that established sclerosis is irreversible, recent studies have emerged to challenge this concept and to focus on developing new therapies to cause regression or reversal of established glomerulosclerosis (Ma et al., 2007), (Ruggenenti et al., 2001). In particular, studies have suggested that treatment with high-dose RAS inhibitor may be effective in causing regression of glomerular lesions in animal models (Ma et al.,

Recently, we reported that transient treatment with an angiotensin receptor blocker (ARB) at a 50-100 times the normal dose in rodents causes regression of glomerulosclerosis in mice (Hayashi et al., 2010). In this study, the effects of treatment with different doses of ARB on established lesions of glomerulosclerosis were examined in the adriamycin nephropathy model, with a focus on whether the regression was sustained after cessation of the ARB treatment. Furthermore, the involvement of matrix metalloproteinase (MMP)-2 in the mechanism of glomerulosclerosis regression were examined both in vitro and in vivo, using a non-specific MMP inhibitor (doxycycline), and knockout (KO) mice with targeted deletion

The principal findings of the study are shown in Fig. 2. and Fig. 3. It was found that transient treatment for two weeks with the ARB candesartan caused a regression of established glomerulosclerosis, which was clearly evident with the high doses of ARB and was sustained 6 months after cessation of all treatments. Moreover, the ARB treatment

Fig. 2. Effects of different doses of ARB (candesartan) on regression of glomerulosclerosis in the adriamycin-nephropathy model. (a) Experimental protocol (b) Effects on glomerular sclerosis (c) Representative photomicrographs. Reproduced with permission from Hayashi

**2.2 Studies on CKD regression**

of MMP-2.

et al. Kidney Int 78:69-78, 2010.

2005), (Teles et al., 2009), (Macconi et al., 2009).

Fig. 1. Relationship between progression and regression of chronic kidney disease.

Glomerulosclerosis occurs because of the excessive deposition of components of the extracellular matrix (ECM) in the glomeruli, resulting in changes in glomerular integrity and albuminuria. This process is triggered by increased synthesis of ECM components, and decreased degradation of ECM components, resulting in net accumulation of ECM (Ma et al., 2007). It is thought that, once renal function declines below a 'point of no return', the decline in glomerular function continues inexorably due to the continuous accumulation of ECM and progression of glomerulosclerosis. Glomerular hypertension has been suggested to play an important role in this process, because the decrease in glomerular filtration leads to a compensatory increase in glomerular hypertension, resulting in a vicious cycle which causes progression of glomerular injury and loss of renal function (Neuringer et al., 1992).

Because of the progressive nature of CKD, one of the optimum strategies for reducing CKD would be to find interventions to prevent new-onset CKD. Multiple clinical studies have shown that the use of RAS inhibitors in patients with and without diabetes can cause a decline in the progression of CKD, which may be mediated, at least in part, by a blood pressure-independent mechanism (Bakris, 2010; Berl, 2009; Stojiljkovic et al., 2007). More recently, several studies have suggested that the use of RAS inhibitors may also be effective in preventing new-onset CKD, especially in patients with diabetes. In particular, Ruggenenti et al. showed in the BENEDICT trial that, in hypertensive patients with type 2 diabetes and no microalbuminuria at baseline, the angiotensin-converting enzyme (ACE) inhibitor trandolapril significantly decreased the risk of developing microalbuminuria compared with conventional therapy (Ruggenenti et al., 2008) . Similarly, in the recent ROADMAP study, the use of the ARB olmesartan was associated with a delayed onset of microalbuminuria (Haller et al.) . These results are important, because they suggest that diabetic nephropathy can be prevented or at least delayed by appropriate intervention (Remuzzi et al., 2006).

At present, it is unclear from clinical studies whether these measures may be effective for prevention of new-onset CKD in non-diabetic patients. However, the data from animal studies are encouraging, and suggest that early intervention with a RAS inhibitor may be effective for the prevention of renal injury due to hypertension (Ishiguro et al., 2007; Nakaya et al., 2001), salt-loading (Nakaya et al., 2002), or irradiation (Moulder et al., 1996).

#### **2.2 Studies on CKD regression**

416 Chronic Kidney Disease

Fig. 1. Relationship between progression and regression of chronic kidney disease.

Glomerulosclerosis occurs because of the excessive deposition of components of the extracellular matrix (ECM) in the glomeruli, resulting in changes in glomerular integrity and albuminuria. This process is triggered by increased synthesis of ECM components, and decreased degradation of ECM components, resulting in net accumulation of ECM (Ma et al., 2007). It is thought that, once renal function declines below a 'point of no return', the decline in glomerular function continues inexorably due to the continuous accumulation of ECM and progression of glomerulosclerosis. Glomerular hypertension has been suggested to play an important role in this process, because the decrease in glomerular filtration leads to a compensatory increase in glomerular hypertension, resulting in a vicious cycle which causes progression of glomerular injury and loss of renal function (Neuringer et al., 1992). Because of the progressive nature of CKD, one of the optimum strategies for reducing CKD would be to find interventions to prevent new-onset CKD. Multiple clinical studies have shown that the use of RAS inhibitors in patients with and without diabetes can cause a decline in the progression of CKD, which may be mediated, at least in part, by a blood pressure-independent mechanism (Bakris, 2010; Berl, 2009; Stojiljkovic et al., 2007). More recently, several studies have suggested that the use of RAS inhibitors may also be effective in preventing new-onset CKD, especially in patients with diabetes. In particular, Ruggenenti et al. showed in the BENEDICT trial that, in hypertensive patients with type 2 diabetes and no microalbuminuria at baseline, the angiotensin-converting enzyme (ACE) inhibitor trandolapril significantly decreased the risk of developing microalbuminuria compared with conventional therapy (Ruggenenti et al., 2008) . Similarly, in the recent ROADMAP study, the use of the ARB olmesartan was associated with a delayed onset of microalbuminuria (Haller et al.) . These results are important, because they suggest that diabetic nephropathy can be prevented or at least delayed by appropriate intervention (Remuzzi et al., 2006).

At present, it is unclear from clinical studies whether these measures may be effective for prevention of new-onset CKD in non-diabetic patients. However, the data from animal studies are encouraging, and suggest that early intervention with a RAS inhibitor may be effective for the prevention of renal injury due to hypertension (Ishiguro et al., 2007; Nakaya

et al., 2001), salt-loading (Nakaya et al., 2002), or irradiation (Moulder et al., 1996).

Although it has been widely accepted that established sclerosis is irreversible, recent studies have emerged to challenge this concept and to focus on developing new therapies to cause regression or reversal of established glomerulosclerosis (Ma et al., 2007), (Ruggenenti et al., 2001). In particular, studies have suggested that treatment with high-dose RAS inhibitor may be effective in causing regression of glomerular lesions in animal models (Ma et al., 2005), (Teles et al., 2009), (Macconi et al., 2009).

Recently, we reported that transient treatment with an angiotensin receptor blocker (ARB) at a 50-100 times the normal dose in rodents causes regression of glomerulosclerosis in mice (Hayashi et al., 2010). In this study, the effects of treatment with different doses of ARB on established lesions of glomerulosclerosis were examined in the adriamycin nephropathy model, with a focus on whether the regression was sustained after cessation of the ARB treatment. Furthermore, the involvement of matrix metalloproteinase (MMP)-2 in the mechanism of glomerulosclerosis regression were examined both in vitro and in vivo, using a non-specific MMP inhibitor (doxycycline), and knockout (KO) mice with targeted deletion of MMP-2.

The principal findings of the study are shown in Fig. 2. and Fig. 3. It was found that transient treatment for two weeks with the ARB candesartan caused a regression of established glomerulosclerosis, which was clearly evident with the high doses of ARB and was sustained 6 months after cessation of all treatments. Moreover, the ARB treatment

Fig. 2. Effects of different doses of ARB (candesartan) on regression of glomerulosclerosis in the adriamycin-nephropathy model. (a) Experimental protocol (b) Effects on glomerular sclerosis (c) Representative photomicrographs. Reproduced with permission from Hayashi et al. Kidney Int 78:69-78, 2010.

Prevention and Regression of Chronic Kidney Disease and Hypertension 419

As shown in Fig. 3, the results of highly-sensitive in situ zymography and immunofluorescence suggested that MMP-2 might be upregulated in glomerular podocytes, but this could not be determined accurately because of the relatively low expression of MMP-2 protein. Therefore, to further characterize the mechanisms of the ARB-induced increase in glomerular MMP-2 activity, we examined the effects of ARB treatment in cultured podocytes. These experiments revealed that ARB treatment of podocytes resulted in a dose-dependent increase in MMP-2 activity in the supernatant. Podocytes are known to express components of the RAS, including renin, angiotensinogen, angiotensin-converting enzyme, and AT1 and AT2 receptors (Durvasula et al., 2006), (Durvasula et al., 2008), (Liebau et al., 2006). Morever, functional expression of the renin-angiotensin system has been documented in both mouse and human podocytes (Durvasula et al., 2008), (Liebau et al., 2006). To examine the possibility that the effects of ARB were mediated through inhibition of the RAS, further studies were performed using an ACE inhibitor, and a nonpeptide Ang II antagonist (Saralasin). The use of these different RAS inhibitors yielded similar results, suggesting that the effects of ARB were mediated by inhibition of the

Moreover, it was observed in vitro that the increase in MMP-2 activity was greatest at the high doses of candesartan (greater than 0.1 umol/L), whereas maximum plasma concentrations in humans administered a standard dose of candesartan are below the nanomolar range (Pfister et al., 1999). Assuming that local (glomerular) concentrations of ARB will be greatest with the high-doses of ARB, these in vitro results are consistent with the in vivo observation that the glomerulosclerosis regression was maximal with the high

In humans, it is known that MMP-1 (collagenase-1) also plays a major role in the breakdown of collagens, in particular type I and type III collagen. It has been reported that rodents lack the human MMP-1 gene, and MMP-13 (collagenase-3) is the main collagenase in mice (Henriet et al., 1992), (Parks et al., 2000.). When the possibility that MMP-13 may also contribute to the observed changes was examined, it was found that ARB treatment did not increase glomerular MMP-13 activity, but rather decreased the activity, suggesting that increased MMP-13 activity did not contribute to the observed regression of

We also examined whether the effects of ARB could be attenuated by pretreating the mice with doxycycline, or by performing studies on mice with a deletion of the MMP-2 gene. It was found that neither inhibition of MMP nor deletion of MMP-2 completely abolished the effects of high-dose ARB, suggesting that other mechanisms may be involved, including the involvement of other proteases such as the serine protease plasminogen activator inhibitor-1 (PAI-1) (Ma et al., 2005). Other studies have suggested that regeneration of glomerular podocyte function may also play a role in the regression of glomerulosclerosis by RAS

It should be noted that the effects of ARB on regression may differ widely in different animal models. In particular, the effects of ARB on regression were less marked in the 5/6 nephrectomy model (Ma et al., 2005). This may be because the adriamycin model relies on a single (acute) injury to the glomeruli, whereas the injury in the 5/6 nephrectomy model is a continuous process. In the studies on the adriamycin nephropathy model, it was found that

glomerulosclerosis in the adriamycin nephropathy model (Hayashi et al., 2010).

intrinsic RAS in podocytes.

inhibitors (Macconi et al., 2009).

doses of ARB.

caused a dose-dependent increase in glomerular MMP-2 activity and decrease in type IV collagen accumulation. The ARB-induced regression of glomerulosclerosis was attenuated by pretreatment with the MMP inhibitor doxycycline, as well as in mice with targeted deletion of the MMP-2 gene, suggesting the possibility that increased expression of MMP-2 may contribute to the regression of glomerulosclerosis and type IV collagen deposition seen in the high-dose ARB-treated groups.

The MMP family constitutes a multigene family of zinc- and calcium-dependent endopeptidases which play a major role in the degradation of collagen and other ECM components (Woessner, 1991), (Baramova et al., 1995), (Sasamura et al., 2005). MMP-2 (also known as gelatinase A) is a MMP which is found in the conditioned media of cultured fibroblasts, and is involved in the cleavage of multiple ECM proteins including type IV collagen (Woessner, 1991), (Baramova et al., 1995). In contrast to gelatinase B (MMP-9), MMP-2 is not highly expressed in normal or diseased glomeruli (Urushihara et al., 2002). However, it has been shown that renal MMP-2 expression and activity are upregulated by ACE inhibitors in rats with diabetes (McLennan et al., 2002), (Sun et al., 2006). Moreover, Turkay et al reported that the ACE inhibitor enalapril also increased hepatic MMP-2 expression in rats with experimental hepatic fibrogenesis (Turkay et al., 2008), while Westermann et al. showed that the ARB irbesartan increased MMP-2 activity in the hearts of mice with cardiomyopathy (Westermann et al., 2007), suggesting that the RAS plays a key role in regulation of MMP-2 expression in the kidney and other tissues.

Fig. 3. Effects of different doses of ARB (candesartan) on glomerular MMP-2 and MMP-9 activity and expression in the adriamycin-nephropathy model. Representative results of (a) highly-sensitive in situ zymography (b) immunofluorescence. Quantification of glomerular MMP activity by (c) in situ zymography (d) ELISA. Reproduced with permission from Hayashi et al. Kidney Int 78:69-78, 2010.

caused a dose-dependent increase in glomerular MMP-2 activity and decrease in type IV collagen accumulation. The ARB-induced regression of glomerulosclerosis was attenuated by pretreatment with the MMP inhibitor doxycycline, as well as in mice with targeted deletion of the MMP-2 gene, suggesting the possibility that increased expression of MMP-2 may contribute to the regression of glomerulosclerosis and type IV collagen deposition seen

The MMP family constitutes a multigene family of zinc- and calcium-dependent endopeptidases which play a major role in the degradation of collagen and other ECM components (Woessner, 1991), (Baramova et al., 1995), (Sasamura et al., 2005). MMP-2 (also known as gelatinase A) is a MMP which is found in the conditioned media of cultured fibroblasts, and is involved in the cleavage of multiple ECM proteins including type IV collagen (Woessner, 1991), (Baramova et al., 1995). In contrast to gelatinase B (MMP-9), MMP-2 is not highly expressed in normal or diseased glomeruli (Urushihara et al., 2002). However, it has been shown that renal MMP-2 expression and activity are upregulated by ACE inhibitors in rats with diabetes (McLennan et al., 2002), (Sun et al., 2006). Moreover, Turkay et al reported that the ACE inhibitor enalapril also increased hepatic MMP-2 expression in rats with experimental hepatic fibrogenesis (Turkay et al., 2008), while Westermann et al. showed that the ARB irbesartan increased MMP-2 activity in the hearts of mice with cardiomyopathy (Westermann et al., 2007), suggesting that the RAS plays a key

role in regulation of MMP-2 expression in the kidney and other tissues.

Fig. 3. Effects of different doses of ARB (candesartan) on glomerular MMP-2 and MMP-9 activity and expression in the adriamycin-nephropathy model. Representative results of (a) highly-sensitive in situ zymography (b) immunofluorescence. Quantification of glomerular MMP activity by (c) in situ zymography (d) ELISA. Reproduced with permission from

in the high-dose ARB-treated groups.

Hayashi et al. Kidney Int 78:69-78, 2010.

As shown in Fig. 3, the results of highly-sensitive in situ zymography and immunofluorescence suggested that MMP-2 might be upregulated in glomerular podocytes, but this could not be determined accurately because of the relatively low expression of MMP-2 protein. Therefore, to further characterize the mechanisms of the ARB-induced increase in glomerular MMP-2 activity, we examined the effects of ARB treatment in cultured podocytes. These experiments revealed that ARB treatment of podocytes resulted in a dose-dependent increase in MMP-2 activity in the supernatant. Podocytes are known to express components of the RAS, including renin, angiotensinogen, angiotensin-converting enzyme, and AT1 and AT2 receptors (Durvasula et al., 2006), (Durvasula et al., 2008), (Liebau et al., 2006). Morever, functional expression of the renin-angiotensin system has been documented in both mouse and human podocytes (Durvasula et al., 2008), (Liebau et al., 2006). To examine the possibility that the effects of ARB were mediated through inhibition of the RAS, further studies were performed using an ACE inhibitor, and a nonpeptide Ang II antagonist (Saralasin). The use of these different RAS inhibitors yielded similar results, suggesting that the effects of ARB were mediated by inhibition of the intrinsic RAS in podocytes.

Moreover, it was observed in vitro that the increase in MMP-2 activity was greatest at the high doses of candesartan (greater than 0.1 umol/L), whereas maximum plasma concentrations in humans administered a standard dose of candesartan are below the nanomolar range (Pfister et al., 1999). Assuming that local (glomerular) concentrations of ARB will be greatest with the high-doses of ARB, these in vitro results are consistent with the in vivo observation that the glomerulosclerosis regression was maximal with the high doses of ARB.

In humans, it is known that MMP-1 (collagenase-1) also plays a major role in the breakdown of collagens, in particular type I and type III collagen. It has been reported that rodents lack the human MMP-1 gene, and MMP-13 (collagenase-3) is the main collagenase in mice (Henriet et al., 1992), (Parks et al., 2000.). When the possibility that MMP-13 may also contribute to the observed changes was examined, it was found that ARB treatment did not increase glomerular MMP-13 activity, but rather decreased the activity, suggesting that increased MMP-13 activity did not contribute to the observed regression of glomerulosclerosis in the adriamycin nephropathy model (Hayashi et al., 2010).

We also examined whether the effects of ARB could be attenuated by pretreating the mice with doxycycline, or by performing studies on mice with a deletion of the MMP-2 gene. It was found that neither inhibition of MMP nor deletion of MMP-2 completely abolished the effects of high-dose ARB, suggesting that other mechanisms may be involved, including the involvement of other proteases such as the serine protease plasminogen activator inhibitor-1 (PAI-1) (Ma et al., 2005). Other studies have suggested that regeneration of glomerular podocyte function may also play a role in the regression of glomerulosclerosis by RAS inhibitors (Macconi et al., 2009).

It should be noted that the effects of ARB on regression may differ widely in different animal models. In particular, the effects of ARB on regression were less marked in the 5/6 nephrectomy model (Ma et al., 2005). This may be because the adriamycin model relies on a single (acute) injury to the glomeruli, whereas the injury in the 5/6 nephrectomy model is a continuous process. In the studies on the adriamycin nephropathy model, it was found that

Prevention and Regression of Chronic Kidney Disease and Hypertension 421

Metabolomics is a discipline dedicated to the global study of metabolites, their dynamics, composition, interactions, and responses to interventions or to changes in their environment (Oresic, 2009), and the recent development of metabolome analysis technology allows the global 'metabolome' to be assessed comprehensively in individual patients. An important advantage of metabolome analysis is the potential to identify new and unidentified metabolites which could have important pathophysiological functions. In a recent study, we obtained serum and urine samples from 15 patients and 7 healthy volunteers, and compared the metabolome profiles of the two groups. Serum or urine samples (100 ul) were added to methanol (900 ul) containing internal standards, deproteinised, and subjected to anionic and cationic capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) analysis

The results of our metabolome analysis suggested that serum and urine levels of several amino acid, nucleic acid, and carbohydrate metabolites were altered in patients from an early stage of CKD (Hayashi et al., 2011). We also found evidence for the presence of several novel metabolites which were markedly increased or decreased in the patients with CKD compared to controls. We are performing further studies to examine the structure of these unidentified products, with the final aim to find new biomarkers of disease regression

It has been recognized that the kidney plays an important role in the control of systemic blood pressure, and is involved in the pathogenesis of hypertension, which is a major risk factor for cardiovascular disorders such as stroke, heart failure, vascular disease, and endstage renal disease, and an important cause of morbidity and mortality. Similar to CKD, the development of hypertension appears to be progressive: the systolic blood pressure of an individual patient rises progressively over time, so that median values of systolic blood

In our laboratory, we have been studying the use of RAS inhibitors to prevent the development of hypertension, using the spontaneously hypertensive rat (SHR) and other animal models of hypertension. Previous studies by Harrap et al. demonstrated that treatment of SHR from age 6 to 10 weeks with an angiotensin-converting enzyme (ACE) inhibitor resulted in the sustained suppression of hypertension at age 25 weeks (Harrap et al., 1986), (Harrap et al., 1990). Studies from the group of Berecek et al. suggested that these results could result from a decrease in arginine vasopressin (AVP) levels (Lee et al., 1991), (Zhang et al., 1996). Similar findings have been reported by other laboratories, using both ACE inhibitors (Giudicelli et al., 1980), (Christensen et al., 1989) and ARBs (Morton et al.,

In our laboratory, it was found that treatment of stroke-prone SHR (SHRSP) with an ACE inhibitor from age 3 to 10 weeks resulted in a sustained suppression of blood pressure, whereas such an effect was not found with the vasodilator hydralazine (Nakaya et al., 2001). The same results were found with an ARB, suggesting that this effect could be explained by the inhibitory actions of ACE inhibitors and ARB on the RAS. Importantly, it was also found

To examine if the effects of RAS inhibitors to suppress the development of hypertension was specific to the SHR and its related strains, studies were performed on the Dahl salt-sensitive

pressure in the population increases at every age (Qureshi et al., 2005).

that the development of renal injury was also suppressed in this model.

which may be utilized in clinical studies.

**3.1 Prevention of hypertension**

1992), (Gillies et al., 1997).

MMP-2 activity decreased to baseline after the ARB treatment was discontinued. The transient increase in MMP-2 was probably sufficient to permanently reverse the glomerulosclerosis in that model, but its effect in other disease states is unclear.

Interestingly, clinical studies using different ARBs (Rossing et al., 2005), (Hollenberg et al., 2007), (Burgess et al., 2009) also suggest that high-dose ARB treatment may have a greater beneficial effect on the kidney compared to standard doses. One potential reason may be that standard doses of ARB do not fully suppress the RAS in the kidneys. Another possibility is that mechanisms unrelated to RAS inhibition may be involved, for example an antioxidant action independent of AT1 receptor blockade (Chen et al., 2008). Currently, we are performing further studies to examine why high-dose ARB is particularly effective in ameliorating glomerular injury.


COVID-19 Pandemic, Mental Health and Neuroscience - New Scenarios for Understanding and Treatment

*Edited by Sara Palermo and Berend Olivier*

Published in London, United Kingdom

COVID-19 Pandemic, Mental Health and Neuroscience - New Scenarios for Understanding and Treatment

http://dx.doi.org/10.5772/intechopen.100841 Edited by Sara Palermo and Berend Olivier

#### Contributors

Amr Ahmed, Amr Ghit, Mahmoud Elkazzaz, Asmaa Houjak, Shoji Nakamura, Jawza F. Alsabhan, Tahani K. Alshammari, Swapan Kumar Chatterjee, Snigdha Saha, Shahin Muhammed T. K., Ole Boe, Samir Rawat, Priya Joshi, Abhijit P. Deshpande, Andrzej Piotrowski, Derebe Madoro, Nixon M. Abraham, Meenakshi Pardasani, Diana Araja, Angelika Krumina, Uldis Berkis, Modra Murovska, Zaiga Nora-Krukle, Margot Gage Witvliet, Kanwar Hamza Shuja, Arfa Mubeen, Sania Mazher, Shazia Tariq, Fernanda Dreux M. Fernandes, Maria Vitoria do Amaral, Cibelle La Higuera Amato, Harpreet Kaur, Asmita Kaundal, John Teibo, Abolaji Olagunju, Titilade Teibo, Olabode Omotoso, Festus Atiba, Ahmad Babalghith, Gaber Batiha, Serefnur Ozturk, Fettah Eren, Chika Eze, Nneka Okafor, Emelda I. Emmanuel, Chinecherem Iloka, Dragana Komnenov, Yusuuf Tunde Gbonjubola, Adesola Oyinkansola Abiodun, Mary Olamide Akinwola, Shinichiro Maeshima, Koki - Kawamura, Aiko Osawa, Hidenori Arai, Robabe Khalili, Leila Karimi, Sara Palermo, Alessandro Giannandrea, Luisa Sist, Monica Martoni, Lara Colombo, Annalisa Grandi, Margherita Zito, Vicenzo Russo, Berend Olivier, Megan E. Breuer, Christiaan H. Vinkers, Jocelien D.A. Olivier

#### © The Editor(s) and the Author(s) 2023

The rights of the editor(s) and the author(s) have been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights to the book as a whole are reserved by INTECHOPEN LIMITED. The book as a whole (compilation) cannot be reproduced, distributed or used for commercial or non-commercial purposes without INTECHOPEN LIMITED's written permission. Enquiries concerning the use of the book should be directed to INTECHOPEN LIMITED rights and permissions department (permissions@intechopen.com).

Violations are liable to prosecution under the governing Copyright Law.

Individual chapters of this publication are distributed under the terms of the Creative Commons Attribution 3.0 Unported License which permits commercial use, distribution and reproduction of the individual chapters, provided the original author(s) and source publication are appropriately acknowledged. If so indicated, certain images may not be included under the Creative Commons license. In such cases users will need to obtain permission from the license holder to reproduce the material. More details and guidelines concerning content reuse and adaptation can be found at http://www.intechopen.com/copyright-policy.html.

#### Notice

Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book.

First published in London, United Kingdom, 2023 by IntechOpen IntechOpen is the global imprint of INTECHOPEN LIMITED, registered in England and Wales, registration number: 11086078, 5 Princes Gate Court, London, SW7 2QJ, United Kingdom

British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library

Additional hard and PDF copies can be obtained from<EMAIL_ADDRESS>
COVID-19 Pandemic, Mental Health and Neuroscience - New Scenarios for Understanding and Treatment Edited by Sara Palermo and Berend Olivier p. cm. Print ISBN 978-1-80355-090-9 Online ISBN 978-1-80355-091-6 eBook (PDF) ISBN 978-1-80355-092-3


*Supporting open minds since 2005*

Gold Nanoparticles - Reaching New Heights http://dx.doi.org/10.5772/intechopen.73366 Edited by Mohammed Rahman and Abdullah Mohammed Asiri

#### Contributors

Ziyauddin Qureshi, Jaseer E.A., Sivakumar Thiripuranthagan, Pablo Gavina, Ana M. Costero, Margarita Parra, Salvador Gil, Samuel Briggs, Khalid Hattar, Young-Seok Shon, Ting-An Chen, Julián Puszkiel, Mohammed Muzibur Rahman

#### © The Editor(s) and the Author(s) 2019

The rights of the editor(s) and the author(s) have been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights to the book as a whole are reserved by INTECHOPEN LIMITED. The book as a whole (compilation) cannot be reproduced, distributed or used for commercial or non-commercial purposes without INTECHOPEN LIMITED's written permission. Enquiries concerning the use of the book should be directed to INTECHOPEN LIMITED rights and permissions department (permissions@intechopen.com).

Violations are liable to prosecution under the governing Copyright Law.

Individual chapters of this publication are distributed under the terms of the Creative Commons Attribution 3.0 Unported License which permits commercial use, distribution and reproduction of the individual chapters, provided the original author(s) and source publication are appropriately acknowledged. If so indicated, certain images may not be included under the Creative Commons license. In such cases users will need to obtain permission from the license holder to reproduce the material. More details and guidelines concerning content reuse and adaptation can be foundat http:// www.intechopen.com/copyright-policy.html.

#### Notice

Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book.

First published in London, United Kingdom, 2019 by IntechOpen eBook (PDF) Published by IntechOpen, 2019 IntechOpen is the global imprint of INTECHOPEN LIMITED, registered in England and Wales, registration number: 11086078, The Shard, 25th floor, 32 London Bridge Street London, SE19SG – United Kingdom Printed in Croatia

British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library

Additional hard and PDF copies can be obtained from<EMAIL_ADDRESS>
Gold Nanoparticles - Reaching New Heights Edited by Mohammed Rahman and Abdullah Mohammed Asiri p. cm. Print ISBN 978-1-78984-998-1 Online ISBN 978-1-78984-957-8 eBook (PDF) ISBN 978-1-83881-999-6