**6. Malignancies associated with CD**

The most important complication of CD is development of cancer. The incidence of gastrointestinal and non-gastrointestinal both is common among CD patients. The commonest among the malignancies is the gastrointestinal lymphomas accounting for 18% of all cancers. The gastrointestinal tract is the predominant site of extranodal lymphoma involvement. Primary lymphomas are less common than secondary lymphomas. Primary lymphomas typically involve any section of gastrointestinal tract from oropharynx to rectum [64]. It can involve single or multiple sites. These are usually non-Hodgkin's lymphomas although Hodgkin's lymphoma has been reported as well. The commonest site of involvement of non-Hodgkin's lymphoma is stomach, present in 68–75%, followed by small bowel than ileocecal junction. Diffuse colonic involvement is present only in 1% [65]. Distribution of primary lymphomas varies among population; gastric lymphoma is more common in United States, while intestinal lymphoma is seen in Middle East and Mediterranean areas. GI Lymphomas are commonly seen in patients with helicobacter pylori infection, autoimmune disease, immunodeficiency and immunosuppressive states, inflammatory bowel disease and CD. Both the T and B cell are commonly seen in patients with CD. The exact etiology of development of these malignancies is under controversy, both the autoimmune and inflammatory factors contribute to the risk. The T cell variant enteropathy-associated T-cell lymphoma (EATL) (**Figure 8**) involving the small intestine mostly, is the commonest malignancy seen in celiac disease, although uncommonly seen [66, 67]. It is most commonly found in adult males with a median age of 60 years. EATL patients mostly presented with acute bleeding, perforation or obstruction, or it should always be suspected if there is clinical deterioration of CD, despite on a strict gluten free diet. It is highly suggested to screen a patient for CD, even if not diagnosed before, if

presented with EATL. Patients with enteropathy associated T cell lymphoma of the small intestine, involving jejunum demonstrates large circumferential ulcer without overt mass. The involved area typically shows lymphoma, while the non-involved sites usually show villous atrophy.

The other variant of EATL, ulcerative enteritis, is another complication of long standing and refractory sprue. It presents with abdominal pain, nausea, vomiting and diarrhea. The other complication of CD includes intestinal ulceration independent of lymphoma and so called refractory sprue and collagenous sprue (**Figure 9**). It is a clinicopathological entity characterized by diarrhea and malabsorption accompanied by the histological findings of subepithelial collagen deposition and severe villous atrophy of small bowel mucosa [68]. The occurrence of collagenous sprue has been seen in patients with celiac disease, tropical sprue, milk intolerance and common variable immunodeficiency states [69]. Regardless of etiology it has a poor prognosis. Collagenous sprue associated with CD usually does not respond to gluten free diet and has a poor prognosis [70].

**Figure 8.** *Lymphoma.*

**79**

*Complications of Celiac Disease*

ment of malignancies in CD.

**7. Hyposplenism in CD**

**9. Kidney disease in CD**

**11. Dental defects in CD**

mended [71, 72].

*DOI: http://dx.doi.org/10.5772/intechopen.80465*

**8. Venous thromboembolism in CD**

tion with other disease is relatively high.

**10. Idiopathic pulmonary hemosiderosis in CD**

The risk of other digestive tract malignancies is also commonly seen in CD patients, including oropharyngeal, colorectal, small intestinal adenocarcinoma and hepatocellular carcinomas. In oropharyngeal carcinomas, the commonest is the squamous cell carcinoma. In contrast to gastrointestinal carcinomas, the nongastrointestinal malignancies, including breast carcinomas are not seen commonly in CD patients. There is no evidence that gluten free diet may decrease the develop-

One of the earliest manifestations of CD is hyposplenism, though the exact mechanism of development of hyposplenism is not known. Due to hyposplenism there is increased susceptibility of infection due to encapsulated bacteria especially. Vaccination against prophylaxis for pneumococcus is not highly recom-

Hypercoagulability with elevated homocysteine level and low vitamin-K-dependent anti-coagulant proteins (protein C & S) are relatively common in CD patients. Due to these factors, i.e. increased homocysteine level and decreased protein C &S, along with autoimmunity of CD, there might be increased susceptibility to venous

Glomerular IgA deposition is common, occurring in as many as one-third of patients. Although the clinical manifestation is not evident, due to no associated complement deficiency. This indicates that a high circulating load of polyclonal IgA is not adequate to cause nephritis, but other abnormalities of IgA are necessary to translate into mesangial activation and glomerular injury. This mesangial IgA deposition is also seen in healthy individuals from 3 to 16% [74]. Thus its associa-

Lane-Hamilton syndrome, the co-existence of CD and idiopathic pulmonary hemosiderosis, is not an uncommon entity in CD patients, although the exact prevalence is not known [75]. It is a rare lung disease characterized by alveolar capillary bleeding and accumulation of hemosiderin in the lungs. Diffuse alveolar hemorrhage is characterized by hemoptysis, dyspnea, alveolar opacities on chest X-ray and anemia. It may lead to iron loss through swallowing of iron-laden alveolar

Oral manifestations are overlooked in CD patients; the long list of clinical signs and symptoms associated with CD includes dental enamel hypoplasia, aphthous

or bronchial epithelial cells. This may lead to functional iron deficiency [76].

thromboembolism. Although not commonly observed in CD patients [73].

**Figure 9.** *Collagenous colitis.*

#### *Complications of Celiac Disease DOI: http://dx.doi.org/10.5772/intechopen.80465*

The risk of other digestive tract malignancies is also commonly seen in CD patients, including oropharyngeal, colorectal, small intestinal adenocarcinoma and hepatocellular carcinomas. In oropharyngeal carcinomas, the commonest is the squamous cell carcinoma. In contrast to gastrointestinal carcinomas, the nongastrointestinal malignancies, including breast carcinomas are not seen commonly in CD patients. There is no evidence that gluten free diet may decrease the development of malignancies in CD.


**2. Photophysical properties of BODIPY dyes**

BODIPY dyes possess interesting photophysical properties such as high fluorescence quantum yields and narrow emission bandwidths with high peak intensities, elevated photostability, relatively high absorption coefficients, and the extra feature of excitation/emission wavelengths in the visible region. The absorption and fluorescence properties of BODIPY dyes are highly influenced by the extent of electron delocalization around the core and through conjugated substituents, and as such, may be tuned to have photophysical characteristics. BODIPY dyes show a strong, narrow absorption band in the visible region signifying the S0-S1 (π-π\*) transition with a shoulder of high energy around 480 nm assigned to the 0–1 vibrational translation. A broad, much weaker band around 350 nm denotes the S0-S2 (π-π\*) transition [38]. Upon excitation to either the S1 or S2 states, an equally narrow emission band of mirror image to the absorption spectra is observed from the S1 state. Most of the BODIPY dyes emit at wavelengths less than 600 nm, routinely providing yellow to green emissions (500–590 nm) [2, 39]. The fluorescence emission wavelength of BODIPY can be controlled by suitable substitution of chemical fragments such as aliphatic carbon, aromatic ring, pi-bond conjugation, halogens, and electron-withdrawing or donating groups. The pi-bond prolongation on 3 and 5 positions of BODIPY core gives the red-shifted fluorescence emission wavelength [1]. On the other hand, the substitution of electron-donating groups such as amine or alkoxy groups on the 8-position (so-called meso-position) of BODIPY gives

**33**

excited state (3

*Photophysics of BODIPY Dyes: Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.92609*

transition and vibrational relaxation [40].

the blue-shifted fluorescence emission wavelength [1]. Unsubstituted BODIPY typically absorbs near 500 nm and emits around 510 nm. Small Stokes' shifts are routinely seen and indicate a modest change in the core structure following S0-S1

The groups that substituted onto the BODIPY scaffold can adjust the photophysical properties of BODIPYs [1]. The addition of functionality at any position of the aromatic core alters the photochemical profile to varying degrees, dependent upon the groups added. BODIPY based dyes containing methyl groups at positions 3- and 5- can be functionalized with aromatic compounds with the help of the Knoevenagel reaction [41]. The 2,6-positions of the BODIPY core tend to give an electrophilic substitution reaction. Decorating the BODIPY skeleton from 3,5-positions generally produces a greater bathochromic shift (ca. 50–100 nm) than adding conjugation through the 2,6-positions, displaying the greatest shift when all four methyls have converted to styryl groups [42]. Although the tetra-styryl BODIPY has been synthesized by activation and subsequent condensation of the 1,3,5,7-methyls [43], an extension of π-conjugation and addition of functionality is most frequently accomplished through the 3,5-methyls. Thus, the visible region of different BODIPY

From past to present, many research groups have been studying BODIPY and its derivatives. Consequently, there are many reported papers about the photophysical properties of BODIPY derivatives, especially in recent years. In 2014, Majumdar et al. [44] reported the synthesis of four styryl-BODIPY-containing Ir(III) complexes which show strong NIR absorption (644–729 nm), strong NIR fluorescence (700–800 nm), and long-lived triplet excited states (92.5–156.5 μs). Investigations of the photophysical properties of these complexes showed that they were strongly fluorescent, although the p-conjugation is present between the BODIPY ligands and the Ir(III) coordination center. Moderate intersystem crossing (ISC) was observed for the complexes, proved by the population of the long-lived intraligand triplet

O2) photosensitizing property. Based

O2 quantum

derivatives can be largely scanned, resulting in a wider range of use.

IL) and the singlet oxygen (1

on the property of NIR absorption/fluorescence and the reasonable 1

efficiency, the complexes were used as multi-functional materials as luminescent bioimaging reagents and in intracellular photodynamic studies. Also, they reported that their results are useful for the preparation of NIR absorbing cyclometalated Ir(III) complexes, and the relevant application of these complexes as multifunctional materials such as a luminescent bioimaging reagent, in photodynamic therapy (PDT) and photocatalysis. At the same year, a 2,6-distyryl-substituted BODIPY dye and a new series of 2,6-p-dimethylaminostyrene isomers containing both α- and β-position styryl substituents were reported by Gai et al. [45]. They used styrene and p-dimethylaminostyrene with an electron-rich diiodo-BODIPY in the synthesis of these compounds. They indicated that the absorption spectra contain red-shifted absorbance bands due to conjugation between the styryl moieties and the main BODIPY fluorophore. Besides, very low fluorescence quantum yields, and significant Stokes shifts were observed for 2,6-distyryl-substituted BODIPYs, concerning like 3,5-distyryl- and 1,7-distyryl-substituted BODIPYs. In spite of the fluorescence of the compound with β-position styryl substituents on both pyrrole fragments and one with both β- and α-position substituents was fully quenched, the compound with only α-position substituents displays weak emission in polar solvents, but strong emission with a quantum yield of 0.49 in hexane. They enounced that 2,6-p-dimethylaminostyrene isomers can be used as sensors for changes in pH. Two novel azomethine-BODIPY dyads were reported by Pan et al. [46]. These two dyads have been synthesized by covalent tethering of tautomeric ortho-hydroxy aromatic azomethine moieties including N-salicylideneaniline (SA) and N-naphthlideneaniline (NA) to a BODIPY fluorophore. Both two dyads showed

### *Photophysics of BODIPY Dyes: Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.92609*

*Photophysics, Photochemical and Substitution Reactions - Recent Advances*

to either equally substituted asymmetric counterpart (substitution from 1,3- or 5,7-positions). However, the greater substitution of the BODIPY core does not necessarily produce a larger bathochromic shift, as depicted upon the comparison of the penta-substituted BODIPY (substitution from 1,3,5,7- and 8-positions) to the tetra-substituted BODIPY (substitution from 1,3,5,7-positions) [8, 9]. Red to near infrared (NIR) shifts are generally attained owing to the straightforward modification to the BODIPY core with the extension of the degree of π-delocalization. Also, the emissive behavior of BODIPY fluorophores is much affected by steric and electronic interactions of substituent moieties. Rotation of pendant components as well as their electron-donating or withdrawing effects on the conjugated core greatly influences both the brightness and absorptive and emissive properties of

Due to these excellent photophysical characteristics, BODIPY dyes increase their potential using in different applications such as fluorescent labels for biomolecules and cellular imaging [11–15], light-emitting devices [16–18], drug delivery agents [19–21], photosensitizers [22–24], fluorescent switches [25], chemosensors [26–29], energy transfer cassettes [30–33], and solar cells [34–37]. In this chapter, general photophysical properties of BODIPY and aza-BODIPY derivatives and recent stud-

BODIPY dyes possess interesting photophysical properties such as high fluorescence quantum yields and narrow emission bandwidths with high peak intensities, elevated photostability, relatively high absorption coefficients, and the extra feature of excitation/emission wavelengths in the visible region. The absorption and fluorescence properties of BODIPY dyes are highly influenced by the extent of electron delocalization around the core and through conjugated substituents, and as such, may be tuned to have photophysical characteristics. BODIPY dyes show a strong, narrow absorption band in the visible region signifying the S0-S1 (π-π\*) transition with a shoulder of high energy around 480 nm assigned to the 0–1 vibrational translation. A broad, much weaker band around 350 nm denotes the S0-S2 (π-π\*) transition [38]. Upon excitation to either the S1 or S2 states, an equally narrow emission band of mirror image to the absorption spectra is observed from the S1 state. Most of the BODIPY dyes emit at wavelengths less than 600 nm, routinely providing yellow to green emissions (500–590 nm) [2, 39]. The fluorescence emission wavelength of BODIPY can be controlled by suitable substitution of chemical fragments such as aliphatic carbon, aromatic ring, pi-bond conjugation, halogens, and electron-withdrawing or donating groups. The pi-bond prolongation on 3 and 5 positions of BODIPY core gives the red-shifted fluorescence emission wavelength [1]. On the other hand, the substitution of electron-donating groups such as amine or alkoxy groups on the 8-position (so-called meso-position) of BODIPY gives

ies on the photophysical properties of these dyes are presented.

**2. Photophysical properties of BODIPY dyes**

**32**

BODIPY [10].

**Figure 1.**

*Chemical structure and numbering of BODIPY core.*

the blue-shifted fluorescence emission wavelength [1]. Unsubstituted BODIPY typically absorbs near 500 nm and emits around 510 nm. Small Stokes' shifts are routinely seen and indicate a modest change in the core structure following S0-S1 transition and vibrational relaxation [40].

The groups that substituted onto the BODIPY scaffold can adjust the photophysical properties of BODIPYs [1]. The addition of functionality at any position of the aromatic core alters the photochemical profile to varying degrees, dependent upon the groups added. BODIPY based dyes containing methyl groups at positions 3- and 5- can be functionalized with aromatic compounds with the help of the Knoevenagel reaction [41]. The 2,6-positions of the BODIPY core tend to give an electrophilic substitution reaction. Decorating the BODIPY skeleton from 3,5-positions generally produces a greater bathochromic shift (ca. 50–100 nm) than adding conjugation through the 2,6-positions, displaying the greatest shift when all four methyls have converted to styryl groups [42]. Although the tetra-styryl BODIPY has been synthesized by activation and subsequent condensation of the 1,3,5,7-methyls [43], an extension of π-conjugation and addition of functionality is most frequently accomplished through the 3,5-methyls. Thus, the visible region of different BODIPY derivatives can be largely scanned, resulting in a wider range of use.

From past to present, many research groups have been studying BODIPY and its derivatives. Consequently, there are many reported papers about the photophysical properties of BODIPY derivatives, especially in recent years. In 2014, Majumdar et al. [44] reported the synthesis of four styryl-BODIPY-containing Ir(III) complexes which show strong NIR absorption (644–729 nm), strong NIR fluorescence (700–800 nm), and long-lived triplet excited states (92.5–156.5 μs). Investigations of the photophysical properties of these complexes showed that they were strongly fluorescent, although the p-conjugation is present between the BODIPY ligands and the Ir(III) coordination center. Moderate intersystem crossing (ISC) was observed for the complexes, proved by the population of the long-lived intraligand triplet excited state (3 IL) and the singlet oxygen (1 O2) photosensitizing property. Based on the property of NIR absorption/fluorescence and the reasonable 1 O2 quantum efficiency, the complexes were used as multi-functional materials as luminescent bioimaging reagents and in intracellular photodynamic studies. Also, they reported that their results are useful for the preparation of NIR absorbing cyclometalated Ir(III) complexes, and the relevant application of these complexes as multifunctional materials such as a luminescent bioimaging reagent, in photodynamic therapy (PDT) and photocatalysis. At the same year, a 2,6-distyryl-substituted BODIPY dye and a new series of 2,6-p-dimethylaminostyrene isomers containing both α- and β-position styryl substituents were reported by Gai et al. [45]. They used styrene and p-dimethylaminostyrene with an electron-rich diiodo-BODIPY in the synthesis of these compounds. They indicated that the absorption spectra contain red-shifted absorbance bands due to conjugation between the styryl moieties and the main BODIPY fluorophore. Besides, very low fluorescence quantum yields, and significant Stokes shifts were observed for 2,6-distyryl-substituted BODIPYs, concerning like 3,5-distyryl- and 1,7-distyryl-substituted BODIPYs. In spite of the fluorescence of the compound with β-position styryl substituents on both pyrrole fragments and one with both β- and α-position substituents was fully quenched, the compound with only α-position substituents displays weak emission in polar solvents, but strong emission with a quantum yield of 0.49 in hexane. They enounced that 2,6-p-dimethylaminostyrene isomers can be used as sensors for changes in pH. Two novel azomethine-BODIPY dyads were reported by Pan et al. [46]. These two dyads have been synthesized by covalent tethering of tautomeric ortho-hydroxy aromatic azomethine moieties including N-salicylideneaniline (SA) and N-naphthlideneaniline (NA) to a BODIPY fluorophore. Both two dyads showed

enol-imine (OH) structures dominating in the crystalline state. For the first dyad, in the enol state is the most stable form at room temperature in most environments, while enol-keto prototropic tautomerism of the NA fragment in solution is maintained in the second dyad, which can be reversibly modified between enol and keto forms in the environment's polarity. Visible lighting of the second dyad in the enol case excites selectively the BODIPY moiety and then counteracts radiatively by emitting green light in the form of fluorescence, while the emission intensity of the second dyad in the keto case is quenched based on the proton-coupled photoinduced electron transfer (PCPET) mechanism. This permits to large fluorescence modulation among the two states of the second dyad and creates a new tautomerisable fluorescent switch. Photophysical properties of a pyrene-based tetramethyl difluoroborondipyrromethane (PYBDP) were investigated by Yang et al. [47]. The PYBDP showed a higher fluorescence quantum efficiency and Stokes shift than other phenyl-substituted laser dyes in the green region. Under transversal pumping conditions, this new dye exhibited highly effective and stable emissions centering at 531 nm. The PYBDP dye exhibited a maximum narrow band amplified spontaneous emission (ASE) lasing yield of 10.86% with an extensive adjustable range (525–560 nm) under demanding transversal pumping at 355 nm in toluene. The lasing efficiency remains unaffected in 1 h but a dramatic decrease or even the loss of the laser action is observed in intermediate or highly polar solvents. The combination of excellent photostability and tunability of ASE makes PYBDP a potentially green-emitting laser dye in the green-orange region. In a reported study from our working group [48] was about the treatment of boron (III) subphthalocyanine chloride with borondipyrromethene derivatives containing either one or two [4-(N,N-dimethylamino)phenyl]ethenyl groups in toluene gave the corresponding axially substituted boron(III) subphthalocyanine dyes (**Figure 2**). Methyl groups on 3- and 5-positions have acidic hydrogens due to electron-withdrawing property of heterocyclic BODIPY ring. This acidic property can be taken advantage of, in the synthesis of other BODIPY fluorophores for example with aromatic aldehydes. For this reason, N,N-dimethyl-4-aminobenzaldehyde was reacted with BODIPY, resulting in extension of conjugation in our study. This extension of conjugation allowed us to shift the absorption and emission spectra to longer wavelengths. The reaction was performed in a solution containing acetic acid and piperidine. The solvent was toluene because any water forming in the reaction should be removed. Dean-Stark apparatus is a good choice because water can be removed azeotropically during reflux. The photophysical properties of these compounds were examined utilizing absorption and fluorescence spectroscopy in dilute benzene solutions. They

**35**

*Photophysics of BODIPY Dyes: Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.92609*

locyanine (SubPc) unit to the BODIPY unit. Increased 1

feature that may be useful for PDT application of these dyes.

exhibited a highly efficient energy transfer process from the excited subphtha-

for BODIPY substituted SubPc compounds relative to their BODIPY precursors; a

The effect of the substituent side groups like phenyl (Ph), phenylethynyl (Ethyn) and styryl moiety at the 2-, 3- or 8- position of the BODIPY scaffold was reported by Orte et al. [49]. A large number of solvents (methanol, acetonitrile, diethyl ether, acetone, ethyl acetate, 2-propanol, isobutyronitrile, dibutyl ether, tetrahydrofuran, 1-pentanol, 1,4-dioxane, dichloromethane, cyclohexane, 1-octanol, chloroform, cyclohexanone, toluene, chlorobenzene) were used for investigation of the photophysical properties of these compounds. A substitution from 3-position is beneficial for producing BODIPYs with sharp absorption bands and high fluorescence quantum yields. Contrarily, substitution at the 2-position yielded BODIPY dyes with large Stokes shifts and broad bands. Substitution at the meso-position produced dyes with features like the 3-substituted ones, except for meso-phenyl BODIPY (8-Ph). Between the phenyl-substituted BODIPY dyes, some differences in absorption behavior were observed. The presence of the p-tert-butylphenyl moiety shifts the absorption maximum, λabs(max) from 516 to 530 nm when this group is at the 2-position (2-Ph) to 513–527 nm and when it is at the 3-position (3-Ph). In these two statuses, λabs(max) is more red-shifted in the more polarizable solvents toluene and chlorobenzene. Conversely, the values of λabs(max) of 8-Ph are blue-shifted concerning those of 2-Ph and 3-Ph and are close to those of unsubstituted BODIPY [50, 51], ranging from 489 nm in acetonitrile to 497 nm in toluene and chlorobenzene. This absorption energy range is in good agreement with that of other BODIPYs substituted at the meso-position with a weak electron acceptor or donor [52, 53]. For the phenylethynyl BODIPYs, the absorption spectra show also the characteristic properties of typical BODIPYs. 2-Ethyn possessed an absorption maximum between 503 and 525 nm, whereas the λabs (max) of 3-Ethyn changes between 525 and 545 nm. For the two dyes, the lowest λabs (max) value was founded in acetonitrile and the highest in cyclohexane. The influence of the substitution positions (2 vs. 3) on λabs(max) is much higher for the phenylethynyl fragment than for the phenyl moiety and moving the p-tert-butylphenyl substituent from the 2-Ph to the 3-Ph causes a 3 nm blue shift of λabs(max), while the similar change from 2-Ethyn to 3-Ethyn results in a ca. 20 nm red shift of λabs(max). 8-Ethyn is bathochromically shifted for 2-Ethyn and 3-Ethyn, with λabs(max) ranging from 537 to 547 mm which is parallel with an increasing refractive index [54]. Styryl-substituted BODIPYs (2-Styryl, 3-Styryl and 8-Styryl) displayed different absorption properties. The λabs(max) values range from 549 to 561 nm, with a typical redshift from acetonitrile to chlorobenzene. The extended conjugation ensured by the styryl functional group reasons an extra bathochromic shift of around 20 nm for 3-Ethyn, and ca. 30 nm for 3-Ph. Conversely, 2-Styryl and 8-Styryl show clear dual-band absorption and emission behavior. The photophysical reaction of two BODIPY-based D−A and A− D−A molecules, where D is the donor and A is the acceptor was reported by Hendel et al. [55]. A BODIPY fragment was given as the A component and was attached through the meso position using a 3-hexylthiophene linker to an N-(2-ethylhexyl) dithieno[3,2-b:2′,3′-d] pyrrole (DTP), which was given as the D component. An A−D−A molecule was compared to its corresponding D − A dyad counterpart. This showed a potential advantage to the A−D−A molecule over the D−A dyad in creating longer-lived excited states. A−D−A possess slightly longer excited-state lifetimes, 42 ps nonradiative decay, and 4.64 ns radiative decay compared to those of D−A, 24 ps nonradiative decay, and 3.95 ns radiative decay. These results show a full picture of the electronic and photophysical properties of D−A and A−D−A that provide contextualization for structure-function relationships between molecules

O2 production was noted

**Figure 2.** *Chemical structure of (a) mono-styryl and (b) distyryl-BODIPY substituted subphthalocyanines.*

*Photophysics, Photochemical and Substitution Reactions - Recent Advances*

enol-imine (OH) structures dominating in the crystalline state. For the first dyad, in the enol state is the most stable form at room temperature in most environments, while enol-keto prototropic tautomerism of the NA fragment in solution is maintained in the second dyad, which can be reversibly modified between enol and keto forms in the environment's polarity. Visible lighting of the second dyad in the enol case excites selectively the BODIPY moiety and then counteracts radiatively by emitting green light in the form of fluorescence, while the emission intensity of the second dyad in the keto case is quenched based on the proton-coupled photoinduced electron transfer (PCPET) mechanism. This permits to large fluorescence modulation among the two states of the second dyad and creates a new tautomerisable fluorescent switch. Photophysical properties of a pyrene-based tetramethyl difluoroborondipyrromethane (PYBDP) were investigated by Yang et al. [47]. The PYBDP showed a higher fluorescence quantum efficiency and Stokes shift than other phenyl-substituted laser dyes in the green region. Under transversal pumping conditions, this new dye exhibited highly effective and stable emissions centering at 531 nm. The PYBDP dye exhibited a maximum narrow band amplified spontaneous emission (ASE) lasing yield of 10.86% with an extensive adjustable range (525–560 nm) under demanding transversal pumping at 355 nm in toluene. The lasing efficiency remains unaffected in 1 h but a dramatic decrease or even the loss of the laser action is observed in intermediate or highly polar solvents. The combination of excellent photostability and tunability of ASE makes PYBDP a potentially green-emitting laser dye in the green-orange region. In a reported study from our working group [48] was about the treatment of boron (III) subphthalocyanine chloride with borondipyrromethene derivatives containing either one or two [4-(N,N-dimethylamino)phenyl]ethenyl groups in toluene gave the corresponding axially substituted boron(III) subphthalocyanine dyes (**Figure 2**). Methyl groups on 3- and 5-positions have acidic hydrogens due to electron-withdrawing property of heterocyclic BODIPY ring. This acidic property can be taken advantage of, in the synthesis of other BODIPY fluorophores for example with aromatic aldehydes. For this reason, N,N-dimethyl-4-aminobenzaldehyde was reacted with BODIPY, resulting in extension of conjugation in our study. This extension of conjugation allowed us to shift the absorption and emission spectra to longer wavelengths. The reaction was performed in a solution containing acetic acid and piperidine. The solvent was toluene because any water forming in the reaction should be removed. Dean-Stark apparatus is a good choice because water can be removed azeotropically during reflux. The photophysical properties of these compounds were examined utilizing absorption and fluorescence spectroscopy in dilute benzene solutions. They

*Chemical structure of (a) mono-styryl and (b) distyryl-BODIPY substituted subphthalocyanines.*

**34**

**Figure 2.**

exhibited a highly efficient energy transfer process from the excited subphthalocyanine (SubPc) unit to the BODIPY unit. Increased 1 O2 production was noted for BODIPY substituted SubPc compounds relative to their BODIPY precursors; a feature that may be useful for PDT application of these dyes.

The effect of the substituent side groups like phenyl (Ph), phenylethynyl (Ethyn) and styryl moiety at the 2-, 3- or 8- position of the BODIPY scaffold was reported by Orte et al. [49]. A large number of solvents (methanol, acetonitrile, diethyl ether, acetone, ethyl acetate, 2-propanol, isobutyronitrile, dibutyl ether, tetrahydrofuran, 1-pentanol, 1,4-dioxane, dichloromethane, cyclohexane, 1-octanol, chloroform, cyclohexanone, toluene, chlorobenzene) were used for investigation of the photophysical properties of these compounds. A substitution from 3-position is beneficial for producing BODIPYs with sharp absorption bands and high fluorescence quantum yields. Contrarily, substitution at the 2-position yielded BODIPY dyes with large Stokes shifts and broad bands. Substitution at the meso-position produced dyes with features like the 3-substituted ones, except for meso-phenyl BODIPY (8-Ph). Between the phenyl-substituted BODIPY dyes, some differences in absorption behavior were observed. The presence of the p-tert-butylphenyl moiety shifts the absorption maximum, λabs(max) from 516 to 530 nm when this group is at the 2-position (2-Ph) to 513–527 nm and when it is at the 3-position (3-Ph). In these two statuses, λabs(max) is more red-shifted in the more polarizable solvents toluene and chlorobenzene. Conversely, the values of λabs(max) of 8-Ph are blue-shifted concerning those of 2-Ph and 3-Ph and are close to those of unsubstituted BODIPY [50, 51], ranging from 489 nm in acetonitrile to 497 nm in toluene and chlorobenzene. This absorption energy range is in good agreement with that of other BODIPYs substituted at the meso-position with a weak electron acceptor or donor [52, 53]. For the phenylethynyl BODIPYs, the absorption spectra show also the characteristic properties of typical BODIPYs. 2-Ethyn possessed an absorption maximum between 503 and 525 nm, whereas the λabs (max) of 3-Ethyn changes between 525 and 545 nm. For the two dyes, the lowest λabs (max) value was founded in acetonitrile and the highest in cyclohexane. The influence of the substitution positions (2 vs. 3) on λabs(max) is much higher for the phenylethynyl fragment than for the phenyl moiety and moving the p-tert-butylphenyl substituent from the 2-Ph to the 3-Ph causes a 3 nm blue shift of λabs(max), while the similar change from 2-Ethyn to 3-Ethyn results in a ca. 20 nm red shift of λabs(max). 8-Ethyn is bathochromically shifted for 2-Ethyn and 3-Ethyn, with λabs(max) ranging from 537 to 547 mm which is parallel with an increasing refractive index [54]. Styryl-substituted BODIPYs (2-Styryl, 3-Styryl and 8-Styryl) displayed different absorption properties. The λabs(max) values range from 549 to 561 nm, with a typical redshift from acetonitrile to chlorobenzene. The extended conjugation ensured by the styryl functional group reasons an extra bathochromic shift of around 20 nm for 3-Ethyn, and ca. 30 nm for 3-Ph. Conversely, 2-Styryl and 8-Styryl show clear dual-band absorption and emission behavior. The photophysical reaction of two BODIPY-based D−A and A− D−A molecules, where D is the donor and A is the acceptor was reported by Hendel et al. [55]. A BODIPY fragment was given as the A component and was attached through the meso position using a 3-hexylthiophene linker to an N-(2-ethylhexyl) dithieno[3,2-b:2′,3′-d] pyrrole (DTP), which was given as the D component. An A−D−A molecule was compared to its corresponding D − A dyad counterpart. This showed a potential advantage to the A−D−A molecule over the D−A dyad in creating longer-lived excited states. A−D−A possess slightly longer excited-state lifetimes, 42 ps nonradiative decay, and 4.64 ns radiative decay compared to those of D−A, 24 ps nonradiative decay, and 3.95 ns radiative decay. These results show a full picture of the electronic and photophysical properties of D−A and A−D−A that provide contextualization for structure-function relationships between molecules

and organic photovoltaic (OPV) devices. A type of fluorescent chemosensor based on tethered hexa-borondipyrromethene cyclotriphosphazene platform (HBTC) (**Figure 3**) linked via triazole groups reported by our working group [56]. Its sensing behavior toward metal ions was investigated. Addition of a Fe2+ ion to a tetrahydrofuran (THF) solution of HBTC gave a visual color change as well as a significantly quenched fluorescence emission, while other tested 19 metal ions (Fe2+, Al3+, Ba2+, Ca2+, Co2+, Ag+ , Cd2+, Cr3+, Cs+ , Cu2+, Fe3+, Hg2+, K+ , Li+ , Mg2+, Mn2+, Na+ , Ni2+, Pb2+, and Zn2+) induced no color or spectral changes. This compound was found to be highly selective and sensitive for Fe2+ with a low limit of detection (2.03 μM). HBTC is a potential selective and sensitive fluorescence chemosensor for imaging Fe2+ in the living cells.

A synthetic approach for palladium-catalyzed direct C(sp3 )-H arylation of the methyl group at the 8-position of BODIPY reported by Chong et al. [57]. This approach permitted attaching electron-donating/withdrawing, halogensubstituted aryls and a heteroaryl with a yield running from 55 to 99%. Novel pH sensors, which in the lack of acid demonstrated the photoinduced electron transfer (PET), were synthesized by linking dimethylaniline to the methyl at the C8-position of BODIPY. The reference compounds with dimethylaniline directly linked to the C8-position were also synthesized and PET showed a charge-transfer emission. Addition of trifluoroacetic acid (TFA) onto toluene and ethanol, the fluorescence intensity was at least an order of magnitude more effective with the synthesized sensors compared to the traditional reference sensors. The developed sensibility of these BODIPY-based pH sensors was connected to less effective proton-coupled electron transfer of the protonated types. This approach could pave a new way for the convenient syntheses of functional BODIPY molecules. Two

**37**

**Figure 4.**

*Photophysics of BODIPY Dyes: Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.92609*

by Kang et al. [59] and the <sup>1</sup>

calculated as 0.075 and 0.44 and the <sup>1</sup>

BODIPY had no positive effect on <sup>1</sup>

position resulted in seemingly increased <sup>1</sup>

were investigated. The <sup>1</sup>

cyclotriphosphazene compounds bearing mono- and distyryl BODIPY substituents reported in 2017 (**Figure 4**) [58]. The photophysical properties of these cyclotriphosphazene compounds were examined in THF solutions. All these heavy atom

owing to the internal charge transfer (ICT) that occurred between BODIPY core and dimethylaminobenzyl groups. These properties were also investigated by the

attitudes of these compounds were dramatically increased after the addition of acid because the ICT effect was blocked owing to the protonation of the nitrogen atoms on the dimethylamine groups. These compounds can be used as potential photosen-

Six different molecules including 3,5-distyryl-BODIPY backbones were reported

BODIPY compounds and two boronic acid ester substituted BODIPY compounds

substituted BODIPYs were not more than 0.07. It was indicating that halogenation on the benzene rings of 3,5 distyryl-BODIPYs or boronate esterification of

the research of BODIPYs and would provide a useful envision for the preparation of powerful BODIPYs drugs for the PDT process. An excited-state intramolecular proton transfer (ESIPT) meso linked BODIPY dyad (Bn-OH-BDY) was reported by Mallah et al. [60]. The fluorescence lifetime of Bn-OH-BDY dyad was recorded 5.71 ns. A large shift of 255 nm has been monitored between excitation and emitted light. Excitation (λexc = 290 nm) of the Bn-OH-BDY dyad leads to emission (λemi = 545 nm) directed by the BODIPY subunits pointing to excitation energy transfer (EET) from the ESIPT to BODIPY core. Two cyclotriphosphazene (Cpz) compounds bearing mono- and distyryl(pyrene) BODIPY dyes (**Figure 5**) reported in 2019 [61]. These compounds indicated intense fluorescence emission even at very low concentrations. In accordance with absorption and emission spectra of Cpz compounds, di-styryl pyrene BODIPY containing Cpz indicated redshift more than

*Chemical structures of (a) mono-styryl and (b) distyryl-BODIPY substituted cyclophosphazenes.*

O2 photosensitizing experiments of dibromo substituted

O2 quantum yields of boronic acid ester

O2 production, while halogenation on the 2/6

O2 efficiencies. The results would enrich

O2 quantum yields of dibromo substituted BODIPYs were

O2 generation

O2 generation

free compounds indicated very limited fluorescence emission and 1

protonation of the studied compounds. Fluorescence emission and <sup>1</sup>

sitizers that can be used as efficient singlet oxygen generators.

**Figure 3.** *Chemical structure of HBTC.*

## *Photophysics of BODIPY Dyes: Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.92609*

*Photophysics, Photochemical and Substitution Reactions - Recent Advances*

, Cd2+, Cr3+, Cs+

A synthetic approach for palladium-catalyzed direct C(sp3

Al3+, Ba2+, Ca2+, Co2+, Ag+

imaging Fe2+ in the living cells.

Na+

and organic photovoltaic (OPV) devices. A type of fluorescent chemosensor based on tethered hexa-borondipyrromethene cyclotriphosphazene platform (HBTC) (**Figure 3**) linked via triazole groups reported by our working group [56]. Its sensing behavior toward metal ions was investigated. Addition of a Fe2+ ion to a tetrahydrofuran (THF) solution of HBTC gave a visual color change as well as a significantly quenched fluorescence emission, while other tested 19 metal ions (Fe2+,

, Ni2+, Pb2+, and Zn2+) induced no color or spectral changes. This compound was found to be highly selective and sensitive for Fe2+ with a low limit of detection (2.03 μM). HBTC is a potential selective and sensitive fluorescence chemosensor for

the methyl group at the 8-position of BODIPY reported by Chong et al. [57]. This approach permitted attaching electron-donating/withdrawing, halogensubstituted aryls and a heteroaryl with a yield running from 55 to 99%. Novel pH sensors, which in the lack of acid demonstrated the photoinduced electron transfer (PET), were synthesized by linking dimethylaniline to the methyl at the C8-position of BODIPY. The reference compounds with dimethylaniline directly linked to the C8-position were also synthesized and PET showed a charge-transfer emission. Addition of trifluoroacetic acid (TFA) onto toluene and ethanol, the fluorescence intensity was at least an order of magnitude more effective with the synthesized sensors compared to the traditional reference sensors. The developed sensibility of these BODIPY-based pH sensors was connected to less effective proton-coupled electron transfer of the protonated types. This approach could pave a new way for the convenient syntheses of functional BODIPY molecules. Two

, Cu2+, Fe3+, Hg2+, K+

, Li+

, Mg2+, Mn2+,

)-H arylation of

**36**

**Figure 3.**

*Chemical structure of HBTC.*

cyclotriphosphazene compounds bearing mono- and distyryl BODIPY substituents reported in 2017 (**Figure 4**) [58]. The photophysical properties of these cyclotriphosphazene compounds were examined in THF solutions. All these heavy atom free compounds indicated very limited fluorescence emission and 1 O2 generation owing to the internal charge transfer (ICT) that occurred between BODIPY core and dimethylaminobenzyl groups. These properties were also investigated by the protonation of the studied compounds. Fluorescence emission and <sup>1</sup> O2 generation attitudes of these compounds were dramatically increased after the addition of acid because the ICT effect was blocked owing to the protonation of the nitrogen atoms on the dimethylamine groups. These compounds can be used as potential photosensitizers that can be used as efficient singlet oxygen generators.

Six different molecules including 3,5-distyryl-BODIPY backbones were reported by Kang et al. [59] and the <sup>1</sup> O2 photosensitizing experiments of dibromo substituted BODIPY compounds and two boronic acid ester substituted BODIPY compounds were investigated. The <sup>1</sup> O2 quantum yields of dibromo substituted BODIPYs were calculated as 0.075 and 0.44 and the <sup>1</sup> O2 quantum yields of boronic acid ester substituted BODIPYs were not more than 0.07. It was indicating that halogenation on the benzene rings of 3,5 distyryl-BODIPYs or boronate esterification of BODIPY had no positive effect on <sup>1</sup> O2 production, while halogenation on the 2/6 position resulted in seemingly increased <sup>1</sup> O2 efficiencies. The results would enrich the research of BODIPYs and would provide a useful envision for the preparation of powerful BODIPYs drugs for the PDT process. An excited-state intramolecular proton transfer (ESIPT) meso linked BODIPY dyad (Bn-OH-BDY) was reported by Mallah et al. [60]. The fluorescence lifetime of Bn-OH-BDY dyad was recorded 5.71 ns. A large shift of 255 nm has been monitored between excitation and emitted light. Excitation (λexc = 290 nm) of the Bn-OH-BDY dyad leads to emission (λemi = 545 nm) directed by the BODIPY subunits pointing to excitation energy transfer (EET) from the ESIPT to BODIPY core. Two cyclotriphosphazene (Cpz) compounds bearing mono- and distyryl(pyrene) BODIPY dyes (**Figure 5**) reported in 2019 [61]. These compounds indicated intense fluorescence emission even at very low concentrations. In accordance with absorption and emission spectra of Cpz compounds, di-styryl pyrene BODIPY containing Cpz indicated redshift more than

**Figure 4.** *Chemical structures of (a) mono-styryl and (b) distyryl-BODIPY substituted cyclophosphazenes.*

### *Photophysics, Photochemical and Substitution Reactions - Recent Advances*

mono-styryl pyrene BODIPY containing Cpz because of mono- and di-styryl bonding positions of pyrene molecules. These Cpz compounds revealed different color and spectral changes throughout reduction and oxidation reactions as compared to BODIPY derivatives and newly synthesized BODIPY molecules, which might have potential applications for electrochromic materials. Extreme properties of these compounds also illustrated probable utilization of these as functional materials for use in electrochemical and photovoltaic applications.

**Figure 5.**

*Chemical structures of (a) mono-styryl and (b) distyryl-pyrene BODIPY substituted cyclophosphazenes.*

**Figure 6.** *Chemical structures of (a) BODIPY and (b) distyryl-BODIPY substituted cyclophosphazenes.*

**39**

7.5 x 104

to 8.5 x 104

M<sup>−</sup><sup>1</sup>

cm<sup>−</sup><sup>1</sup>

*Photophysics of BODIPY Dyes: Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.92609*

IL/1

(intraligand)/1

impacted both the 1

substitution leads to lower 1

mental and biological applications.

**3. Photophysical properties of aza-BODIPY dyes**

Synthesis, photophysics, and photobiological activities of a series of neutral heteroleptic cyclometalated iridium (III) complexes including BODIPY substituted N-heterocyclic carbene (NHC) ligands reported by Liu et al. [62]. The effect of the substitution position of BODIPY on the NHC ligands, either on C4 of the phenyl ring or C5 of the benzimidazole unit, and its linker type on the photophysical properties was investigated. All complexes showed BODIPY-localized intense 1

and 1,3IL/1,3CT (charge transfer) emission at 582–610 nm. However, the lowest

was demonstrated that the position of the BODIPY pendant on the NHC ligand

effects. The effect of BODIPY substitution position at the NHC ligand is more cleared on the photobiological activities than on the photophysical properties. Two water-soluble cyclotriphosphazene derivatives by "click" reactions between cyclotriphosphazene derivative with hydrophilic glycol side groups and BODIPY's (**Figure 6**) were reported in 2019 [63]. The photophysical properties of these compounds were examined inside the water and many organic solvents such as acetone, THF, dichloromethane, dimethyl sulfoxide, etc., and the results were compared with each other. These compounds have good solubility in many different organic solvents and especially acetone: water systems that are suitable to use in environ-

Replacement of the meso-carbon with nitrogen creates a similar class of compounds mentioned as aza-BODIPYs (**Figure 7**). In contrast to the well-known BODIPYs, aza-BODIPYs have not been extensively studied. Aza-BODIPY skeletons are generally prepared from nitromethane adducts to the corresponding chalcone, but butanol, rather than methanol or solvent-free conditions, are the preferred medium. The syntheses are completed by adding BF3.OEt2 at room temperature [1]. Like BODIPY derivatives, aza-BODIPY derivatives also have high molar extinction coefficients and moderate fluorescence quantum yields (ca. 0.20–0.40). The addition of the lone pair on the nitrogen properly affects the HOMO-LUMO energy gap owing to stabilization [1]. This improved stability causes a red-shift in the absorption and emission profiles into the 650–850 nm range [64]. Aza-BODIPY core offers several advantages including ease of synthesis and an inherent bathochromic shift in the absorption maxima in comparison to the carbon analog. Aza-BODIPY dyes have a marked red shift of the absorption and emission bands relative to traditional BODIPY dyes can be accomplished without modifying the key properties of BODIPY dyes, such as their high molar absorption coefficients, narrow and structured absorption and emission bands, small Stokes shifts, high fluorescence quantum yields, and photostability. The UV absorption maxima of the aza-BODIPY dyes are comparatively insensible to solvent polarity; only small blue shifts tend to be observed (6–9 nm) when switching solvents from toluene to ethanol. Their absorptions are strong, with a full width at a half-maximum height changing from 51 to 67 nm in aqueous solution and 47–57 nm in chloroform indicating that the dyes do not aggregate under those conditions. The extinction coefficients range from

study indicated that the substitution position of BODIPY on the NHC ligand plays an important role in the cytotoxicity and photocytotoxicity of this new type of complexes. BODIPY-substitution at C5 of benzimidazole compared to C4-phenyl

triplet excited state of these complexes is the BODIPY-localized <sup>3</sup>

MLCT (metal-to-ligand charge transfer) absorption at 530–543 nm

MLCT absorption and 1,3IL/1,3CT emission bands. This

O2 quantum efficiencies but more efficient phototoxic

. Fluorescence emission spectra of the aza-BODIPY

IL

π,π\* states. It

*Photophysics of BODIPY Dyes: Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.92609*

*Photophysics, Photochemical and Substitution Reactions - Recent Advances*

use in electrochemical and photovoltaic applications.

mono-styryl pyrene BODIPY containing Cpz because of mono- and di-styryl bonding positions of pyrene molecules. These Cpz compounds revealed different color and spectral changes throughout reduction and oxidation reactions as compared to BODIPY derivatives and newly synthesized BODIPY molecules, which might have potential applications for electrochromic materials. Extreme properties of these compounds also illustrated probable utilization of these as functional materials for

*Chemical structures of (a) mono-styryl and (b) distyryl-pyrene BODIPY substituted cyclophosphazenes.*

**38**

**Figure 6.**

**Figure 5.**

*Chemical structures of (a) BODIPY and (b) distyryl-BODIPY substituted cyclophosphazenes.*

Synthesis, photophysics, and photobiological activities of a series of neutral heteroleptic cyclometalated iridium (III) complexes including BODIPY substituted N-heterocyclic carbene (NHC) ligands reported by Liu et al. [62]. The effect of the substitution position of BODIPY on the NHC ligands, either on C4 of the phenyl ring or C5 of the benzimidazole unit, and its linker type on the photophysical properties was investigated. All complexes showed BODIPY-localized intense 1 IL (intraligand)/1 MLCT (metal-to-ligand charge transfer) absorption at 530–543 nm and 1,3IL/1,3CT (charge transfer) emission at 582–610 nm. However, the lowest triplet excited state of these complexes is the BODIPY-localized <sup>3</sup> π,π\* states. It was demonstrated that the position of the BODIPY pendant on the NHC ligand impacted both the 1 IL/1 MLCT absorption and 1,3IL/1,3CT emission bands. This study indicated that the substitution position of BODIPY on the NHC ligand plays an important role in the cytotoxicity and photocytotoxicity of this new type of complexes. BODIPY-substitution at C5 of benzimidazole compared to C4-phenyl substitution leads to lower 1 O2 quantum efficiencies but more efficient phototoxic effects. The effect of BODIPY substitution position at the NHC ligand is more cleared on the photobiological activities than on the photophysical properties. Two water-soluble cyclotriphosphazene derivatives by "click" reactions between cyclotriphosphazene derivative with hydrophilic glycol side groups and BODIPY's (**Figure 6**) were reported in 2019 [63]. The photophysical properties of these compounds were examined inside the water and many organic solvents such as acetone, THF, dichloromethane, dimethyl sulfoxide, etc., and the results were compared with each other. These compounds have good solubility in many different organic solvents and especially acetone: water systems that are suitable to use in environmental and biological applications.


**4. Amino acid radiotracers**

Amino acids are the building blocks of proteins and critical to nearly every biological process in the human body. They serve as components in metabolic cycles which are upregulated in cancer cells with increased proliferative activity. Because the brain uses glucose almost

exclusively for fuel (except during prolonged starvation), PET imaging of brain tumours with amino acid and amino acid analogue radiotracers has a significant advantage of high tu‐ mour-to-background contrast (**Figure 3**).

**Figure 3.** F-18 FDG PET/CT (*top row*) and F-18 FDOPA PET/CT (*bottom row*) of a left frontotemporal low-grade nonenhancing cerebral glioma showing the high tumour-to-background contrast of amino acid imaging compared with metabolic imaging.

#### **4.1. Methionine**

Methionine (MET) is a sulphur-containing naturally occurring amino acid (**Figure 4**) whose transport into malignant glioma cells and the supporting vasculature of these tumours is strongly upregulated [20–22].

**Figure 4.** Chemical structure of methionine.

C-11 MET is one of the most widely used amino acid radiotracers for PET imaging in neuro‐ oncology, mainly due to its relative ease of production that can be performed rapidly with high yield and without the need for complicated purification steps.

The overall sensitivity of MET PET for malignant gliomas ranges from 76 to 95%, with higher rates of detection for higher grade tumours [23]. Increased uptake of MET is also seen in lowgrade gliomas—with reported sensitivities of 65–85% [23, 24]—in which there is typically little or absent contrast enhancement on MRI and low uptake on FDG PET [24, 25].

MET is also generally regarded as the reference in prognostication of disease, image-guided biopsy and radiotherapy planning, and the detection of tumour recurrence [26–34], making it the most important radiotracer in the amino acid category.

The main limitation of C-11 MET is its short half-life (20 min), confining its use to centres with a cyclotron on-site or very nearby. It has also been shown to accumulate in brain abscesses and inflammation (cerebritis) [35], important false positives to exclude in the diagnosis of brain tumour.

F-18 has a much longer half-life (110 min) than C-11 and opens up the possibility of radiotrac‐ er transport to another centre for diagnostic imaging. F-18 labelled amino acids include F-18 labelled fluoroethyltyrosine (FET) and dihydroxyfluorophenylalanine (FDOPA).

#### **4.2. Fluoroethyltyrosine**

exclusively for fuel (except during prolonged starvation), PET imaging of brain tumours with amino acid and amino acid analogue radiotracers has a significant advantage of high tu‐

**Figure 3.** F-18 FDG PET/CT (*top row*) and F-18 FDOPA PET/CT (*bottom row*) of a left frontotemporal low-grade nonenhancing cerebral glioma showing the high tumour-to-background contrast of amino acid imaging compared with

Methionine (MET) is a sulphur-containing naturally occurring amino acid (**Figure 4**) whose transport into malignant glioma cells and the supporting vasculature of these tumours is

C-11 MET is one of the most widely used amino acid radiotracers for PET imaging in neuro‐ oncology, mainly due to its relative ease of production that can be performed rapidly with

The overall sensitivity of MET PET for malignant gliomas ranges from 76 to 95%, with higher rates of detection for higher grade tumours [23]. Increased uptake of MET is also seen in low-

high yield and without the need for complicated purification steps.

mour-to-background contrast (**Figure 3**).

188 Neurooncology - Newer Developments

metabolic imaging.

**4.1. Methionine**

strongly upregulated [20–22].

**Figure 4.** Chemical structure of methionine.

FET is an artificial amino acid (**Figure 5**) taken up by upregulated tumour cells but not incorporated into proteins (unlike naturally occurring amino acids such as methionine). As such, its use in the characterisation of brain lesions and the grading of gliomas requires dynamic analysis of activity over time [36]. Its overall accuracy in the diagnosis of gliomas is comparable to MET [37, 38]. It is an excellent tool for differentiating tumour from non-tumour causes in the initial evaluation of newly diagnosed brain lesions [39] (**Figure 6**). FET PET can also distinguish active tumour from radiation necrosis following treatment [40, 41].

**Figure 5.** Chemical structure of F-18 fluoroethyltyrosine.

**Figure 6.** FET PET/CT (*left-sided panels*) and pre/post intravenous gadolinium MRI (*right-sided panels*) in a patient with two small cerebral melanoma metastases (*red and blue arrows*).

#### **4.3. Fluorodihydroxyphenylalanine**

FDOPA was originally developed for imaging the DOPA-decarboxylase pathway in Parkinson's disease and other neurodegenerative diseases. It is a fluorinated form of L-DOPA (**Figure 7**) which is used to increased dopamine concentrations in the treatment of Parkinson's disease. FDOPA has since been shown to be a marker of amino acid transport in brain tumours and metastases.

**Figure 7.** Chemical structure of F-18 fluorodihydroxyphenylalanine.

FDOPA uptake has been shown to correlate with tumour proliferation and grade [42], and more accurate than FDG for evaluating low-grade tumours and distinguishing tumour recurrence from radiation necrosis [43].

It also accumulates in neuroendocrine tumours (NETs) such as phaeochromocytomas and paragangliomas.

## **5. Fluorothymidine**

Thymidine (T) is the pyrimidine deoxynucleoside in DNA that pairs with deoxyadenosine (A). F-18 fluorothymidine (FLT) is a thymidine analogue (**Figure 8**) and a substrate for thymi‐ dine kinase 1 (responsible for synchronising cells in G1/early S phase), but unlike thymidine, FLT is a poor substrate for mitochondrial thymidine kinase 2 and its uptake is therefore specific to the cell cycle and a marker of cellular proliferation.

**Figure 8.** Chemical structure of F-18 fluorothymidine.

FLT uptake in normal brain cells is limited by the blood–brain barrier, thus FLT PET pro‐ vides higher tumour-to-background contrast than FDG PET. FLT is more sensitive than FDG PET for the detection of recurrent high-grade glioma and also correlates better with tumour progression and survival [44].

However, its use as a quantitative marker of the activity of DNA synthesis in gliomas remains a subject of debate, particularly whether FLT can discriminate moderately proliferative tumours driven by thymidine salvage pathway utilisation from highly proliferative tumours primarily driven by de novo synthesis of thymidine. Quantitative FLT PET with kinetic modelling may also beusefulfordistinguishing glioma recurrence from radiation necrosis [45].


*3.2. Path Length*

In a complex network, the number of edges included in a route between any two points represents the path length of these two points. The average of the shortest path lengths between any two points reflects the size of the network, called the feature path length. If there is no path between the two points, the path length between the two points is infinite.

The length of the feature path is computed by Equation (3). In Equation (3), *l* is the length of the network feature; *N* refers to the number of network nodes; and *dij* is the path length between two points. The maximum path length between all pairs of nodes represents the diameter of the network. The path length and network diameter measure the transmission performance and efficiency of the network.

$$d = \frac{1}{N(N-1)} \sum\_{i \neq j} d\_{ij} \tag{3}$$


**2.2.3 Production of recombinant proteins**

The mammary gland and blood of transgenic domestic animals, including sheep, goats, cows, pigs and rabbits, have been successfully used as bioreactor to produce numerous recombinant proteins, such as antibodies (Grosse-Hovest et al., 2004), growth factors (Schnieke et al., 1997) and pharmaceuticals (reviewed by Melo et al., 2007). Using various mammary gland-specific or blood-specific promoters to drive the expression of specific protein-coding genes, transgenic domestic animals can continuously produce the recombinant proteins in large quantities in their milk or blood. Recombinant proteins, including human von Willebrand factor (Lee et al., 2009), human erythropoietin (Park et al., 2006), human insulin-like growth factor-I (Monaco et al., 2005), human factor VIII (Paleyanda et al., 1997) and bovine alpha-lactalbumin (Bleck et al., 1998) have been produced in the milk of transgenic pigs. Transgenic goats, capable of synthesizing human butyrylcholinesterase (Huang et al., 2007) and human longer acting tissue plasminogen activator (Ebert et al., 1991) in their milk have also been created. Human salmon calcitonin in milk of transgenic rabbits (McKee et al., 1998); human factor IX (Schnieke et al., 1997) and alpha-1-antitrypsin (Wright et al., 1991) in milk of transgenic sheep; and human lactoferrin (van Berkel et al., 2002; Yang et al., 2008), human growth hormone (Salamone et al., 2006) and human α-lactalbumin (Wang et al., 2008) in milk of transgenic cows are all additional examples of using transgenic domestic animals and the mammary gland as a bioreactor for production of recombinant proteins. Table 2 summarizes some recombinant proteins expressed in milk or blood of cloned transgenic domestic animals. One of the major advantages of using domestic animals for this purpose is that the produced protein is thought to undergo more accurate posttranslational processing to ensure their biological activity. While this application of transgenic technology to produce recombinant protein products is rapidly developing, research efforts exploring the efficacy of these products are still needed.

### **2.2.4 Biomedical models of human diseases**

Another important application of genetically modified domestic animals is to create better and novel biomedical models of human diseases. Pig models of different human diseases, including retinitis pigmentosa, cardiovascular disease, diabetes, Huntington's disease, cystic fibrosis and Alzheimer's disease have been well discussed by Prather et al. (2008). Many of these biomedical models created by SCNT are listed in Table 2.


**Abstract**

This chapter deals with the ozonization process of the emu oil, the objective of this study was to quantitatively determine the peroxide value (PV) to measure the degree of ozonation, the peroxide value measures the number of peroxide groups in the ozonized oil. The ozone oxidizes the unsaturated chemical functions present in the oil giving a high cure rate for epidermal wounds. The healing process is not completely understood and there are different approaches, therefore, it was determined qualitatively if it has healing and inflammation properties, but the results of our studies have shown that the length and width of the wounds were healing quickly thanks to the peroxidation rate of the oils. In addition, both tests were correlated to obtain a greater appreciation of their functions, the mechanism involves a decrease in the inflammation of the wounds and stimulates the process of scar formation.

**Keywords:** ozonization, emu oil, peroxide value, healing, inflammation

#### **1. Introduction**

The skin is a fibroelastic membrane, considered the "outer covering of the body"; It is an organ that performs a wide range of functions including thermoregulation, protection against external aggressions, the absorption of ultraviolet radiation and the production of vitamin D. Additionally, it has an important function of immune recognition, it is an effective protection barrier against pathogenic microorganisms, being the largest organ of the integumentary system and a powerful receptor of sensory stimuli [1]. The frequent exposure to environmental aggressions makes this organ susceptible to suffer injuries that compromise its integrity altering the normal development of its functions [2]. One of the factors that compromise the continuity of this tissue are chronic wounds such as pressure ulcers (PPU), which have been a public health problem that mainly affects those persons who must remain in bed for long periods of time as consequence of chronic diseases [3] or acute dermatitis [4], which affects all human races and more frequently women. Pressure ulcers (PPU) can be presented at any age; however, it predominates in childhood, being more frequent before 5 years of age and persists in adulthood in up to 60–70% of patients [5]. Emu oil is known for the use that the natives of Australia gave it as a remedy to alleviate different ailments for 200 years [6]. In the First World War, ozonated oils were used for therapeutic purposes, as well as the healing of wounds and fissures [7]. Ozonated oils showed their role as modulators of wound healing [8]. The reaction of ozone with the unsaturations present in the fatty acids and other free acids of natural oils generate products such as ozonides and peroxides with germicidal activity and tissue regeneration [9]. The application of ozonated vegetable oil for wound healing quantification in mice, has shown that this oil must be ozonated until a "mean degree" of peroxidation is reached (PV = 1631 ± 64 mEq/kg) [10]. On the other hand, the periodic application of completely ozonated olive oil (iodine value = 0) caused in the skin hypersensitivity to contact and loss of hair in the application zone [11]. Furthermore, it is commonly observed that these ozonated oils present a delayed action [12]. A few crude oils from vegetable origin have the property of healing, once ozonized they acquire this property [13]. The search in the main platforms of scientific information on the ozonization of oils of animal origin throws information that lacks depth to know the effects of the products or by-products in the human body, which does not allow to find a relationship between different ozonized oils, in order to develop a synthetic ozonized oil. Therefore, a need is created to develop research that help to clarify the mechanisms of action of ozonized animal oil, for its greater compression and create the possibility of application. The objective of this work is to quantitatively determine the peroxide value (PV) to measure the degree of ozonation, determine qualitatively if it has healing and inflammation properties, in addition, correlate both tests to obtain a greater appreciation of its functions.


**1. Introduction**

Benign prostatic hyperplasia (BPH) is a term exclusively used for describing benign histological patterns in the European Association of Urology (EAU) and the American Urological Association (AUA) guidelines [1,2]. BPH could lead to benign prostatic enlargement (BPE) or benign prostatic obstruction (BPO) resulting in male lower urinary tract symptoms (LUTS). LUTS are grouped into three categories: storage (increased daytime frequency, nocturia, urgency, and urinary incontinence), voiding (hesitancy, slow stream, intermittent stream, straining, and terminal dribble), and post-micturition (post-micturition dribble and feeling of incomplete emptying) symptoms [3]. In addition to BPH, other causes of male LUTS include structural or functional abnormalities of the bladder and its surrounding tissues, and some non-urological conditions [4]. Lower urinary tract dysfunction (LUTD) is defined as signs observed by the physician, including simple means, to verify and quantify symptoms [3]. From a clinical perspective, BPH usually refers to LUTD caused by BPE or BPO.

We conducted a review of published literature in Pubmed, using Botulinum toxin, BPH, bladder outlet obstruction (BOO), inflammation, LUTS, and prostatitis as the key words. We reviewed the mechanisms of BPH pathogenesis and anti-inflammatory effects of BoNT-A. We tried to determine the role of botulinum toxin A (BoNT-A) in treatment of LUTS/BPH.


**NEW PERSPECTIVES IN FLUID DYNAMICS**

Edited by **Chaoqun Liu**

### **New Perspectives in Fluid Dynamics**

http://dx.doi.org/10.5772/59432 Edited by Chaoqun Liu

### **Contributors**

Jorge Flores-Velazquez, José Simão Antunes Do Carmo, Daniel Marinho, Pedro Forte, Tiago Barbosa, Daniel Almeida Almeida Marinho, Medzid Muhasilovic, Chaoqun Liu

### **© The Editor(s) and the Author(s) 2015**

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, 2015 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

Legal deposit, Croatia: National and University Library in Zagreb

Additional hard and PDF copies can be obtained from<EMAIL_ADDRESS>
New Perspectives in Fluid Dynamics Edited by Chaoqun Liu p. cm. ISBN 978-953-51-2228-9 eBook (PDF) ISBN 978-953-51-6644-3


**2.2 Algorithmic focused system level design**

The focus on this chapter will center around Matlab and especially on Simulink. The two major FPGA providers Xilinx (Xilinx, 2011b) and Altera (Altera, 2011a), make available libraries that allow efficient block level modeling of wireless communications algorithms and its automatic conversion to RTL. The code can be either downloaded to the FPGA for standalone algorithm implementation or used with hardware in the loop (HIL) functionality that allows a particular block of the system to be emulated using an FPGA device, this is with the purpose of performing hardware acceleration.

Nowadays the common first step taken by researchers is to test their ideas in Matlab's m-code. Matlab as a system level platform allows a very fast and efficient algorithm implementation of complete systems. Matlab does not include the conception of time; it is more comparable to high level programming languages; has a vast set of libraries or toolboxes in many disciplines; and it is not limited to math or engineering. Matlab has become an indispensable tool in modern electronic design and engineering in general.

If the designer would like to model the system including time as another design dimension, Simulink could be used to design complete dynamic systems that are time aware and also include a large number of libraries or toolboxes for a large number of disciplines.