**Author details**

Paul M. Meaney\* and Keith D. Paulsen Dartmouth College, Hanover, USA

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© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


*2.6. Protein Secretion Assays*

Properdin levels in cell culture supernatants were determined using a sandwich ELISA, as previously described [37]. C3 quantification was performed using a newly developed C3 ELISA (cat# HK366-01; Hycult Biotech, Uden, Netherlands) according to the manufacturer's protocol. CFH was

quantified in an in-house ELISA with mouse anti-CFH monoclonal antibody (BioRad, Feldkirchen, Germany) as a capture antibody and goat anti-CFH polyclonal antibody (Merck, Darmstadt, Germany) as a detection antibody (Supplementary Materials, Table S1). A comparison of properdin, C3, and CFH levels in supernatants of lower and higher ARPE-19 passages was performed using a MILLIPLEX MAP Human Complement Panel (Merck, Darmstadt, Germany). Interleukin (IL)-1β und IL-6 concentrations were determined according to the protocol of a custom ProcartaPlex® multiplex immunoassay kit (ThermoFisher, Waltham, MA, USA). IL-8 was analyzed using xMAP technology, anti-IL-8 beads (cat# 171-BK31MR2; BioRad, Feldkirchen, Germany), and anti-IL-8 biotin (cat# 171-BK31MR2; BioRad, Feldkirchen, Germany) according to the manufacturer's protocol. The readout of the multiplex assays (IL-1β, IL-6, and IL-8) was performed using a Magpix instrument (Luminex, Austin, TX, USA). Vascular endothelial growth factor (VEGF)-α concentrations were determined using a human VEGF Quantikine ELISA Kit (R&D system, Minneapolis, MN, USA).


**7. Conclusion**

356 Viscoelasticity – From Theory to Biological Applications

1 0

2

A, B, k, l: parameters depending on the initial density

**Figure 24.** One of realized projects in France

Given the approximation of 4

becomes:

t: time, t0: initial time, dp: density of plastic d0: initial density

0

1 1 K ln

*p k l*

33 4

*t ff dd d d t*

0 0 0

 3 4 2

,

*f K*

*d d t*

2 33 3

1 1 . ; 2

*f K f f*

*t d d*

*f* , we can neglect

*f*

1 1 . ln

3 3 12 1 0

*p k l*

*t f dd d d t*

0 0 0

1 1 ln

*p k l*

1 and

0 0 0

3 by comparison to (1) and 4

*f*

The development of mono axial and biaxial testing, the design and implementation of an appropriate apparatus helped us to perform many tests. Therefore, the characteristic functions of the material were determined satisfactorily. This allowed us to identify the essential parameters to the theoretical models developed.

In a particular field of stress up to 200 kPa, the simplified model gives good satisfaction. The results are acceptable and the difference between theoretical and experimental ones does not overstep the bounds of uncertainty both in physical measurement and caracteristics variability due to the material anisotropy.

However, in several cases of application, the model in its many forms helps us to conceive and design structures by using this technique. Indeed, many projects were conceived and realized in France (fig.24).