Optimisation of a Novel Bio-Substrate as a Treatment for Atrophic Age-Related Macular Degeneration

Abstract

Atrophic age-related macular degeneration (AMD) is the most common form of AMD accounting for 90% of patients. During atrophic AMD the waste/exchange pathway between the blood supply (choroid) and the retinal pigment epithelium (RPE) is compromised. This results in atrophy and death of the RPE cells and subsequently the photoreceptors leading to central blindness. Although the mechanisms behind AMD are unknown, the growth of fatty deposits known as drusen, have been shown to play a role in the disease. There is currently no treatment or cure for atrophic AMD. Much research focuses on developing a synthetic substrate in order to transplant healthy cells to the native Bruch's membrane (BM), however, the diseased native BM and related structures still leave potential for transplanted cells to succumb to disease. In this proof-of-concept work we electrospun poly(ethylene terephthalate) (PET) to fabricate a nanofibrous cytocompatible synthetic BM. The apical surface of the membrane was cultured with ARPE-19 cells and the underside was decorated with poly(lactic acid-co-glycolic acid) (PLGA) or poly(glycolic acid) (PGA) degradable nanoparticles by electrospraying. The membrane exhibited hydrophilicity, high tensile strength and structurally resembled the native BM. ARPE-19 cells were able to form a monolayer on the surface of the membrane and no cell invasion into the membrane was seen. The presence of both PLGA and PGA nanoparticles increased ARPE-19 cell metabolism but had no effect on cell viability. There was a decrease in pH of ARPE-19 cell culture media 7 days following culturing with the PLGA nanoparticles but this change was eliminated by 2 weeks; PGA nanoparticles had no effect on cell culture media pH. The fluorescent dye FITC was encapsulated into nanoparticles and showed sustained release from PLGA nanoparticles for 2 weeks and PGA nanoparticles for 1 day. Future work will focus on encapsulating biologically active moieties to target drusen. This could allow this novel bioactive substrate to be a potential treatment for atrophic AMD that would function twofold: deliver the required monolayer of healthy RPE cells to the macula on a synthetic BM and remove diseased structures within the retina, restoring the waste/exchange pathway and preventing vision loss.

Biomaterials for corneal endothelial cell culture and tissue engineering

“…The idea being that the substrate will act two-fold, to deliver cells to the required area while delivering drugs/growth factors to the eye long-term to maintain transplanted cell health. 77 Preliminary studies using polyethylene terephthalate (PET), an FDA approved nondegradable polymer, electrospun from a solution dissolved in 1,1,1-3,3,3-hexafluoroisopropanol, are described here. Fibers were collected on a grounded, static collection plate modified with insulated sections (Figure 10(a) and (b)).…”

Challenges in Corneal Endothelial Cell Culture

“…Similarly, nanoparticles fabricated by electrospraying to encapsulate biologically active compounds decorated on electrospun membranes are also being investigated. The idea is that the substrate will act two-fold to deliver cells to the required area while delivering drugs/growth factors to the eye long-term to maintain transplanted cell health [119].…”

Biotechnology and Biomaterial-Based Therapeutic Strategies for Age-Related Macular Degeneration. Part II: Cell and Tissue Engineering Therapies

“…In their attempt to create artificial BrM, ( McCormick et al, 2020 ) generated a poly (ethylene terephthalate) (PET) scaffold with poly (lactic acid-co-glycolic acid) (PLGA) or poly (glycolic acid) (PGA) degradable nanoparticles that exhibited a continuous release of a fluorescent dye from PLGA particles for 2 weeks and from PGA particles for 1 day.…”

“…In addition, artificial membranes must be porous, thin (less than 10 μm, mimicking BrM) and mechanically competent to withstand manipulation during surgery. Since damaged BrM can also compromise the success of cell transplantation, several researchers dedicated their efforts to the development of artificial membranes allowing successful transplantation of RPE cells ( Srivastava et al, 2011 ; Hu et al, 2012 ; Warnke et al, 2013 ; McHugh et al, 2014 ; Stanzel et al, 2014 ; Ilmarinen et al, 2015 ; Peng et al, 2016 ; Calejo et al, 2017 ; Harris et al, 2019 ; McCormick et al, 2020 ).…”

“…Synthetic BrMs consisting of PET scaffolds and degradable nanoparticles were developed by McCormick et al (2020) . ARPE-19 cells cultured on these scaffolds were able to form monolayers and were maintained for up to 3 months without any cytotoxic effect.…”