Introduction
Age-related macular degeneration (AMD) is a leading cause of blindness. Wet AMD involves the degeneration of the retinal pigment epithelium (RPE), which causes abnormal neovascularization. This is currently treated by monthly intravitreal injections of anti-VEGF (vascular endothelial growth factor) agents. However, this practice is invasive and costly, and it is not a definitive solution since it does not target the RPE degeneration. Our innovative approach aims to design a single-injection hydrogel able to instruct cells for regeneration and to control neovascularization by bioconjugated anti-VEGF bevacizumab (BVZ).
Methods
Hyaluronic acid (HA) was chemically functionalized with aldehydic (HA-Ald) or hydrazide groups (HA-Hydra Fig. 1 A) and the degree of functionalization (DF) was assessed by Nuclear Magnetic Resonance (NMR). Shiff’s base hydrogels were formed using a 1:1 Ald:Hydra ratio. BVZ was conjugated to HA to form BVZ-conjugated hydrogels, which were characterized in terms of BVZ release, rheology, and microstructure. RPE cells were seeded on hydrogels and relevant markers were monitored, i.e., proliferating cell nuclear antigen (PCNA), retinoid isomerohydrolase (RPE-65), zonula occludens (ZO-1).
Results
NMR demonstrated polymer functionalization over a broad range (2-50%) as a function of time and reagent amount. BVZ-conjugated hydrogels showed a favorable 3-fold reduction in the burst release compared to controls (Fig. 1 B). Rheological data showed gelation within seconds and values of Storage Modulus (G’) similar to that of the human retina (12-20 kPa). Hydrogels displayed shear-thinning behaviour and prompt shape recovery post-injection (Figure 1 C). Hydrogels were injected through a 27G needle relevant for in vivo administration, and displayed a shape-stable, microporous structure (Fig. 1 D). Cells expressed relevant markers, indicating proliferation and differentiation (Fig.1 E).
Conclusions
Hydrogels exhibited adequate injectability, BVZ conjugation and supported RPE cells differentiation. This underscores the potential of these hydrogels as promising stimulus-sensitive materials against AMD.

Jesús Merayo-Lloves

Appearances