Electroretinographic Assessment of Retinal Function in Response to Intravitreal Injection of Thermo-Responsive Hydrogel Drug Delivery System

Abstract

Purpose: : The main objective is to assess the biocompatibility of thermo-responsive hydrogels using electroretinography (ERG) and to determine the suitability of hydrogels as an ocular drug delivery system.

Methods: : Hydrogels were synthesized using poly(N-isopropylacrylamide) and crosslinked with poly(ethylene glycol) diacrylate. Approximately 3 µL of sterile hydrogel was injected into the vitreous cavity of Long-Evans rat via a 30-gauge needle. Dark-adapted, full-field stimuli corneal ERGs were recorded before injection and each week for one month post injection. Single flashes of varying intensity (0.01-310.8 sc cd s m^-2) were used to determine the sensitivity of the ERG a-wave and b-wave. Single flash ERG responses were also filtered to isolate oscillatory potentials (OPs). The full time course of the derived rod response was obtained for two test flash strengths (0.11 and 11.8 sc cd s m^-2).

Results: : The sensitivity of the ERG a-wave and b-wave did not change significantly during the investigated period. OP amplitudes showed no significant change from the control values. The time courses of the derived rod responses did not show significant changes post-injection for either investigated test flash strength.

Conclusions: : The thermo-responsive hydrogel had no significant effect on the ERG a-wave or derived rod responses, suggesting that the outer retina was unaffected by the hydrogel. The sensitivity of the ERG b-wave and amplitude of the OPs also showed no significant changes, indicating that the inner retina was unaffected. The current data suggest that the thermo-responsive hydrogel has minimal or no impact on the retinal function and may be a promising new drug delivery platform.

Keywords: electroretinography: non-clinical • retina