Abstract
Purpose :
Anti-scarring agents are integral to glaucoma filtration surgery success. When injected as a solution or applied via sponge, rapid washout from the subconjunctival tissues limits long-term efficacy. Chitosan-based thermosensitive hydrogels (ThermoGels) are injectable liquids at room temperature that solidify into gels at temperatures approximating the subconjunctival space. In this study, we evaluate ThermoGels' thermosensitive properties, resistance to outflow, and biocompatibility with human Tenon's capsule fibroblasts (hTCFs) with the goal to develop an injectable sustained-release anti-fibrotic drug depot and in situ bleb scaffold.
Methods :
Hydrogels were prepared by dissolving chitosan in 2% acetic acid, dialyzing to remove the acid, and adding beta-glycerophosphate (β-gp). Various recipes were tested for gelation time vs temperature using the tube inversion test. Biocompatibility was tested by culturing hTCFs on chitosan gels at 37°C. Resistance to flow was tested by measuring afferent pressure when perfusing a gel-filled flow chamber with saline at the rate of aqueous humor production (2.6µL/min). Drug release was tested by measuring acetylsalicylic acid (ASA) or bovine serum albumin (BSA) in the effluent when perfusing drug-loaded gels with saline at 2.6 µL/min.
Results :
Gelation time of chitosan/β-gp solutions is inversely related to temperature and the concentration of β-gp used. 5% and 6% β-gp mixtures gelled the quickest at 37°C. MTT and LDH assays showed that chitosan hydrogels have no significant effect on cellular metabolic activity or necrosis compared to vehicle controls. Perfusion of the hydrogel demonstrated a reproducible, transient increase in afferent pressure of 5.0 ± 1.5 (SD) mmHg compared to no gel. However, this was transient and fully resolved by 9 hours. ASA and BSA were successfully loaded into chitosan gels and perfusion with saline elicited a delayed release of ASA/BSA.
Conclusions :
Chitosan/β-gp hydrogels solidify at eye-surface temperatures or higher, are biocompatible with ocular fibroblasts, do not substantially affect outflow capacity, and can be loaded with small molecules or proteins to act as a delayed-release drug depot. These properties support the potential subconjunctival injection of ThermoGel to provide sustained drug-release and structural support for the bleb.
This is a 2021 ARVO Annual Meeting abstract.