Drug sustained release from degradable drug-loaded in-situ hydrogels in the posterior eye: A mechanistic model and analytical method.

Biodegradable in-situ hydrogels as drug release carriers injected into the eye can treat Neovascular age-related macular degeneration (NV-AMD). Obviously, the biodegradation behavior of hydrogels affects the drug diffusion process in the eye, which can influence the drug concentration distribution and development in the macula. Herein, the intraocular diffusion process of the drugs which are released from the biodegradable hydrogel was studied by using finite element method, with the effect of the biodegradation behavior of hydrogels on the drug release process was considered. The effects of the initial average mesh size, rate constant of biodegradation, and position of hydrogels on the drug release process were analyzed. The results showed that the biodegradation behavior of hydrogels decreases the drug release rate by gradually expanding the mesh size, prolonging the duration of drug treatment in the macula. The biodegradable hydrogels' position, initial mesh size, and biodegradation rate constant also affect drug delivery. Different locations of hydrogels denote different distances between the drug and macula, which affects the diffusion time and further influence the macular drug concentration. The initial mesh size alters the initial drug release rate, which affects the duration of hydrogels' drug release process and drug concentration and duration in the macula. The hydrogel degradation rate affects the development of its mesh size, which affects the drug diffusion in hydrogels, and further affects the drug concentration in the macular region.