In vivo evaluation of hyaluronic acid based in situ hydrogel for prolonged release of Avastin by intravitreal injection

Abstract

Purpose: To evaluate the biocompatibility and 6 months in vivo release of Avastin from a hyaluronic acid based in situ hydrogel after intravitreal injection in rabbit eye.

Methods: The in situ hydrogel is formed by the chemical crosslinking of two polymer solutions, the vinylsulfonate hyaluronic acid (HA-VS) and thiolated dextran (Dex-SH) using catalyst-free click chemistry in aqueous phase (Yu and Chau 2012). The pH 7.4 buffered HA-VS, Dex-SH and Avastin were mixed on ice and injected to the vitreous of rabbits with 30 G needle. The biocompatibility was evaluated by binocular indirect ophthalmoscope (BIO), full-field ERG and histology at various time points from 1 week to 3 months. The concentrations of both total and active Avastin in rabbit vitreous were determined by ELISA assay.

Results: A transparent gel is seen in the vitreous after injection. The low viscosity of the mixture made injection easy even through 30G needle, and the fast gelation at body temperature (<10 seconds) ensure almost immediately gelation after injection. BIO images, ERG and histology showed that the gel does not induce hemorrhage, retinal detachment, inflammation or other gross pathological changes in rabbit eye after injection (figure 1). While the bolus intravitreal injection of native Avastin follows the first order elimination kinetics in rabbit eye, the in situ gel formation was able to extend the retention of Avastin in rabbit eye above therapeutic concentration for at least 6 months (figure 2). The concentration of Avastin 3 months and 6 months after injection was 100 and 109 times higher than bolus injection after the same period of time.

Conclusions: The new in situ hydrogel formulation of Avastin was transparent, biocompatible and able to prolong the retention of drug in rabbit eye in vivo for at least 6 months.