Shear sensitive injectable hydrogels of cross-linked tragacanthic acid for ocular drug delivery: Rheological and biological evaluation

Drug delivery to posterior segment of eye has always been challenging. The aim of the present study was to provide a novel injectable, shear sensitive hydrogel based on tragacanthic acid (TA) with three kinds of acetate salts as cross-linker. Rheological properties by strain and shear stress sweep measurements and also dynamic rheological experiments including frequency and time sweep measurements were studied. Biological studies comprising, cell culture, Draize test on rabbit eyes and histopathological tests were done. The results showed the optimized hydrogel was biocompatible, injectable and owning acceptable firmness in rest state after injection. Healing time of the hydrogel was 46 s and was shear-sensitive. It showed no cytotoxicity on HUVEC cells. No allergic reaction was seen in Draize test and histological examination showed integrity of the retinal layers with no evidence of pathological changes, such as deformations, degeneration, or inflammation. TA hydrogel is promising in ocular drug delivery. (C) 2020 Published by Elsevier B.V.