In situ forming hydrogels based on modified gellan gum/chitosan for ocular drug delivery of timolol maleate.

In situ forming hydrogels are suitable candidates for increasing drug residence time in ocular drug delivery. In this study, gellan gum (GG) was oxidized to form aldehyde groups and in situ gelling hydrogels were synthesized based on a Schiff-base reaction between oxidized GG (OGG) and chitosan (CS) in the presence of β-glycerophosphate. The effect of OGG and CS concentration on the physical and chemical properties of the resulting hydrogels was investigated. The FT-IR spectroscopy confirmed the chemical modification of OGG as well as the functional groups of the prepared hydrogels. The scanning electron microscope (SEM) revealed the highly porous structure of hydrogels. The obtained hydrogels indicated a high swelling degree and degradability. Also, the rheological studies demonstrated self-healing behavior, shear thinning, thixotropy, and mucoadhesion properties for the developed hydrogels. The results of in vitro and ex vivo studies showed that the timolol-loaded hydrogel with a higher amount of OGG has a higher release rate. Moreover, the MTT cytotoxicity test on bone marrow mesenchymal stem cells (BMSCs) confirmed that developed hydrogels are not toxic. The obtained results revealed that the developed hydrogels can be a desirable choice for the ocular drug delivery of timolol in the treatment of glaucoma.