Synthesis, characterization of thiolated karaya gum and evaluation of effect of pH on its mucoadhesive and sustained release properties

•Thiolated gum karaya was found to contain 5.026mM of thiol groups/gm of polymer.•Thiolation led to conjugates with improved properties than unmodified one.•Swelling and mucoadhesion was increased with increase in pH from 1.2 to 6.8.•TK tablets sustained the release of drug with no disintegration throughout study.•Thiolation did not affect biocompatibility of the polymer. Present study aims at synthesis and characterization of thiolated gum karaya by reacting karaya gum with 80% thioglycolic acid resulting in esterification and immobilization of thiol groups on polymeric backbone. Immobilized thiol groups were found to be 5.026mM/g determined by Ellman's method. It was characterized by FTIR, DSC and XRD. Directly compressible tablets prepared using thiolated gum displayed more disintegration time, swelling and mucoadhesion with increase in pH of medium simulating gastric and intestinal environment than plain gum. Controlled drug release for more than 24h by Fickian diffusion following Korsemeyer-Peppas model was observed with Metoprolol Succinate as a model drug as compared to plain gum which released more than 90% of the drug within 2h. Synthesized thiomer showed no cytotoxicity determined using HepG2 cell line. According to these results, thiolated gum karaya seems to be promising excipient for the development of mucoadhesive drug delivery systems.