Hyaluronic acid L-cysteine conjugate exhibits controlled-release potential for mucoadhesive drug delivery.

Hyaluronic acid-L-cysteine conjugate, a novel thiolated polymer, was synthesized and characterized for mucoadhensive drug delivery. L-Cysteine was covalently attached to hyaluronic acid via the formation of an amide bond. Adhesion studies on the mucosa indicated a 4.82-fold increase in the adhesion force of the obtained conjugate (containing 210.58 mu mol thiol groups per gram polymer) versus unmodified hyaluronic acid. The results of a peptidase inhibition study revealed that the inhibitory effect of hyaluronic acid toward trypsin and chymotrypsin was significantly improved compared to hyaluronic acid. Permeation studies utilizing a MDCK cell monolayer system demonstrated a sustained drug release. Based on these features the novel thiolated polymer might represent a promising multifunctional excipient for various drug delivery systems.