Synthesis, Characterization, and Stimuli Responsive On/Off Switching of Cross‐Linked Hydroxyethyl Starch: A Smart Material for Intelligent Drug Delivery

Abstract

This study reports cross-linking of hydroxyethyl starch (HES) using citric acid to from cross-linked HES-citrate. The HES-citrate as obtained is characterized using FTIR and 1 H NMR. The cross-linked product HES-citrate shows remarkable swelling in different media simulated to the physiological systems of human body, i.e., deionized water (DW), pH 6.8 and 7.4, and followed second order swelling kinetics. The HES-citrate exhibits reversible swelling/deswelling in different combinations of stimuli, i.e., at pH 7.4 and 1.2, in DW and normal saline and in DW and ethanol which makes it a potential candidate for intelligent drug delivery. Therefore, cross-linked product shows extraordinary stimuli-responsiveness under different physiological conditions such as in presence electrolytes and solvents and at different temperatures. HES-citrate-based aceclofenac tablet is formulated that demonstrates sustained-release under conditions mimicked to gastrointestinal tract (GIT) in terms of pH and transit time.