The present study develops on insulin-release studies from the chitosan-amide-modified stimuli-responsive polymers formed from various fatty acids including stearic acid, oleic acid, linoleic acid, and linolenic acid. This is the continuation of an earlier reported study that investigates the insulin-release profiles of chitosan-modified fatty acid amides (without stimuli responsive polymers). Following the synthesis and characterization of many different fatty acid amides with a varying amount of unsaturation, the insulin drug loading and release effects were compared among N-isopropylacrylamide (NIPAm), a thermo-responsive polymer, and 2-acrylamide-2-methylpropane sulfonic acid (AMPS), a pH-responsive polymer-modified hydrogel that is expected to enhance environmental response and the controllability of release. Finally, drug release effects were studied to investigate the drug release mechanisms with the help of five different pharmacokinetic models including the zero-order, first-order, Higuchi, Korsmeyers-Peppas, and Hixson models. The results indicate that the Higuchi and Hixson models are valid in terms of the operation of the NIPAm and AMPS matrices during the delivery of insulin.
Keywords: 2-acrylamide-2-methylpropane sulfonic acid (AMPS); N-isopropylacrylamide (NIPAm); drug release kinetics; insulin delivery; modified chitosan; pH-based release.