Characterization of a novel lyophilized chitosan hydrogel complex for the controlled release of a highly water soluble drug, niacinamide

The purpose of this research was to prepare and characterize a novel lyophilized chitosan-based hydrogel complex (termed CS-M) for controlled drug delivery applications using a highly water soluble model drug, niacinamide. Characterization studies were undertaken to evaluate the physical-chemical properties, polymer swelling, in vitro controlled release kinetics, tissue bioadhesion, intestinal permeability and stability of the novel chitosan complex. Additionally, a comparative analysis was conducted with commercial polymers namely, Carbopol 974P-NF® and hydroxypropyl methylcellulose (HPMC K4M). FT–IR and 1H NMR studies confirmed that despite alteration in physical structure and morphology of the chitosan complex the chemical properties remained unchanged, when compared to the parent chitosan compound. Polymer swelling studies showed consistency in the structural integrity and water uptake of CS-M compared to other polymers which showed inconsistent swelling and disintegration behavior over a 5 h period. In vitro controlled release profiles of CS-M showed a slower, more controlled release rate of niacinamide than other polymers indicating the influence of polymer swelling capacity on water uptake and subsequent drug release. CS-M demonstrated an overall increase in bioadhesion to intestinal tissue when compared to commercial polymers at same concentrations. Similarly, drug transport through everted sac intestinal tissue showed enhanced absorption properties of CS-M when compared to other polymers. Finally, a 3 month accelerated stability study showed all polymers including CS-M to be stable when formulated with niacinamide. Overall, the modified chitosan-based hydrogel polymer, CS-M, demonstrated enhanced characteristics indicating its potential to be used as a controlled release excipient in oral drug formulations. Keywords: Chitosan hydrogel complex, controlled drug delivery, niacinamide, lyophilization, Carbopol 974P-NF, HPMC K4M