pH-responsive hydrogel membranes based on modified chitosan: water transport and kinetics of swelling

Abstract

pH-responsive membranes prepared by treating chitosan (Ch) with glutaraldehyde (GA) or with GA and sulfuric acid (SA) were studied. The structure and properties of the membranes were characterized by Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elemental analysis. The effect of the cross-linking process both on the dynamic swelling behaviour of the hydrogel membranes and on the mechanism of water transport through those membranes was investigated in buffer solutions of different pH (1.2-9.5). The mechanism of water transport through the hydrogel chitosan membranes was affected by membrane composition and pH of the swelling medium. Non-cross-linked Ch membrane showed a non-Fickian swelling behaviour in the pH range 6.5-9.5. Chitosan membrane cross-linked with GA (Ch/GA) showed less-Fickian or Fickian swelling behaviour in all buffer solutions. In the case of chitosan membrane cross-linked with GA and SA (Ch/GA/SA), at low pH (lower than the pK a of the hydrogel) the water transport was controlled more by polymer relaxation than by penetrant diffusion. The experimental data clearly suggested that the swelling process in all buffer solutions obeyed second-order kinetics. Values of an apparent swelling rate constant for Ch/ GA and Ch/GA/SA membranes were of the same order of magnitude for acidic and neutral swelling media but they increased for alkaline solutions.

Toxicity, Biocompatibility, pH-Responsiveness and Methotrexate Release from PVA/Hyaluronic Acid Cryogels for Psoriasis Therapy

“…The variation of the kinetic parameter values is asociated with the p K a values of the components and their interactions by functional groups, as was demonstrated for other pH-responsive systems [ 62 , 63 , 64 , 65 , 66 ], and in this case those of MTX and HA.…”

β-cyclodextrin chitosan-based hydrogels with tunable pH-responsive properties for controlled release of acyclovir: design, characterization, safety, and pharmacokinetic evaluation

“…This results in the formation of low molecular weight polymeric segments within the hydrogel network or shorter graft chains that could not undergo extension and relaxation to allow surrounding media to penetrate. Thus, the resulting hydrogels demonstrated a decrease in swelling dynamics (Ostrowska-Czubenko et al, 2015).…”

Examining the Impact of Squaric Acid as a Crosslinking Agent on the Properties of Chitosan-Based Films

“…According to our previous findings [ 2 , 28 ], and based on the knowledge that Schiff bases absorb in the range 1620–1660 cm −1 [ 29 ], it is reasonable to assume that the intense band at ca. 1631 cm −1 is a result of overlapping of the amide I vibration of chitosan and the C=N stretching of a Schiff base.…”