Self-Assembled Hydrogel Based on (Bio)polyelectrolyte Complex of Chitosan–Gelatin: Effect of Composition on Physicochemical Properties

Taking into account the trends in the field of green chemistry and the desire to use natural materials in biomedical applications, (bio)polyelectrolyte complexes ((bio)PECs) based on a mixture of chitosan and gelatin seem to be relevant systems. Using the approach of self-assembly from the dispersion of the coacervate phase of a (bio)PEC at different ratios of ionized functional groups of chitosan and gelatin (<i>z</i>), hydrogels with increased resistance to mechanical deformations and resorption in liquid media were obtained in this work in comparison to a hydrogel from gelatin. It was found that at <i>z</i> ≥ 1 a four-fold increase in the elastic modulus of the hydrogel occurred in comparison to a hydrogel based on gelatin. It was shown that hydrogels at <i>z</i> ≈ 1 had an increased sorption capacity and water sorption rate, as well as increased resistance to the in vitro model environment of phosphate-buffered saline (<i>PBS</i>) solution containing lysozyme at 37 °C. It was also shown that in <i>PBS</i> and simulated gastric fluid (<i>SGF</i>) solutions, the effect of the polyelectrolyte swelling of the hydrogels was significantly suppressed; however, at <i>z</i> ≥ 1, the (bio)PEC hydrogels had increased stability compared to the samples at <i>z</i> < 1 and based on gelatin.