Semi-Interpenetrated Polymeric Networks of Chitosan and Poly(γ-Glutamic Acid) with Potential Biomedical Applications

Hydrogels are polymeric matrices very similar to living tissue due to their elasticity, porosity, and ability to absorb high water content. They are highly attractive materials for a wide range of biomedical applications, such as tissue engineering, wound healing, and drug delivery. In this regard, hydrogels of semi-interpenetrating polymer networks (semi-IPNs) based on the biopolymers chitosan and poly-(γ-glutamic acid) (γ-PGA) were prepared as systems with improved properties compared to hydrogels of individual polymers. The resulting hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), porosity testing, compressive strength, cell viability, and swelling capacity. FTIR spectra of the semi-IPNs confirmed the presence of the functional groups of each polymer. SEM images revealed a porous structure of the hydrogels, which became denser and more compact with increasing γ-PGA content. This behavior was corroborated by the porosity test, which decreased with the formation of the γ-PGA-reinforced network. The swelling capacity study of the hydrogels demonstrated their sensitivity to pH and temperature. For the semi-IPN hydrogels, SF1 had the highest swelling ratio (20.55) at pH 3.6 and T = 37 °C. The formation of the semi-IPNs brought about improvements in mechanical properties compared to the chitosan hydrogel. The presence of γ-PGA contributed to improved biocompatibility of the materials, especially in formulations with 0.025 and 0.05 g of this biopolymer. These results suggest that the obtained chitosan/γ-PGA semi-interpenetrating networks may be promising materials with great potential for use in biomedical applications.