Chitosan/hydroxyapatite Composite Incorporated with Copper Nanoparticles: Production Using CO2-Based Solvent and Investigation of Physico-Chemical and Antibacterial Properties

Composite chitosan (Cht) scaffolds containing stabilized hydroxyapatite (HA) and copper (Cu) particles were synthesized using a two-phase CO2/H2O system under high pressure. The study systematically investigated the influence of key factors-such as the method of HA incorporation (in situ vs. ex situ), chitosan concentration, and temperature conditions-on the structural properties of the Cht/HA_Cu composite materials. Characterization techniques including SEM, XRD, and IR-ATR were employed to analyze the resulting structures. It was found that composites produced from a more concentrated polymer solution (2%) had twice the Young's modulus compared to those produced from a 1.5% chitosan solution. The addition of HA at a ratio of 1:2 with polymer and copper nanoparticles increased the values of Young's modulus by up to 8-10 times, allowing for an index of 3 MPa to be achieved. The composites exhibited high porosity (phi similar to 75-80%), excellent water absorption capacity (eta similar to 80-90%), and pronounced antimicrobial activity against both Gram-positive and Gram-negative bacteria with an activity index of about (I similar to 40%) relative to both bacterial strains. As the production process is biocompatible, the final product is expected to be non-toxic, non-pyrogenic, and potentially supportive of cell proliferation. These properties highlight its potential as a promising material for bone repair applications.