Freeze-Thawing Condition to Obtain the Chitosan-Calcium Phosphate Composites with Controllable Degradation Degree

Synthesized hybrid material for potential use as nerve conductors (conduits) in the form of a chitosan matrix with uniformly distributed brushite microparticles. The applied multistage synthesis includes a 5-fold process of freezing at a temperature of −18°C and thawing (at room temperature and under the influence of microwave irradiation (MW)) of the calcium (Ca)/chitosan (CS) colloidal suspension. Further gradient thawing in sodium hydrogen phosphate solution promotes in situ formation of nanocrystalline amorphous calcium phosphate (ACP) and brushite microparticles. SEM micrograph, XRD, porosity, degradation and swelling capacity were analyzed. The technique allows to the creation of mechanically strengthened material with a low degree of swelling (115-138%) and a biodegradation period of 75–200 days depending on the freeze-thaw method, which corresponds to the healing time of the damaged nerve. The application of MW reduces the degree of porosity and increases the content of brushite, which acts as a reinforcing bioactive admixture and a source of Ca
²⁺
ions, affecting the direct regeneration of neurons.