A Novel Complex of Chitosan⁻Sodium Carbonate and Its Properties

Chitosan has excellent properties, as it is nontoxic, mucoadhesive, biocompatible, and biodegradable. However, the poor water solubility of chitosan is a major disadvantage. Here, a novel chitosan-sodium carbonate complex was formed by adding a large amount of sodium carbonate to a chitosan/acetic acid solution, which is water-soluble. Fourier transform infrared spectroscopy, energy dispersive spectrometry, scanning electron microscopy, and solid-state nuclear magnetic resonance techniques were used to detect and characterize the aforementioned complex, which appeared to be a neat flake crystal. Solid-state nuclear magnetic resonance (SSNMR) was used to verify the connections between carbonate, sodium ions, and the protonated amino group in chitosan on the basis of ¹³C signals at the chemical shift of 167.745 ppm and 164.743 ppm. Further confirmation was provided by the strong cross-polarization signals identified by the SSNMR 2D ¹³C⁻¹H frequency-switched Lee⁻Goldberg heteronuclear correlation spectrum. The cytotoxicity of a film prepared using this complex was tested using rat fibroblasts. The results show that the film promoted cell proliferation, which provides evidence to support its nontoxicity. The ease of film-forming and the results of cytocompatibility testing suggest that the chitosan-sodium carbonate complex has the potential for use in tissue engineering.