Influence of Chitosan Purification on the Immunomodulator Potential of Chitosan Nanoparticles on Human Monocytes

The deproteinization of chitosan is a necessary purification process for materials with biomedical purposes; however, chitosan sourcing and purification methods can modify its molecular weight, deacetylation degree, and residual proteins. These factors affect the reactive groups that affect the immunomodulatory activities of cells, particularly macrophages and monocytes; considering this activity is key when developing successful and functional biomaterials. Here, two brands of chitosan were purified and used to synthesize nanoparticles to evaluate their immunomodulatory effect on monocyte and macrophage differentiation. Chitosan FT-IR showed bands related to its purification process, with increased OH group intensity. Nanoparticles (CtsNps) synthesized with purified chitosan were of a smaller size compared to those using unpurified chitosan due to the alkaline purification process's shortening of the polymeric chain. At low concentrations (50 μg/mL), CtsNps showed a lower expression of CD80 and CD14, corroborating the differentiation effect of chitosan. Inducible nitric oxide synthase (iNOS) is related to a pro-inflammatory response and M1 macrophage polarization was detected in monocytes treated with purified and unpurified nanoparticles. Sigma-purified chitosan nanoparticles (CtsNps SigmaP), at 300 μg/mL, showed arginase production related to an anti-inflammatory response and M2 macrophage polarization. The chitosan purification process induces a shift in the polarization of macrophages to an anti-inflammatory M2 profile. This effect is concentration-dependent and should be further studied in each use case to favor the suitable biological response.