Thiolated chitin nanocrystals: Colloidal-chemical properties, toxicity, emulsion stabilization and UV sensitivity

Chemical modification of chitin nanocrystals (ChNC) surfaces significantly influences their colloidal-chemical properties and serves as a means to impart new characteristics to chitin-based materials. In this work, the ChNC surface was chemically modified with SH-containing acids by acylation of free amino groups using N-acetylcysteine and thioglycolic acid (ChNC-SH). Hydrosols of ChNC-SH exhibit a higher yield point, and the introduction of an oxidizer results in a more pronounced liquefaction of their sol structure, accompanied by a notable decrease in dynamic viscosity. Laser Doppler electrophoresis method revealed a shift in the isoelectric point of both types of SH derivatives from the alkaline to the neutral region. ChNC-SH forms more physically stable oil-in-water emulsions, which, compared to ChNC, are characterized by increased dynamic viscosity, a more significant increase with rising temperature, and enhanced stability in the presence of an electrolyte. ChNC-SH also act as photocatalytic reducers of Cr(VI), with both the rate and efficiency of reduction increasing as pH decreases from 4.0 to 2.0. The synthesized SH-containing nanocrystals exhibit no acute toxicity, LD50 was established in vivo (mice, orally). SH-modification of the ChNC surface has the greatest effect on the rheological properties and the formation of the interface surface.