Synthesis and structural characterization of new chitosan-thiamine hydrochloride molecular complexes

• Mechanochemistry was successfully used to obtain new molecular complexes with potential anticancer properties. • The integration of thiamine hydrochloride through the polymeric structure of chitosan led to structural interconnections. • Optimizing the preparation process is directly influenced by the mass ratio of the components in the formulation. • Spectroscopic techniques validated the interaction between the pharmaceutical molecular complexes. Chitosan is one of the natural cationic polymers used for drug delivery due to its unique properties as an antimicrobial and antioxidant agent. In this work, three new molecular complexes were obtained by mechanically grinding a mixture of chitosan and thiamine hydrochloride in weight ratios of 4:1, 3:2, and 1:1, with a few drops of acetic acid and sodium citrate solutions. Complementary analyses, including X-ray powder diffraction, differential thermal analyses, thermogravimetric analyses, Fourier transform infrared spectroscopy, and CP/MAS 13 C NMR, were performed to characterize the new molecular complexes. X-ray diffraction revealed the transformation of chitosan from a semi-crystalline to an amorphous state after mechanochemical grinding. Infrared spectroscopy showed changes in the vibrations of the functional groups C O, O H, and N H in the structure of the developed compounds, indicating the interconnection of the components. Solid-state nuclear magnetic resonance spectroscopy recorded shifts of the resonance lines present in the ball-milled samples, compared to the initial compounds, along with the appearance of new lines, supporting the formation of chitosan-thiamine hydrochloride complexes. Thermal analyses confirmed the successful development of new molecular complexes by the appearance of two new exothermic signals at lower temperatures than those observed for chitosan.