Original: https://doi.org/10.1016/j.carpta.2025.101062
Natural sulfated polysaccharides (NSPs) are commonly used in food, medicine, and cosmetics. To recreate the properties of these natural materials, chemical sulfation is usually needed. However, traditional sulfation methods often rely on toxic solvents, large amounts of chemicals, and long heating steps.
In this study, we report for the first time that cellulose and oxidized-chitin nanomaterials can be sulfated using a mechanochemical method with a sulfur trioxide–pyridine complex. This approach is more environmentally friendly than conventional techniques.
Compared with the original (unmodified) materials, the sulfated products—S-NanoCel, S-NanoChit, and SO-NanoChit—showed much lower turbidity values (25, 45, and 158 NTU). This indicates that they disperse very well in water. The successful attachment of sulfate groups was confirmed using FTIR spectroscopy, which showed characteristic peaks near 1250 and 820 cm⁻¹, as well as by 13C NMR data.
Elemental analysis showed degrees of substitution (DS) from 0.22 to 0.78, with S-NanoCel having the highest DS. X-ray diffraction results revealed that the original nanomaterials had crystallinity levels between 80% and 93%. After sulfation, crystallinity dropped and could no longer be precisely measured, although the underlying crystalline structure was still visible. The lattice arrangement still corresponded to aligned polysaccharide chains.
Finally, biological testing showed that the sulfated oxidized chitin had the strongest inhibitory effect on heparanase (IC₅₀ = 0.7 µg·mL⁻¹), suggesting that it could serve as a promising heparan sulfate–like material.