FT Raman investigation of novel chitosan sulfates exhibiting osteogenic capacity

Chitosan sulfates (CHS) exhibiting various total degrees of substitution ascribed to sulfate groups (DSS) were synthesized. The sulfation could be under homogeneous or non-homogeneous conditions. The obtained CHS were characterized and total DSS of up to 1.73 were determined. Using chlorosulfonic acid as sulfating agent, CS with total DSS between 0.86 and 1.67 were obtained and the total DSS can be regulated by varying the sulfation parameters. Using other sulfating agents, CS with distinct total DSS of up to 1.73 were prepared. By means of FT Raman spectroscopy, marker bands at 1070 cm−1 or 1014 cm−1 attributed to vibrations of sulfation groups can be applied for quantifying the total DSS of CHS. Calibration curves with correlation coefficients of more than 0.95 were established, suggesting the feasibility of Raman spectroscopy for quantifying the total DSS of CHS. Finally, the capacity of CHS to improve the osteogenic activity of bone morphogenetic protein-2 (BMP-2) was presented.