Three kinds of sulfonated chitosans

i.e.3

6-O-sulfonated chitosan (OCS)

2-N-sulfonated chitosan(NCS) and 2-N-sulfopropyl chitosan (PCS) were synthesized.Their chemical structures were verified by FTIR and 1H-NMR.The sulfonation degree of the sulfonated chitosan

which was determined by elemental analysis

could be varied by changing the amount of sulfonation reagent or the reaction time.To evaluate the growth factor-protective ability of sulfonated chitosans

basic fibroblast growth factor (bFGF)

which is one of the most important growth factors in tissue repair

was used as the target protein.By in vitro cell culture

the morphology of fibroblasts cultured in different conditions was observed by the costaining of cytoskeleton and cell nuclei

according to which the cell shape indexes such as perimeter

area and aspect ratio were analyzed.The results showed that bFGF/Heparin has the highest values in all cell shape indexes.However

compared to the pristine chitosan (CS)

the combination of bFGF with all sulfonated chitosan did not show any effect on the fibroblasts morphology.By cell viability test

the influence of sulfonated chitosan on protecting bFGF activity was studied.Similar to the results of cell morphology

heparin also showed the strongest ability to promote bFGF activity.However

the sulfonated chitosans showed different protecting ability.For OCS and PCS

no significantly effect on bFGF activity was observed.However

NCS could promote the bFGF activity effectively

since the cell viability was significantly higher than that of bFGF/CS

and reached about 70% of bFGF/Hep.Meanwhile

the effect of sulfonation degree was also studied

showing that the cell viability was not affected by the sulfonation degree of chitosan.All these results indicate that the sulfonation position is the key point of the growth factor-protective ability of sulfonated chitosans.