Ca（II） ions are added in the spinning dope to adjust the solidification rate of regenerated silk fibroin （RSF） solution during the wet-spinning process since Ca（II） ions are proved to be favorable to maintain the stable silk fibroin network in our previous work. The results show that when Ca（II）/RSF ratios are 1/50 and 1/20, the resulted RSF fibers exhibit good performance with the breaking energy more than 70 kJ/kg. However, higher Ca（II）/RSF ratio （for example, 1/10） hinders the solidification of spinning dope and results in poor RSF fibers. These observations together with earlier papers from this laboratory confirm that to produce tough silk fibers the spinning conditions must allow sufficient time for the adjustment of silk fibroin molecular chains.
Chitosan-graft-poly（L-glutamic acid）（CS-g-PGA） copolymer was successfully synthesized by grafting polymerization of γ-benzyl-L-glutamate N-carboxyanhydride onto the modified chitosan chains. The self-assembly behavior of such a CS-g-PGA amphiphilic copolymer was studied. The results show that spherical nanoparticles have been formed. The size of CS-g-PGA nanoparticles is found to be controlled by the grafting ratio of PGA. These bio-based polysaccharide/polypeptide hybrid nanoparticles with controllable size may have great potential application in biomedical fields, such as drug delivery systems.
LIU Ye-zhuoYAO Jin-rongCAO HengLENG Bo-xunSHAO Zheng-zhongCHEN Xin
