Modified Carboxymethyl Chitin Hydrogels

Hydrogels are hydrophilic three-dimensional network with high water content.Their structural similarity to natural extracellular matrixes(ECM)makes themselves attractive in biomedical field.Chitin,as a kind of abundant and important polysaccharide in nature,has been widely studied in biomaterial field due to its superior biocompatibility and biodegradability.Carboxymethyl chitin(CMCH)is one of the most attractive derivatives of chitin as biomaterial owing to its good solubility.But Carboxymethyl chitin which can be completely dissolved in pure water exhibits no gelling ability and weak mechanical properties.In this thesis,soluble CMCH was used to construct hydrogels,and at the same times,a novel reinforcing component was introduced.The main research contents and conclusions of this thesis are listed as follows:(1)Methacrylated carboxymethyl chitin(Me-CMCH)hydrogel:In this work,carboxymethyl chitin(CMCH)synthesized homogenously was further modified with methacrylic anhydride and photocrosslinked into hydrogel with tunable degradation and mechanical properties.This new methacrylated carboxymethyl chitin(Me-CMCH)hydrogel formed in-situ photocrosslinked under UV irradiation showed much higher storage modulus than that of the thermosensitive in-situ forming physical-crosslinking CMCH hydrogel.The Me-CMCH hydrogels remained stable and continuous porous structure under physiological conditions and could be degraded by lysozyme.Cytotoxicity test indicated that the photo-induced Me-CMCH hydrogels were non-cytotoxic.The mechanical property,morphology,swelling and biodegradation behavior of the Me-CMCH hydrogels could be tuned by controlling the degree of methacrylation of Me-CMCH.These biodegradable photocrosslinkable Me-CMCH hydrogels may hold great promises for various biomedical applications.(2)Graphene oxide/carboxymethyl chitin(GO/CMCH)composite hydrogel:GO was introduced into CMCH polymer network in the presence of cross-linker(BDDE)to successfully prepare novel GO/CMCH composite hydrogel.Mechanical property and swelling behavior of CMCH-based hydrogel were dramatically influenced due to the introduction of GO.To be specific,the mechanical performances of the composite hydrogels were reinforced significantly.Compared with the pure one which contained no GO,the failure stress and compressive modulus of the composite hydrogel containing 1.0 wt%GO were enhanced by 250%and 150%,respectively.The changes of swelling behavior were as follows.With 0.1 wt%GO,the composite hydrogel exhibited the highest swelling ratio,and with the content of GO going up,the swelling ratio decreased.When 1.0 wt%GO was used,the swelling ratio of the composite hydrogel was lower than that of a pure one.In conclusion,the mechanical property and swelling behavior were tunable by the content of GO,which made GO/CMCH composite hydrogel promising in biomaterial field.