Preparation and characterization of an in situ crosslinkable glycol chitosan thermogel for biomedical applications

Thermogels have been extensively utilized as one of representative in situ forming hydrogel systems for biomedical applications. However, most thermogels often suffer from a weak mechanical strength and low physical stability. To overcome these intrinsic weaknesses of conventional thermogels, we developed a new in situ crosslinkable thermogel system with enhanced and tunable physicochemical properties. Thermosensitive N-hexanoyl glycol chitosans (HGCs) were synthesized by N-hexanoylation of glycol chitosan and further modified to yield methacrylated HGCs (M-HGCs) and thiolated HGCs (SH-HGCs). A mixture of M-HGCs and SH-HGCs (M/SH-HGCs) retained not only their thermogelling properties but also their reactive functionalities for chemical crosslinking at physiological temperature. Compared to conventional thermogels, the M/SH-HGC thermogels showed enhanced mechanical properties due to physical and chemical crosslinking mechanisms. The physicochemical properties of the M/SH-HGC thermogels were characterized in terms of the sol–gel transition temperature, gelation time, mechanical strength, and biodegradability. They showed negligible toxicity in cells, and the in situ crosslinking step did not affect cell viability. These results suggest that our crosslinkable thermogel system is useful not only as a new in situ forming hydrogel but also as a biomaterial for various biomedical applications due to its thermogelling characteristics and enhanced and tunable physicochemical properties.