title: Thermosensitive injectable in-situ forming carboxymethyl chitin hydrogel for three-dimensional cell culture.
abstract: Injectable hydrogels have gained great attentions for cell therapy and tissue regeneration as a result of the applications in minimally invasive surgical procedures with the ease of handling and complete filling of the defect area. Here, a novel biodegradable, thermosensitive and injectable carboxymethyl chitin (CMCH) hydrogel was developed for three-dimensional (3D) cell culture. The obtained CMCH solution remained transparent liquid flowing easily at low temperatures and gelled rapidly at 37°C. The gelation time of CMCH hydrogels could be easily tuned by varying temperature and the degree of carboxymethylation, which facilitates the cell encapsulation process at room temperature and in-situ forming hydrogel at body temperature. Moreover, the CMCH-14 hydrogels in PBS buffer remained stable and continuous porous structure and could be degraded in the presence of lysozyme or hyaluronidase. HeLa cells proliferated sustainably and self-assembled to form 3D multicellular spheroids with high cell activity on the surface of CMCH-14 hydrogel. Encapsulation of COS-7 cells within the in-situ forming CMCH hydrogel demonstrated that CMCH hydrogels promoted cell survival and proliferation. In vivo mouse study of the CMCH hydrogels showed good in-situ gel formation and tissue biocompatibility. Thus, the biodegradable thermosensitive injectable CMCH hydrogels hold potential for 3D cell culture and biomedical applications.
  
  
  CONCLUSIONS
  Biodegradable hydrogels have been widely studied for cell therapy and tissue regeneration. Herein, we report a novel thermosensitive injectable carboxymethyl chitin (CMCH) hydrogel for 3D cell culture, which was synthesized homogeneously from the bioactive natural chitin through the "green" process avoiding using organic solvent. The CMCH solutions exhibited rapid thermoresponsive sol-to-gel phase transition behavior at 37°C with controllable gelation times, which facilitates the cell encapsulation process at room temperature and in-situ forming hydrogel at body temperature. Importantly, in vitro 3D cell culture and in vivo mouse study of the CMCH hydrogel showed promotion of cell survival and proliferation, good in-situ gel formation and biocompatibility. We believe that such thermosensitive injectable CMCH hydrogels would be very useful for biomedical applications, such as tumor model for cancer research, post-operative adhesion prevention, the regeneration of cartilage and central nervous system and so on.
authors.affiliation: Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan 430072, PR China.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.affiliation: Center for Tissue Engineering and Regenerative Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, PR China.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: Center for Tissue Engineering and Regenerative Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, PR China.
authors.forename: Chao
authors.initials: C
authors.lastname: Qi
authors.affiliation: Glyn O. Phillips Hydrocolloid Research Centre, Hubei University of Technology, Wuhan 43006, PR China.
authors.forename: Yapeng
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Department of Chemistry, Wuhan University, Wuhan 430072, PR China.
authors.forename: Lina
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan 430072, PR China.
authors.forename: Renxi
authors.initials: R
authors.lastname: Zhuo
authors.affiliation: Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan 430072, PR China. Electronic address: xljiang@whu.edu.cn.
authors.forename: Xulin
authors.initials: X
authors.lastname: Jiang
mesh_terms: D000818:Animals; D019556:COS Cells; D018929:Cell Culture Techniques / Q000379:methods*; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000633:toxicity; D002522:Chlorocebus aethiops; D006367:HeLa Cells; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry* / Q000633:toxicity; D007267:Injections; D008422:Materials Testing; D008810:Mice, Inbred C57BL; D066244:Proton Magnetic Resonance Spectroscopy; D012996:Solutions; D018874:Spheroids, Cellular / Q000166:cytology; D013696:Temperature; D013997:Time Factors
chemical_list: D012996:Solutions; D002686:Chitin; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; C044872:O-(carboxymethyl)chitin
keywords: 3D cell culture; Biodegradable; Carboxymethyl chitin; Injectable hydrogel; Tissue engineering