Preparation of chitosan injectable hydrogel for bone tissue engineering

Abstract

This research was purposed to prepare chitosan derivative as injectable hydrogel for bone tissue engineering via inclusion gelation. In order to apply chitosan as injectable hydrogel, chitosan should not only be soluble in water, but it also could form hydrogel under physiological condition. α-cyclodextrin (α-CD) was selected to modify onto chitosan. Since, it had tremendous hydrophilic hydroxyl groups which provided chitosan for water solubility as well as hydrophobic cavities which function as crosslinking points by inclusion complex with poly(ethylene glycol), PEG. The conjugation between α-CD and chitosan was performed via water soluble carboxymethyl chitosan precursor (CM-chitosan) which provided carboxyl groups for conjugation. Hydrogel was prepared by inclusion gelation of mixing between α-CD conjugated chitosan and PEG. CM-chitosan-g-α-CD showed FTIR characteristic peak of β-pyranyl vibration of chitosan and the characteristic peak of α-pyranyl vibration of α-CD at 898 and 952 cm-1, respectively. For NMR spectra, CM-chitosan-g-α-CD showed peak H-1 of α-CD and H-2 of chitosan. The results indicated that α-CD was successfully conjugated onto CM-chitosan. The optimum molar ratio of α-CD to PEG was 2 to 4 and threading number was 2.5. The concentration of CM-chitosan-g-α-CD was 15%(w/v) to prepare hydrogel. The mix solution formed hydrogel within 450±10 min. The solution could be drawn into syringe and injected into mold. The morphology of hydrogel was observed by Scanning Electron Microscope. It was found that the hydrogel appeared porosity. The porosity was interconnecting pore in order to transport nutrients to cells. Therefore, this injectable hydrogel would be a novel candidate approaching for bone tissue engineering injectable scaffolds.