ABSTRACT
Chitosan is a deacetylated polymer of chitin that is extracted mainly from the exoskeleton of crustaceans and is the second-most abundant polymer in nature. Chitosan hydrogels are preferred for a variety of applications in bio-related fields due to their functional properties, such as antimicrobial activity and wound healing effects; however, the existing hydrogelation methods require toxic reagents and exhibit slow gelation times, which limit their application in biological fields. Therefore, a mild and rapid gelation method is necessary. We previously demonstrated that the visible light-induced gelation of chitosan obtained through phenol crosslinking (ChPh) is a rapid gelation method. To further advance this method (<10 s), we propose a dual-crosslinked chitosan hydrogel obtained by crosslinking phenol groups and crosslinking sodium tripolyphosphate (TPP) and the amino groups of chitosan. The chitosan hydrogel was prepared by immersing the ChPh hydrogel in a TPP solution after phenol crosslinking via exposure to visible light. The physicochemical properties of the dual-crosslinked hydrogels, including Young's moduli and water retentions, were subsequently investigated. Young's moduli of the dual-crosslinked hydrogels were 20 times higher than those of the hydrogels without TPP ion crosslinking. The stiffness could be manipulated by varying the immersion time, and the water retention properties of the ChPh hydrogel were improved by TPP crosslinking. Ion crosslinking could be reversed using an iron chloride solution. This method facilitates chitosan hydrogel use for various applications, particularly tissue engineering and drug delivery.
ABSTRACT
Three-dimensional bioprinting has attracted much attention for biomedical applications, including wound dressing and tissue regeneration. The development of functional and easy-to-handle inks is expected to expand the applications of this technology. In this study, aqueous solutions of chitosan derivatives containing sodium persulfate (SPS) and Tris(2,2'-bipyridyl) ruthenium(II) chloride (Ru(bpy)3) were applied as inks for both extrusion-based and vat polymerization-based bioprinting. In both the printing systems, the curation of ink was caused by visible light irradiation. The gelation time of the solution and the mechanical properties of the resultant hydrogels could be altered by changing the concentrations of SPS and Ru(bpy)3. The 3D hydrogel constructs with a good shape fidelity were obtained from the chitosan inks with a composition that formed gel within 10 s. In addition, we confirmed that the chitosan hydrogels have biodegradability and antimicrobial activity. These results demonstrate the significant potential of using the visible light-curable inks containing a chitosan derivative for extrusion and vat polymerization-based bioprinting toward biomedical applications.