Degradation-Dependent Protein Release from Enzyme Sensitive Injectable Glycol Chitosan Hydrogel.

Abstract

Glycol chitosan (GC) is a hydrophilic chitosan derivative, known for its aqueous solubility. Previously, we have demonstrated the feasibility of preparing injectable, enzymatically crosslinked hydrogels from HPP [3-(4-Hydroxyphenyl)-propionic acid (98%)]-modified GC. However, HPP-GC gels showed very slow degradation, which presents challenges as an <i>in vivo</i> protein delivery vehicle. This study reports the potential of acetylated HPP-GC hydrogels as a biodegradable hydrogel platform for sustained protein delivery. Enzymatic crosslinking was used to prepare injectable, biodegradable hydrogels from HPP-GC with various degrees of acetylation (DA). The acetylated polymers were characterized using Fourier transform infrared and nuclear magnetic resonance spectroscopy. Rheological methods were used to characterize the mechanical behavior of the hydrogels. <i>In vitro</i> degradation and protein release were performed in the presence and absence of lysozyme. <i>In vivo</i> degradation was studied using a mouse subcutaneous implantation model. Finally, two hydrogel formulations with distinct <i>in vitro</i>/<i>in vivo</i> degradation and <i>in vitro</i> protein release were evaluated in 477-SKH1-Elite mice using live animal imaging to understand <i>in vivo</i> protein release profiles. The lysozyme-mediated degradation of the gels was demonstrated <i>in vitro</i> and the degradation rate was found to be dependent on the DA of the polymers. <i>In vivo</i> degradation study further confirmed that gels formed from polymers with higher DA degraded faster. <i>In vitro</i> protein release demonstrated the feasibility to achieve lysozyme-mediated protein release from the gels and that the rate of protein release can be modulated by varying the DA. <i>In vivo</i> protein release study further confirmed the feasibility to achieve differential protein release by varying the DA. The feasibility to develop degradable enzymatically crosslinked GC hydrogels is demonstrated. Gels with a wide spectrum of degradation time ranging from less than a week and more than 6 weeks can be developed using this approach. The study also showed the feasibility to fine tune <i>in vivo</i> protein release by modulating HPP-GC acetylation. The hydrogel platform therefore holds significant promise as a protein delivery vehicle for various biomedical and regenerative engineering applications. Impact statement The study describes the feasibility to develop a novel enzyme sensitive biodegradable and injectable hydrogel, where in the <i>in vivo</i> degradation rate and protein release profile can be modulated over a wide range. The described hydrogel platform has the potential to develop into a clinically relevant injectable and tunable protein delivery vehicle for a wide range of biomedical applications.