Fabrication of Injectable, Porous Hyaluronic Acid Hydrogel Based on an In-Situ Bubble-Forming Hydrogel Entrapment Process

Injectable hydrogels have been widely applied in the field of regenerative medicine. However, current techniques for injectable hydrogels are facing a challenge when trying to generate a biomimetic, porous architecture that is well-acknowledged to facilitate cell behaviors. In this study, an injectable, interconnected, porous hyaluronic acid (HA) hydrogel based on an in-situ bubble self-generation and entrapment process was developed. Through an amide reaction between HA and cystamine dihydrochloride activated by EDC/NHS, CO2 bubbles were generated and were subsequently entrapped inside the substrate due to a rapid gelation-induced retention effect. HA hydrogels with different molecular weights and concentrations were prepared and the effects of the hydrogel precursor solution's concentration and viscosity on the properties of hydrogels were investigated. The results showed that HA10-10 (10 wt.%, MW 100,000 Da) and HA20-2.5 (2.5 wt.%, MW 200,000 Da) exhibited desirable gelation and obvious porous structure. Moreover, HA10-10 represented a high elastic modulus (32 kPa). According to the further in vitro and in vivo studies, all the hydrogels prepared in this study show favorable biocompatibility for desirable cell behaviors and mild host response. Overall, such an in-situ hydrogel with a self-forming bubble and entrapment strategy is believed to provide a robust and versatile platform to engineer injectable hydrogels for a variety of applications in tissue engineering, regenerative medicine, and personalized therapeutics.