In Situ-Formed Tissue-Adhesive Macroporous Scaffolds Enhance Cell Infiltration and Tissue Regeneration

Macroporous hydrogels have shown significant promise in tissue engineering and regenerative medicine. However, conventional macroporous scaffold fabrications are complex and incompatible with in situ customization and fabrication. Here, we propose a highly translational approach for the in situ formation of adhesive macroporous scaffolds through microfluidic homogenization of gas into a self-crosslinkable gelatin and transglutaminase (TG) mixture using a double syringe system. Using this strategy, the tissue defect can be evaluated, and the precursor, with the desired composition and volume, foamed and administered in situ. The TG-induced crosslinking stabilizes the pores, leading to strong tissue adhesion and accurate defect geometry approximation. We demonstrate precise control over the porosity, by changing the foaming parameters, and crosslinking kinetics, by adjusting the concentration of gelatin and TG. The resulting foam scaffolds offer controlled pore distribution, flexibility, tissue adhesion, stability, sustained protein release profile, and cell permissibility, with a faster biodegradation profile compared to bulk hydrogel compartments. Consequently, enhanced cell infiltration and reduced fibrous capsule formation are observed upon subcutaneous injection of foams compared to bulk hydrogels. Finally, the scaffolds demonstrate significant improvements in the rate and quality of the healing compared to the bulk hydrogels for the treatment of full-thickness cutaneous wounds in mice. STATEMENT OF SIGNIFICANCE: A highly translational method is presented for the in situ formation of tissue-adhesive macroporous scaffolds through microfluidic homogenization of gas into a self-crosslinkable hydrogel precursor using a double syringe system. This approach allows precise control over porosity and pore size, facilitating cell infiltration, tissue integration, and improved wound healing compared to bulk hydrogels, highlighting their potential in regenerative medicine.