Biohybrid microstructured hydrogels obtained via <i>in situ</i> extracellular matrix deposition and decellularization using supercritical CO₂

In recent decades, our understanding of biomaterials has shifted from seeing them simply as physical supports for cells or drug delivery platforms to recognizing their active and dynamic role in tissue repair, guided by their physicochemical, mechanical, and biological properties. Biologically derived materials such as the decellularized extracellular matrix (dECM) offer the advantage of replicating the biomolecular cellular environment and have been proposed for tissue regeneration. However, their use as scaffolds is hindered by poor mechanical properties and limited tunability of physical features. Herein, we fabricated a bioinspired hybrid hydrogel by integrating a chemically cross-linked microporous polysaccharide scaffold with native ECM directly secreted by cells. First, the scaffold synthesis and culture conditions were optimized to enhance ECM deposition by fibroblasts. To obtain an acellular scaffold, decellularization using supercritical CO₂was performed and compared to a conventional method, demonstrating its superiority in ensuring efficient decellularization while preserving an enriched ECM lining the surface of the pores and preventing scaffold damage. The biohybrid hydrogel was characterized by a very low amount of DNA (<5 ng DNA mg^-1) and a network of highly interconnected pores covered by an abundant ECM including collagen I, collagen IV, fibronectin, elastin and laminin. This work presents a new versatile strategy that can be adapted to various tissues to engineer biomimetic microstructured materials overcoming the limitations associated with polymer-based and dECM-based strategies when used independently.