Biofunctionalization of ADA‐GEL Hydrogels Based on the Degree of Cross‐Linking and Polymer Concentration Improves Angiogenesis

The biocompatibility of alginate dialdehyde (ADA) and gelatin (GEL) hydrogels cross-linked with human transglutaminase (hTG) is demonstrated in vivo with a high degree of stability and angiogenic potential. The additional enzymatic cross-linker hTG and the increased concentration improve stability and angiogenic potential. The X-ray microscopy (XRM) is employed for the first time. It allows visualization and precise analysis of the vascular network, provided that effective perfusion of the vessels is achieved by the contrast agent.

Abstract

The creation of bioartificial tissues is a promising option for the reconstruction of large-volume defects. The vascularization of tissue engineering constructs, as well as the material properties of the carrier matrix, are important factors for successful clinical application. In this regard, hydrogels are promising biomaterials, providing an extracellular matrix-like milieu that enables the possibility of cell transplantation and de novo tissue formation. Furthermore, biofunctionalization allows for a certain fine-tuning of angiogenic properties. This study aims to investigate vascularization and tissue formation of highly cross-linked alginate dialdehyde (ADA) and gelatin (GEL). This highly cross-linked network is created using a dural cross-linking mechanism combining ionic (Ca²⁺ ions) and enzymatic (human transglutaminase (hTG)) cross-linking, resulting in reduced swelling and moderate degradation rates. Vascularization of the ADA-GEL-hTG constructs is induced surgically using arteriovenous (AV) loops. Biocompatibility, tissue formation, and vascularization are analyzed by histology and X-ray microscopy. After only 2 weeks, vascularization of the ADA-GEL-hTG constructs is already present. After 4 weeks, both de novo tissue formation and vascularization of the ADA-GEL-hTG matrix increase. In conclusion, ADA-GEL-hTG-based hydrogels are shown to be promising scaffold materials for tissue engineering applications.