Recent progress on functional hydrogels as biomaterial for biomedicine

As a polymer material with a three-dimensional network structure, hydrogel has broad application prospects in the field of biomedical due to its high moisture content, porosity, flexibility, biocompatibility and controllable physical and chemical properties. This paper systematically reviews the latest research progress and challenges of functional hydrogels in vitro and in vivo. In vitro applications, hydrogels significantly improve the limitations of traditional two-dimensional cell culture by simulating the microenvironment of extracellular matrix (ECM), providing an ideal platform for 3D cell culture, organoid construction and drug screening. Although natural polymer hydrogels (such as collagen and Matrigel) have good biological activity, they have problems of batch differences and insufficient mechanical properties; synthetic polymer hydrogels (such as polyethylene glycol) can achieve controllable performance through chemical modification, but their biological inertia needs to be optimized through compound strategies. Compound hydrogels combined with nanomaterials or 3D bioprinting technology further enhance the conductivity, antibacteriality and mechanical adaptability, and promote the development of precise tissue engineering. In vivo applications, hydrogels are outstanding as soft tissue fillers, wound dressings and tissue repair stents. For example, self-crosslinked hyaluronic acid hydrogel overcomes the degradation problem of traditional fillers, and silver nanocomposite hydrogels significantly improve antibacterial performance through photothermal/photodynamic synergistic effects. In addition, the application of hydrogels in bone, heart, cartilage and nerve repair demonstrates its multi-organ repair potential, such as decellularized ECM hydrogels promoting bone regeneration, and 3D printed alginate/gelin hydrogels to build artificial heart valves. Despite the significant results, the long-term biocompatibility, immune response and standardized preparation of hydrogels in clinical transformation are challenges that need to be solved urgently. In the future, combined with 3D printing, microfluidic technology and functional design, hydrogels are expected to play a more important role in personalized medical care and complex tissue regeneration, becoming the next generation of core biomaterials.