Recent advances on gelatin methacrylate hydrogels with controlled microstructures for tissue engineering.

Hydrogels with high water content and porous structures are excellent 3D scaffolds for various applications in tissue engineering. Gelatin methacryloyl (GelMA) hydrogels with cell responsive RGD and MMP peptide sequences have been widely used in tissue engineering because of their adjustable mechanical properties, good processing performance and excellent biocompatibility. Advanced manufacturing technologies such as 3D printing and electrospinning can achieve precise control of GelMA-based hydrogel microstructures. Different microstructures of GelMA hydrogels, such as microspheres, microfibers, microchannels, microgrooves/microridges and microwells/micropillars have been fabricated and studied to simulate natural extracellular matrix and regulate the proliferation, migration and differentiation of different cells. In this review, recent efforts in GelMA-based hydrogel microstructures are discussed, including their preparation methods, unique characteristics, and specific applications in cell culture and tissue engineering. Finally, the remaining challenges and future direction of microstructured GelMA hydrogels are also suggested. We believe that with these recent advances and numerous ongoing efforts, GelMA-based hydrogels can be precisely fabricated with controlled microstructures, possessing great potentials as universal scaffolds for tissue engineering.