Photocrosslinked gelatin methacryloyl/hyaluronic acid methacryloyl composite hydrogels loaded with bone morphogenetic protein 2-black phosphorus nanosheets for bone regeneration.

Black phosphorus nanosheets (BP) have been widely used in bone tissue engineering due to their superior properties and good biocompatibility, as well as the fact that they are composed of only a single element of phosphorus, which is highly homologous to the inorganic components of natural bone. Hydrogels based on gelatin methacryloyl (GelMA)/hyaluronic acid methacryloyl (HAMA) composites were prepared by photocrosslinking. The physicochemical properties of the prepared GelMA/HAMA, GelMA/HAMA/BP, GelMA/HAMA/BMP₂ and GelMA/HAMA/BP@BMP₂ hydrogels were characterized using Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). In addition, the mechanical properties, swelling rate and degradation rate of the hydrogels were investigated, and the results showed that GelMA/HAMA/BP@BMP₂ possessed good physicochemical and mechanical properties, which were suitable for cell adhesion growth and proliferation. BP as a carrier could ensure the stable and sustained release of the bioactive factor: bone morphogenetic protein 2 (BMP₂), which could promote the recruitment and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), and its degradation and binding to surrounding calcium ions can promote biomineralization. Therefore, this BMP₂-modified black phosphorus hydrogel system provides a new strategy for bone regeneration.