Black phosphorus biomaterials for photo-controlled bone tissue engineering

Over the past decades, black phosphorus (BP) emerges as an effective photothermal material with clinically favorable biocompatibility and biodegradation that receives broad attention for tissue engineering. BP nanosheets with tunable sizes and morphologies could be exfoliated from bulk BP via top-bottom or bottom-up methods, thus endowing versatile photothermal performance. Due to its intrinsic degradability in the presence of oxygen and water, various surface modifications are usually warranted to enhance the biostability of BP in physiological environment during bone repair. Compared with traditional bone implant materials , BP-based materials not only enable high selective and efficient photothermal therapy ( PTT ) that can stimulate bone regeneration via up-regulating expression levels of heat shock proteins (HSPs), but also generate abundant phosphate to support the mineralization of extracellular matrix and promote new bone formation after near-infrared (NIR) irradiation treatment. Inspired by the immense application potential of BP-based biomaterials for bone-related engineering, here we provide a comprehensive analysis regarding the surface modification methods of BP, BP-mediated biological mechanisms to trigger osteogenic differentiation , and BP-induced biomineralization for promoting bone formation. This review may inspire more successful explorations for BP-mediated bone repair in the future.