Spontaneously promoted osteogenic differentiation of MC3T3-E1 preosteoblasts on ultrathin layers of black phosphorus

Recently, black phosphorus (BP) has garnered great attention as one of newly emerging two-dimensional nanomaterials. Especially, the degraded platelets of BP in the physiological environment were shown to be nontoxic phosphate anions, which are a component of bone tissue and can be used for mineralization. Here, our study presents the potential of BP as biofunctional and biocompatible nanomaterials for the application to bone tissue engineering and regeneration. An ultrathin layer of BP nanodots (BPNDs) was created on a glass substrate by using a flow-enabled self-assembly process, which yielded a highly uniform deposition of BPNDs in a unique confined geometry. The BPND-coated substrates represented unprecedented favorable topographical microenvironments and supportive matrices suitable for the growth and survival of MC3T3-E1 preosteoblasts. The prepared substrates promoted the spontaneous osteodifferentiation of preosteoblasts, which had been confirmed by determining alkaline phosphatase activity and extracellular calcium deposition as early- and late-stage markers of osteogenic differentiation, respectively. Furthermore, the BPND-coated substrates upregulated the expression of some specific genes (i.e., RUNX2, OCN, OPN, and Vinculin) and proteins, which are closely related to osteogenesis. Conclusively, our BPND-coating strategy suggests that a biologically inert surface can be readily activated as a cell-favorable nanoplatform enabled with excellent biocompatibility and osteogenic ability.