Abundant nucleation sites-available liquid crystal hydrogel mimics bone ECM mineralization to boost osteogenesis

Bone extracellular matrix (ECM) is a unique organic-inorganic composite material derived from highly mineralized liquid crystal (LC) organic substrate. However, it remains a substantial challenge to design bone ECM-like LC materials with sufficient available nucleation sites to mimic the mineralization process of natural bone. Herein, we designed a bioinspired hydrogel with bone ECM-like LC organic substrate and inorganic phosphate mineralization nucleation sites for robust cell biomineralization and bone regeneration. Black phosphorus (BP) nanosheet was firstly loaded by bioactive layered double hydroxide (LDH) based on electrostatic attraction to improve the stability and photothermal performance of BP. Then, the LDH@BP was creatively added into chitin whisker/poly (ethylene glycol) diacrylate (CHW/PEGDA) LC hydrogel, abbreviated as LCgel, to fabricate LCgel/LDH@BP to highly mimic the mineralization microenvironment of bone ECM. The bone ECM-like LC topology of LCgel/LDH@BP is conducive to facilitating cell adhesion, proliferation and osteogenic differentiation. More importantly, the in-situ phosphate mineralization nucleation sites combined with mild hyperthermia induced by BP can further synergistically reinforce biomineralization of cells adhered on bone ECM-like LC substrate, thus substantially promoting cell biomineralization-mediated osteogenesis in vitro and in vivo. This study opens a new insight for the design of bioinspired hydrogel for cell biomineralization-mediated osteogenesis.