Injectable biomimetic hetero-structured short-fiber microspheres for constructing micro-ossification centers for bone regeneration

The ossification center serves as the foundation for bone development and its biologically heterogeneous structure provides an ideal microenvironment for bone tissue regeneration. However, mimicking the heterogeneous structure and function of ossification centers remains a substantial challenge. In this study, inorganic/organic composite zinc-doped calcium phosphate-mineralized microspheres were highly entangled with short fibers mimicking the extracellular matrix via charge coupling and electrospray microfluidic techniques, and the growth factor, PDGF-BB, was dynamically self-assembled with the short-fiber microspheres through π-π conjugation and dopamine catechol groups, successfully constructing the injectable biomimetic heterogeneous short-fiber microspheres (ZnCaP@NF-GF). ZnCaP@NF-GF features a unique fibrous network on its surface, enabling long-term anchoring in bone-defect regions through extracellular matrix interactions. PDGF-BB effectively recruits endogenous stem cells via the CXCR axis, whereas the sustained release of calcium ions significantly induces stem cells osteogenic differentiation via the MAPK/ERK signaling pathway. Concurrently, the sustained release of zinc ions promotes the generation of new vascular networks via the ERBB/ERK signaling axis. Ultimately, ZnCaP@NF-GF functioned as nucleation sites for the formation of biomineralized “bone islands.” Thus, ZnCaP@NF-GF provides new ideas for the regeneration of defective bone tissue by accurately simulating the structure and function of the ossification center. Schematic illustration of the design and preparation of the artificial micro-ossification center Short Fiber Microspheres (ZnCaP@NF-GF). Inspired by the physiological processes of ossification centers that guide the formation of mineralized matrices, this study proposes injectable biomimetic heterogeneous short-fiber microspheres engineered to precisely recapitulate the ossification center architecture. These short-fiber microspheres achieved localized matrix anchoring, endogenous stem cell recruitment, sustained matrix mineralization, and vascularization, offering a feasible strategy for guiding biomineralization and bone defect regeneration. • Short-fiber microspheres ZnCaP@NF-GF precisely replicate the heterogeneous architecture and biological functions of the ossification center to better support stem cell recruitment, proliferation, and tissue regeneration. • Short-fiber microspheres ZnCaP@NF-GF possess a unique three-dimensional fibrous network on their surface that facilitates long-term anchoring within bone defect regions through interactions with the extracellular matrix. • Short-fiber microspheres ZnCaP@NF-GF act as nucleation sites for biologically mineralized “bone islands”, continuously and sequentially facilitating bone tissue regeneration .