Polydopamine-assisted biomineralized fibrous membrane and short fiber-reinforced spheroids for bone bioengineering

Self-assembled spheroids provide substantial cell-cell interactions and cytoarchitectural complexity. However, the lack of bio-instructive cues can hinder cell differentiation, prompting the adoption of fiber-reinforced spheroids in tissue engineering. Herein, electrospun nanofibrous membrane were photochemically crosslinked, fragmented into short nanofibers (SNFs), and then surface-modified with mussel-inspired polydopamine (pDA). pDA-coated SNFs (pDA-SNFs) were incubated in simulated body fluid to induce nucleation and growth of a nanoscale hydroxyapatite layer in order to form mineralized pDA-SNFs (M-pDA-SNFs). We studied the structural properties, surface chemistry, thermal properties, crystallinity, and chemical composition (Ca/P ratio) of SNFs, pDA-SNFs, mineralized SNFs, and M-pDA-SNFs. We then produced M-pDA-SNFs reinforced spheroids with MC3T3-E1 cells using a low-adhesion U-bottom microplate. Our results highlighted that pDA modification activated the fiber surface and promoted uniform apatite deposition with a Ca/P ratio similar to that of biological apatite. Hydroxyapatite deposition subsequently enhances the roughness, thermal, and bioactive properties of scaffolds. The mineralized pDA-SNFs were biocompatible and supported osteogenic differentiation and matrix maturation more than non-mineralized fibers. Furthermore, M-pDA-SNFs not only promoted the assembly of MC3T3-E1 pre-osteoblasts into spheroids but also directed osteogenic lineage commitment, thereby providing a cell-instructive, bone-mimetic milieu essential for advanced bone regeneration.