Stepwise Surface Engineering of Sr10-HA-g-PBLG Porous Microspheres: Precise Functionalization for In Situ Scaffold Formation via Dynamic Crosslinking

This study develops a sequential surface functionalization strategy for strontium-substituted hydroxyapatite-graft-poly(γ-benzyl-L-glutamate) (Sr10-HA- g -PBLG) porous microspheres to enable in situ scaffold assembly. Hydrazine hydrate-mediated aminolysis and alkaline hydrolysis introduced surface amino (2.87 × 10 −2 mol/g) and carboxyl (1.76 × 10 −2 mol/g) groups, respectively, while preserving structural integrity (verified by FT-IR/XRD/SEM). Subsequent EDC/NHS-activated grafting of 3-amino-1,2-propanediol (AP) achieved 90% efficiency, followed by NaIO 4 oxidation to generate aldehyde functionalities (2.65 × 10 −3 mol/g). Through dynamic imine crosslinking between aldehyde- and amino-functionalized microspheres, 3D scaffolds were formed in situ. The scaffolds exhibited hierarchical porosity (pore size: 40–60 μm, porosity: 85.4% ± 2.3%), exceptional hydration capacity (613.6% ± 24.1% water retention), and enhanced mechanical properties (storage modulus > 13,000 Pa, compressive strength: 0.53 ± 0.02 MPa, tensile strength: 0.068 ± 0.02 MPa). Controlled degradation in PBS (pH = 7.4) showed 46.24% mass loss over 31 weeks. This interfacial engineering approach provides a versatile platform for designing polymer-ceramic hybrids with tailorable surface reactivity and structural adaptability. Adipose-derived stem cells were cultured in vitro, and the dual-fluorescence tracking strategy revealed spatially coordinated cellular colonization patterns, demonstrating porous microsphere scaffold's potential for precision-controlled 3D cell delivery in tissue engineering applications.