Engineering a Haversian-gyroid biomimetic scaffold: NIR-triggered photothermal-NO cascade antibacterial, hydroxyapatite enhanced pH balance and cell osteogenic differentiation

Biomimetic hierarchical bone scaffold: outer Haversian canals and inner Gyroid pores for high memchanical strength. • Cascade antibacterial: thermal cleaves biofilms and Fe-NO bonds, releasing NO into bacteria to kill S. aureus and E. coli • Synergistic osteogenesis: thermal activates HSP70, synergizing with Ca 2+ and PO 4 3- to boost osteogenic differentiation. • pH regulation: amine groups from oxidative self-polymerization increase the pH value, enhancing scaffold stability. Poly- L -lactic acid (PLLA) is widely used in bone scaffold engineering due to its favorable biocompatibility, biodegradability, and processability. However, its mechanical properties are limited by insufficient crystallinity during fabrication. Moreover, bone repair is often accompanied by early bacterial infection and local pH reduction, which challenge the antibacterial effect, osteogenic capacity and structural stability of PLLA scaffolds. Herein, PLLA and hydroxyapatite (HA) are melt-blended into PLLA/HA (PHA). followed by self-polymerization of polydopamine (PDA) and electrostatic adsorption sodium nitroprusside of (SNP). The composite is then prepared into a PHA@PDA-SNP scaffold, with an outer Haversian canal layer and inner Gyroid-perforated. Ingeniously, the scaffold utilizes photothermal produced by near-infrared light to cleave biofilm and the Fe-NO bond in SNP, promoting NO release and entry into bacteria. Meanwhile, thermal can activate HSP70, synergizing with Ca 2+ and PO 4 3- released by PHA to boost osteogenic differentiation. Moreover, the amine groups retained during the oxidation process of PDA can weaken the acidic environment and enhance scaffold stability. Results show that the bone scaffold mimics the natural bone structure with high compressive strength (162.9 MPa) by biomimetic manufacturing. Scaffold exhibits cell osteogenic differentiation as evidenced by a 70% upregulation of HSP70 and Ca 2+ influx, and a 4.5-fold increase of ALP and ARS. Scaffold utilizes photothermal and NO to achieve antibacterial rates of 97.4% and 98.2% against S. aureus and E. coli , respectively. Download: Download high-res image (194KB) Download: Download full-size image