Nanostructured porous silicon (pSi) is a synthetic silicon-based material. Its biocompatibility and bioresorbability in body fluids make pSi an appealing biomaterial for tissue engineering, with surfaces characteristics facilitating human cell adhesion and differentiation. The resorption kinetics of such porous biomaterials is crucial for in vivo bone regeneration, in order to adapt biomaterial resorption to tissue formation, and to control the release of loaded bioactive molecules. We investigated pSi as a bioactive scaffold for bone tissue engineering, with an emphasis on kinetics of pSi resorption and silicon release. PSi particles and chips were fabricated from crystalline silicon, and functionalized by oxidation and chemical grafting of amine groups to mimic biological structures. Materials resorption over time was investigated with Raman spectroscopy, infrared spectroscopy, and Scanning Electron Microscopy. Silicon release was followed by mass spectrometry. Particle degradation and inclusion in newly formed bone were studied in vivo. The in vitro experiments revealed that non-oxidized pSi had an accelerated initial dissolution in ddH₂O and an inhibition of initial Si release in SBF. This high reactivity also led to transformation towards amorphous non-resorbable silica when incubated in SBF. PSi resorption started immediately with a maximal dissolution in the first 24 h. Later, the dissolution rate decreased over time. In comparison, the resorption process of oxidized pSi seemed delayed, but more continuous. This delayed dissolution increased the bioactivity and stability, leading to enhanced bone formation in vivo. Delayed pSi degradation provided a constant surge of silicic acid over time and promoted bone regeneration, demonstrating the high potential of pSi for bone tissue engineering: Oxidized pSi were almost completely resorbed after 2 months of healing, with remaining partially dissolved particles surrounded by newly formed bone. On the contrary, non-oxidized particles were still obviously present after 2 months with limited bone regeneration. This delayed resorption is consistent with the in vitro observations in SBF, and particles’ transformation towards silica.

Bone regeneration in critical-size defects requires biomaterials that provide both structural support and appropriate osteoinductive cues. Natural nacre contains an organic matrix rich in acidic macromolecules with reported osteogenic activity; however, its in vivo regenerative potential remains insufficiently explored. This study evaluated the bone regenerative capacity of nacre-derived materials alone and combined with oxidized porous silicon microparticles (pSi-MP), a bioactive material known to release silicic acid and support mineralized tissue formation. Critical-size defects were created in four caudal vertebrae of Wistar rats and filled with nacre, pSi-MP, a nacre–pSi composite, or left empty. After 60 days, bone formation was assessed using micro-computed tomography and non-decalcified histology. Empty defects failed to regenerate, whereas nacre and pSi-MP individually promoted partial mineralized tissue deposition. The nacre–pSi composite produced the most extensive repair, showing near-complete defect bridging, higher bone mineral density, and seamless integration of particles within newly formed bone. No inflammation or adverse reactions were observed, and osteoid deposition occurred directly on material surfaces. These findings demonstrate that nacre-derived materials exert intrinsic osteogenic effects in vivo and that combining nacre with porous silicon yields a synergistic response that significantly enhances bone regeneration. The composite represents a promising candidate for future bone repair strategies.