Hierarchical Silica–Cellulose Nanoarchitectures from Rice Straw: A Waste-to-Value Platform for Autonomous Osteogenic Bone Regeneration

Current bone regeneration strategies face significant constraints, relying either on synthetic scaffolds with slow degradation that require biochemical supplements or on bioactive fillers. Recently, the focus has shifted towards functional natural biomaterials with inherent osteoinductive potential. This study presents a promising candidate based on a silica-containing plant-derived scaffold fabricated from rice straw, a sustainable resource with >20 wt.% silica. Morphological analyses revealed that the decellularised rice straw scaffold exhibits a unique surface pattern with a three-dimensional nanoarchitecture featuring parallel fibrillar protrusions and cellulosic spikes evenly distributed across the surface. Elemental mapping revealed abundant silicon, with minor traces of calcium and phosphorus, all of which are crucial components of bioactive minerals. The scaffold was highly biodegradable, with 81.7% weight loss after 90 days, attributed to its high water absorption (337%). The scaffold demonstrated excellent biocompatibility, maintaining MG63 cell viability and promoting robust adhesion and proliferation, with relative metabolic activity increasing from 105% at day 5 to 125% at day 7 relative to TCPS controls. Most remarkably, when seeded with adipose-derived human mesenchymal stem cells (hMSCs) in the absence of osteogenic medium, the scaffold induced significant biomineralisation. This osteoinductive capacity is attributed to its unique surface pattern, high roughness, and polar cellulosic substrate, together with bioactive silica that releases soluble silicon species. This work represents how agricultural waste can be upcycled for autonomous bone regeneration.