Bioinspired Hydroxyapatite-Mineralized Silk Fibroin/Ionic Liquid Interpenetrating Hydrogels for Biomedical Applications

Abstract

Surgical site infection remains a critical barrier to successful bone tissue engineering, and silk fibroin (SF)-based scaffolds, despite their excellent biocompatibility, lack intrinsic antibacterial activity. Here, we report a multifunctional biohybrid nanocomposite hydrogel that integrates methacrylated silk fibroin (SFMA) with an antibacterial imidazolium-based ionic liquid monomer, 1-vinyl-3-hexylimidazolium bromide ([C6VIm]Br), fabricated via a bioinspired bidirectional freeze-casting strategy followed by in situ biomineralization with hydroxyapatite (HAp). Successful methacrylation (degree of substitution = 35%) and ionic liquid synthesis were confirmed by NMR spectroscopy, while FT-IR, TGA/DTG, and XRD analyses verified the formation of the interpenetrating SF/IL network and progressive HAp deposition, with mineral content rising from 12.1 to 32.9 wt % over successive mineralization cycles. SEM imaging and elemental mapping revealed a highly interconnected, anisotropic porous architecture with uniform calcium/phosphorus distribution, closely emulating native bone microstructure, and mineralization enhanced the swelling capacity to approximately 170%. Biologically, the ionic liquid component conferred potent, additive-free antibacterial activity against both Staphylococcus aureus and Escherichia coli, while HAp incorporation improved MG-63 osteoblast-like cell adhesion and the viability of mesenchymal stem cells (MSCs), with MSC viability exceeding 120% of the control in the mineralized sample. All formulations exhibited hemolysis well below accepted safety limits, confirming excellent hemocompatibility. By combining intrinsic antibacterial function, bioinspired anisotropic architecture, and biomimetic mineralization within a single platform, this work offers a promising, metal- and antibiotic-free strategy for infection-resistant scaffolds for bone tissue engineering, with significant potential for advancing bone tissue engineering and regenerative medicine.