Core–Shell Structures of Bioactive Glass Nanoparticles and MIL-100 Framework: Properties and Biomedical Applications

A novel core-shell hybrid material composed of bioactive glass (BG) nanoparticles and the metal-organic framework (MOF) MIL-100(Fe) (Fe₃O(H₂O)₂OH(BTC)₂·nH₂O, BTC: 1,3,5-benzenetricarboxylate) was synthesized using a layer-by-layer strategy. The formation of the MIL-100(Fe) shell on the BG core was directly confirmed by high-resolution transmission electron microscopy, which revealed a continuous MOF layer with an average thickness of 6.1 ± 0.9 nm. Complementary characterization by infrared spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, N₂ sorption, and synchrotron-based X-ray absorption spectroscopy (XAS) confirmed the coexistence of MIL-100(Fe) and BG components and their structural integrity within the hybrid material. Notably, for the first time, a synchrotron-based technique (XAS) was used to characterize the MOF@BG system, providing unique insight into its local coordination environment and structural evolution. The hybrid material demonstrated favorable cytocompatibility in a long-term (21-day) assay on mouse osteoblast precursor cells (MC3T3) and human dermal fibroblasts (HDF). At the same time, it did not induce ex vivo hemolysis at concentrations up to 1000 μg/mL. The induction of osteogenic differentiation in MC3T3 cells in the presence of MIL-100(Fe)@BG was confirmed by early osteogenic markers, including alkaline phosphatase (ALP) activity and alizarin red staining (ARS). Bioactivity studies in Dulbecco's phosphate-buffered saline (DPBS) and simulated body fluid (SBF) revealed rapid formation of nanohydroxyapatite, beginning within the first hours of incubation. Importantly, under physiological conditions, the MIL-100(Fe) shell undergoes a controlled structural transformation, yielding highly dispersed nanoscale Fe₂O₃ particles. These nanoparticles induce the production of reactive oxygen species (ROS) and contribute to antibacterial activity, thereby inhibiting E. coli and S. aureus without the need for external antimicrobial agents. The combination of bioactivity, osteogenic potential, hemocompatibility, and intrinsic antibacterial functionality positions MIL-100(Fe)@BG as a promising multifunctional platform for bone regeneration and infection control.