In vitro osteogenic potential of melatonin-loaded magnesium-containing mesoporous bioactive glass nanoparticles

Abstract

A multifunctional nanoscale system was engineered by incorporating melatonin into magnesium-containing mesoporous bioactive glass (Mg-MBG) through adsorption within its porous network. The resulting formulation was designed to enable site-specific melatonin delivery while supporting applications in bone tissue regeneration. A surfactant-mediated sol–gel process employing CTAB was used to fabricate the Mg-containing mesoporous glass particles. Their physicochemical characteristics, both prior to and following melatonin incorporation, were investigated through XRD, FTIR/ATR-FTIR, FESEM coupled with EDS, DLS, surface-charge measurements, and nitrogen adsorption–desorption analyses using the BET and BJH models. The diffraction profiles of the unloaded and melatonin-containing formulations lacked distinct crystalline reflections, confirming their largely amorphous structures. Electron microscopy further revealed that both formulations consisted mainly of rounded particles with dimensions below one micrometer. FTIR analysis demonstrated preservation of the characteristic Si–O–Si bands and the appearance or overlap of melatonin-associated vibrations after loading, while EDS confirmed the presence of Si, Ca, Mg, and P and detected carbon and nitrogen in MLT-Mg-MBG. Both formulations displayed highly negative zeta potential values, indicating favorable colloidal stability. The presence of an interconnected mesoporous architecture was verified by nitrogen sorption measurements, which yielded characteristic type IV adsorption–desorption profiles accompanied by distinct hysteresis loops. Melatonin incorporation caused a pronounced reduction in the BET surface area, from 156.38 m²/g in pristine Mg-MBG to 20.581 m²/g in MLT-Mg-MBG. This substantial decrease indicates that melatonin molecules were accommodated within the mesoporous network, obstructed some pore entrances, and partially accumulated on the outer particle surfaces. The loading procedure achieved an encapsulation efficiency of 63.18%. Melatonin release followed a two-stage pattern: 51.98 ± 2.34% of the loaded compound was liberated within the initial 48 h, whereas subsequent gradual diffusion increased the cumulative release to 85.41 ± 3.95%. Cell-based experiments further revealed no evident cytotoxic effects for either formulation, with L929 fibroblasts retaining their metabolic activity following exposure to both Mg-MBG and MLT-Mg-MBG. Both formulations demonstrated in vitro bioactivity, as evidenced by their capacity to induce apatite deposition following immersion in simulated body fluid. In hAD-MSC cultures, MLT-Mg-MBG produced greater ALP activity than Mg-MBG, particularly on days 14 and 21, suggesting enhanced early osteogenic activity. Overall, MLT-Mg-MBG represents a promising mesoporous carrier for sustained melatonin delivery and shows preliminary in vitro osteogenic potential. Further validation through quantitative mineral-deposition measurements, gene- and protein-level analyses of osteogenic markers, and appropriate in vivo models is still necessary to establish the bone-regenerative potential of this formulation.