SPIO-Au core–shell nanoparticles for promoting osteogenic differentiation of MC3T3-E1 cells: Concentration-dependence study

This work aims to explore the concentration-dependence of SPIO-Au core–shell nanoscale particles (NPs) (17.3 ± 1.2 nm in diameter) on biocompatibility and osteogenic differentiation of preosteoblast MC3T3-E1 cells. The stability of NPs was first investigated by UV–vis absorption spectra and zeta potential measurement. Then concentration effects of NPs (1–80 μg/mL) were evaluated on viability, morphology, proliferation, cellular uptake, and alkaline phosphate (ALP) activity levels. Results have shown strong stability and no acute toxicity (viability > 93%) or morphological difference at all concentration levels of NPs. The proliferation results indicated that the concentration of NPs below 40 μg/mL does not affect the cell proliferation for 7 days of incubation. Transmission electron microscopy images revealed the successful internalization of NPs into MC3T3-E1 cells and the dose-dependent accumulation of NPs inside the cytoplasm. The ALP level of MC3T3-E1 cells was improved by 49% (of control) after treated with NPs at 10 μg/mL for 10 days, indicating their positive effect on early osteogenic differentiation. This study confirmed the excellent biocompatibility of SPIO-Au NPs and their great potential for promoting osteogenic differentiation and promised the future application for these NPs in bone engineering including drug delivery, cell labeling, and activity tracking within scaffolds.