Safety evaluation and cellular response of nano-ferrite particles for 3D artificial autogenous bone

<p>[Introduction]</p><p>To develop artificial autologous bone, novel ferromagnetic nano-ferrite particles (NFPs) are taken up by cells under control of a magnetic field to produce 3D cell-derived artificial bone and calcification. This study evaluated the safety and cellular response of NFPs engineered by our group in osteoblasts (OBs).</p><p>[Methods]</p><p>NFPs of approximately 20 nm were prepared with iron oxide and measured by scanning electron microscopy. Cell viability was evaluated by the Alamar Blue method after exposure to NFPs at 0.04-0.57 mg/mL for 24 h. NFP uptake was evaluated by flow cytometry (FCM), and NFP uptake images were visualized by transmission electron microscopy (TEM). OB calcification function was quantitatively assessed after Alizarin Red staining.</p><p>[Results]</p><p>TEM showed that NFPs accumulated in large amounts in OBs, which exhibited high cell viability. FCM revealed maximum NFP uptake at concentrations of 0.14 mg/mL or higher. Uptake peaked at 4 days of exposure. The calcification ability of OBs changed with NFP concentration and became affected above 0.57 mg/mL.</p><p>[Discussion]</p><p>Considerable NFP accumulation in OBs was seen, with limited effect on survival. The NFP uptake peak at 4 days of exposure suggested long-term safety. Since calcification was inhibited at higher NFP concentrations, the non-internalized extracellular NFPs might have disrupted the formation of calcified nodules.</p><p>[Prospects]</p><p>NFPs appear well-tolerated and safe in OBs. Future studies will evaluate 3D modeling and calcification of NFP-encapsulated OBs to develop tailor-made artificial autogenous bone.</p>