Surface-modified hydroxyapatite nanoparticle for microRNA delivery to regulate gene expression in human mandibular osteoblast cells

Abstract

Hydroxyapatite nanoparticles (HA-NPs) are proposed for a miRNA delivery system with additional value in bone engineering because of its osteogenic activity. HA-NPs were synthesized by hydrothermal method, and surface-modified with two cationic functional groups 3-aminopropyltriethoxysilane (HA-NPs-APTES) and poly2-(dimethylamino)ethyl methacrylate (HA-NPs-PDMAEMA). The particles were visualized under a transmission electron microscope and then characterized for their physical properties, cell compatibility, and efficiency of miRNA binding. The FitC-tagged particles internalized in human mandibular osteoblasts (HMOBs) demonstrated insufficient miRNA binding and internalization of the unmodified particles. HA-NPs-APTES particles were in 150–200 nm elongated shape and demonstrated positive surface charge with the highest miRNA binding efficiency. HA-NPs-APTES was highly internalized in HMOBs without significantly changing cell metabolism. In contrast, PDMAEMA-modified particles demonstrated an increase in size and surface charge, and are thus potentially toxic to cells. The level of delivered miRNA in total RNA was determined by qPCR, and the HA-NP delivery system was analyzed. The HA-NP delivery system efficiently delivered miRNA, and the miRNA-targeted GAPDH expression was diminished by three- to tenfold. The GAPDH level was suppressed after 50 μg/mL or 100 μg/mL HA-NPs-APTES, significantly lower than the effect by Dharmafect. In conclusion, HA-NPs-APTES demonstrates optimal efficiency in miRNA delivery and gene regulation in the osteoblast in vitro model.