Fluorescent Nanodiamonds are Efficient, Easy-to-Use Cyto-Compatible Vehicles for Monitored Delivery of Non-Coding Regulatory RNAs

MicroRNAs are short molecules of RNA regulating most cellular processes via the mechanism of RNA interference. Their dysregulation leads to a disease burden, making them important therapeutic targets. For the successful development of a therapeutic device, the uptake of a functionalized carrier by live cells and the sufficient release of effector therapeutic molecules are limiting factors. Here for the first time, the inhibition of oncogenic microRNA-21 in CT-26 colon cancer cells is achieved, using an advanced nanosystem consisting of fluorescent nanodiamond and antisense RNA. Stable nanocomplexes efficiently deliver antisense RNA into cell cytoplasm, encouraging further study of microRNA-21 function in target cells. Engaging the fluorescent nanoparticle enables monitoring of transfection and release of the antisense RNA load into cell cytoplasm. Importantly, the internalized antisense RNA effectively destroys target microRNA-21 in CT-26 cancer cells. The absence of oncogenic microRNA-21 liberates tumor suppressor genes Pdcd4 and Timp3 from silencing, and results in a decrease of cell invasion and migration, and in the induction of apoptotic cell death. This study uses a nanodiamond-based imaging and delivery system, and shows that the multidimensional performance of the presented device makes nanodiamond-based complexes promising therapeutic devices.