Smart magnetic fluorescent nanoparticle imaging probes to monitor microRNAs.

An imaging system that can be used to evaluate the expression levels of microRNAs during neuronal development can provide noninvasive information for investigating a variety of biological phenomena related to microRNAs (miRNAs, miRs). Herein, the development of a novel imaging platform to monitor intracellular miR124a during neuronal differentiation is reported using rhodamine-coated cobalt ferrite magnetic fluorescent (MF) nanoparticles linked to a quenching molecular system containing an miR124a binding sequence (MF-miR124a beacon). During neuronal differentiation, in vitro fluorescence signals of the MF-miR124a beacon are significantly increased under conditions where miR124a is highly expressed, and dramatically return to the original quenched fluorescence after anti-miR124a treatment. In vivo fluorescence images show enhanced fluorescence signals in mice with P19 cells within a poly-L-lactic acid scaffold after induction of neuronal differentiation. In addition, magnetic resonance (MR) images provide in vivo tracking of cells containing the MF-miR124a beacon. These studies represent the first step toward the use of nanotechnological imaging of mature miRNA, and this technique could be used for cellular tracking with a MR imaging system as well as for simultaneous monitoring of the miRNA expression pattern in vivo.