A reverse complementary multimodal imaging system to visualize microRNA9-involved neurogenesis using peptide targeting transferrin receptor-conjugated magnetic fluorescence nanoparticles.

Multimodal imaging systems may eliminate the disadvantages of individual imaging modality by providing complementary information about cellular and molecular activites. In this sutdy, we developed a reverse complementary multimodal imaging system to image microRNAs (miRNA, miR) during neurognesis using transferrin receptor (TfR) and a magnetic fluorescence (MF) nanoparticle-conjugated peptide targeting TfR (MF targeting TfR). Both in vitro and in vivo imaging demonstrated that, in the absence of miR9 during pre-differentiation of P19 cells, the MF targeting TfR nanoparticles greatly targeted TfR and were successfully internalized into P19 cells, resulting in high fluorescence and low MR signals. When the miR9 was highly expressed during neurogenesis of P19 cells, the MF targeting TfR nanoparticles were hardly targeted due to the miR9 function, which represses the expression and functional activity of TfR from the miRNA TfR reproter gene, resulting in low fluorescence and high MR signals. The reverse complementary multimodal miRNA imaging system may serve as a new imaging probe to montior miRNA-involved cellular developments and diseases.