MicroRNAs (miRNAs) are a class of post-transcriptional gene regulators involved in various physiological processes including carcinogenesis, and they have emerged as potential targets for tumor theranostics. However, the employment of antisense oligonucleotides, termed anti-miRs, for antagonizing miRNA functions in vivo has largely been impeded by a lack of effective delivery carriers. Here, we describe the development of polyamidoamine (PAMAM) dendrimer and polyethylene glycol (PEG)-functionalized nanographene oxide (NGO) conjugate (NGO-PEG-dendrimer) for the efficient delivery of anti-miR-21 into non-small-cell lung cancer cells. To monitor the delivery of anti-miR-21 into cells and tumors, we also constructed an activatable luciferase reporter (Fluc-3xPS) containing three perfectly complementary sequences against miR-21 in the 3' untranslated region (UTR) of the reporter. Compared with bare dendrimer and Lipofectamine 2000 (Lipo2000), NGO-PEG-dendrimer showed considerably lower cytotoxicity and higher transfection efficiency. As demonstrated by in vitro bioluminescence imaging and Western blotting assays, NGO-PEG-dendrimer effectively delivered anti-miR-21 into the cytoplasm and resulted in the upregulation of luciferase intensity and PTEN target protein expression in a dose-dependent manner. Moreover, transfection with anti-miR-21 by NGO-PEG-dendrimer led to stronger inhibition of cell migration and invasion than did bare dendrimer or Lipo2000 transfection. The intravenous delivery of anti-miR-21 via NGO-PEG-dendrimer induced a significant increase in the bioluminescence signal within the Fluc-3xPS reporter-transplanted tumor areas. These results suggest that NGO-PEG-dendrimer could be an efficient and a potential nanocarrier for delivering RNA oligonucleotides. In addition, the strategy of combining NGO-PEG-dendrimer with an activatable luciferase reporter allows the image-guided monitoring of the delivery process, which can provide insights into the RNA-based cancer treatments.
Keywords: bioluminescence imaging; dendrimer; graphene oxide; luciferase reporter; miRNA delivery.