Detection of extracellular RNAs in cancer and viral infection via tethered cationic lipoplex nanoparticles containing molecular beacons.

Noninvasive early detection methods have the potential to reduce mortality rates of both cancer and infectious diseases. Here, we present a novel assay by which tethered cationic lipoplex nanoparticles containing molecular beacons (MBs) can capture cancer cell-derived exosomes or viruses and identify encapsulated RNAs in a single step. A series of ultracentrifugation and Exoquick isolation kit were first used to isolate exosomes from the cell culture medium and human serum, respectively. Cationic lipoplex nanoparticles linked onto the surface of a thin glass plate capture negatively charged viruses or cell-secreted exosomes by electrostatic interactions to form larger nanoscale complexes. Lipoplex/virus or lipoplex/exosome fusion leads to the mixing of viral/exosomal RNAs and MBs within the lipoplexes. After the target RNAs specially bind to the MBs, exosomes enriched in target RNAs are readily identified by the fluorescence signals of MBs. The in situ detection of target extracellular RNAs without diluting the samples leads to high detection sensitivity not achievable by existing methods, e.g., quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Here we demonstrate this concept using lentivirus and serum from lung cancer patients.