Molecular beacon–quantum dot–Au nanoparticle hybrid nanoprobes for visualizing virus replication in living cells

Here we describe a new hybrid fluorescent nanoprobe composed of a nuclease-resistant molecular beacon (MB) backbone, CdSe-ZnS core-shell quantum dots (QDs) as donors, and gold nanoparticles (Au NPs) as quenchers, for the real-time visualization of virus replication in living cells. By using a Au NP-MB to QD ratio of 6 : 1, a 7.3-fold increase in fluorescent signal was achieved upon target binding. For living cell experiments, a hexahistidine-appended Tat peptide was self-assembled onto the QD surface to provide nearly 100% non-invasive delivery of the QD-MB-Au NP probes within 2 h. By directly visualizing the fluorescent complexes formed with the newly synthesized viral RNA, this QD-MB-Au NP probe provided sensitive and real-time detection of infectious viruses as well as the real-time visualization of cell-to-cell virus spreading.