Molecular beacons of xeno-nucleic acid for detecting nucleic acid

Molecular beacons (MBs) of DNA and RNA have aroused increasing interest because they allow a continuous readout, excellent spatial and temporal resolution to observe in real time. This kind of dual-labeled oligonucleotide probes can differentiate between bound and unbound DNA/RNA in homogenous hybridization with a high signal-to-background ratio in living cells. This review briefly summarizes the different unnatural sugar backbones of oligonucleotides combined with fluorophores that have been employed to sense DNA/RNA. With different probes, we epitomize the fundamental understanding of driving forces and these recognition processes. Moreover, we will introduce a few novel and attractive emerging applications and discuss their advantages and disadvantages. We also highlight several perspective probes in the application of cancer therapeutics.