Enzyme-free amplified detection of nucleic acids based on self-sustained replication of RNAzyme and its application in tumor cell detection

A system based on exponential amplification of self-sustained replication of RNAzyme was developed for quantitative detection of linker DNA that can be recognized by base complementarity. The hybridization of the linker DNA with two RNA ligase subunits formed an RNA enzyme that catalyzes the joining of two oligonucleotide substrates. The ligated product opens a hairpin molecular beacon, resulting in the generation of a higher fluorescence intensity. The product of this reaction depends on the concentration of the linker DNA, allowing one to determine the concentration of target DNA in a sample. Furthermore, based on the high specificity and affinity of cell aptamer with its target cells, this amplification strategy has been successfully applied in detection of cancer cells. The exceptional amplification power of the RNAzyme along with the simple assay protocol makes direct cell detection possible in real-world samples with minimal sample pretreatments. This process is analogous to quantitative PCR (qPCR) but can be applied to the detection of nucleic acid and cells, as well as proteins and small molecules that are relevant to medical diagnostics. (C) 2013 Elsevier B.V. All rights reserved.