Peptide Nucleic Acid-Assisted Label-free Detection of Single-Nucleotide Polymorphisms Based on Light Scattering of Carbon Nanotubes

With the help of peptide nucleic acid (PNA) and single-stranded (ss) DNA-specific nucleases, a simple, rapid, and label-free nanosensor is demonstrated for the sensitive and accurate detection of single-nucleotide polymorphisms (SNPs) in a homogeneous solution based on the light scattering (LS) of carbon nanotubes. PNAs are non-natural analogues of DNA with extraordinary stability toward enzymatic degradation, and DNAs in the fully matched DNA/PNA duplexes can be effectively protected from ssDNA-specific nucleases, whereas the DNAs in DNA/PNA duplexes involving a mismatch are cleaved into small fragments. This difference could be easily monitored by measuring the LS signal of single-walled carbon nanotubes (SWNTs) for the different binding affinities of SWNTs to ssPNA and PNA/DNA duplexes that can be used for the detection of SNPs. As a proof-of-principle analyte, the SNPs in the human tumor suppressor gene TP53 have been successfully genotyped by this method. The assay does not involve any chemical modification of probes, which is simple and universal. Moreover, the LS technique and the use of a sequence-specific PNA probe impart high sensitivity and selectivity. In principle, this assay can be used to detect any kind of gene mutations by simply changing the PNA sequences of the specific probe.