XNAs: A Troubleshooter for Nucleic Acid Sensing

The strategies for nucleic acid sensing based on nucleic acid hybridization between the target sequence and the capture probe sequence are considered to be largely successful as far as detection of a specific target of known sequence is concerned. However, when compared with other complementary methods, like direct sequencing, a number of results are still found to be either "false positives" or "false negatives". This suggests that modifications in these strategies are necessary to make them more accurate. In this minireview, we propose that one way toward improvement could be replacement of the DNA capture probes with the xeno nucleic acid or XNA capture probes. This is because the XNAs, especially the locked nucleic acid, the peptide nucleic acid, and the morpholino, have shown better single nucleobase mismatch discrimination capacity than the DNA capture probes, indicating their capacity for more precise detection of nucleic acid sequences, which is beneficial for detection of gene stretches having point mutations. Keeping the current trend in mind, this minireview will include the recent developments in nanoscale, fluorescent label-free applications, and present the cases where the XNA probes show clear advantages over the DNA probes.