G-triplex based molecular beacon with duplex-specific nuclease amplification for the specific detection of microRNA.

High sequence homology among miRNA members challenges miRNA analysis. In this paper, we developed a simple and highly selective method based on a novel G-triplex molecular beacon (MBG3) and duplex-specific nuclease signal amplification (DSNSA) for miRNA detection. Herein, this MBG3 is a label-free molecular beacon with a special G-triplex probe. The excellent controllablity of the G-triplex probe allowed our MBG3 to have a short stem, which protected it from DSN digestion. Therefore, DSN cleavage induced false positive signals in most DSN signal amplification strategies have been minimised efficiently without special modifications. Importantly, the improved recognition ability of MBG3, together with the sensitive substrate selectivity of DSN, makes our novel method suitable for miRNA detection with high selectivity. The signal response of similar miRNA sequences with one-base difference has been reduced from 37% to 8% compared to the traditional linear ssDNA probe-DSN-based method.