Ultrasensitive detection of cancer biomarker microRNA by amplification of fluorescence of lanthanide nanoprobes

Sensitive detection of cancer biomarker microRNAs (miRNAs) is of vital importance for cancer diagnosis and treatment. Nonetheless, the detection sensitivity in the existing miRNA bioassays is severely limited by the structural characteristics of miRNA (including small length and high sequence homology) because most of these methods are based on target amplification. Herein, we report a novel approach to sensitive and specific detection of low-abundance miRNA via a unique strategy of nanoprobe dissolution-enhanced fluorescence amplification, in which a capture probe featuring molecular beacon structure is designed. By means of this strategy, miRNA-21 was detected in a linear range from 10 fM to 100 pM with a detection limit as low as 1.38 fM. High selectivity of the newly developed biosensor was demonstrated by the good discrimination against a target with a single-base mismatch. Furthermore, this assay was used for the detection of miRNA-21 added into fetal bovine serum samples with the recovery in the range of 90.2%–108% and coefficients of variation below 10.1%, indicating its promising applications to RNA immunoassays and early cancer diagnosis.