Label-Free and Multiplexed Quantification of microRNAs by Mass Spectrometry Based on...

MicroRNAs (miRNAs) are important biomarker candidates for cancer screening and early detection research. Generally, miRNAs undergo synergistic adjustments in tumor cells. Herein, a mass-spectrometric method based on a duplex-specific-nuclease (DSN)-enzyme-assisted signal-amplification technique was proposed for label-free and multiplexed detection of multiple miRNAs, and applied to the quantification of three miRNAs (i.e., miRNA-141, miRNA-21, and let-7a) in samples of HeLa and MDA-MB231 cell extracts. Experimental results showed that the digestion modes of DSN against three different DNAs complementary to miRNA-141, miRNA-21, and let-7a in their DNA-miRNA heteroduplexes were quite different, verifying the multiplexed-detection capability of the proposed method. Moreover, an advanced calibration model was derived for the quantitative analysis of the complex mass-spectral data measured during the label-free and multiplexed detection of miRNA-141, miRNA-21, and let-7a by the proposed mass-spectrometric method. With the aid of the advanced calibration model, the proposed mass-spectrometric method achieved quite reliable quantitative results for miRNA-141, miRNA-21, and let-7a in samples of HeLa and MDA-MB231 cell extracts, with recovery rates within the range of 89.2 to 111.6%. The limits of detection (LODs) of the proposed mass-spectrometric method for miRNA-141, miRNA-21, and let-7a in standard samples were estimated to be 42, 41, and 95 pM, respectively. Therefore, it is reasonable to expect that the proposed mass-spectrometric method can be a competitive alternative for the label-free and multiplexed detection of multiple miRNAs in clinical diagnosis.