A review of sample preparation for purification of microRNAs and analysis by mass spectrometry methods

MicroRNAs (miRNAs) play an important role in regulation of different bioprocesses, including multiple diseases, such as cancer, neurodegenerative and immune-related disorders. Analysis of miRNA biomarkers in biological fluids requires accurate, sensitive, reproducible, and multiplexed methods. This review covers miRNA purification and measurement, which are the core of these analytical methods, and critically affect the output of biomarker research studies. With regard to miRNA measurement, the typical bioanalytical methods (e.g. reverse transcription polymerase chain reaction, RT-PCR), which have been extensively reviewed elsewhere, have been excluded to focus on less conventional methods based on mass spectrometry (MS). This review provides a broad overview of liquid-phase and solid-phase extraction purification methods for miRNA clean-up and enrichment and a critical insight into direct and indirect MS-based methods to disclose the true potential of MS in the field.