Rapid and Non-Targeted Qualitative and Quantitative Detection of miRNA in Complex Biological Samples Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry with a 3-Aminoquinoline and 2',4',6'-Trihydroxyacetophenone Ionic Liquid Matrix.

A novel ionic liquid MALDI matrix, 3-aminoquinoline/2',4',6'-trihydroxyacetophenone monohydrate (3-AQ/THAP), was developed for the rapid qualitative and quantitative detection of miRNA from biological samples. Compared to the traditional matrix 2,5-dihydroxybenzoic acid (DHB) and previously reported oligonucleotide-specific matrices, such as 3-aminopicolinic acid (3-APA), 3-hydroxypicolinic acid (3-HPA), and 6-aza-2-thiothymine (ATT), the 3-AQ/THAP matrix offers several advantages. It produces fewer alkali metal adduct peaks, exhibits higher sensitivity, and ensures better spot-to-spot repeatability. The 3-AQ/THAP matrix provides broader mass coverage and can effectively detect oligonucleotides ranging from 3-mer to 50-mer while delivering single-base resolution and sequence information. Additionally, it significantly reduces the "sweet spot" effect with an RSD of less than 7% over 36 single-spot analyses. For oligonucleotides ranging from 16-mer to 26-mer, the linear range extends from 0.4 μM to 40 μM per spot, with an R² greater than 0.988. Finally, miRNA in human plasma, fetal equine serum, and fetal bovine serum was successfully identified both qualitatively and quantitatively using the 3-AQ/THAP matrix. This matrix demonstrated excellent practicability for the detection of multiple miRNAs in complex biological samples.