High-Throughput and Sensitive Fluorimetric Strategy for MicroRNAs in Blood Using Wettable Microwells Array and Silver Nanoclusters with Red Fluorescence Enhanced by Metal Organic Frameworks

A high-throughput and sensitive fluorimetric analysis method has been developed with wettable microwells array for probing short-chain microRNAs (miRNAs) in blood using silver nanoclusters (AgNCs) with red fluorescence amplified and stabilized by metal organic frameworks (MOFs). Glass slides were first spotted with polyacrylic acid to form hydrophilic microdots and then patterned with hydrophobic hexadecyltrimethoxysilane, followed by etching the microdots to yield the microwells array. Furthermore, the DNA capture probes with silver-binding G sequences were covalently bound onto the functionalized microwells to hybridize with targeting miRNAs. Exonuclease I catalytic digestion was then conducted to remove any single-strand DNA probes unhybridized. Eventually, AgNCs were applied to specifically recognize the G sequences of DNA probes survived to be further coated with MOFs of zeolitic imidazolate framework (ZIF-8). Unexpectedly, the red fluorescence of AgNCs probes could be dramatically enhanced due to the "electron-donor effect" of nitrogen-containing ligands of ZIF-8 coatings, together with improved sensing stability. High detection sensitivity and reproducibility could thereby be expected for detecting miRNAs in the blood with the concentrations linearly ranging from 0.175 to 500 pM. Markedly different from the common sandwiched DNA detection methods, the developed fluorimetric strategy using AgNCs coated with MOFs and DNA probes designed with silver-recognizing sequences would be tailored for quantifying various kinds of short-chain miRNAs with low levels in the complicated blood media.