MicroRNAs are small RNAs which regulate gene expression by translational repression or degradation of messenger RNAs. Regards to important role of these biomolecules in human disease progress, to produce sensitive, simple and cost-effective assays for microRNAs are in urgent demand. miR-137 in Alzheimer's patients has demonstrated its potential as non-invasive biomarkers in blood for Alzheimer's disease diagnosis and prognosis. This paper describes a novel, sensitive and specific microRNA assay based on Colorimetric detection of gold nanoparticles and hybridization chain reaction amplification (HCR). The new strategy eliminates the need for enzymatic reactions, chemical changes, separation processes and sophisticated equipment. The detection process is visible with the naked eyes and detection limit for this method is 0.25nM which is less than or at least comparable with the previous methods based on colorimetric of AuNPs. The important features of this method are high sensitivity and specificity to differentiate between perfectly matched, mismatched and non-complementary target microRNAs and also decent response in the real sample analysis with blood plasma. In conclusion, the simple and fast nanobiosensor can clinically be used for the early detection of Alzheimer's disease by direct detection of the plasma miR-137 in real clinical samples, without a need for sample preparation, RNA extraction and/or amplification.
Keywords: Alzheimer’s disease; Colorimetric; Gold nanoparticles; Hybridization Chain Reaction; Nanobiosensor; microRNAs.