Abstract
Multiplex assays for detection of biomarkers, provide advantageous analyses of different factors related to diagnoses of diseases. The Alzheimer's disease (AD) is one of the most common disease in old people in societies which is increasing, significantly. A group of microRNAs (miRNAs) play an important role in developing the disease which can be considered as early stage biomarkers. Since, selective, sensitive, simple and rapid method for detection of these miRNAs in a single test is critical for early diagnosis and efficient therapy of the disease, herein, we report a sensitive fluorescence assay based on enzyme-free and isothermal hybridization chain reaction with SYBR Green and graphene oxide (GOX) for early detection of miR-137 and miR-142, as two Alzheimer's biomarkers. Fluorescence spectrophotometry based on SYBR Green signal and GOX as the fluorescence quencher was used for detection and quantification of targets' miRNAs and change in fluorescence intensity due to absence and presence of the targets was measured. The limit of detection in the newly designed nanobiosensor was achieved as 82 pM with a sensitive detection of the miRNAs from 0.05 to 5 nM, that is critical for detecting the biomarkers. Given the real range of concentrations of miRNAs in blood (from nanomolar to femtomolar values), the method holds great promise in dual and multiple targets detection due to its sensitivity, rapidness, inexpensive and specificity which provides a convenient detection method of Alzheimer's in early stage.