Hairpin-Functionalized Gold Nanoparticles as an Adaptable Platform for Detecting MicroRNA Signatures

Early, accurate, and fast diagnosis is essential to ensure positive health outcomes, through effective treatment interventions and disease control, as well as the study of physiological changes related to gene expression. Liquid biopsies and point-of-care (PoC) detection are valuable tools to achieve this goal, allowing the study and monitoring of a patients molecular profile in a timely and simple manner. MicroRNAs (or miRNAs) have been proposed as biomarkers for detection in liquid biopsies, as they are stable in body fluids and their dysregulation is associated with many diseases. In this work, a sensor based on gold nanoparticles (AuNPs) functionalized with oligonucleotides is reported, aiming for the detection of nucleic acids, in particular miRNAs. This sensor is based on the recognition of target sequences by hairpin-shaped oligonucleotide probes, which allows the modulation of the colloidal stability of the AuNPs, producing color changes detectable with the naked eye. The system is used to detect a panel of miRNAs, demonstrating its versatility for the detection of relevant nucleic acid signatures. The sensor detects single miRNAs with good sensitivity and selectivity and, what is more, it can be used to recognize several miRNAs simultaneously at picomolar concentrations. The system was further adapted to a lateral flow assay (LFA) format, producing a visible colored line on lateral flow test strips, and coupled with isothermal amplification to reach femtomolar detection levels. Its properties make it suitable for use in the point-of-care (PoC), contributing to fast and early detection of pathological and physiological molecular profiles.