Chip-based visual detection of microRNA using DNA-functionalized gold nanoparticles

In the present study, we developed a highly sensitive and convenient biosensor consisting of gold nanoparticle (AuNP) probes and a gene chip to detect microRNAs (miRNAs). Specific oligonucleotides were attached to the glass surface as capture probes for the target miRNAs, which were then detected via hybridization to the AuNP probes. The signal was amplified via the reduction of HAuCl₄ by H₂O₂. The use of a single AuNP probe detected 10 pmol L^-1 of target miRNA. The recovery rate for miR-126 from fetal bovine serum was 81.5%–109.1%. The biosensor detection of miR-126 in total RNA extracted from lung cancer tissues was consistent with the quantitative PCR (qPCR) results. The use of two AuNP probes further improved the detection sensitivity such that even 1 fmol L^-1 of target miR-125a-5p was detectable. This assay takes less than 1 h to complete and the results can be observed by the naked eye. The platform simultaneously detected lung cancer related miR-126 and miR-125a-5p. Therefore, this low cost, rapid, and convenient technology could be used for ultrasensitive and robust visual miRNA detection.