A fluorescence and colorimetric dual-mode biosensor based on the catalytic activity of gold nanoparticles and magnetic upconversion nanoparticles for the detection of microRNAs

The overexpression of microRNA-21 (miRNA-21) is closely associated with gastric cancer (GC) and may be used as a biomarker to diagnose GC early. Here, a colorimetry and fluorescence dual-mode biosensor for the detection of miRNA-21 was developed from polydopamine-coated magnetic upconversion nanoparticles (Fe₃O₄@UCNP@PDA) and aptamer-modified gold nanoparticles (AuNP-apt). The strong adsorption of single-stranded DNA by PDA results in close proximity between the energy donors (UCNPs) and acceptors (AuNPs), resulting in luminescence quenching of the UCNPs. The miRNA-21 can hybridize with the apt-conjugated AuNPs, and the AuNPs move away from the UCNPs, which results in the luminescence recovery of the UCNPs and the catalytic activity of the AuNPs. After H₂O₂ and tetrapaminophenylethylene were added, the yellow solution turned green and gradually deepened with increasing miRNA-21 concentration. Under optimal conditions, the detection limits of miRNA-21 by fluorescence and colorimetry assays are 8.90 pM and 185 pM, respectively. In addition, the developed approach was utilized to measure miRNA-21 in serum samples, and the recovery rates ranged from 105.4-107.1% and 98.5–109.3%, respectively. The above results indicate great promise for the early diagnosis of GC because of its high sensitivity and selectivity.