Peroxidase-mimicking Prussian blue nanoparticles versus HRP for high colorimetric detection of miRNA-141 in competitive RNA–RNA systems

Rapid and efficient early-stage tumor detection is crucial in cancer diagnostics. Recent research indicates that microRNA-141 expression levels serve as a predictive biomarker for prostate cancer cell count in the human body. In this study, we developed an original competitive system for miRNA-141 detection using Prussian blue nanoparticles (PBNPs), comparing it with a horseradish peroxidase (HRP)-based competitive system for the same target. The competitive system involved miRNA-141 and biotin-miRNA-141 on a magnetic bead-modified capture probe specific to miRNA-141. The synthesized PBNPs were conjugated to avidin, resulting in the formation of avidin–PBNPs. These conjugates were used as a substitute for streptavidin–HRP. The peroxidase-like activity of PBNPs catalyzed the colorimetric substrate (3,3′,5,5′-tetramethylbenzidine), producing a distinct blue color measured at 630 nm. Under optimal conditions, both PBNPs and HRP-based systems exhibited a linear response to miRNA-141 concentrations (50 pM to 300 pM and 80 pM to 500 pM, respectively). Among the two systems investigated in this study, the PBNPs-based bio-assay demonstrated exceptional sensitivity, achieving a remarkably low LOD of 0.61 pM and an analysis time of 32 minutes. These biosensors successfully determined miRNA-141 levels in spiked human serum.