NiCl2@g-C3N4-based Label-free Dual-mode Sensing Platform for Highly Sensitive and Selective Detection of MicroRNA-183-5p in Serum

MicroRNA-183-5p is a clinically relevant biomarker, yet its detection is hindered by short sequence length, high homology, and low abundance in complex biological fluids. We report a hydrothermally synthesized nickel chloride-decorated graphitic carbon nitride (NiCl 2 @g-C 3 N 4 ) with intrinsic peroxidase-like and fluorescence activities for label-free dual-mode detection. Characterized by multiple spectroscopic and microscopic techniques, the nanocomposite enables quantitative analysis via π-π stacking and van der Waals interactions between the probe and target, eliminating the need for enzymes or fluorescent labels. Under optimal conditions, using the formula LOD = 3Sb/b, the detection limit was calculated as 0.69. This material with broad linear ranges, excellent selectivity, month-long stability, and recovery rates of 97.7-101.6% in spiked serum. This facile and cost-effective platform offers a promising tool for sensitive miRNA quantification in clinical diagnostics.