A Sensitive Sensor for Silver Ion Detection Based on FRET and Microfluidic Chip Using a Dual-Color Fluorescence Strategy

Simple, sensitive, and cost-effective detection of Ag+ is important for environmental safety. A dual-color fluorescence sensor based on fluorescence resonance energy transfer (FRET) and cytosine (C)-silver ion (Ag+)-cytosine (C–Ag+–C) structures was developed for the detection of Ag+ on a microfluidic chip. The sensor leverages the high selective binding affinity of cytosine for Ag+ to form C–Ag+–C structures, inducing a transition from single-stranded to double-stranded DNA structures. This transition shortens the distance between fluorescently labeled groups on the DNA chains, triggering the FRET effect and enabling sensitive detection of Ag+. The FRET effect requires spectral overlap between the donor’s emission and the acceptor’s excitation spectra, ensuring energy transfer occurs only between target molecules, effectively reducing nonspecific reactions and background fluorescence interference. Additionally, the microfluidic chip design of the sensor allows for parallel detection of multiple samples, significantly reducing reagent consumption and enhancing detection efficiency. The sensor exhibits excellent performance for Ag+ detection, with a detection range of 1 pM to 10 nM and a limit of detection as low as 0.17 pM. The sensor’s application potential extends beyond Ag+. Its structure can be adjusted to detect other ions by modifying DNA base pairs and optimizing fluorescent probe combinations, demonstrating good versatility. This sensing strategy, which does not require toxic solvents and offers rapid response, provides an economical and effective method for the field of biomolecule detection with broad application prospects.