The Cu Nanocluster-Sensitized and Filter-Concentrated Strategy for Rapid and Ultrasensitive Naked-Eyed Colorimetric Detection of Pathogens

The urgent need for rapid, low-cost pathogen diagnostics in resource-limited settings drives the development of point-of-care technologies that balance sensitivity, specificity, simplicity, and cost. Here, we present a biosensing platform by integrating an aptamer-poly-T DNA strand for rapidly loading copper nanoclusters (Cu NCs) on the target pathogen and size-exclusion filtration to concentrate the pathogen onto a membrane, enabling ultrasensitive visual detection of low-abundance pathogens within 20 min by naked eyes. The aptamer domain enables the pathogen-specific recognition (validated by <i>Salmonella</i> and SARS-CoV-2 pseudovirus), while the poly-T template facilitates the rapid (<5 min) loading of Cu NCs to the target. The Cu NC-labeled target pathogens were then concentrated on the membrane, while the matrix interferents (salts, proteins), as well as the unbound Cu NCs can be washed away from the membrane due to their relatively small sizes. The efficient release of thousands of Cu²⁺ from the Cu NCs enables the sensitive coloration of the membrane in the presence of TEA, yielding a 10,000-fold sensitivity gain over colloidal gold assays. This cascaded mechanism achieves a detection limit of 10 particles/μL in undiluted serum. The sensing platform is applicable to other biological particles such as exosomes (cancer biomarkers) with low cost (a per-test cost < $1). By merging molecular specificity with field-deployable robustness, this technology redefines decentralized diagnostics for emerging bacterial or viral threats, offering transformative potential for epidemic surveillance and precision public health interventions.