NAPTUNE: nucleic acids and protein biomarkers testing via ultra-sensitive nucleases escalation
image: Overview of the NAPTUNE detection process. Probe 1 binds to a specific RNA target, where the enzyme APE1 makes a precise cut, initiating a chain reaction. The resulting DNA fragment activates another enzyme, PfAgo, which then sequentially cuts Probes 2 and 3. Each cutting step releases a fluorescent signal, leading to a stepwise increase in brightness. This cascade allows for highly sensitive detection of the target material.
Credit: Nature Communications
Scientists from the National University of Singapore (NUS) have developed NAPTUNE, short for Nucleic Acids and Protein biomarkers Testing via Ultra-sensitive Nucleases Escalation, a point-of-care assay that identifies trace amounts of disease-related genetic material, including nucleic acid and protein markers, in less than 45 minutes. Importantly, it accomplished this without the need for laboratory equipment or complex procedures.
Lying at the heart of many modern diagnostics, polymerase chain reaction (PCR) and real-time immunoassays provide high accuracy. However, they are hindered by lengthy processing time, the need for specialised thermal cyclers and skilled personnel. These constraints hamper rapid outbreak management, early cancer screening and bedside decision-making, especially in low-resource settings.
NAPTUNE tackles these challenges by replacing bulky amplification steps with a tandem nuclease cascade that converts biological signals directly into readily detectable DNA fragments, streamlining the diagnostic process.
The findings were published in the scientific journal Nature Communications on 4 February 2025.
The study was led by Assistant Professor Chunyi HU from the NUS Department of Biological Sciences, NUS in collaboration with Dr Chuanxia CHEN from the University of Jinan, China and Dr Chuning XU from the Lingang Laboratory Shanghai, China.
A two-enzyme relay boosts sensitivity to the attomolar realm
At the core of the NAPTUNE platform is a two-stage enzymatic system. The first stage uses the human DNA-repair enzyme APE1, which recognises abasic (AP) sites engineered into a reporter duplex and releases 5′-phosphorylated DNA guides. These fragments immediately activate a heat-tolerant Argonaute protein from Pyrococcus furiosus (PfAgo). Acting as the second-stage “booster”, PfAgo cleaves complementary fluorophore-quencher probes in a cascading reaction, producing a fluorescence signal proportional to the concentration of the target. This enzymatic relay improves detection sensitivity from the femtomolar range achieved with APE1 alone to the attomolar (10⁻¹⁸ M) level, setting a new benchmark for amplification-free detection.
A palm-sized device for true point-of-care use
To demonstrate practical deployment, the researchers miniaturised the assay into disposable tubes controlled by a battery-powered heater and a bluetooth-enabled fluorescence reader. Weighing under 200 grams, real-time results are streamed directly from the device to a mobile app, paving the way for on-site virus surveillance, rapid clinical screening and decentralised cancer monitoring.
Asst Prof Hu said, “By chaining two naturally occurring nucleases in an orthogonal circuit, we achieve PCR-class sensitivity without touching a thermocycler. Our vision is to place laboratory-grade diagnostics directly into the hands of community health workers.”
Looking ahead
The team is currently validating NAPTUNE for tuberculosis detection in sputum samples and for wastewater-based surveillance. They are also exploring lyophilised reagent kits suitable for tropical environments and plan to expand the nuclease toolbox to enable electrochemical and lateral-flow readouts, accelerating commercial translation.