Rapid fluorescent nucleic acid sensing with ultra-thin gold nanosheets

Fluorescently labeled DNA oligonucleotides and gold nanospheres have been frequently utilized in biosensors, providing efficient nucleic acid detection. Nevertheless, the restricted loading capacity of gold nanospheres undermines overall sensitivity. In this study, we employed four-atom-thick ultrathin gold nanosheets (AuNSs), utilizing a "pre-mix model" for rapid target nucleic acid detection. In this approach, fluorescently labeled DNA probes were pre-incubated with the target nucleic acid, followed by the addition of AuNSs for probe adsorption and fluorescence quenching. With the developed method, we efficiently and rapidly detected the SARS-CoV-2 N gene sequence within 30 min, involving a brief 15-min target pre-incubation and a subsequent 15-min adsorption of free probes and fluorescence quenching by AuNSs. This method exhibited heightened sensitivity compared to gold nanospheres, boasting a limit of detection (LOD) of 0.808 nM. Furthermore, exceptional recovery was achieved in simulated biological samples. The study introduces an effective strategy for nucleic acid sensing characterized by rapidity, heightened sensitivity, ease of operation, and robustness. These findings encourage further development of rapid biomarker sensing methods employing 2D nanomaterials.