Ultrafast Plasmonic Nanocavity Thermocycler for Direct Real-Time Reverse Transcription PCR at a Point-of-Care Level

Rapid molecular diagnostics remain constrained by two fundamental bottlenecks: nucleic acid extraction and slow thermocycling, which together limit true point-of-care deployment. Here we report ultrafast plasmonic nanocavity thermocycler (PNT) for direct real-time reverse transcription PCR (DRT-qPCR) at a point-of-care level. The PNT features a plasmonic nanocavity of clustered Au, silicon dioxide (SiO₂), and Au thin film, with Pt resistance temperature detector and a white light-emitting diode (WLED). Under WLED illumination, the PNT shows highly efficient photothermal conversion with rapid heating (20.4 °C/s) and cooling (7.5 °C/s) rates, completing 40 thermocycles in 269 s. The PNT is compactly integrated with a microlens array fluorescence camera and a disposable PCR cartridge into a palm-sized real-time PCR system. The DRT-qPCR completes sample preparation, reverse transcription, and PCR amplification in less than 15 min, achieving amplification efficiency comparable to a commercial benchtop PCR machine. Clinical validation with 60 SARS-CoV-2 samples demonstrates 87.1% sensitivity, 100% specificity, and 93.3% diagnostic accuracy, with all false negatives successfully detected upon retesting. The PNT-based DRT-qPCR can provide a precise and scalable solution for rapid molecular diagnostics in decentralized and time-sensitive settings across diverse infectious diseases.