Rapid detection of SARS-CoV-2 with a mobile device based on pulse controlled amplification

In the past, vast research has been conducted on biosensors and point-of-care (PoC) diagnostics. Despite rapid advances especially during the SARS-CoV-2 pandemic in this research field a low-cost molecular biosensor exhibiting the user-friendliness of a rapid antigen test, and also the sensitivity and specificity of a PCR test, has not been developed yet. To this end we developed a novel microfluidics based and handheld PoC device, that facilitates viral detection at PCR sensitivity and specificity in less than 40 min, including 15 min sample preparation. This was attained by incorporation of pulse controlled amplification (PCA), a method which uses short electrical pulses to rapidly increase the temperature of a small fraction of the sample volume. In this work, we present a low-cost PCA device with a microfluidic consumable intended for the use in a decentralized or home-setting. We used finite element analysis (FEA) simulations to display the fundamental principle and highlight the critical parameter dependency of PCA, such as pulse length and resistor shape. Furthermore, we integrated a simple and fast workflow for sample preparation and evaluated the limit of detection (LoD) for SARS-CoV-2 viral RNA, which is 0.88 copies/μL (=44 copies/reaction), and thus, comparable to conventional RT-qPCR. Additionally, target specificity of the device was validated. Our device and PCA approach enables cost-effective, rapid and mobile molecular diagnostics while remaining highly sensitive and specific.