Ready-To-Use Microwave Sensor Modified by Antibody-AuNPs Nanoconjugate for Highly Sensitive and Selective Detection of the SARS-CoV-2 Virus

The COVID-19 outbreak has led to notable developments in point-of-care (POC) diagnostic devices, as they can be valuable resources in identifying and managing the spread of the pandemic. Currently, the majority of techniques demand advanced laboratory equipment and professionals to execute precise, efficient, accurate, and sensitive testing. In this work, we report a new method to significantly enhance the sensitivity of microwave sensing of the SARS-CoV-2 virus by functionalizing the sensor surface using anti-SARS-CoV-2 spike antibody-gold nanoparticle (AuNPs) conjugates. AuNPs were surface-functionalized with the antispike antibody by EDC/NHS chemistry via PEG as a linker to form the conjugate (Ab-PEG-AuNPs). The Ab-PEG-AuNPs nanoconjugate was then coated onto the sensor through APTES and used for selectively capturing the spike protein on the SARS-CoV-2 virus. The sensing performance of the modified sensor was demonstrated via both experimental measurements and numerical simulations. Our sensor exhibited high sensitivity, achieving a limit of detection of 1,000 copies/mL of the SARS-CoV-2 virus within a 60 min time frame while requiring a minimal sample volume of 100 μL. The sensor exhibits outstanding specificity in distinguishing SARS-CoV-2 from other viruses, including influenza A and B, SARS-CoV-1, and MERS-CoV. Overall, this sensor provides a sensitive and label-free alternative for COVID-19 POC diagnosis.