Ultrafast, Sensitive, and Portable Detection of COVID-19 Antibody IgG Using Flexible Organic Electrochemical Transistors for Post-Pandemic Monitoring
To curb the outbreak of COVID-19 and its continued spread, antibody testing is essential for infection diagnosis, seroepidemiological analysis and vaccine evaluation which takes key role in this protracted battle. However current antibody detection techniques remain difficult in achieving accuracy and portability simultaneously. PolyU researcher has developed an ultrafast, accurate and portable SARS-CoV-2 immunoglobulin G (IgG) detection platform based on organic electro-chemical transistors (OECTs), which provides effective antibody testing to show evidence of response to vaccination or previous infections.
In addition to serum-based assays, SARS-CoV-2 IgG can be detected in saliva with advantages of non-invasive process and the possibility of self-collection of samples. OECT-based biosensors have the advantages of high sensitivity, low cost, easy fabrication, and mechanical flexibility and are suitable for high-throughput and multiplexing detections of biomarkers. The gate electrodes of the OECTs are modified with SARS-CoV-2 spike proteins that can selectively capture the antibody IgG through the specific antibody-antigen reaction. The positively charged IgG molecules in aqueous solutions form electrical dipoles on gate surfaces and modulate the channel currents of the OECTs.
By optimizing the measurement conditions, including electrolyte ion concentration and pH value, the device can detect SARS-CoV-2 IgG with an ultralow detection limit of 1fM in aqueous solutions and 10fM in serum and saliva. The ultralow detection limit in saliva can also satisfy the needs of exquisite analytical sensitivity. The detection range in serum is from 10fM to 100nM, which encompasses the range of serum SARS-CoV-2 IgG levels in humans. These portable sensors show promise for use in diagnosis and prognosis of COVID-19. To accelerate the testing process, the research team has developed a novel technique by applying voltage pulses on the gate during incubation, which can decrease the incubation time of about 50%. The whole test time can be completed within 5 min due to the rapid reaction of antigens and antibodies and the label-free approach.
In view of the application on point-of-care testing and screening of large populations, the device is connected to a wireless portable meter consists of a microcontroller, OECT-based sensor, and Bluetooth transmission system, thus the testing process can be remotely operated and reviewed with a mobile phone via Bluetooth. It is expected that the biosensors can also be used in the fast detections of many other diseases that may generate antibodies. The team plans to develop this technology into products that can be used for fast and disposable antibody tests.
