SARS-CoV-2 Surveillance in Indoor Air Using Electrochemical Sensor for Continuous Monitoring and Real-Time Alerts

Abstract

The severe acute respiratory syndrome related coronavirus 2 (SARS-CoV-2) has spread globally and there is still a lack of rapid detection techniques for SARS-CoV-2 surveillance in indoor air. In this work, two test rigs were developed that enable continuous air monitoring for the detection of SARS-CoV-2 by sample collection and testing. The collected samples from simulated SARS-CoV-2 contaminated air were analyzed using an ultra-fast COVID-19 diagnostic sensor (UFC-19). The test rigs utilized two air sampling methods: cyclone-based collection and internal impaction. The former achieved a limit of detection (LoD) of 0.004 cp/L in the air (which translates to 0.5 cp/mL when tested in aqueous solution), lower than the latter with a limit of 0.029 cp/L in the air. The LoD of 0.5 cp/mL using the UFC-19 sensor in aqueous solution is significantly lower than the best-in-class assays (100 cp/mL) and FDA EUA RT-PCR test (6250 cp/mL). In addition, the developed test rig provides an ultra-fast method to detect airborne SARS-CoV-2. The required time to test 250 L air is less than 5 min. While most of the time is consumed by the air collection process, the sensing is completed in less than 2 s using the UFC-19 sensor. This method is much faster than both the rapid antigen (<20 min) and RT-PCR test (<90 min).

Selective Electrochemical Detection of SARS-CoV-2 Using Deep Learning

“…UFC-19 technology is a nickel-based electrochemical sensor that analyzes electrochemical interactions between the sensor probe and SARS-CoV-2 spike proteins contained in saliva or water in the presence of an electrolyte (electrode/electrolyte interface) in less than a second. As described in our previous works, the UFC-19 prototype uses nickel (McMaster-Carr Multipurpose 400 Nickel Rods 1 4 " diameter, one end machined to 2 mm diameter) as the working electrode, and platinum as the counter and pseudo reference electrodes of size 0.02" in diameter with a length of 2.75" and 1.25" respectively (ESPI metals, Ashland, OR, USA; 3N5 purity) [17,18,22]. The UFC-19 prototypes use commercially available sterile 5 mL screw cap vials (Grainger, Lake Forest, IL, USA, Item# 52JV50) for testing and the sample volume, typically 0.2 mL is diluted in a standardized potassium hydroxide solution (0.1 M from ACROS Organics TM , Fair Lawn, NJ, USA, Lot# A0411825) to a total volume 2.0 mL.…”

“…More details about the method can be found in the literature. The working electrode was rotated during testing at 400 rpm to flow the electrolyte containing SARS-CoV-2 towards the electrode surface [17,18,22]. UFC-19 senses the presence of SARS-CoV-2 electrochemically by producing a current response when an electric potential is applied.…”

“…The concentration being tested for all the viruses in the matrix was fixed at 0.1 cp/mL. In our previous work (detection of SARS-CoV-2 in air), we had determined that the limit of detection (LoD) was 0.5 cp/mL in aqueous solution collected after the virus was captured in the sample vial [18]. This LoD was related with the air system being tested and includes the viral losses at different components of the air capturing system.…”

“…The baseline and sample current responses were compared to determine the result. Based on the interaction between SARS-CoV-2 proteins and the electrodes, a higher current response reading was observed especially at the 1 ms point [17,18,22]. The current response examples of baseline (true negative) and SARS-CoV-2 samples with 0.1 cp/mL concentration are shown in Figure 1.…”

“…Ultra-fast COVID-19 Diagnostic Sensor (UFC- 19) is one such alternate sensor based on electrochemical technology which detects the spike protein of SARS-CoV-2 within a second in saliva and water samples [17,18]. Although this sensor was tested for specificity against HIV in the initial stages of pandemic, viruses that closely resemble SARS-CoV-2 were not studied in detail [17].…”