Existing testing strategies for COVID-19 are primarily based on RT-qPCR, serological, or antigen tests. However, the need for rigorous transportation conditions, cold storage for expensive and sensitive reagents such as fluorescent probes, enzymes, primers, antibodies, and complex workflows that require trained operators, hinder the expanded global use of these tests. To address these issues, we have combined the unique characteristics of nanofluidics with resistive pulse sensing to generate a nano-Coulter counter (nCC). To achieve a favorable concentration limit-of-detection, the nCC uniquely consists of five in-plane nanopores of 360 nm effective diameter injection molded into a cyclic olefin polymer substrate. The thermoplastic surface was activated by exposing the chip to UV/O<sub>3</sub> that created surface confined carboxylic acid groups reducing the water contact angle of the surfaces. The sample was driven into the device using hydraulic flow (1 µL/min) with a -5 V bias applied across the nanopores, and the change in current was recorded using a miniaturized transimpedance amplifier circuit. The frequency, amplitude, and half width of current transients gave the concentration, size, and dwell time of the virions, respectively. The LOD for the nCC was 2,500 particles/mL and the entire sample processing was completed in 5 min. We increased the specificity of the enumeration by integrating to the nCC an upstream microfluidic affinity capture and release chip to isolate SARS-CoV-2 virions from patient saliva samples for nCC enumeration. To improve the throughput and limit-of-detection of the device, we modified the fluidic network to have 25 nanopores and integrating the nCC with an affinity microfluidic device packaged into a palm sized instrument with miniaturized electronics, and fluidic cartridge. By using alternative affinity agents for the selection process, the nCC can be used to detect different strains of SARS-CoV-2, seasonal viruses, and even for cancer by enumerating extracellular vesicles.

Label free detection of SARS-CoV-2 virions using a plastic nano-coulter counter chip

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.