Liquid Crystal Sensor offers breakthrough for rapid COVID-19 diagnostic test

The global outbreak of COVID-19 has prompted scientists to focus their research on rapid and robust diagnostic tests. Reverse-transcription polymerase chain reaction (RT-PCR) assays – the ‘gold-standard’ for molecular clinical diagnostics – became available quickly, however, this provides relatively long characterization times and the need for specialized equipment.

Researchers at OSU have subsequently designed a liquid crystal (LC) based diagnostic kit and a smartphone-based application to enable automatic detection of SARS-CoV-2 ssRNA, which could be used for reliable self-test of SARS-CoV-2 at home without the need for complex equipment or procedures.

Prof Xiaoguang (William) Wang, Ph.D. led the research team at OSU, and commented on his decision to consider LCs as a prospective diagnostic technology to meet the need: “It is well known that thermotropic LCs are ultrasensitive to small chemical modulations, and we felt that we could use this property to develop a rapid LC-based detection method for SARS CoV-2 virus that could be contained in a portable and economical sensor.”

A series of experiments were required to prove this concept and develop a prototype sensor, which included three key steps.

The characterization of a substrate layer that had been ‘functionalized’ with a liquid crystal mixture.

Validation of the reliable binding of an ssDNA ‘probe’ to this layer.

The detection and quantitation of ssRNAcov extracted from the virus as it bound to the probe. 

Important for this last step was holding the temperature of the system at precisely 48.7°C, the melting temperature of ssRNA. The Linkam PE120 stage was integral to this phase and gave the team at OSU the reproducible control of the temperature of the sensor they needed during the process.

The PE120 Peltier system is straightforward to integrate with microscopes and other equipment, and ensures precise control of the temperature of microscope slides to +/-0.1°C at temperatures between 25°C to 120°C.

Prof Wang’s research has recently been published, and it has shown that LC-based sensors offer a highly sensitive, reproducible and robust method of detection of target ssRNAcov – with detection limits in the nanomolar to femtomolar range.

Commenting on the work, Robert Gurney Ph.D., Marketing and Applications Specialist at Linkam Scientific, said: “What Prof Wang and his colleagues have achieved is extremely exciting. It’s great that one of the Linkam temperature control stages has played a key part in the team’s proof-of-concept studies, and I’m looking forward to seeing the results of the next stage – trials of the sensor with patient samples.”

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