Conventional and Microfluidic Methods for the Detection of Nucleic Acid of SARS-CoV-2

A SAW-Based Programmable Controlled RNA Detecting Device: Rapid In Situ Cytolysis-RNA Capture-RNA Release-PCR in One Mini Chamber

Viral RNA detection is crucial in preventing and treating early infectious diseases. Traditional methods of RNA detection require a large amount of equipment and technical personnel. In this study, proposed a programmable controlled surface acoustic wave (SAW)-based RNA detecting device has been proposed. The proposed device can perform the entire viral RNA detection process, including cell lysis by cell-microparticle collision through SAW-induced liquid whirling, RNA capture by SAW-suspended magnetic beads, RNA elution through SAW-induced high streaming force, and PCR thermal cycling through SAW-generated heat. The device has completed all RNA detection steps in one mini chamber, requiring only 489 µl reagents for RNA extraction, much smaller than the amount used in manual RNA extraction (2065 µl). The experimental results have shown that PCR results from the device are comparable to those achieved via commercial qPCR instrumental detection. This work has demonstrated the potential of SAW-based lab-on-a-chip devices for point-of-care testing and provided a novel approach for rapidly detecting infectious diseases.

On-Chip Nucleic Acid Purification Followed by ddPCR for SARS-CoV-2 Detection

We developed a microfluidic chip integrated with nucleic acid purification and droplet-based digital polymerase chain reaction (ddPCR) modules to realize a 'sample-in, result-out' infectious virus diagnosis. The whole process involved pulling magnetic beads through drops in an oil-enclosed environment. The purified nucleic acids were dispensed into microdroplets by a concentric-ring, oil-water-mixing, flow-focusing droplets generator driven under negative pressure conditions. Microdroplets were generated with good uniformity (CV = 5.8%), adjustable diameters (50-200 μm), and controllable flow rates (0-0.3 μL/s). Further verification was provided by quantitative detection of plasmids. We observed a linear correlation of R² = 0.9998 in the concentration range from 10 to 10⁵ copies/μL. Finally, this chip was applied to quantify the nucleic acid concentrations of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The measured nucleic acid recovery rate of 75 ± 8.8% and detection limit of 10 copies/μL proved its on-chip purification and accurate detection abilities. This chip can potentially be a valuable tool in point-of-care testing.

Application of microfluidic technologies on COVID-19 diagnosis and drug discovery

The ongoing coronavirus disease 2019 (COVID-19) pandemic has boosted the development of antiviral research. Microfluidic technologies offer powerful platforms for diagnosis and drug discovery for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnosis and drug discovery. In this review, we introduce the structure of SARS-CoV-2 and the basic knowledge of microfluidic design. We discuss the application of microfluidic devices in SARS-CoV-2 diagnosis based on detecting viral nucleic acid, antibodies, and antigens. We highlight the contribution of lab-on-a-chip to manufacturing point-of-care equipment of accurate, sensitive, low-cost, and user-friendly virus-detection devices. We then investigate the efforts in organ-on-a-chip and lipid nanoparticles (LNPs) synthesizing chips in antiviral drug screening and mRNA vaccine preparation. Microfluidic technologies contribute to the ongoing SARS-CoV-2 research efforts and provide tools for future viral outbreaks.

Biomedical Applications of Microfluidic Devices: A Review

Both passive and active microfluidic chips are used in many biomedical and chemical applications to support fluid mixing, particle manipulations, and signal detection. Passive microfluidic devices are geometry-dependent, and their uses are rather limited. Active microfluidic devices include sensors or detectors that transduce chemical, biological, and physical changes into electrical or optical signals. Also, they are transduction devices that detect biological and chemical changes in biomedical applications, and they are highly versatile microfluidic tools for disease diagnosis and organ modeling. This review provides a comprehensive overview of the significant advances that have been made in the development of microfluidics devices. We will discuss the function of microfluidic devices as micromixers or as sorters of cells and substances (e.g., microfiltration, flow or displacement, and trapping). Microfluidic devices are fabricated using a range of techniques, including molding, etching, three-dimensional printing, and nanofabrication. Their broad utility lies in the detection of diagnostic biomarkers and organ-on-chip approaches that permit disease modeling in cancer, as well as uses in neurological, cardiovascular, hepatic, and pulmonary diseases. Biosensor applications allow for point-of-care testing, using assays based on enzymes, nanozymes, antibodies, or nucleic acids (DNA or RNA). An anticipated development in the field includes the optimization of techniques for the fabrication of microfluidic devices using biocompatible materials. These developments will increase biomedical versatility, reduce diagnostic costs, and accelerate diagnosis time of microfluidics technology.