RESUMEN
A novel coronavirus (severe acute respiratory syndrome coronavirus 2, SARS-CoV-2) emerged in late 2019, causing an outbreak of pneumonia [coronavirus disease 2019 (COVID-19)] in Wuhan, China, which then rapidly spread globally. Although the use of ready-made reaction mixes can enable more rapid PCR-based diagnosis of COVID-19, the need to transport and store these mixes at low temperatures presents challenges to already overburdened logistics networks. Here, we present an optimized freeze-drying procedure that allows SARS-CoV-2 PCR mixes to be transported and stored at ambient temperatures, without loss of activity. Additive-supplemented PCR mixes were freeze-dried. The residual moisture of the freeze-dried PCR mixes was measured by Karl-Fischer titration. We found that freeze-dried PCR mixes with [~]1.2% residual moisture are optimal for storage, transport, and reconstitution. The sensitivity, specificity, and repeatability of the freeze-dried reagents were similar to those of freshly prepared, wet reagents. The freeze-dried mixes retained activity at room temperature (18[~]25{degrees}C) for 28 days, and for 14 and 10 days when stored at 37{degrees}C and 56{degrees}C, respectively. The uptake of this approach will ease logistical challenges faced by transport networks and make more cold storage space available at diagnosis and hospital laboratories. This method can also be applied to the generation of freeze-dried PCR mixes for the detection of other pathogens.
RESUMEN
Point-of-care testing (POCT) is a test method performed on the sampling site or patient bedside. Accurate results can be achieved rapidly by the application of portable analytical instruments and compatible reagents. It has been widely used in the field of in vitro diagnosis (IVD). Paper-based microfluidics technology has great potential in developing POCT due to its advantages in low cost, simple operation, rapid detection, portable equipment, and unrestricted application conditions. In recent years, the development of paper-based microfluidic technology and its integration with various new technologies and methods have promoted the substantial development of POCT technology and methods. The classification and characteristic of the paper are summarized in this review. Paper-based microfluidic sample pretreatment methods, the flow control in the process of reaction and the signal detecting and analyzing methods for the testing results are introduced. The research progress of various kinds of microfluidic paper-based analytical devices (μPADs) toward POCT in recent years is reviewed. Finally, remaining problems and the future prospects in POCT application of paper-based microfluidics are discussed.