Point-of-care testing detection methods for COVID-19

A simple and innovative sample preparation method for on-site SARS-CoV-2 molecular diagnostics

Nucleic acid amplification is a widely used diagnostic tool, although it requires a relatively time-consuming and complicated extraction step. To address this issue outside the laboratory, we investigated a sample preparation system and determined that a silica membrane and silica-coated beads are powerful tools for the extraction from raw samples: nucleic acids are kept in the silica membrane, retained during a single wash step, and released at the elution step. The eluent is appropriate for the quantitative real-time polymerase chain reaction (qPCR) and loop-mediated amplification (LAMP) assay in terms of purity and quantity. We also built an innovative equipment-free nucleic acid extraction squeeze system which requires less than 20 min. The sample with improved purity augments the specificity and sensitivity. This system is simple, user-friendly, low-cost, and equipment-free, thus making nucleic acid extraction more accessible and affordable for researchers and untrained users. Furthermore, when combined with the reverse-transcription quantitative real-time polymerase chain reaction method, the method will accelerate the detection of diseases. The same goes when combined with the LAMP assay, especially in developing countries.

Quality Management for Point-Of-Care Testing of Pathogen Nucleic Acids: Chinese Expert Consensus

COVID-19 continues to circulate globally in 2021, while under the precise policy implementation of China's public health system, the epidemic was quickly controlled, and society and the economy have recovered. During the pandemic response, nucleic acid detection of SARS-CoV-2 has played an indispensable role in the first line of defence. In the cases of emergency operations or patients presenting at fever clinics, nucleic acid detection is required to be performed and reported quickly. Therefore, nucleic acid point-of-care testing (POCT) technology for SARS-CoV-2 identification has emerged, and has been widely carried out at all levels of medical institutions. SARS-CoV-2 POCT has served as a complementary test to conventional polymerase chain reaction (PCR) batch tests, thus forming an experimental diagnosis platform that not only guarantees medical safety but also improves quality services. However, in view of the complexity of molecular diagnosis and the biosafety requirements involved, pathogen nucleic acid POCT is different from traditional blood-based physical and chemical index detection. No guidelines currently exist for POCT quality management, and there have been inconsistencies documented in practical operation. Therefore, Shanghai Society of Molecular Diagnostics, Shanghai Society of Laboratory Medicine, Clinical Microbiology Division of Shanghai Society of Microbiology and Shanghai Center for Clinical Laboratory have cooperated with experts in laboratory medicine to generate the present expert consensus. Based on the current spectrum of major infectious diseases in China, the whole-process operation management of pathogen POCT, including its application scenarios, biosafety management, personnel qualification, performance verification, quality control, and result reporting, are described here. This expert consensus will aid in promoting the rational application and robust development of this technology in public health defence and hospital infection management.

Mix-and-read, one-minute SARS-CoV-2 diagnostic assay: development of PIFE-based aptasensor

We developed a one-minute, one-step SARS-CoV-2 antigen assay based on protein-induced fluorescence enhancement of a DNA aptamer. The system showed significant selectivity and sensitivity towards both nucleocapsid protein and SARS-CoV-2 virus lysate, but with marked improvements in speed and manufacturability. We hence propose this platform as a mix-and-read testing strategy for SARS-CoV-2 that can be applied to POC diagnostics in clinical settings, especially in low- and middle-income countries.

A Novel Rapid Test to Detect Anti-SARS-CoV-2 N Protein IgG Based on Shear Horizontal Surface Acoustic Wave (SH-SAW)

Since the Coronavirus disease 2019 (COVID-19) pandemic outbreak, many methods have been used to detect antigens or antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), including viral culture, nucleic acid test, and immunoassay. The shear-horizontal surface acoustic wave (SH-SAW) biosensor is a novel pathogen detection platform with the advantages of high sensitivity and short detection time. The objective of this study is to develop a SH-SAW biosensor to detect the anti-SARS-CoV-2 nucleocapsid antibody. The rabbit sera collected from rabbits on different days after SARS-CoV-2 N protein injection were evaluated by SH-SAW biosensor and enzyme-linked immunosorbent assay (ELISA). The results showed that the SH-SAW biosensor achieved a high correlation coefficient (R = 0.9997) with different concentrations (34.375–1100 ng/mL) of the “spike-in” anti-N protein antibodies. Compared to ELISA, the SH-SAW biosensor has better sensitivity and can detect anti-N protein IgG signals earlier than ELISA on day 6 (p < 0.05). Overall, in this study, we demonstrated that the SH-SAW biosensor is a promising platform for rapid in vitro diagnostic (IVD) testing, especially for antigen or antibody testing.

A Portable Device for LAMP Based Detection of SARS-CoV-2

This paper reports the design, development, and testing of a novel, yet simple and low-cost portable device for the rapid detection of SARS-CoV-2. The device performs loop mediated isothermal amplification (LAMP) and provides visually distinguishable images of the fluorescence emitted from the samples. The device utilises an aluminium block embedded with a cartridge heater for isothermal heating of the sample and a single-board computer and camera for fluorescence detection. The device demonstrates promising results within 20 min using clinically relevant starting concentrations of the synthetic template. Time-to-signal data for this device are considerably lower compared to standard quantitative Polymerase Chain Reaction(qPCR) machine (~10–20 min vs. >38 min) for 1 × 10² starting template copy number. The device in its fully optimized and characterized state can potentially be used as simple to operate, rapid, sensitive, and inexpensive platform for population screening as well as point-of-need severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) detection and patient management.

Rapid and Efficient Detection of the SARS-CoV-2 Spike Protein Using an Electrochemical Aptamer-Based Sensor

The availability of sensors able to rapidly detect SARS-CoV-2 directly in biological fluids in a single step would allow performing massive diagnostic testing to track in real time and contain the spread of COVID-19. Motivated by this, here, we developed an electrochemical aptamer-based (EAB) sensor able to achieve the rapid, reagentless, and quantitative measurement of the SARS-CoV-2 spike (S) protein. First, we demonstrated the ability of the selected aptamer to undergo a binding-induced conformational change in the presence of its target using fluorescence spectroscopy. Then, we engineered the aptamer to work as a bioreceptor in the EAB platform and we demonstrated its sensitivity and specificity. Finally, to demonstrate the clinical potential of the sensor, we tested it directly in biological fluids (serum and artificial saliva), achieving the rapid (minutes) and single-step detection of the S protein in its clinical range.

Deciphering the role of nanostructured materials in the point-of-care diagnostics for COVID-19: a comprehensive review

The infamous COVID-19 outbreak has left a crippling impact on the economy, healthcare infrastructure, and lives of the general working class, with all the scientists determined to find suitable and efficient diagnostic techniques and therapies to contain its ramifications. This article presents the complete outline of the diagnostic platforms developed using nanoparticles in the detection of SARS-CoV-2, delineating the direct and indirect use of nanomaterials in COVID-19 diagnosis. The properties of nanostructured materials and their relevance in the development of novel point-of-care diagnostic approaches for COVID-19 are highlighted. More importantly, the advantages of nanotechnologies over conventional reverse transcriptase-polymerase chain reaction technique and few other methods used in the detection of SARS-CoV-2 along with the viewpoints are discussed. Also, the future perspectives highlighting the commercial aspects of the nanotechnology-based diagnostic tools developed to combat the COVID-19 pandemic are presented.

Pushing the detection limits: strategies towards highly sensitive optical-based protein detection

Proteins are one of the main constituents of living cells. Studying the quantities of proteins under physiological and pathological conditions can give valuable insights into health status, since proteins are the functional molecules of life. To be able to detect and quantify low-abundance proteins in biofluids for applications such as early disease diagnostics, sensitive analytical techniques are desired. An example of this application is using proteins as biomarkers for detecting cancer or neurological diseases, which can provide early, lifesaving diagnoses. However, conventional methods for protein detection such as ELISA, mass spectrometry, and western blotting cannot offer enough sensitivity for certain applications. Recent advances in optical-based micro- and nano-biosensors have demonstrated promising results to detect proteins at low quantities down to the single-molecule level, shining lights on their capacities for ultrasensitive disease diagnosis and rare protein detection. However, to date, there is a lack of review articles synthesizing and comparing various optical micro- and nano-sensing methods of enhancing the limits of detections of the antibody-based protein assays. The purpose of this article is to critically review different strategies of improving assay sensitivity using miniaturized biosensors, such as assay miniaturization, improving antibody binding capacity, sample purification, and signal amplification. The pros and cons of different methods are compared, and the future perspectives of this research field are discussed.

Current state of diagnostic, screening and surveillance testing methods for COVID-19 from an analytical chemistry point of view

Since December 2019, we have been in the battlefield with a new threat to the humanity known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this review, we describe the four main methods used for diagnosis, screening and/or surveillance of SARS-CoV-2: Real-time reverse transcription polymerase chain reaction (RT-PCR); chest computed tomography (CT); and different complementary alternatives developed in order to obtain rapid results, antigen and antibody detection. All of them compare the highlighting advantages and disadvantages from an analytical point of view. The gold standard method in terms of sensitivity and specificity is the RT-PCR. The different modifications propose to make it more rapid and applicable at point of care (POC) are also presented and discussed. CT images are limited to central hospitals. However, being combined with RT-PCR is the most robust and accurate way to confirm COVID-19 infection. Antibody tests, although unable to provide reliable results on the status of the infection, are suitable for carrying out maximum screening of the population in order to know the immune capacity. More recently, antigen tests, less sensitive than RT-PCR, have been authorized to determine in a quicker way whether the patient is infected at the time of analysis and without the need of specific instruments.

Detection of SARS-CoV-2 at the point of care

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of COVID-19. Testing for SARS-CoV-2 infection is a critical element of the public health response to COVID-19. Point-of-care (POC) tests can drive patient management decisions for infectious diseases, including COVID-19. POC tests are available for the diagnosis of SARS-CoV-2 infections and include those that detect SARS-CoV-2 antigens as well as amplified RNA sequences. We provide a review of SARS-CoV-2 POC tests including their performance, settings for which they might be used, their impact and future directions. Further optimization and validation, new technologies as well as studies to determine clinical and epidemiological impact of SARS-CoV-2 POC tests are needed.

Rapid PCR powered by microfluidics: A quick review under the background of COVID-19 pandemic

PCR has been widely used in different fields including molecular biology, pathogen detection, medical diagnosis, food detection and etc. However, the difficulty of promoting PCR in on-site point-of-care testing reflects on challenges relative to its speed, convenience, complexity, and even cost. With the emerging state-of-art of microfluidics, rapid PCR can be achieved with more flexible ways in micro-reactors. PCR plays a critical role in the detection of SARS-CoV-2. Under this special background of COVID-19 pandemic, this review focuses on the latest rapid microfluidic PCR. Rapid PCR is concluded in two main features, including the reactor (type, size, material) and the implementation of thermal cycling. Especially, the compromise between speed and sensitivity with microfluidic PCR is explored based on the system ratio of (thermal cycling time)/(reactor size). Representative applications about the detection of pathogens and SARS-CoV-2 viruses based on rapid PCR or other isothermal amplification are discussed as well.

Stretch-driven microfluidic chip for nucleic acid detection

Molecular diagnosis is an essential means to detect pathogens. The portable nucleic acid detection chip has excellent prospects in places where medical resources are scarce, and it is also of research interest in the field of microfluidic chips. Here, the article developed a new type of microfluidic chip for nucleic acid detection where stretching acts as the driving force. The sample entered the chip by applying capillary force. The strain valve was opened under the action of tensile force, and the spring pump generated the power to drive the fluid to flow to the detection chamber in a specific direction. The detection of coronavirus disease 2019 (COVID-19) was realized on the chip. The RT-LAMP amplification system was adopted to observe the liquid color in the detection chamber to decide whether the sample tested positive or negative qualitatively.