Paper-based electrochemical biosensor for diagnosing COVID-19: Detection of SARS-CoV-2 antibodies and antigen.

Collection of nasopharyngeal samples using swabs followed by the transfer of the virus into a solution and an RNA extraction step to perform reverse transcription polymerase chain reaction (PCR) is the primary method currently used for the diagnosis of COVID-19. However, the need for several reagents and steps and the high cost of PCR hinder its worldwide implementation to contain the outbreak. Here, we report a cotton-tipped electrochemical immunosensor for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus antigen. Unlike the reported approaches, we integrated the sample collection and detection tools into a single platform by coating screen-printed electrodes with absorbing cotton padding. The immunosensor was fabricated by immobilizing the virus nucleocapsid (N) protein on carbon nanofiber-modified screen-printed electrodes which were functionalized by diazonium electrografting. The detection of the virus antigen was achieved via swabbing followed by competitive assay using a fixed amount of N protein antibody in the solution. A square wave voltammetric technique was used for the detection. The limit of detection for our electrochemical biosensor was 0.8 pg/mL for SARS-CoV-2, indicating very good sensitivity for the sensor. The biosensor did not show significant cross-reactivity with other virus antigens such as influenza A and HCoV, indicating high selectivity of the method. Moreover, the biosensor was successfully applied for the detection of the virus antigen in spiked nasal samples showing excellent recovery percentages. Thus, our electrochemical immunosensor is a promising diagnostic tool for the direct rapid detection of the COVID-19 virus that requires no sample transfer or pretreatment.

Development of a Low-Cost Cotton-Tipped Electrochemical Immunosensor for the Detection of SARS-CoV-2.

The management of the COVID-19 pandemic has relied on cautious contact tracing, quarantine, and sterilization protocols while we await a vaccine to be made widely available. Telemedicine or mobile health (mHealth) is well-positioned during this time to reduce potential disease spread and prevent overloading of the healthcare system through at-home COVID-19 screening, diagnosis, and monitoring. With the rise of mass-fabricated electronics for wearable and portable sensors, emerging telemedicine tools have been developed to address shortcomings in COVID-19 diagnostics, monitoring, and management. In this Perspective, we summarize current implementations of mHealth sensors for COVID-19, highlight recent technological advances, and provide an overview on how these tools may be utilized to better control the COVID-19 pandemic.

Emerging Telemedicine Tools for Remote COVID-19 Diagnosis, Monitoring, and Management.

The development of new methods for direct viral detection using streamlined and ideally reagent-free assays is a timely and important, but challenging, problem. The challenge of combatting the COVID-19 pandemic has been exacerbated by the lack of rapid and effective methods to identify viral pathogens like SARS-CoV-2 on-demand. Existing gold standard nucleic acid-based approaches require enzymatic amplification to achieve clinically relevant levels of sensitivity and are not typically used outside of a laboratory setting. Here, we report reagent-free viral sensing that directly reads out the presence of viral particles in 5 minutes using only a sensor-modified electrode chip. The approach relies on a class of electrode-tethered sensors bearing an analyte-binding antibody displayed on a negatively charged DNA linker that also features a tethered redox probe. When a positive potential is applied, the sensor is transported to the electrode surface. Using chronoamperometry, the presence of viral particles and proteins can be detected as these species increase the hydrodynamic drag on the sensor. This report is the first virus-detecting assay that uses the kinetic response of a probe/virus complex to analyze the complexation state of the antibody. We demonstrate the performance of this sensing approach as a means to detect, within 5 min, the presence of the SARS-CoV-2 virus and its associated spike protein in test samples and in unprocessed patient saliva.

Detection of SARS-CoV-2 Viral Particles Using Direct, Reagent-Free Electrochemical Sensing.

COVID-19 is an acute respiratory disease caused by SARS-CoV-2, which has high transmissibility. People infected with SARS-CoV-2 can develop symptoms including cough, fever, pneumonia and other complications, which in severe cases could lead to death. In addition, a proportion of people infected with SARS-CoV-2 may be asymptomatic. At present, the primary diagnostic method for COVID-19 is reverse transcription-polymerase chain reaction (RT-PCR), which tests patient samples including nasopharyngeal swabs, sputum and other lower respiratory tract secretions. Other detection methods, e.g., isothermal nucleic acid amplification, CRISPR, immunochromatography, enzyme-linked immunosorbent assay (ELISA) and electrochemical sensors are also in use. As the current testing methods are mostly performed at central hospitals and third-party testing centres, the testing systems used mostly employ large, high-throughput, automated equipment. Given the current situation of the epidemic, point-of-care testing (POCT) is advantageous in terms of its ease of use, greater approachability on the user's end, more timely detection, and comparable accuracy and sensitivity, which could reduce the testing load on central hospitals. POCT is thus conducive to daily epidemic control and achieving early detection and treatment. This paper summarises the latest research advances in POCT-based SARS-CoV-2 detection methods, compares three categories of commercially available products, i.e., nucleic acid tests, immunoassays and novel sensors, and proposes the expectations for the development of POCT-based SARS-CoV-2 detection including greater accessibility, higher sensitivity and lower costs.

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

The outbreak of SARS-CoV-2 is posing serious global public health problems Facing the emergence of this pandemic, we established a portable microfluidic immunoassay system for easy-to-use, sensitive, rapid (<15 min), multiple, and on-site detection of IgG/IgM/Antigen of SARS-CoV-2 simultaneously This integrated method was successfully applied for detecting SARS-CoV-2 IgM and IgG antibodies in clinical human serum as well as SARS-CoV-2 antigen in pharyngeal swabs from 26 patients with COVID-19 infection and 28 uninfected people The assay demonstrated high sensitivity and specificity, which is promising for the diagnosis and monitoring as well as control of SARS-CoV-2 worldwide

Microfluidic Immunoassays for Sensitive and Simultaneous Detection of IgG/IgM/Antigen of SARS-CoV-2 within 15 min.

Washing-free centrifugal microchip fluorescence immunoassay for rapid and point-of-care detection of protein.

The invention relates to a paper diaper with urine test function. The paper diaper comprises a surface waterproof layer, an absorbing layer and a urine insulation layer; a urine test device is also fixed at the outer side of the paper diaper; the urine test device comprises a testing area water-absorbing layer and a urine testing area fixed on the testing area water-absorbing layer; the urine testing area comprises at least one of a urine routine testing area and an acute renal injury testing area; the urine testing area comprises at least one urine routine testing chromogenic block; the acuterenal injury testing area comprises a sample pad, a conjugate release pad, a reaction film and a water absorbing pad which are sequentially connected. The invention also relates to a preparation method of the diaper. Compared with the prior art, the paper diaper prepared by the method can conveniently realize real-time monitoring for urinary tract infection-related diseases and acute renal injury, omits the steps of sampling and adding a sample, and is convenient to use; the paper diaper provided by the invention not only can be used for monitoring the health of infants in a family in real time, but also can be used for monitoring the health of a child patient in a ward of children or a post-discharge child patient, thus discovering the disease state in time.

Paper diaper with urine test function as well as preparation method of paper diaper

The utility model provides a micro -fluidic kit that detects chip and be used for detection of many indexs of whole blood. Detecting the chip and containing two -layerly, the upper strata is the sample preparation layer, and the lower floor is the conversion zone, sample preparation layer orientation the surface of conversion zone is equipped with the fluid passage more than 2, and two -layer inseparable coincide is in order to form inclosed fluid passage system at chip. The kit includes micro -fluidic detection chip. The utility model discloses utilize the micro -fluidic chip technique, detect a plurality of biochemical indexes based on colorimetry survey simultaneously in a small -size test card, like liver function, renal function, blood fat, electrolyte etc. The utility model overcomesthe difficult point that current micro -fluidic technology used, it is low to the check out test set requirement, easily be applied to on -the -spot instant the detection, be applicable to large, medium and small medical institution, emergency department, community hospital, family's detection and scientific research etc..

Micro -fluidic kit that detects chip and be used for detection of many indexs of whole blood

The invention provides a microfluidic detection chip, a kit and a whole blood multi-index detection method based on the same and an application of the microfluidic detection chip. The detection chip comprises two layers, the upper layer is a sample processing layer and the lower layer is a reaction layer, two or more fluid channels are arranged on the surface, facing the reaction layer, of the sample processing layer, and the two layers are closely overlapped to form a closed fluid channel system inside the chip. A plurality of biochemical indexes based on colorimetric measurement, such as liver function, kidney function, blood fat, electrolyte and the like are detected simultaneously in a small test card with a microfluidic chip technology. Difficulties in the application of the existingmicrofluidic technology are overcome, and the chip has low requirements for detection equipment, can be easily applied on site for POCT (point-of-care testing), and is applicable to large, medium andsmall medical institutions, emergency departments, community hospitals, family detection, scientific research and the like.

Wu Jing

Papers

Microfluidic Immunoassays for Sensitive and Simultaneous Detection of IgG/IgM/Antigen of SARS-CoV-2 within 15 min.

Washing-free centrifugal microchip fluorescence immunoassay for rapid and point-of-care detection of protein.

Paper diaper with urine test function as well as preparation method of paper diaper

Micro -fluidic kit that detects chip and be used for detection of many indexs of whole blood

Microfluidic detection chip, kit and whole blood multi-index detection method based on same and application of microfluidic detection chip