A self-powered temperature sensor based on Seebeck effect transduction was designed for photothermal-thermoelectric coupled immunoassay of α-fetoprotein (AFP). In this system, glucose oxidase ...(GOx)-conjugated detection antibody was first captured onto the microplate by target-induced sandwich-type immunoreaction. Thereafter, the as-generated hydrogen peroxide via the GOx-glucose system oxidized 3,3',5,5'-tetrametylbenzidine (TMB) into photothermal product oxidized TMB (ox-TMB). Under near-infrared (NIR) laser irradiation, the temperature change of ox-TMB was read out in an electrical signal by the flexible thermoelectric module in a 3D-printed integrated detection device. Under optimal conditions, the photothermal-thermoelectric coupled immunoassay exhibited a limit of detection of 0.39 ng mL
AFP over a dynamic linear range from 0.5 to 60 ng mL
. Impressively, such a strategy presented herein offers tremendous potentials for applying many other high-efficiency thermoelectric materials in ultrasensitive biosensors.
Nanozymes have great potential to be used as an alternative to natural enzymes in a variety of fields. However, low catalytic activity compared with natural enzymes limits their practical use. It is ...still challenging to design nanozymes comparable to their natural counterparts in terms of the specific activity. In this study, a surface engineering strategy is employed to improve the specific activity of Ru nanozymes using charge‐transferrable ligands such as polystyrene sulfonate (PSS). PSS‐modified Ru nanozyme exhibits a peroxidase‐like specific activity of up to 2820 U mg−1, which is twice that of horseradish peroxidase (1305 U mg−1). Mechanism studies suggest that PSS readily accepts negative charge from Ru, thus reducing the affinity between Ru and ·OH. Importantly, the modified Ru‐peroxidase nanozyme is successfully used to develop an immunoassay for human alpha‐fetoprotein and achieves a 140‐fold increase in detection sensitivity compared with traditional horseradish‐peroxidase‐based enzyme‐linked immunosorbent assay. Therefore, this work provides a feasible route to design nanozymes with high specific activity that meets the practical use as an alternative to natural enzymes.
Surface modification can engineer charge transfer between Ru and ligands and facilitate intermediate radicals to react with colorimetric substrate, which significantly improves the peroxidase‐like activity of Ru nanozymes superior to horseradish peroxidase. Following such a mechanism, polystyrene‐sulfonate‐modified Ru nanozymes can be used as an enzyme alternative in enzyme‐linked immunosorbent assay to improve detection sensitivity up to 140‐fold, validated with human alpha‐fetoprotein.
A paper-based electrochemical immunosensor was developed for the detection of cancer antigen 125 (CA125) by screen-printing technique. The reduced graphene oxide/thionine/gold nanoparticles ...(rGO/Thi/AuNPs) nanocomposites were compounded and coated onto the working electrode of immunosensor for CA125 antibody (anti-CA125) immobilization and detection signal amplification. The detection principle was based on the fact that the immunocomplex formed by specify binding of CA125 antibody and antigen could reduce the current response of thionine, which was proportional to the corresponding concentration of CA125 antigen. The immunoassay results showed that the linear range of CA125 was from 0.1 U mL−1 to 200 U mL−1 with the limit of detection (LOD) of 0.01 U mL−1 at signal to noise of 3. Quality control serum samples measured by our proposed immunosensor showed acceptable agreement with traditional ELISA method with the relative error less than 8.05%. The immunosensor exhibited good electrochemical performance with high reproducibility, reliability, stability and accuracy. The proposed immunosensor could be used for the determination of CA125 and had the potential for point-of-care testing (POCT) of other tumor marker.
•A novel electrochemical immunosensor based on rGO/Thi/AuNPs nanocomposites was developed for the determination of CA125.•The rGO/Thi/AuNPs nanocomposites were synthesized to improve the sensitivity of immunosensor.•The immunosensor showed acceptable agreement with traditional ELISA method in clinical diagnosis.•It could be used for point-of-care testing of tumor markers and had the potential for disease screening in remote region.
A novel enhanced chemiluminescent immunoassay (CLIA) for ultrasensitive and excellent precisive determination of cardiac troponin I (cTnI) was reported. The method made full use of poly(N-isopropyl ...acrylamide)-co-(methacrylic acid) (P(NIPAM-co-MAA)) microspheres as new potential signal enhancers and magnetic fluorescent nanoparticles as internal standards for better precision. This protocol involved a sandwich format, in which the antigen in the sample was captured by the immobilized antibodies on the surface of magnetic fluorescent beads and recognized by the other antibodies labeled with acridinium ester (AE)-loaded P(NIPAM-co-MAA) microspheres. The combination of the remarkable sensitivity of the enhanced CLIA method and the use of P(NIPAM-co-MAA) microspheres as anti-cTnI carriers for acridinium ester signal amplification provided an extremely sensitive limit of blank (LoB) at 0.097 pg mL
, a limit of detection (LoD) at 0.116 pg mL
, and a limit of quantitation (LoQ) at 0.606 pg mL
, much greater than those achieved by the classical chemiluminescence immunoassay (CLIA, Getein). Moreover, the intra-day variable coefficient can be improved to 1.21-2.12%, and inter-day variability was 2.01-3.49% under the application of magnetic fluorescent beads as an internal standard. The sensitivity and precision have reached a high level, comparable with the current commercial detection kits. The results showed a good correlation with a commercial chemiluminescence assay (CLIA, Abbott), with a correlation coefficient of 0.9883. This proposed method has been successfully applied to the clinical determination of cTnI in the human serum.
The ability to rapidly detect viable pathogens in food is important for public health and food safety reasons. Culture-based detection methods, the traditional means of demonstrating microbial ...viability, tend to be laborious, time consuming and slow to provide results. Several culture-independent methods to detect viable pathogens have been reported in recent years, including both nucleic acid–based (PCR combined with use of cell viability dyes or reverse-transcriptase PCR to detect messenger RNA) and phage-based (plaque assay or phage amplification and lysis plus PCR/qPCR, immunoassay or enzymatic assay to detect host DNA, progeny phages or intracellular components) methods. Some of these newer methods, particularly phage-based methods, show promise in terms of speed, sensitivity of detection and cost compared with culture for food testing. This review provides an overview of these new approaches and their food testing applications, and discusses their current limitations and future prospects in relation to detection of viable pathogens in food.
Key points
• Cultural methods may be ‘gold standard’ for assessing viability of pathogens, but they are too slow.
• Nucleic acid–based methods offer speed of detection but not consistently proof of cell viability.
• Phage-based methods appear to offer best alternative to culture for detecting viable pathogens.
Background Coronavirus disease 2019, abbreviated to COVID-19, represents an emerging health threat worldwide as, after initial reports in China, it has continued to spread rapidly. The clinical ...spectrum of the disease varies from mild to severe acute respiratory distress syndrome (ARDS). Moreover, many patients can be asymptomatic, thus increasing the uncertainty of the diagnostic work-up. Laboratory tests play a pivotal role in the diagnosis and management of COVID-19, the current gold standard being real-time reverse transcription polymerase chain reaction (rRT-PCR) on respiratory tract specimens. However, the diagnostic accuracy of rRT-PCR depends on many pre-analytical and analytical variables. The measurement of specific COVID-19 antibodies (both IgG and IgM) should serve as an additional, non-invasive tool for disease detection and management. Methods The imprecision of the MAGLUMI™ 2000 Plus 2019-nCov IgM and IgG assays (Snibe, Shenzhen, China) was assessed by adopting the Clinical and Laboratory Standards Institute (CLSI) EP15-A3 protocol. Linearity of dilution and recovery was evaluated by means of mixes of high-level pools and low-level pools of serum samples. Immunoglobulin time kinetics were evaluated using a series of serum samples, repeatedly collected from COVID-19-positive patients at different times, from <5 days up to 26-30 days. Results Findings at the analytical validation of the assay carried out according to the CLSI EP15-A3 guideline demonstrated that imprecision and repeatability were acceptable (repeatability was <4% and <6% for IgM and IgG, respectively, whilst intermediate imprecision was <6%). In addition, results of dilution and recovery studies were satisfactory. The kinetics of COVID-19 antibodies confirmed previously reported findings, showing a rapid increase of both IgM and IgG after 6-7 days from the symptom onset. IgG had 100% sensitivity on day 12, whilst 88% was the higher positive rate achieved for IgM after the same time interval. Conclusions The findings of this study demonstrate the validity of the MAGLUMI 2000 Plus CLIA assay for the measurement of specific IgM and IgG in sera of COVID-19 patients, and for obtaining valuable data on the kinetics of both (IgM and IgG) COVID-19 antibodies. These data represent a pre-requisite for the appropriate utilization of specific antibodies for the diagnosis and management of COVID-19 patients.
Microfluidics offer economy of reagents, rapid liquid delivery, and potential for automation of many reactions, but often require peripheral equipment for flow control. Capillary microfluidics can ...deliver liquids in a pre-programmed manner without peripheral equipment by exploiting surface tension effects encoded by the geometry and surface chemistry of a microchannel. Here, we review the history and progress of microchannel-based capillary microfluidics spanning over three decades. To both reflect recent experimental and conceptual progress, and distinguish from paper-based capillary microfluidics, we adopt the more recent terminology of capillaric circuits (CCs). We identify three distinct waves of development driven by microfabrication technologies starting with early implementations in industry using machining and lamination, followed by development in the context of micro total analysis systems (μTAS) and lab-on-a-chip devices using cleanroom microfabrication, and finally a third wave that arose with advances in rapid prototyping technologies. We discuss the basic physical laws governing capillary flow, deconstruct CCs into basic circuit elements including capillary pumps, stop valves, trigger valves, retention valves, and so on, and describe their operating principle and limitations. We discuss applications of CCs starting with the most common usage in automating liquid delivery steps for immunoassays, and highlight emerging applications such as DNA analysis. Finally, we highlight recent developments in rapid prototyping of CCs and the benefits offered including speed, low cost, and greater degrees of freedom in CC design. The combination of better analytical models and lower entry barriers (thanks to advances in rapid manufacturing) make CCs both a fertile research area and an increasingly capable technology for user-friendly and high-performance laboratory and diagnostic tests.
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