Fast-responsive and multi-applicable fluorescent turn-off chemodosimeter for monitoring hypochlorite: application to test strips, water samples, disinfectants and bioimaging

Due to the twin-demic of COVID-19 and flu virus, disinfectants containing ClO- have been widely used nowadays. Therefore, it is urgent to develop a sensor capable of efficiently detecting toxic hypochlorite. We present the invention and assessment of a fast-responsive and multi-applicable chemodosimeter sensor ETA (2-(2-((1E,2E)-3-(4-(dimethylamino)phenyl)allylidene)hydrazineyl)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride) for monitoring ClO‑. In pure water, adding ClO- to ETA caused a turn-off fluorescence within 2 sec. These changes made it possible to quickly detect ClO- with a high level of selectivity. ETA displayed a low detection limit (0.68 μM) to ClO-. Using UV-vis titrations, ESI-MS and DFT calculations, we were able to demonstrate the detection mechanism, in which ETA was cleaved by ClO-. In particular, we established the possibility for reliable ClO- detection in environmental systems such as actual water samples, disinfectants, living cells, zebrafish and celery, in addition to confirming the practicality of ETA utilizing test strips.

Silent Antibodies Start Talking: Enhanced Lateral Flow Serodiagnosis with Two-Stage Incorporation of Labels into Immune Complexes.

The presence of pathogen-specific antibodies in the blood is widely controlled by a serodiagnostic technique based on the lateral flow immunoassay (LFIA). However, its common one-stage format with an antigen immobilized in the binding zone of a test strip and a nanodispersed label conjugated with immunoglobulin-binding proteins is associated with risks of very low analytical signals. In this study, the first stage of the immunochromatographic serodiagnosis was carried out in its traditional format using a conjugate of gold nanoparticles with staphylococcal immunoglobulin-binding protein A and an antigen immobilized on a working membrane. At the second stage, a labeled immunoglobulin-binding protein was added, which enhanced the coloration of the bound immune complexes. The use of two separated steps, binding of specific antibodies, and further coloration of the formed complexes, allowed for a significant reduction of the influence of non-specific immunoglobulins on the assay results. The proposed approach was applied for the serodiagnosis using a recombinant RBD protein of SARS-CoV-2. As a result, an increase in the intensity of test zone coloration by more than two orders of magnitude was demonstrated, which enabled the significant reduction of false-negative results. The diagnostic sensitivity of the LFIA was 62.5% for the common format and 100% for the enhanced format. Moreover, the diagnostic specificity of both variants was 100%.

Detection of Antibodies for COVID-19 from Reflectance Spectrum Using Supervised Machine Learning

Since the coronavirus disease 2019 occurred, the lateral flow immunoassay (LFIA) test strip has become a global testing tool for convenience and low cost. However, some studies have shown that LFIA strips perform poorly compared to other professional testing methods. This paper proposes a new method to improve the accuracy of LFIA strips using spectral signals. A spectrochip module is applied to disperse the reflected light from the LFIA strips. The obtained spectral signals will be used for supervised machine learning. After training, the trained model has 93.8% accuracy compared to the standard test. This result indicated that the evaluation method based on the spectrum of LFIA strips could enhance the detection performance. © 2022 IEEE.

Serological survey of SARS-CoV-2 in companion animals in China.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can be transmitted from human to companion animals. The national wide serological surveillance against SARS-CoV-2 was conducted among pet animals, mainly in cats and dogs, 1 year after the first outbreak of COVID-19 in China. All sera were tested for SARS-CoV-2 IgG antibodies using an indirect enzyme linked immunosorbent assay (ELISA) based on the receptor binding domain (RBD) of spike protein. This late survey takes advantage of the short duration of the serological response in these animals to track recent episode of transmission. A total of 20,592 blood samples were obtained from 25 provinces across 7 geographical regions. The overall seroprevalence of SARS-CoV-2 infections in cats was 0.015% (2/13397; 95% confidence intervals (CI): 0.0, 0.1). The virus infections in cats were only detected in Central (Hubei, 0.375%) and Eastern China (Zhejiang, 0.087%) with a seroprevalence estimated at 0.090 and 0.020%, respectively. In dogs, the seroprevalence of SARS-CoV-2 infections was 0.014% (1/7159; 95% CI: 0.0, 0.1) in the entire nation, seropositive samples were limited to Beijing (0.070%) of Northern China with a prevalence of 0.054%. No seropositive cases were discovered in other geographic regions, nor in other companion animals analyzed in this study. These data reveal the circulation of SARS-CoV-2 in companion animals, although transmission of the virus to domestic cats and dogs is low in China, continuous monitoring is helpful for the better understand of the virus transmission status and the effect on animals.

Development of colorimetric cellulose-based test-strip for the rapid detection of antibodies against SARS-CoV2 virus.

Given the pandemic situation, there is an urgent need for an accurate test to monitor antibodies anti-SARS-CoV-2, providing crucial epidemiological and clinical information to monitor the evolution of coronavirus disease in 2019 (COVID-19) and to stratify the immunized and asymptomatic population. Therefore, this paper describes a new cellulose-based test strip for rapid and cost-effective quantitative detection of antibodies to SARS-CoV2 virus by colorimetric transduction. For this purpose, Whatman paper was chemically modified with sodium metaperiodate to introduce aldehyde groups on its surface. Subsequently, the spike protein of the virus is covalently bound by forming an imine group. The chemical control of cellulose paper modification was evaluated by Fourier transform infrared spectroscopy, thermogravimetry and contact angle analysis. Colorimetric detection of the antibodies was performed by a conventional staining method using Ponceau S solution as the dye. Color analysis was performed after image acquisition with a smartphone using Image J software. The color intensity varied linearly with the logarithm of the anti-S concentration (from 10 ng/mL to 1 µg/mL) in 500-fold diluted serum samples when plotted against the green coordinate extracted from digital images. The test strip was selective in the presence of nucleocapsid antibodies, urea, glucose, and bovine serum albumin with less than 15% interference, and detection of antibodies in human serum was successfully performed. Overall, this is a simple and affordable design that can be readily used for mass population screening and does not require sophisticated equipment or qualified personnel. Supplementary Information: The online version contains supplementary material available at 10.1007/s10570-022-04808-y.

Detection of environmentally hazardous hypochlorite in pure water with a novel fluorescent chemosensor: Application to water samples, commercial disinfectants, test strips, and zebrafish

With the increasing use of chlorinated disinfectants or bleaches such as sodium hypochlorite in the coronavirus disease 2019 (COVID-19) pandemic, the effectual detection of toxic hypochlorite is very important. In this study, a novel hydrazide-based fluorescence chemosensor DHT-Cl ((E)-2-(2-(3,5-dichloro-2-hydroxybenzylidene)hydrazinyl)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride) was synthesized. DHT-Cl could selectively detect environmentally hazardous hypochlorite in pure water through a fluorescence turn-off process. The detection limit for hypochlorite was determined to be 0.57 μM. DHT-Cl can monitor hypochlorite with little interference even in the presence of other analytes. Practically, DHT-Cl detected hypochlorite in water samples, commercial disinfectants, test strips, and living zebrafish. The hypochlorite detection mechanism through cleavage of the CN bond was illustrated by 1H NMR spectroscopy titration, ESI-mass spectrometry and quantum calculations.

Technologies of "Dry" Chemistry and their Use for Implementation of Express Analysis at the Patient’s Place of Stay (Review of Modern Information)

The article describes the methodology and technology of laboratory research using the methods of "dry" chemistry that are are implemented using test strips of the first and second generation. The modern information about the design of test systems of different generations and the distinctive features of the chemical-analytical processes performed in them is presented. An idea of the equipment used for objective registration of the results of analytical research is given. The sequence of its implementation is given;attention is paid to the factors that can distort the results of the study. The areas of possible application of test systems for diagnostics of various somatic diseases are characterized. An idea is given about the laboratory diagnostic panels as combinations of indicators of laboratory tests traditionally used for laboratory diagnostics of diseases of the vital organs and various forms of infectious pathology. The set of different panels created in the second generation test strips that implement the immunochromatographic analysis makes a kind of "laboratory in a pocket" that can be used by a general practitioner directly at the patient’s location. © The Authors.

Lateral Flow Immunoassay of SARS-CoV-2 Antigen with SERS-Based Registration: Development and Comparison with Traditional Immunoassays.

The current COVID-19 pandemic has increased the demand for pathogen detection methods that combine low detection limits with rapid results. Despite the significant progress in methods and devices for nucleic acid amplification, immunochemical methods are still preferred for mass testing without specialized laboratories and highly qualified personnel. The most widely used immunoassays are microplate enzyme-linked immunosorbent assay (ELISA) with photometric detection and lateral flow immunoassay (LFIA) with visual results assessment. However, the disadvantage of ELISA is its considerable duration, and that of LFIA is its low sensitivity. In this study, the modified LFIA of a specific antigen of the causative agent of COVID-19, spike receptor-binding domain, was developed and characterized. This modified LFIA includes the use of gold nanoparticles with immobilized antibodies and 4-mercaptobenzoic acid as surface-enhanced Raman scattering (SERS) nanotag and registration of the nanotag binding by SERS spectrometry. To enhance the sensitivity of LFIA-SERS analysis, we determined the optimal compositions of SERS nanotags and membranes used in LFIA. For benchmark comparison, ELISA and conventional colorimetric LFIA were used with the same immune reagents. The proposed method combines a low detection limit of 0.1 ng/mL (at 0.4 ng/mL for ELISA and 1 ng/mL for qualitative LFIA) with a short assay time equal to 20 min (at 3.5 h for ELISA and 15 min for LFIA). The results obtained demonstrate the promise of using the SERS effects in membrane immuno-analytical systems.

Multicentric evaluation of a novel point of care electrochemical ELISA platform for SARS-CoV-2 specific IgG and IgM antibody assay.

New diagnostics technologies for the efficient detection and quantification of SARS-CoV-2 antibodies are very crucial to manage the COVID-19 pandemic, especially in the context of emerging vaccination paradigms. Herein, we report on a novel point-of-care Electrochemical ELISA platform with disposable screen printed electrodes functionalized with SARS-CoV-2 Spike Glycoprotein S1, to enable fast and accurate quantitative estimation of total antibody concentration (IgG and IgM) in clinical samples. The quantification is performed with a comparison of electrochemical redox current against the current produced by the spiked monoclonal antibodies with known concentration. The assay is validated through multicentric evaluation against 3 different FDA authorized Laboratory standard techniques, using both EDTA whole blood and serum samples. We demonstrate that the proposed assay has excellent sensitivity and specificity, making it a suitable candidate for epidemiological surveys and quantification of antibodies in COVID-19 vaccination programs.