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In this paper, we developed a simple and disposable electrochemical paper-based immunosensor (e-PI) based on manual screen printing method via patterned sticker label film on paper. The proposed electrochemical sensors provide the opportunity for economical singleuse analysis of biological samples. The e-PI was constructed with hydrophobic glossy paper layers on a wax paper substrate to define three-electrode system. A carbon ink was used for construction of e-PI which composed of the graphite powder and cellulose acetate. The stability of the e-PI was evaluated using electrochemical methods. Carbohydrate antigen 15-3 (CA15-3) antibodies to the target CA15-3 antigen were immobilized on gold-modified graphite electrodes on the e-PI. Electrochemical properties of e-PI were investigated by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. The fabricated e-PI offers a vast linear range from 0.5 to 200 U mL-1 with a low limit of detection 0.15 U mL-1. Furthermore, the fabricated e-PI has acceptable stability, accuracy and high sensitivity. [ABSTRACT FROM AUTHOR]

A rapid and simple paper-based elution assay for red blood cell antigen typing by the indirect antiglobulin test (IAT) was established. This allows to type blood using IgG antibodies for the important blood groups in which IgM antibodies do not exist. Red blood cells incubated with IgG anti-D were washed with saline and spotted onto the paper assay pre-treated with anti-IgG. The blood spot was eluted with an elution buffer solution in a chromatography tank. Positive samples were identified by the agglutinated and fixed red blood cells on the original spotting area, while red blood cells from negative samples completely eluted away from the spot of origin. Optimum concentrations for both anti-IgG and anti-D were identified to eliminate the washing step after the incubation phase. Based on the no-washing procedure, the critical variables were investigated to establish the optimal conditions for the paper-based assay. Two hundred ten donor blood samples were tested in optimal conditions for the paper test with anti-D and anti-Kell. Positive and negative samples were clearly distinguished. This assay opens up new applications of the IAT on paper including antibody detection and blood donor-recipient crossmatching and extends its uses into non-blood typing applications with IgG antibody-based diagnostics. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The objective of the present work was to standardize and evaluate indirect plate and dot- enzyme linked immunosorbent assay (ELISA) using purified Paramphistomum epiclitum homologous antigens in the small ruminants. Electrophoretic separation of somatic antigen (PeSAg) in reducing condition on 15% polyacrylamide gel resolved into 16 proteins of the molecular weight ranging from 14 -100 kDa. Two step ethanolic precipitation of supernatant of in-vitro culture of the fluke yielded P. epiclitum excretory-secretory antigen (PeESAg) of molecular weight 28 kDa. The animals (Goats=123; Sheep=91) were broadly kept into post-mortem and faecal examined groups. At many occasion the PeSAg found to cross reacts with other helminths parasites thus minimizing the specificity of the tests and antigens. There was no any direct correlation between the parasites load and ELISA reactivity pattern. The noted prevalence rate after combining the results of post-mortem examination and PeESAg based ELISA (plate and paper/ dot) was 30.08% (37/123) in goats and 28.57% (26/91) in sheep. While using PeESAg, the calculated overall sensitivity% was 92.86 (goats)/ 100 (sheep) in both plate and dot- ELISA, specificity% was 91.58 (goats)/ 91.55 (sheep) in plate ELISA while 88.42 (goats)/ 92.96 (sheep) in dot-ELISA, positive predictive value% was 76.47 (goats)/ 76.92 (sheep) in plate ELISA while 70.27 (goats)/ 80 (sheep) in dot-ELISA and negative predictive value% was 97.75 (goats)/ 100 (sheep) in plate ELISA while 97.67 (goats)/ 100 (sheep) in dot- ELISA, these values were optimum for the field sera sample so the tests and PeESAg can be recommended for the detection P. epiclitum infection in the small ruminants. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The current approaches of diagnostic platforms for detecting SARS-CoV-2 infections mostly relied on adapting the existing technology. In this work, a simple and low-cost electrochemical sensing platform for detecting SAR-CoV-2 antigen was established. The proposed sensor combined the innovative disposable paper-based immunosensor and cost-effective plant-based anti-SARS-CoV-2 monoclonal antibody CR3022, expressed in Nicotiana benthamiana. The cellulose nanocrystal was modified on screen-printed graphene electrode to provide the abundant COOH functional groups on electrode surface, leading to the high ability for antibody immobilization. The quantification of the presence receptor binding domain (RBD) spike protein of SARS-CoV-2 was performed using differential pulse voltammetry by monitoring the changing current of [Fe(CN) 6 ]3-/4- redox solution. The current change of [Fe(CN) 6 ]3-/4- before and after the presence of target RBD could be clearly distinguished, providing a linear relationship with RBD concentration in the range from 0.1 pg/mL to 500 ng/mL with the minimum limit of detection of 2.0 fg/mL. The proposed platform was successfully applied to detect RBD in nasopharyngeal swab samples with satisfactory results. Furthermore, the paper-based immunosensor was extended to quantify the RBD level in spiked saliva samples, demonstrating the broadly applicability of this system. This electrochemical paper-based immunosensor has the potential to be employed as a point-of-care testing for COVID-19 diagnosis. [Display omitted] • The electrochemical paper-based device integrated with a label-free immunoassay was developed for detecting SARS-CoV-2. • A novel plant-based mAb CR3022 offers a remarkable simplicity and cost-effectiveness in terms of Ab production. • CNC containing the abundant COOH functional groups has the potential to be used as the immobilizing material. • The proposed immunosensor was successfully applied to detect SARS-CoV-2 from nasopharyngeal swabs and saliva samples. [ABSTRACT FROM AUTHOR]