Sandwich ELISA for hemoglobin A2 quantification and identification of β-thalassemia carriers

Colorimetric cellulose-based test-strip for rapid detection of amyloid β-42

An innovative sensing assay is described for point-of-care (PoC) quantification of a biomarker of Alzheimer's disease, amyloid β-42 (Aβ-42). This device is based on a cellulose paper-dye test strip platform in which the corresponding detection layer is integrated by applying a molecularly imprinted polymer (MIP) to the cellulose paper surface. Briefly, the cellulose paper is chemically modified with a silane to subsequently apply the MIP detection layer. The imprinting process is confirmed by the parallel preparation of a control material, namely a non-imprinted polymer (NIP). The chemical changes of the surface were evaluated by Fourier transform infrared spectroscopy (FTIR), contact angle, and thermogravimetric analysis (TG). Proteins and peptides can be quantified by conventional staining methods. For this purpose, Coomassie blue (CB) was used as a staining dye for the detection and quantification of Aβ-42. Quantitative determination is made possible by taking a photograph and applying an appropriate mathematical treatment to the color coordinates provided by the ImageJ program. The MIP shows a linear range between 1.0 ng/mL and 10 μg/mL and a detection limit of 0.71 ng/mL. Overall, this cellulose-based assay is suitable for the detection of peptides or proteins in a sample by visual comparison of color change. The test strip provides a simple, instrument-free, and cost-effective method with high chemical stability, capable of detecting very small amounts of peptides or proteins in a sample, and can be used for the detection of any (bio)molecule of interest.

A modified sandwich ELISA for accurate measurement of HbF in α-thalassemia carriers containing Hb Bart's and Hb Portland 1

Hemoglobin F (HbF) in blood lysate can be accurately measured by various methods, including immunoassay. In this study, we have produced polyclonal antibody (pAb) against HbF and established a modified sandwich-type ELISA for HbF quantification in blood lysates. The modified sandwich ELISA utilized anti-γ-globin monoclonal antibody clones Thal N/B as the capture antibody (Ab) coated on solid-phase, fluorescein isothiocyanate (FITC)-labeled pAb as the detecting Ab, and HPR-labeled anti-FITC Ab as the signal-generating Ab. By using an optimized blood lysate dilution, the HbF could be measured with no interference from hemoglobin Bart's (Hb Bart's) and hemoglobin Portland (Hb Portland 1) presented in α-thalassemia carriers. HbF levels measured by the modified sandwich ELISA were comparable to those quantified by the standard cation-exchange high performance liquid chromatography. We suggested that this modified sandwich ELISA was able to accurately measure HbF levels even in α-thalassemia carriers containing Hb Bart's and Hb Portland 1 and be an alternative method for HbF measurement.

Production of Monoclonal Antibodies against Human Trefoil Factor 3 and Development of a Modified-Sandwich ELISA for Detection of Trefoil Factor 3 Homodimer in Saliva

Background

Human trefoil factor (TFF) peptides consist of three members: TFF1, TFF2 and TFF3. TFF3 is the most abundant TFF peptide in saliva. TFF3 homodimer was suggested to be involved in apoptosis inhibition and malignancy. Determination of TFF3 homodimer expression profiles in saliva may lead to new information about oral biology and diseases. The objective of this study was to generate monoclonal antibodies (mAbs) against TFF3 and apply the produced mAbs for the establishment of ELISA for quantification of dimeric TFF3 in saliva.

Results

With our modified hybridoma technique, three hybridoma clones producing anti-TFF3 mAbs having IgG isotype were generated. The mAbs were specific for TFF3 with no cross-reactivity to other TFFs. Using the generated mAbs, a modified-sandwich ELISA with high sensitivity for the quantification of dimeric TFF3 in saliva was developed. Using this ELISA, the amount of dimeric TFF3 in saliva could be measured.

Conclusions

A modified-sandwich ELISA for the quantification of TFF3 dimeric form was established. The established ELISA will be a valuable tool for facilitating the investigation of the physiological roles and the diagnostic values of TFF3 in oral diseases. The concept of this modified-sandwich ELISA may be applied for the determination of other homodimeric peptides of interest.

Production and characterization of monoclonal antibodies against α-globin chain-containing human hemoglobins for detecting α-thalassemia disease

Monoclonal antibodies against α-globin containing human Hbs, named AMS-Alpha1 and AMS-Alpha 2, were produced by the hybridoma technique using spleen cells enriched by the newly developed B lymphocyte enrichment protocol. These two monoclonal antibodies were of IgM class, reacting to only intact form of human Hbs A, A2, E, and F, which contain α-globin chain. By the indirect ELISA, the AMS-Alpha1 and AMS-Alpha 2 quantified less amount of α-globin chain containing hemoglobins in HbH disease than the SEA-α thalassemia 1 carriers and normal individuals. It was thus anticipated that these monoclonal antibodies can be used for detecting Hb Bart's hydrops fetalis in which no α-globin chain is produced.