FACTORS AFFECTING THE BINDING AND IMMUNOREACTIVITY OF IMMUNOGLOBULINS ON SOLID SURFACES

THIS PAPER DESCRIBES THE STUDY OF PARAMETERS THAT AFFECT THE BINDING OF MODIFIED AND UNMODIFIED IMMUNOGLOBULINS ON ETHANOL- TREATED AND UNTREATED SOLID SURFACES AND ALSO THE IMMUNOADSORPTION OF IMMUNOGLOBULINS ON SECOND ANTIBODY, CORALENTLY COUPLED ON SOLID SURFACES. IN ALL CASES THE PARAMETERS WERE CHECKED BY THE IMMUNOREACTION OF RADIOIODINATED TRIIODOTHYRONINE WITH SPECIFIC ANTIBODY RAISEDAGAINST IT IN RABBIT. A SUBSTANTIAL INCREASE OF THE MEASURED IMMUNOREACTIVITY WAS OBSERVED, WHEN IMMUNOGLOBULINS WERE ADSORBED ON ETHANOL TREATED SOLID SURFACES, COMPARED TO UNTREATED ONES.ΣΤΗΝ ΕΡΓΑΣΙΑ ΜΕΛΕΤΑΤΑΙ Η ΠΡΟΣΔΕΣΗ ΤΡΟΠΟΠΟΙΗΜΕΝΩΝ ΚΑΙ ΜΗ ΑΝΟΣΟΣΦΑΙΡΙΝΩΝ ΣΕ ΣΤΕΡΕΕΣ ΕΠΙΦΑΝΕΙΕΣ ΚΑΤΕΡΓΑΣΜΕΝΕΣ ΚΑΙ ΜΗ ΚΑΤΕΡΓΑΣΜΕΝΕΣ ΜΕ ΑΙΘΑΝΟΛΗ ΚΑΘΩΣ ΕΠΙΣΗΣ ΚΑΙ ΗΑΝΟΣΟΠΡΟΣΡΟΦΗΣΗ ΣΕ ΣΤΕΡΕΕΣ ΕΠΙΦΑΝΕΙΕΣ ΣΤΙΣ ΟΠΟΙΕΣ ΕΙΧΕ ΠΡΟΣΔΕΘΕΙ ΟΜΟΙΟΠΟΛΙΚΑ ΔΕΥΤΕΡΟ ΑΝΤΙΣΩΜΑ. ΣΕ ΟΛΕΣ ΤΙΣ ΠΕΡΙΠΤΩΣΕΙΣ Η ΜΕΛΕΤΗ ΕΓΙΝΕ ΜΕΣΩ ΤΗΣ ΑΝΟΣΟΑΝΤΙΔΡΑΣΗΣ ΡΑΔΙΟΙΩΔΙΩΜΕΝΗΣ ΤΡΙΙΩΔΟΘΥΡΟΝΙΝΗΣ ΜΕ ΕΙΔΙΚΑ ΩΣ ΠΡΟΣ ΑΥΤΗΝ ΠΡΟΣΔΕΔΕΜΕΝΑ ΑΝΤΙΣΩΜΑΤΑ. ΠΑΡΑΤΗΡΗΘΗΚΕ ΣΗΜΑΝΤΙΚΗ ΑΥΞΗΣΗ ΤΗΣ ΜΕΤΡΟΥΜΕΝΗΣ ΑΝΟΣΟΔΡΑΣΤΙΚΟΤΗΤΑΣ ΑΝΑ ΣΦΑΙΡΙΔΙΟ ΕΝΑΝΤΙ ΤΩΝ ΜΗ ΚΑΤΕΡΓΑΣΜΕΝΩΝ ΣΦΑΙΡΙΔΙΩΝ ΚΑΙ ΣΥΓΚΡΙΤΙΚΑ ΜΕ ΑΛΛΕΣ ΒΙΒΛΙΟΓΡΑΦΙΚΕΣ ΜΕΘΟΔΟΥΣ

Label-Free Biosensors Based onto Monolithically Integrated onto Silicon Optical Transducers

The article reviews the current status of label-free integrated optical biosensors focusing on the evolution over the years of their analytical performance. At first, a short introduction to the evanescent wave optics is provided followed by detailed description of the main categories of label-free optical biosensors, including sensors based on surface plasmon resonance (SPR), grating couplers, photonic crystals, ring resonators, and interferometric transducers. For each type of biosensor, the detection principle is first provided followed by description of the different transducer configurations so far developed and their performance as biosensors. Finally, a short discussion about the current limitations and future perspectives of integrated label-free optical biosensors is provided

Optical Immunosensors for Bacteria Detection in Food Matrices

Optical immunosensors are one of the most popular categories of immunosensors with applications in many fields including diagnostics and environmental and food analysis. The latter field is of particular interest not only for scientists but also for regulatory authorities and the public since food is essential for life but can also be the source of many health problems. In this context, the current review aims to provide an overview of the different types of optical immunosensors focusing on their application for the determination of pathogenic bacteria in food samples. The optical immunosensors discussed include sensors based on evanescent wave transduction principles including surface plasmon resonance (SPR), fiber-optic-, interferometric-, grating-coupler-, and ring-resonator-based sensors, as well as reflectometric, photoluminescence, and immunosensors based on surface-enhanced Raman scattering (SERS). Thus, after a short description of each transduction technique, its implementation for the immunochemical determination of bacteria is discussed. Finally, a short commentary about the future trends in optical immunosensors for food safety applications is provided

Fast Deoxynivalenol Determination in Cereals Using a White Light Reflectance Spectroscopy Immunosensor

Deoxynivalenol (DON) is a mycotoxin produced by certain Fusarium species and found in a high percentage of wheat and maize grains cultured worldwide. Although not so toxic as other mycotoxins, it exhibits both chronic and acute toxicity, and therefore methods for its fast and accurate on-site determination are highly desirable. In the current work, we employ an optical immunosensor based on White Light Reflectance Spectroscopy (WLRS) for the fast and sensitive immunochemical label-free determination of DON in wheat and maize samples. The assay is completed in 12 min and has a quantification limit of 2.5 ng/mL in buffer corresponding to 125 μg/kg in whole grain which is lower than the maximum allowable concentrations set by the regulatory authorities for grains intended for human consumption. Several extraction protocols have been compared, and the highest recovery (>90%) was achieved employing distilled water. In addition, identical calibration curves were received in buffer and wheat/maize extraction matrix providing the ability to analyze the grain samples using calibrators in buffer. Recoveries of DON from spiked wheat and maize grain samples ranged from 92.0(±4.0) to 105(±4.0)%. The analytical performance of the WLRS immunosensor, combined with the short analysis time and instrument portability, supports its potential for on-site determinations

Monolithically Integrated Label-Free Optical Immunosensors

Amongst label-free optical sensors, those relying on silicon photonics are especially promising for the development of small-sized devices appropriate for applications at the point-of-need. In this context, our work over the last 10 years has focused on the development of silicon photonic chips that combine all optical components, both active and passive, onto the same substrate. The approach followed for this monolithic integration, as well as the application of the different silicon photonic chip versions as immunosensors for the determination of single or panels of analytes, related to biodiagnostics or the food safety sector, will be presented

Simultaneous Detection of SARS-CoV-2 Nucleoprotein and Receptor Binding Domain by a Multi-Area Reflectance Spectroscopy Sensor

The COVID-19 pandemic has emphasized the urgent need for point-of-care methods suitable for the rapid and reliable diagnosis of viral infections. To address this demand, we report the rapid, label-free simultaneous determination of two SARS-CoV-2 proteins, namely, the nucleoprotein and the receptor binding domain peptide of S1 protein, by implementing a bioanalytical device based on Multi Area Reflectance Spectroscopy. Simultaneous detection of these two proteins is achieved by using silicon chips with adjacent areas of different silicon dioxide thickness on top, each of which is modified with an antibody specific to either the nucleoprotein or the receptor binding domain of SARS-CoV-2. Both areas were illuminated by a single probe that also collected the reflected light, directing it to a spectrometer. The online conversion of the combined reflection spectra from the two silicon dioxide areas into the respective adlayer thickness enabled real-time monitoring of immunoreactions taking place on the two areas. Several antibodies have been tested to define the pair, providing the higher specific signal following a non-competitive immunoassay format. Biotinylated secondary antibodies and streptavidin were used to enhance the specific signal. Both proteins were detected in less than 12 min, with detection limits of 1.0 ng/mL. The assays demonstrated high repeatability with intra- and inter-assay coefficients of variation lower than 10%. Moreover, the recovery of both proteins from spiked samples prepared in extraction buffer from a commercial self-test kit for SARS-CoV-2 collection from nasopharyngeal swabs ranged from 90.0 to 110%. The short assay duration in combination with the excellent analytical performance and the compact instrument size render the proposed device and assay suitable for point-of-care applications