Immunochemical Approaches for Rapid Detection of Biologically Active Compounds

Abstract

Abstract:Express immunochemical techniques for determination of toxic compounds and pathogenic cells have been developed. Separation of reactants based on interaction between oppositely charged polyelectrolytes, namely polycation poly-N-ethyl-4-vinylpyridium and polyanion polymethacrylate, were used to reduce assay time. An extremely high rate and affinity of this interaction allowed formation of an immune complex in the solution followed by a quick separation of reactants. The polyelectrolyte-based assays were performed in both homogeneous and filtration formats. Total duration of the assay was 15-20 min, limit of pesticides detection -down to 0.2 ng/ml. The polyelectrolyte separation has been also used in electrochemical immunosensors. The assay protocol is based on the measurement of pH changes induced by a peroxidase label. A field-effect transistor is the sensitive element of the sensor, and specific immune complexes are formed at disposable porous membranes. An alternative approach is based on the application of screen-printed electrode with impregnated peroxidase. The set of reactants was used together with a portable amperometric device designed for express monitoring of hazardous compounds under out-of-lab conditions. The total assay time was 20 min, and the detection limit was 0.2 ng/ml. Immunochromatographic tests based on colloidal gold particles conjugated with antibodies have been developed for detection of low molecular weight antigens and bacterial cells. The method allows detection of bacterial cells including Mycobacterium tuberculosis and Legionella pneumophila during 10 min in concentrations down to 10 4 cell/mlImmunochemical methods are very effective for the detection of different biologically active compounds. High affinity of the antigen-antibody 1.

Rapid colorimetric detection of proteins and bacteria using silver reduction/precipitation catalyzed by gold nanoparticles

“…In conjunction with commonly used detection schemes such as fluorometric [3,7], spectrophotometric, electrochemical [8], and optical [9], among others, immunoassays are becoming more prominent due to their specificity and reliability. Immunoassays are based on the biospecific molecular recognition interaction of antibodies with the target substances (antigens) to be detected and have been widely used to measure low concentrations of antigens in clinical specimens such as blood and other body fluids [1,10] and the detection of trace amounts of drugs, chemicals (e.g., pesticides), bacteria and viruses in biological and environmental samples [11]. Immunoassays can be enzyme-based (such as the enzyme linked immunosorbent assay or ELISA), fluorescent (with a fluorescent molecule covalently linked to a biomolecule), chemiluminescent (luminescence due to chemical reaction), bioluminescent (luminescence due to biological reaction) or metallo-immunoassay (metal-based labels such as metal ions or colloidal metal nanoparticles).…”