Particulate tracers for homogeneous immunoassay - comprising antibody, antigen or hapten linked to particulate material without true light absorption

摘要

Particulate tracers for use in immunoassays comprise an immunoreactive substance (I) and a particulate label (II), (I) is an antibody, antigen or hapten; and (II) is a particle with a max. dimension of at least 0.2 micron comprising a lyophobic or amphilyophilic material having a surface with some (inherent or induced) hydrophilicity and is without true absorption in the visible/near-IR spectrum. The visible/near-IR spectra of the tracers and their aggregates in an aq. medium are the same, irrespective of the particle size attained by antibody-antigen agglutination reaction. Also claimed is a photometric immunoassay method for determn. of an immunoreactive analyte, comprising (a) attaching an antibody, antigen or hapten, by covalent coupling or physical adsorption, to a particulate label whose max. dimension is at least 0.2 micron; (b) contacting the resulting tracer with the analyte in an aq. medium; (c) irradiating the mixt. with light of wavelength 320-1000 nm; and (d) measuring the intensity of the light transmitted by the reaction medium. USE/ADVANTAGE - The method may be used in biological and medical analysis, e.g. for detection of PCR amplification prods. (claimed) or for determn. of serum proteins, drugs such as gentamicin or theophylline, or pathogens such as Toxoplasma gondii. The method is simple, uses stable reagents, and gives detection limits in the ng/ml range with good reproducibility.