Latex Immunoagglutination Assays

Latex immunoagglutination assays continue to be widely used in biology and medicine for the detection of small quantities of an antibody or antigen of interest in fluid test samples. Main characteristics of preparation and use of these assays are examined here. Physical adsorption of proteins onto latex particles surface, with special relevance to immunoglobulins, is analyzed with major attention to those factors that influence adsorption: medium conditions such as pH and ionic strength, surface characteristics as type and amount of charge, or hydrophobicity. Different functionalized latexes for covalent linking are also presented, as well as the corresponding chemical reactions. Techniques for the detection and quantification of the immunoreaction are briefly summarized, including visual observation, light scattering, turbidimetry, nephelometry, and angular anisotropy. Finally, some problems of colloidal stability of these latex assays are analyzed, as well as the different solutions applied by scientists to solve them.