Amino, chloromethyl and acetal-functionalized latex particles for immunoassays: a comparative study

Latex particles with different functionalized surface groups (amino, acetal and chloromethyl) for the covalent linking of protein molecules were synthesized and characterized. Immunopurified anti-ferritin antibodies were then covalently coupled with a mean efficiency rate (protein covalently bound to latex particles with respect to the total amount of protein added) of 60%. The reagents developed were applied to the measurement of serum ferritin concentration in a turbidimetric procedure, showing a good measuring range and a lowest detection limit of 3.5 ng/ml in the case of the amino-modified particles. These immunological reagents were compared with a commercial nephelometric method, showing a good linear correlation in all cases but no transferability in the acetal and chloromethyl latexes with additional carboxyl groups, probably due to interference with other serum components. The differences among latexes found in this study indicate that it would be necessary to optimize the assay conditions for each type of particle, in order to achieve a maximum immunoreactivity.