Electrochemical immunosensing using micro and nanoparticles.

A model immunosensor based on a labeling method using gold nanoparticles (AuNPs) and electrochemical detection is developed. Microparamagnetic beads (MB) as primary antibody immobilization platforms and AuNPs modified with a secondary antibody as high sensible electrochemical labels have been used. The carbon electrode used as transducer incorporates a magnet that allows the collection/ immobilization on its surface of the immunological sandwich attached to the MB. Briefly, the sandwich type assay consists in the incubation of streptavidin-coupled-MB with an antihuman IgG biotin conjugate, and then, the immunological reaction with the human IgG antigen takes place. After that, a gold labeled anti-human IgG reacts with the antigen, and finally the AuNPs are electrochemically detected. This approach allows the obtaining of an immunosensor with a low antigen detection limit with special interest for several applications in protein analysis.