Chitosan stabilized gold nanoparticle based electrochemical ractopamine immunoassay

The authors describe an electrochemical immunoassay for the β-adrenergic agonist ractopamine (RAC). It is based on the use of chitosan-stabilized gold nanoparticles (chit-AuNPs). Antibodies against RAC (anti-RAC) readily adsorb on the surface of the chit-AuNPs due to their high bio-affinity. The amount of chitosan used to synthesize chit-AuNPs does not affect the size and distribution of the NPs but amplifies the electrochemical signal of the electrode. The assay has a detection limit as low as 2.3 pg∙mL −1 (equivalent to a 6.7 fM concentration), with a response that is linear in the 0.01 to 5 ng∙mL −1 RAC concentration range. The assay is selective, acceptably reproducible, stable, and well applicable to the detection of RAC. Chitosan-stabilized gold nanoparticles (chit-AuNPs) were prepared for electrochemical immunoassay of the ractopamine (RAC). The assay exhibits a detection limit of 2.3 pg·mL −1 (equal to 6.7 fM), is highly selective, acceptably reproducible, and stable.