Ultrasensitive Electrochemical Sensing of Biotin-Avidin Interaction on Gold Electrode Bio-Conjugated With Silver Nanoparticles

The influence of silver nanoparticles (AgNP) labeled with biomolecules on the electrochemical sensing of avidin-biotin interaction was investigated. Self-assembled monolayers of mercapto propionic acid on gold wire electrode were coupled with AgNP labeled biotin or avidin through bio-conjugation of complementary biomolecules. The electrochemical sensing of biotin-avidin interaction on the gold electrode modified with AgNP labeled biomolecules was compared with that of the unlabeled biomolecule layers. The sensing performances were studied using cyclic voltammetry and electrochemical impedance spectroscopy methods in ferric/ferrous redox system with varying concentration of bio-affinity molecules. The peak currents of AgNP labeled layers were gradually increased as concentration of bio-affinity molecules was increased in the electrolyte while opposite effect was observed for unlabeled layers. Here, the sensing mechanism was established to explain the role of AgNP as the electron transfer mediator. The AgNP modified electrode might be considered as ultrasensitive probe to detected biotin-avidin couple below 20 ng L
^-1
and to sense change of concentration above 10 or 20 ng L
^-1
at higher concentration region as well. This type of ultrasensitive detection of biotin-avidin interaction should be considered to explore robust and highly sensitive assays in combination with other primary-secondary antibodies for the bio-analyses, separations and clinical diagnostics.