Highly sensitive electrochemical detection of biotin-avidin interaction on gold electrode modified with silver nanoparticles through bilayer assembly

Abstract

The trifunctional l-cysteine containing carboxylic acid, amine and thiol is chemisorbed on the gold electrode surface via the thiol groups to form the self-assembled monolayer. Then the bilayer is assembled stepwise on the cysteine modified gold electrode. A layer of 3-marcaptopropionic acid functionalized silver nanoparticles is covalently coupled with amine group of cysteine and other layer of amine functional group containing biotin or avidin molecules is covalently coupled with carboxylic acid functional groups of cysteine. The improvement of electrochemical properties are noted for the cysteine modified gold electrode coupled with biomolecules first followed by coupling with the functionalized silver nanoparticles. This modified gold electrode is used to study the electrochemical sensing response of respective complementary biomolecule immobilized gold electrode towards the biotin or avidin. As revealed the avidin modified electrode is found to have better sensing performances toward biotin in terms of sensitivity and detection limit over the other one. The sensitivity of 1.243 Ω (ng)-1 L mm-2 and detection limit of 1.4 × 10−3 ng/L is observed for avidin sensing on biotin layer. For biotin sensing on avidin layer a sensitivity of 6.143 Ω (ng)-1 L mm-2 and detection limit of 1.2 × 10−5 ng/L is obtained from the calibration plot.