Electrochemical and Surface-Plasmon Correlation of a Serum-Autoantibody Immunoassay with Binding Insights: Graphenyl Surface versus Mercapto-Monolayer Surface
By Premaratne, Gayan; Niroula, Jinesh; Patel, Manoj K.; Zhong, Wei; Suib, Steven L.; Kalkan, A. Kaan; Krishnan, Sadagopan
Published in Analytical Chemistry
2018
Abstract
We present here the correlation of picomolar affinities between surface-plasmon and electrochemical immunoassays for the binding of serum glutamic acid decarboxylase 65 autoantibody (GADA), a biomarker of type 1 diabetes (T1D), to its antigen GAD-65. Carboxylated (?5.0%)-graphene-modified immunoassembly on a gold surface-plasmon chip or on an electrochemical array provided significantly larger binding affinity, higher sensitivity, and lower detection limits than a self-assembled monolayer surface of mercaptopropionic acid (MPA). Estimation of the relative surface ?COOH groups by covalent tagging of an electroactive aminoferrocene showed that the graphenyl surface displayed a greater number of ?COOH groups (9-fold) than the MPA surface. X-ray-photoelectron-spectroscopy analysis showed more C