Novel peptidylated surfaces for interference-free electrochemical detection of cardiac troponin I

Novel peptidylated surfaces were designed to minimise interferences when electrochemically detecting cardiac troponin I in complex biological samples. Disulfide-cored peptide dendrons featuring carbomethoxy groups were self-assembled on gold electrodes. The carbomethoxy groups were deprotected to obtain carboxylic groups used to immobilise antibodies for cardiac troponin I marker. The chemisorption of two types of peptides, one containing triazole and the other with native peptide bonds, on a gold substrate was studied by quartz crystal microbalance (QCM), surface plasmon resonance (SPR) and X-ray photoelectron spectroscopy (XPS). Peptides formed ordered self-assembled monolayers, contributing to a more efficient display of the subsequently immobilised antibodies towards their binding to the antigen. As a result, electrochemical immunosensors prepared by self-assembly of peptides afforded higher sensitivities for cardiac troponin I than those prepared by the chemisorption of alkane thiolated compounds. Triazolic peptide-modified immunosensors showed extraordinary sensitivity towards cardiac troponin I [1.7 mu A/(ng/mL) in phosphate buffer], but suffered from surface fouling in 10% serum. Modification with non-triazolic peptides gave rise to anti-fouling properties and still enabled the detection of cardiac troponin I at pg/mL concentrations in 10% serum without significant matrix effects.