Label-Free Detection of Cardiac Troponin-I Using Carbon Nanofiber Based Nanoelectrode Arrays

A sensor platform based on vertically aligned carbon nanofibers (CNFs) has been developed. Their inherent nanometer scale, high conductivity, wide potential window, good biocompatibility and well-defined surface chemistry make them ideal candidates as biosensor electrodes. A carbon nanofiber (CNF) multiplexed array has been fabricated with 9 sensing pads, each containing 40,000 carbon nanofibers as nanoelectrodes. Here, we report the use of vertically aligned CNF nanoelectrodes for the detection of cardiac Troponin-I for the early diagnosis of myocardial infarction. Antibody, antitroponin, probe immobilization and subsequent binding to human cardiac troponin-I were characterized using electrochemical impedance spectroscopy and cyclic voltammetry techniques. Each step of the modification process resulted in changes in electrical capacitance or resistance to charge transfer due to the changes at the electrode surface upon antibody immobilization and binding to the specific antigen. This sensor demonstrates high sensitivity, down to 0.2 ng/mL, and good selectivity making this platform a good candidate for early stage diagnosis of myocardial infarction

Immunoassay for troponin I using a glassy carbon electrode modified with a hybrid film consisting of graphene and multiwalled carbon nanotubes and decorated with platinum nanoparticles

This article describes a bioelectrode for the determination of human cardiac troponin-I (cTnI). A glassy carbon electrode was coated with a hybrid film of graphene and multiwalled carbon nanotube (G-MWCNT) and modified with platinum nanoparticles (Pt NPs) that were capped with mercaptopropionic acid. The PtNPs were anchored on the G-MWCNT hybrid film via the cross-linker 1-pyrenemethylamine and subsequently functionalized with antibody against troponin (anti-cTnI). The bioelectrode was characterized by transmission electron microscopy, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The performance of the immunoelectrode was investigated by electrochemical impedance spectroscopy, and response was fit to Randle's equivalent circuit model. The charge transfer resistance (R-et) at a.c. frequencies of < 1 Hz is found to be a viable sensing parameter. The dissociation constant of the immunoreaction between surface immobilized anti-cTnI and the analyte cTnI is 0.29 nM (with a Hill coefficient of 0.23), this indicating a negative cooperativity and high binding affinity of cTnI for anti-cTnI on the electrode surface. The EIS response is linear in the 1.0 pg mL(-1) to 10 ng mL(-1) concentration range, and the R-et sensitivity is 145.5 a"broken vertical bar cm(2) per decade

Electrochemical Impedance Analysis of Biofunctionalized Conducting Polymer-Modified Graphene-CNTs Nanocomposite for Protein Detection

We report an electrodeposited poly(pyrrole-co-pyrrolepropylic acid) copolymer modified electroactive graphene-carbon nanotubes composite deposited on a glassy carbon electrode to detect the protein antigen (cTnI). The copolymer provides pendant carboxyl groups for the site-specific covalent immobilization of protein antibody, anti-troponin I. The hybrid nanocomposite was used as a transducer for biointerfacial impedance sensing for cTnI detection. The results show that the hybrid exhibits a pseudo capacitive behaviour with a maximum phase angle of 49 degrees near 1 Hz, which is due to the inhomogeneous and porous structure of the hybrid composition. The constant phase element of copolymer is 0.61 (n = 0.61), whereas, it is 0.88 (n = 0.88) for the hybrid composites, indicating a comparatively homogeneous microstructure after biomolecular functionalization. The transducer shows a linear change in charge transfer characteristic (R-et) on cTnI immunoreaction for spiked human serum in the concentration range of 1.0 pg mL(-1) - 10.0 ng mL(-1). The sensitivity of the transducer is 167.8 +/- 14.2 Omega cm(2) per decade, and it also exhibits high specificity and good reproducibility