Gold and Silver Nanoparticles for Electrochemical Detection of Cardiac Troponin I Based on Stripping Voltammetry

Clinical relevance and advances in detection of translational biomarker cardiac troponin

Cardiovascular diseases (CVD) are a range of diseases, pointing the functional hindrances in the heart and blood vessels of the human system that contributes to 48.6 % of the world's adult death rate. The diagnosis of CVD relies upon the Electro Cardio Gram (ECG) and detection of muscle markers such as troponins. Among the cardiac trio, Cardiac Troponin I (cTnI) weighing 23 KiloDalton (kDa) is a sorted biomarker for CVD. cTnI remains high in the blood after 1-2 weeks of myocardial damage. Testing of cTnI in CVD patients aids in diagnosis and risk stratification of the disease. Different determination systems including optical, electrochemical, and acoustic have been put forward for monitoring the cTnI which are Point of Care (POC) that promotes simple and sensitive detection of cTnI. The modern era has paved way to high-sensitivity Troponin I (hscTnI) devices that can detect up to 0.01 ng/ml in human blood/plasma/serum. Yet, the practice of hscTnI is impracticable due to cost inefficiency. Development of new hscTnI devices with minimal investment and maximal detection range will meet the global requirement. This review gives an over view on different detection systems of cardiac troponin I which stands as a translational detection molecule for CVDs.

Electrochemical biosensor for trypsin activity assay based on cleavage of immobilized tyrosine-containing peptide

In this work, we proposed a biosensor for trypsin proteolytic activity assay using immobilization of model peptides on screen-printed electrodes (SPE) modified with gold nanoparticles (AuNPs) prepared by electrosynthetic method. Sensing of proteolytic activity was based on electrochemical oxidation of tyrosine residues of peptides. We designed peptides containing N-terminal cysteine residue for immobilization on an SPE, modified with gold nanoparticles, trypsin-specific cleavage site and tyrosine residue as a redox label. The peptides were immobilized on SPE by formation of chemical bonds between mercapto groups of the N-terminal cysteine residues and AuNPs. After the incubation with trypsin, time-dependent cleavage of the immobilized peptides was observed by decline in tyrosine electrochemical oxidation signal. The kinetic parameters of trypsin, such as the catalytic constant (k_cat), the Michaelis constant (K_M) and the catalytic efficiency (k_cat/K_M), toward the CGGGRYR peptide were determined as 0.33 ± 0.01 min^-1, 198 ± 24 nM and 0.0016 min^-1 nM^-1, respectively. Using the developed biosensor, we demonstrated the possibility of analysis of trypsin specificity toward the peptides with amino acid residues disrupting proteolysis. Further, we designed the peptides with proline or glutamic acid residues after the cleavage site (CGGRPYR and CGGREYR), and trypsin had reduced activity toward both of them according to the existing knowledge of the enzyme specificity. The developed biosensor system allows one to perform a comparative analysis of the protease steady-state kinetic parameters and specificity toward model peptides with different amino acid sequences.

Label-Free Electrochemical Immunosensor Based on a Functionalized Ionic Liquid and Helical Carbon Nanotubes for the Determination of Cardiac Troponin I

A label-free electrochemical immunosensor for cardiac troponin I was prepared by using a helical carbon nanotube-supported aldehyde-functionalized ionic liquid. Because of the good conductivity of ionic liquid and helical carbon nanotubes, high sensitivity of the immunosensor was obtained. Functionalized ionic liquid provided binding sites for antibody, which simplified the process of sensor construction. Cardiac troponin I was detected by this immunosensor with a linear range of 0.05-30 ng/mL and a detection limit of 0.03 ng/mL. The electrochemical immunosensor had satisfactory reproducibility, high sensitivity, and acceptable specificity.

Manganese doped CdS sensitized graphene/Cu2MoS4 composite for the photoelectrochemical immunoassay of cardiac troponin I

As a newly emerged photoactive material, Cu₂MoS₄ has motivated wide research interests in the field of photoelectrochemistry. Based on manganese doped CdS (CdS:Mn) sensitized graphene (G)/Cu₂MoS₄ composite, we developed a label-free photoelectrochemical (PEC) immunosensor for the detection of cardiac troponin I (cTnI). G as an excellent 2D conductive material, combined with Cu₂MoS₄ could improve its charge transfer efficiency. CdS:Mn nanoparticles (NPs) loaded on G/Cu₂MoS₄ further enlarged the light absorption range of Cu₂MoS₄ and restrained the electron-hole pairs recombination. Under optimal conditions, the proposed PEC immunosensor responded sensitively to cTnI with a low detection limit of 0.18 pg/mL and a wide linear range (0.005-1000 ng/mL). Moreover, as-fabricated immunosensor also exhibited high sensitivity, excellent selectivity and good stability. This work also was extended to real samples analysis and obtained satisfied results.

Recent advances in designing nanomaterial based biointerfaces for electrochemical biosensing cardiovascular biomarkers

Early diagnosis of cardiovascular disease (CVD) is critically important for successful treatment and recovery of patients. At present, detection of CVD at early stages of its progression becomes a major issue for world health. The nanoscale electrochemical biosensors exhibit diverse outstanding properties, rendering them extremely suitable for the determination of CVD biomarkers at very low concentrations in biological fluids. The unique advantages offered by electrochemical biosensors in terms of sensitivity and stability imparted by nanostructuring the electrode surface together with high affinity and selectivity of bioreceptors have led to the development of new electrochemical biosensing strategies that have introduced as interesting alternatives to conventional methodologies for clinical diagnostics of CVD. This review provides an updated overview of selected examples during the period 2005-2018 involving electrochemical biosensing approaches and signal amplification strategies based on nanomaterials, which have been applied for determination of CVD biomarkers. The studied CVD biomarkers include AXL receptor tyrosine kinase, apolipoproteins, cholesterol, C-reactive protein (CRP), D-dimer, fibrinogen (Fib), glucose, insulin, interleukins, lipoproteins, myoglobin, N-terminal pro-B-type natriuretic peptide (BNP), tumor necrosis factor alpha (TNF-α) and troponins (Tns) on electrochemical transduction format. Identification of new specific CVD biomarkers, multiplex bioassay for the simultaneous determination of biomarkers, emergence of microfluidic biosensors, real-time analysis of biomarkers and point of care validation with high sensitivity and selectivity are the major challenges for future research.

Recent progress on the sensitive detection of cardiovascular disease markers by electrochemical-based biosensors

Cardiovascular disease is the most reason for deaths in all over the world. Hence, biomarkers of cardiovascular diseases are very crucial for diagnosis and management process. Biomarker detection demand is opened the important way in biosensor development field. Rapid, cheap, portable, precise, selective and sensitive biomarker sensing devices are needed at this point to detect and predict disease. A cardiac biomarker can be orderable as C-reactive protein, troponin I or T, myoglobin, tumor necrosis factor alpha, interleukin-6, interleukin-1, lipoprotein-associated phospholipase, low-density lipoprotein and myeloperoxidase. They are used for prediction of cardiovascular diseases. There are many methods for early diagnosis of cardiovascular diseases, but these have long time process and expensive devices. In recent studies, different biosensors have been developed to remove the problems in this field. Electrochemical devices and developed biosensors have many superiorities than others such as low cost, mobile, reliable, repeatable, need a little amount of solution. In this review, recent studies were presented as details for cardiovascular disease biomarkers detection using electrochemical methods.

An electrochemical immunosensor for cardiac Troponin I using electrospun carboxylated multi-walled carbon nanotube-whiskered nanofibres

A sandwich-type nanostructured immunosensor based on carboxylated multi-walled carbon nanotube (CMWCNT)-embedded whiskered nanofibres (WNFs) was developed for detection of cardiac Troponin I (cTnI). WNFs were directly fabricated on glassy carbon electrodes (GCE) by removing the sacrificial component (polyethylene glycol, PEG) after electrospinning of polystyrene/CMWCNT/PEG nanocomposite nanofibres, and utilised as a transducer layer for enzyme-labeled amperometric immunoassay of cTnI. The whiskered segments of CMWCNTs were activated and utilised to immobilise anti-cTnT antibodies. It was observed that the anchored CMWCNTs within the nanofibres were suitably stabilised with excellent electrochemical repeatability. A sandwich-type immuno-complex was formed between cTnI and horseradish peroxidase-conjugated anti-cTnI (HRP-anti-cTnI). The amperometric responses of the immunosensor were studied using cyclic voltammetry (CV) through an enzymatic reaction between hydrogen peroxide and HRP conjugated to the secondary antibody. The nanostructured immunosensor delivered a wide detection range for cTnI from the clinical borderline for a normal person (0.5-2ngmL^-1) to the concentration present in myocardial infarction patients (> 20ngmL^-1), with a detection limit of ~ 0.04ngmL^-1. It also showed good reproducibility and repeatability for three different cTnI concentration (1, 10 and 25ngmL^-1) with satisfactory relative standard deviations (RSD). Hence, the proposed nanostructured immunosensor shows potential for point-of-care testing.

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° 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 Ω cm² per decade, and it also exhibits high specificity and good reproducibility.

Impedimetric immunosensor for detection of cardiovascular disorder risk biomarker

We report the construction and characterization of a novel, level free impedimetric immunosensor for rapid, sensitive and selective detection of myoglobin (Mb). Monoclonal anti-myoglobin (anti-Mb-IgG) antibody was immobilized on screen-printed multiwalled carbon nanotubes electrode for signal amplification without the need of natural enzymes. The fabrication of resulting immunosensor was extensively characterized by using scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Electrochemical impedance spectroscopy (EIS) technique offered a linear detection range (0.1-90ngmL(-1)) of myoglobin with sensitivity of 0.74kΩngmL(-1) (correlation coefficient, R(2)=0.97) and detection limit of 0.08ngmL(-1) (S/N=3). The mean percentage recovery of Mb in serum samples using this working biosensor is 97.33%. Furthermore, the proposed strategy can be a promising alternative for detection of Mb related cardiovascular disorders.

[Electrochemical methods for biomedical investigations]

In the review, authors discussed recently published experimental data concerning highly sensitive electrochemical methods and technologies for biomedical investigations in the postgenomic era. Developments in electrochemical biosensors systems for the analysis of various bio objects are also considered: cytochrome P450s, cardiac markers, bacterial cells, the analysis of proteins based on electro oxidized amino acids as a tool for analysis of conformational events. The electroanalysis of catalytic activity of cytochromes P450 allowed developing system for screening of potential substrates, inhibitors or modulators of catalytic functions of this class of hemoproteins. The highly sensitive quartz crystal microbalance (QCM) immunosensor has been developed for analysis of bio affinity interactions of antibodies with troponin I in plasma. The QCM technique allowed real-time monitoring of the kinetic differences in specific interactions and nonspecific sorption, with out multiple labeling procedures and separation steps. The affinity binding process was characterized by the association (ka) and the dissociation (kd) kinetic constants and the equilibrium association (K) constant, calculated using experimental data. Based on the electroactivity of bacterial cells, the electrochemical system for determination of sensitivity of the microbial cells to antibiotics cefepime, ampicillin, amikacin, and erythromycin was proposed. It was shown that the minimally detectable cell number corresponds to 106 CFU per electrode. The electrochemical method allows estimating the degree of E.coli JM109 cells resistance to antibiotics within 2-5 h. Electrosynthesis of polymeric analogs of antibodies for myoglobin (molecularly imprinted polymer, MIP) on the surface of graphite screen-printed electrodes as sensor elements with o- phenylenediamine as the functional monomer was developed. Molecularly imprinted polymers demonstrate selective complementary binding of a template protein molecule (myoglobin) by the "key-lock" principle.

Electroactive graphene-multi-walled carbon nanotube hybrid supported impedimetric immunosensor for the detection of human cardiac troponin-I

We report a sensitive and stable electrochemical impedance immunosensor prepared with electroactive three-dimensional graphene-multi-walled carbon nanotube hybrid deposited on a glassy carbon electrode.