Smartphone-Aided Fluorescence Detection of Cardiac Biomarker Myoglobin by a Ratiometric Fluorescent AuNCs-QDs Nanohybrids Probe with High Sensitivity

Simple and sensitive detection of cardiac biomarkers is of great significance for early diagnosis and prevention of acute myocardial infarction (AMI). Here, a ratiometric fluorescent nanohybrids probe (AuNCs-QDs) was synthesized through the coupling of bovine serum albumin-functionalized gold nanoclusters (AuNCs) with CdSe/ZnS quantum dots (QDs) to realize simple and sensitive detection of cardiac biomarker myoglobin (Mb). The AuNCs-QDs probe shows pink fluorescence under UV light, with two emission peaks at 468 nm and 630 nm belonging to QDs and AuNCs, respectively. Importantly, the presence of Mb caused fluorescence quenching of the blue-emitting QDs, thereby inhibiting the fluorescence resonance energy transfer (FRET) process between QDs and AuNCs, and reducing the fluorescence intensity ratio (F468/F630) of AuNCs-QDs probe effectively. As the concentration of Mb increases, the ratiometric fluorescent probe also exhibits a visible fluorescence color change. The detection limit was as low as 4.99 μg/mL, and the response of the probe to Mb showed a good linear relationship up to 0.52 mg/mL. Moreover, the probe has excellent specificity for Mb. Besides, the AuNCs-QDs has been applied to detect Mb of urine samples. More importantly, we also developed an AuNCs-QDs probe modified smartphone-aided paper-based strip for on-site monitoring of Mb. As far as we know, this is the first report of a smartphone-aided paper-based strip for on-site quick monitoring of Mb, which provides a useful approach for AMI biomarker monitoring and may can be extended to other medical diagnostics.

Electrochemical Biosensors for Whole Blood Analysis: Recent Progress, Challenges, and Future Perspectives

Whole blood, as one of the most significant biological fluids, provides critical information for health management and disease monitoring. Over the past 10 years, advances in nanotechnology, microfluidics, and biomarker research have spurred the development of powerful miniaturized diagnostic systems for whole blood testing toward the goal of disease monitoring and treatment. Among the techniques employed for whole-blood diagnostics, electrochemical biosensors, as known to be rapid, sensitive, capable of miniaturization, reagentless and washing free, become a class of emerging technology to achieve the target detection specifically and directly in complex media, e.g., whole blood or even in the living body. Here we are aiming to provide a comprehensive review to summarize advances over the past decade in the development of electrochemical sensors for whole blood analysis. Further, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms.

Label-Free Myoglobin Biosensor Based on Pure and Copper-Doped Titanium Dioxide Nanomaterials

In this study, using pure and copper-doped titanium dioxide (Cu-TiO₂) nanostructures as the base matrix, enzyme-less label free myoglobin detection to identify acute myocardial infarction was performed and presented. The Cu-TiO₂ nanomaterials were prepared using facile sol-gel method. In order to comprehend the morphologies, compositions, structural, optical, and electrochemical characteristics, the pure and Cu-TiO₂ nanomaterials were investigated by several techniques which clearly revealed good crystallinity and high purity. To fabricate the enzyme-less label free biosensor, thick films of synthesized nanomaterials were applied to the surface of a pre-fabricated gold screen-printed electrode (Au-SPE), which serves as a working electrode to construct the myoglobin (Mb) biosensors. The interference study of the fabricated biosensor was also carried out with human serum albumin (HSA) and cytochrome c (cyt-c). Interestingly, the Cu-doped TiO₂ nanomaterial-based Mb biosensor displayed a higher sensitivity of 61.51 µAcm^-2/nM and a lower detection limit of 14 pM with a response time of less than 10 ms.

Development of novel aptasensor for ultra-sensitive detection of myoglobin via electrochemical signal amplification of methylene blue using poly (styrene)-block-poly (acrylic acid) amphiphilic copolymer

Amplification of electrochemical signal in order to betterment of limit of detection in determination of biomarkers has an important role in early detection of some dangerous diseases such as cancers. For this purpose, in this research, two types of poly (styrene)-block-poly (acrylic acid) amphiphilic copolymer (PS₆₁-b-PAA₅₉₆ and PS₅₉₆-b-PAA₆₁) were synthesized by controlled radical polymerization method via reversible addition-fragmentation chain transfer polymerization (RAFT) technique. Chemical structure of block copolymers was confirmed by FT-IR spectroscopy and their surface morphology was assessed by scanning electron microscopy (SEM). Self-assembly of these block copolymers into polymeric vesicles (polymersomes), loading and release efficiency of methylene blue as an electroactive indicator were investigated in DMF and THF solvents. On the basis of our findings PS₆₁-b-PAA₅₉₆ has better capability for loading and release of MB than PS₅₉₆-b-PAA₆₁. Then the obtained methylene blue-loaded polymersome successfully used for development of an aptasensor toward determination of trace amounts of myoglobin. The proposed aptasensor showed a wide linear range from 1.0 aM to 1.0 μM with an ultra-low detection limit of 0.73 aM. Applying this amplification strategy, determination of myoglobin in real samples was successfully performed.

A spatially resolved ratiometric electrochemiluminescence immunosensor for myoglobin detection using Au@Ag2S as signal amplification tags

A spatially resolved ratiometric ECL immunosensor for myoglobin detection was developed via resonance energy transfer for signal amplification.

Nanodiamonds and hydrogen-substituted graphdiyne heteronanostructure for the sensitive impedimetric aptasensing of myocardial infarction and cardiac troponin I

A novel heteronanostructure of nanodiamonds (NDs) and hydrogen-substituted graphdiyne (HsGDY) (denoted as HsGDY@NDs) was prepared for the impedimetric aptasensing of biomarkers such as myoglobin (Myo) and cardiac troponin I (cTnI). Basic characterizations revealed that the HsGDY@NDs were composed of nanospheres with sizes of 200-500 nm. In these nanospheres, NDs were embedded within the HsGDY network. The HsGDY@NDs nanostructure, which integrated the good chemical stability and three-dimensional porous networks of HsGDY, and the good biocompatibility and electrochemical activity of NDs, could immobilize diverse aptamer strands and recognize target biomarkers. Compared with HsGDY- and NDs-based aptasensors, the HsGDY@NDs-based aptasensors exhibited superior sensing performances for Myo and cTnI, giving low detection limits of 6.29 and 9.04 fg mL^-1 for cTnI and Myo, respectively. In addition, the HsGDY@NDs-based aptasensors exhibited high selectivity, good stability, reproducibility, and acceptable applicability in real human serum. Thus, the construction of HsGDY@NDs-based aptasensor is expected to broaden the application of porous organic frameworks in the sensing field and provide a prospective approach for the early detection of disease biomarkers.

Impedimetric Immunosensor Utilizing Polyaniline/Gold Nanocomposite-Modified Screen-Printed Electrodes for Early Detection of Chronic Kidney Disease

The presence of small amounts of human serum albumin (HSA) in urine or microalbuminuria (30–300 µg/mL) is a valuable clinical biomarker for the early detection of chronic kidney disease (CKD). Herein, we report on the development of an inexpensive and disposable immunosensor for the sensitive, specific, and label-free detection of HSA using electrochemical impedance spectroscopy (EIS). We have utilized a simple one-step screen-printing protocol to fabricate the carbon-based three-electrode system on flexible plastic substrates. To enable efficient antibody immobilization and improved sensitivity, the carbon working electrode was sequentially modified with electropolymerized polyaniline (PANI) and electrodeposited gold nanocrystals (AuNCs). The PANI matrix serves as an interconnected nanostructured scaffold for homogeneous distribution of AuNCs and the resulting PANI/AuNCs nanocomposite synergically improved the immunosensor response. The PANI/AuNCs-modified working electrode surface was characterized using scanning electron microscopy (SEM) and the electrochemical response at each step was analyzed using EIS in a ferri/ferrocyanide redox probe solution. The normalized impedance variation during immunosensing increased linearly with HSA concentration in the range of 3–300 µg/mL and a highly repeatable response was observed for each concentration. Furthermore, the immunosensor displayed high specificity when tested using spiked sample solutions containing different concentrations of actin protein and J82 cell lysate (a complex fluid containing a multitude of interfering proteins). Consequently, these experimental results confirm the feasibility of the proposed immunosensor for early diagnosis and prognosis of CKD at the point of care.

Fluorometric determination of cardiac myoglobin based on energy transfer from a pyrene-labeled aptamer to graphene oxide

The authors describe a fluorometric assay for cardiac myoglobin (Mb), a marker for myocardial infarction. An Mb-binding aptamer was labeled with pyrene and adsorbed on the surface of graphene oxide (GO) via noncovalent and reversible binding forces. This causes the fluorescence of pyrene (best measured at excitation/emission wavelengths of 275/376 nm) to be quenched. However, fluorescence is restored on addition of pyrene due to the strong affinity between Mb and aptamer which causes its separation from GO. Fluorescence increases linearly in the 5.6-450 pM Mb concentration range, and the lower detection limit is 3.9 pM (S/N = 3). The assay was applied to the determination of cardiac Mb in spiked serum, and satisfactory results were obtained. Graphical abstract Schematic presentation of the detection of Mb (cardiac myoglobin) by using a fluorometric method based on pyrene-modified anti-Mb aptamer and GO (graphene oxide) through fluorescence quenching and subsequent recovery.

Electrochemical cardiovascular platforms: Current state of the art and beyond

Cardiovascular diseases (CVD) remain the leading cause of death within industrialized nations as well as an increasing cause of mortality and morbidity in many developing countries. Smoking, alcohol consumption and increased level of blood cholesterol are the main CVD risk factors. Other factors, such as the prevalence of overweight/obesity and diabetes, have increased considerably in recent decades and are indirect causes of CVD. Among CVDs, the acute coronary syndrome (ACS) represents the most common cause of emergency hospital admission. Since the prognosis of ACS is directly associated with timely initiation of revascularization, missed, misdiagnosis or late diagnosis have unfavorable medical implications. Early ACS diagnosis can reduce complications and risk of recurrence, finally decreasing the economic burden posed on the health care system as a whole. To decrease the risk of ACS and related CVDs and to reduce associated costs to healthcare systems, a fast management of patients with chest pain has become crucial and urgent. Despite great efforts, biochemical diagnostic approaches of CVDs remain difficult and controversial medical challenges as cardiac biomarkers should be rapidly released into the blood at the time of ischemia and persistent for a sufficient length of time to allow diagnostics, with tests that should be rapid, easy to perform and relatively inexpensive. Early biomarker assessments have involved testing for the total enzyme activity of aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK), which cardiac troponins being the main accepted biomarkers for diagnosing myocardial injury and acute myocardial infarction (AMI). To allow rapid diagnosis, it is necessary to replace the traditional biochemical assays by cardiac biosensor platforms. Among the numerous of possibilities existing today, electrochemical biosensors are important players as they have many of the required characteristics for point-of-care tests. Electrochemical based cardiac biosensors are highly adapted for monitoring the onset and progress of cardiovascular diseases in a fast and accurate manner, while being cheap and scalable devices. This review outlines the state of the art in the development of cardiac electrochemical sensors for the detection of different cardiac biomarkers ranging from troponin to BNP, N-terminal proBNP, and others.

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.

Plastic antibodies tailored on quantum dots for an optical detection of myoglobin down to the femtomolar range

A highly sensitive fluorescence detection probe was developed by tailoring plastic antibodies on the external surface of aqueous soluble quantum dots (QDs). The target was Myoglobin (Myo), a cardiac biomarker that quenched the intrinsic fluorescent emission of cadmium telluride (CdTe) QDs capped with mercaptopropionic acid (CdTe-MPA-QDs). The QDs were incubated with the target protein and further modified with a molecularly-imprinted polymer (MIP) produced by radical polymerization of acrylamide and bisacrylamide. The main physical features of the materials were assessed by electron microscopy, dynamic light scattering (DLS), UV/Vis spectrophotometry and spectrofluorimetry. The plastic antibodies enabled Myo rebinding into the QDs with subsequent fluorescence quenching. This QD-probe could detect Myo concentrations from 0.304 to 571 pg/ml (50.6 fM to 95 pM), with a limit of detection of 0.045 pg/ml (7.6 fM). The proposed method was applied to the determination of Myo concentrations in synthetic human serum. The results obtained demonstrated the ability of the modified-QDs to determine Myo below the cut-off values of myocardial infarction. Overall, the nanostructured MIP-QDs reported herein displayed quick responses, good stability and sensitivity, and high selectivity for Myo, offering the potential to be explored as new emerging sensors for protein detection in human samples.

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.

Nonmediated, Label-Free Based Detection of Cardiovascular Biomarker in a Biological Sample

Direct electrochemical (EC) monitoring in a cell culture medium without electron transporter as called mediator is attractive topic in vitro organoid based on chip with frequently and long-time monitoring since it can avoid to its disadvantage as stability, toxicity. Here, direct monitoring with nonmediator is demonstrated based on impedance spectroscopy under the culture medium in order to overcome the limitation of mediator. The applicability of EC monitoring is shown by detecting alpha-1-anti trypsin (A1AT) which is known as biomarkers for cardiac damage and is widely chosen in organoid cardiac cell-based chip. The validity of presented EC monitoring is proved by observing signal processing and transduction in medium, mediator, medium-mediator complex. After the observation of electron behavior, A1AT as target analyte is immobilized on the electrode and detected using antibody-antigen interaction. As a result, the result indicates limit of detection is 10 ng mL^-1 and linearity for the 10-1000 ng mL^-1 range, with a sensitivity of 3980 nF (log [g mL])^-1 retaining specificity. This EC monitoring is based on label-free and reagentless detection, will pave the way to use for continuous and simple monitoring of in vitro organoid platform.

Critical overview on the application of sensors and biosensors for clinical analysis

Sensors and biosensors have been increasingly used for clinical analysis due to their miniaturization and portability, allowing the construction of diagnostic devices for point-of-care testing. This paper presents an up-to-date overview and comparison of the analytical performance of sensors and biosensors recently used in clinical analysis. This includes cancer and cardiac biomarkers, hormones, biomolecules, neurotransmitters, bacteria, virus and cancer cells, along with related significant advances since 2011. Some methods of enhancing the analytical performance of sensors and biosensors through their figures of merit are also discussed.

Electrosynthesis and binding properties of molecularly imprinted poly-o-phenylenediamine for selective recognition and direct electrochemical detection of myoglobin

Electrosynthesis of molecularly imprinted polymer (MIP) templated with myoglobin (Mb) and the reference non-imprinted polymer (NIP) was examined with o-phenylenediamine (o-PD) as a monomer. Mass-sensitive quartz crystal microbalance with dissipation monitoring supplied by an electrochemical module (EQCM-D) was applied to characterize and optimize MIP/NIP electrosynthesis. Mb rebinding was detected by direct electrocatalytic reduction of Mb by square wave voltammetry (SWV) or differential pulse voltammetry (DPV). The results obtained showed high specificity of polymeric antibodies to template Mb, with an imprinting factor determined as a ratio Imax(MIP)/Imax(NIP) of 2-4. The prepared MIP sensor is characterized by an apparent dissociation constant of (3.3±0.5)×10(-9)M and has a broad range of working concentrations of 1nM-1μМ, with the detection limit of 0.5nM (9ng/ml). Mb rebinding was examined in Mb-free diluted human serum spiked with Mb as well as in plasma samples of patients with acute myocardial infarction (AMI) and in control plasma of healthy donors in order to demonstrate the potential medical application of developed MIP sensors.

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.

An ultrasensitive and incubation-free electrochemical immunosensor using a gold-nanocatalyst label mediating outer-sphere-reaction-philic and inner-sphere-reaction-philic species

This communication reports a new nanocatalytic scheme based on the facts that the redox reaction between a highly outer-sphere-reaction-philic (OSR-philic) species and a highly inner-sphere-reaction-philic (ISR-philic) species is slow and that an OSR- and ISR-philic Au-nanocatalyst label can mediate the two different types of redox species. This scheme allows highly sensitive and incubation free detection of creatine kinase-MB.

Immunosensors in Clinical Laboratory Diagnostics

The application of simple, cost-effective, rapid, and accurate diagnostic technologies for detection and identification of cardiac and cancer biomarkers has been a central point in the clinical area. Biosensors have been recognized as efficient alternatives for the diagnostics of various diseases due to their specificity and potential for application on real samples. The role of nanotechnology in the construction of immunological biosensors, that is, immunosensors, has contributed to the improvement of sensitivity, since they are based in the affinity between antibody and antigen. Other analytes than biomarkers such as hormones, pathogenic bacteria, and virus have also been detected by immunosensors for clinical point-of-care applications. In this chapter, we first introduced the various types of immunosensors and discussed their applications in clinical diagnostics over the recent 6 years, mainly as point-of-care technologies for the determination of cardiac and cancer biomarkers, hormones, pathogenic bacteria, and virus. The future perspectives of these devices in the field of clinical diagnostics are also evaluated.

[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.

Facilitated biosensing via direct electron transfer of myoglobin integrated into diblock copolymer/multi-walled carbon nanotube nanocomposites

Sequential drop-casting of a MWCNTs suspension and a amphiphilic copolymer micellar solution onto an electrode results in a favorable nanocomposite for integration of myoglobin, showing facilitated direct electron transfer.

Point-of-care diagnostics, a major opportunity for change in traditional diagnostic approaches: potential and limitations

'Point-of-care' (POC) diagnostics are a powerful emerging healthcare approach. They can rapidly provide statistically significant results, are simple to use, do not require specialized equipment and are cost-effective. For these reasons, they have the potential to play a major role in revolutionizing the diagnosis, initiation and monitoring of treatment of major global diseases. This review focuses on antibody-based POC devices that target four major global diseases: cardiovascular diseases, prostate cancer, HIV infection and tuberculosis. The key statistics and pathology of each disease is described in detail, followed by an in-depth discussion on emerging POC devices that target each disease, highlighting their potential and limitations.

Screening of DNA aptamers against myoglobin using a positive and negative selection units integrated microfluidic chip and its biosensing application

An aptamer screening method using a positive and negative selection units integrated microfluidic chip was introduced. Here, myoglobin (Myo), one of the early markers to increase after acute myocardial infarction, was used as the model. After 7-round selection, the aptamers, which exhibited dissociation constants (K(d)) in the nanomolar range (from 4.93 to 6.38 nM), were successfully obtained using a positive and negative selection units integrated microfluidic chip. The aptamer with the highest affinity (K(d) = 4.93 nM) was then used for the fabrication of a label-free supersandwich electrochemical biosensor for Myo detection based on target-induced aptamer displacement. The detection limit of this aptamer-based electrochemical biosensor was 10 pM, which was significantly lower than that of those previous antibody-based biosensors for Myo detection. This work may not only develop a strategy for screening aptamer but also offer promising alternatives to the traditional analytical and immunological methods for Myo detection.

Synthesis and characterization of reduced graphene oxide supported gold nanoparticles-poly(pyrrole-co-pyrrolepropylic acid) nanocomposite-based electrochemical biosensor

A conducting poly(pyrrole-co-pyrrolepropylic acid) copolymer nanocomposite film (AuNP-PPy-PPa) incorporating gold nanoparticles (AuNP) was electrochemically grown using a single step procedure over electrochemically reduced graphene oxide (RGO) flakes deposited on a silane-modified indium-tin-oxide (ITO) glass plate. The RGO support base provided excellent mechanical and chemical stability to the polymer nanocomposite matrix. The porous nanostructure of AuNP-PPy-PPa/RGO provided a huge accessible area to disperse AuNP, and it avoided metallic agglomeration within the polymer matrix. The AuNP-PPy-PPa/RGO was characterized by high-resolution transmission electron microscopy (HRTEM), contact angle measurements, Fourier transform infrared spectroscopy (FTIR), and electrochemical techniques. The pendant carboxyl group of AuNP-PPy-PPa/RGO was covalently bonded with myoglobin protein antibody, Ab-Mb, for the construction of a bioelectrode. Electrochemical impedance spectroscopy technique was used for the characterization of the bioelectrode and as an impedimetric biosensor for the detection of human cardiac biomarker, Ag-cMb. The bioelectrode exhibited a linear impedimetric response to Ag-cMb in the range of 10 ng mL(-1) to 1 μg mL(-1), in phosphate-buffered solution (PBS) (pH 7.4, 0.1 M KCl) with a sensitivity of 92.13 Ω cm(2) per decade.

Cardiovascular disease detection using bio-sensing techniques

Universally, cardiovascular disease (CVD) is recognised as the prime cause of death with estimates exceeding 20 million by 2015 due to heart disease and stroke. Facts regarding the disease, its classification and diagnosis are still lacking. Hence, understanding the issues involved in its initiation, its symptoms and early detection will reduce the high risk of sudden death associated with it. Biosensors developed to be used as rapid screening tools to detect disease biomarkers at the earliest stage and able to classify the condition are revolutionising CVD diagnosis and prognosis. Advances in interdisciplinary research areas have made biosensors faster, highly accurate, portable and environmentally friendly diagnostic devices. The recent advances in microfluidics and the advent of nanotechnology have resulted in the development of improved diagnostics through reduction of analysis time and integration of several clinical assays into a single, portable device as lab-on-a-chip (LOC). The development of such affinity based systems is a major drive of the rapidly growing nanotechnology industry which involves a multidisciplinary research effort encompassing nanofluidics, microelectronics and analytical chemistry. This review summarised the classification of CVD, the biomarkers used for its diagnosis, biosensors and their application including the latest developments in the field of heart-disease detection.

A label-free electrochemical immunosensor based on an ionic organic molecule and chitosan-stabilized gold nanoparticles for the detection of cardiac troponin T

A immunosensor based on an ionic organic molecule and chitosan-stabilized gold nanoparticles was developed for the detection of cardiac troponin T (cTnT).

Bio-functionalized Pt nanoparticles based electrochemical impedance immunosensor for human cardiac myoglobin

We report the covalent immobilization of three-dimensional carboxyl-functionalized Pt(MPA) nanoparticles with myoglobin protein antibody by carbodiimide coupling reaction deposited onto an indium-tin-oxide-coated glass plate for the construction of a bioelectrode.

Designing label-free electrochemical immunosensors for cytochrome c using nanocomposites functionalized screen printed electrodes

We have designed here a label-free direct electrochemical immunosensor for the detection of cytochrome c (cyt c), a heme containing metalloprotein using its specific monoclonal antibody. Two nanocomposite-based electrochemical immunosensor platforms were evaluated for the detection of cyt c; (i) self-assembled monolayer (SAM) on gold nanoparticles (GNP) in polypyrrole (PPy) grafted screen printed electrodes (SPE) and (ii) carbon nanotubes (CNT) integrated PPy/SPE. The nanotopologies of the modified electrodes were confirmed by scanning electron microscopy. Electrochemical impedance spectroscopy and cyclic voltammetry were employed to monitor the stepwise fabrication of the nanocomposite immunosensor platforms. In the present method, the label-free quantification of cyt c is based on the direct electron transfer between Fe (III)/Fe (II)-heme redox active site of cyt c selectively bound to anti-cyt c nanocomposite modified SPE. GNP/PPy and CNT/PPy nanocomposites promoted the electron transportation through the conductive pore channels. The overall analytical performance of GNP/PPy based immunosensor (detection limit 2 nM; linear range: 2 nM to 150 µM) was better than the anti-cyt c/CNT/PPy (detection limit 10 nM; linear range: 10 nM to 50 µM). Further, the measurement of cyt c release in cell lysates of cardiomyocytes using the GNP/PPy based immunosensor gave an excellent correlation with standard ELISA.

Employing denaturation for rapid electrochemical detection of myoglobin using TiO2 nanotubes

An alternative antibody-free strategy for the rapid electrochemical detection of cardiac myoglobin has been demonstrated here using hydrothermally synthesized TiO₂ nanotubes (Ti-NT). The denaturant induced unfolding of myoglobin led to easy access of the deeply buried electroactive heme center and thus the efficient reversible electron transfer from protein to electrode surface. The sensing performance of the Ti-NT modified electrodes were compared vis a vis commercially available titania and GCEs. The tubular morphology of the Ti-NT led to facile transfer of electrons to the electrode surface, which eventually provided a linear current response (obtained from cyclic voltammetry) over a wide range of Mb concentration. The sensitivity of the Ti-NT based sensor was remarkable and was equal to 18 μA mg^-1 ml (detection limit = 50 nM). This coupled with the rapid analysis time of a few tens of minutes (compared to a few days for ELISA) demonstrates its potential usefulness for the early detection of acute myocardial infarction (AMI).