Nanostructured zinc oxide film amalgamated with functionalized carbon nanotubes for facile electrochemical determination of nifedipine.

An innovative approach has been employed for the detection of nifedipine at glassy carbon electrode fabricated with zinc oxide nanoparticles embedded on functionalized multi walled carbon nanotubes. Herein, square wave voltammetry being an expeditious electrochemical technique has been utilized for the first time for the determination of nifedipine. Instrumental variables were altered to acquire optimized operational parameters. The electrochemical oxidation peak of nifedipine was procured at ∼ 807 mV which was recorded versus Ag/AgCl reference electrode. The oxidation peak was used to quantify the analyte in the dynamic linear range of 1 nM to 40 µM with highest sensitivity and lowest detection limit of 21.8 µA µM-1 and 0.49 nM respectively. The influence of common physiological interferents on the current signal of the analyte was examined. Pronounced stability and reproducibility of fabricated sensor was attained by the neoteric electrochemical approach. The developed protocol was efficaciously applied to quantify nifedipine in pharmaceutical formulations. The urine and blood serum sample of patients being treated for hypertension was effectively detected with nifedipine for the first time. The biological sample assay without the interference of the metabolites coexisting in the samples outlined the insight of selectivity of the developed sensor.

Nanoscale determination of antiviral drug acyclovir engaging bifunctionality of single walled carbon nanotubes - nafion film.

An elementary and exemplary approach is proposed for the accurate monitoring of antiviral drug acyclovir (ACV) utilizing glassy carbon electrode (GCE) fabricated with single-walled carbon nanotubes and nafion composite film employing square wave voltammetry for the first time. The developed sensor exhibits effective and sustained electron mediating behavior displaying higher peak currents at lower potential than those obtained at bare GCE. At optimal experimental conditions, oxidation current showed a wide linear response for ACV in the concentration range from 10 nM to 30 µM. The proposed sensor exhibited pronounced analytical performance for the determination of ACV with limit of detection corresponding to 1.8 nM and high sensitivity of 15.4 µA µM-1. The modified sensor showcased high recognition selectivity, fair reproducibility and long term stability of signal response in the physiological environment. The developed prototype was successfully implemented to quantify ACV in several commercially available pharmaceuticals. The versatile method described herein was efficaciously applied further in detecting ACV in real human urine sample of patient undergoing pharmacological treatment with ACV. The results explicitly demonstrate the applicability of the developed sensor in quality control, pharmacokinetic studies and clinical analysis.

Sensitive detection of brucine an anti-metastatic drug for hepatocellular carcinoma at carbon nanotubes - nafion composite based biosensor.

A neoteric approach for the electrochemical analysis of brucine in biological environment has been developed. The glassy carbon electrode modified with single walled carbon nanotubes and nafion composite film is delineated for the first time to determine brucine employing square wave voltammetry. The quantification of brucine at physiological pH 7.2 manifests remarkable performance at the developed biosensor. The effect of several operational parameters has been studied in the present investigation. Under optimized conditions, a dynamic linear range from 1nM to 8µM with a high sensitivity of 340.8µAµM-1 and limit of detection corresponding to 0.11nM was achieved. The interfering effect of some coexisting metabolites on the current response of brucine has been reported. The method was successfully applied for the detection of brucine in traditional pharmaceutical formulations. The biological relevance of the present method has been demonstrated by the analysis of the alkaloid in human serum and urine samples. The analytical utility was further assessed by the selective determination of brucine in Strychnos nux-vomica seeds exhibiting considerable potential as a diagnostic tool.

Nanomaterials based electrochemical sensors for biomedical applications.

A growing variety of sensors have increasingly significant impacts on everyday life. Key issues to take into consideration toward the integration of biosensing platforms include the demand for minimal costs and the potential for real time monitoring, particularly for point-of-care applications where simplicity must also be considered. In light of these developmental factors, electrochemical approaches are the most promising candidate technologies due to their simplicity, high sensitivity and specificity. The primary focus of this review is to highlight the utility of nanomaterials, which are currently being studied for in vivo and in vitro medical applications as robust and tunable diagnostic and therapeutic platforms. Highly sensitive and precise nanomaterials based biosensors have opened up the possibility of creating novel technologies for the early-stage detection and diagnosis of disease related biomarkers. The attractive properties of nanomaterials have paved the way for the fabrication of a wide range of electrochemical sensors that exhibit improved analytical capacities. This review aims to provide insights into nanomaterials based electrochemical sensors and to illustrate their benefits in various key biomedical applications. This emerging discipline, at the interface of chemistry and the life sciences, offers a broad palette of opportunities for researchers with interests that encompass nanomaterials synthesis, supramolecular chemistry, controllable drug delivery and targeted theranostics in biology and medicine.

Electrochemical determination of methylglyoxal as a biomarker in human plasma.

A novel electrochemical approach for the quantitative analysis of methylglyoxal as a biomarker in human plasma has been developed. An electrochemical sensor employing a single walled carbon nanotube modified glassy carbon electrode for the sensitive detection of methylglyoxal is delineated for the first time using square wave voltammetry. This modified electrode exhibits potent and sustained electron-mediating behavior and a well-defined reduction peak in response to methylglyoxal was observed. Under optimized experimental conditions, a wide linear dynamic range, from 0.1 to 100 µM, and high sensitivity of 76.3 nA µM⁻¹ were achieved for the detection of methylglyoxal. The interfering effect of common coexisting metabolites in human whole blood has also been investigated. The developed assay was shown to be specific and sensitive for the analysis of plasma levels of methylglyoxal in healthy volunteer and diabetic patients.

Voltammetric detection of the α-dicarbonyl compound: methylglyoxal as a flavoring agent in wine and beer.

A simple, rapid and highly selective method for the determination of the most abundant α-dicarbonyl compound in wine and beer has been developed for the first time by employing square wave voltammetry. A novel electrochemical sensor, based on the electrodeposition of platinum nanoparticles onto single wall carbon nanotubes that were cast on a glassy carbon electrode (GCE) substrate, is presented in this paper. This modified electrode exhibited excellent catalytic activity in the electroreduction of methylglyoxal, showing much higher peak currents than those measured on an unmodified GCE. The effects of different experimental and instrumental parameters, such as solution pH and square wave frequency, were examined. The reduction peak current showed a linear range of from 0.1×10(-6) to 100×10(-6)M with a 0.9979 correlation coefficient; and a low detection limit of 2.8×10(-9)M was also obtained. The proposed methodology was successfully applied to the quantitative analysis of methylglyoxal in wine and beer samples. The developed sensor possesses advantageous properties such as a high active surface area, stability, and rapid electron transfer rate, which cumulatively demonstrate high performance toward the electrocatalytic reduction and detection of methylglyoxal.

Functionalization of carbon buckypaper for the sensitive determination of hydrogen peroxide in human urine.

Here we report on a new approach for the electrochemical detection of hydrogen peroxide (H(2)O(2)) based on the co-immobilization of horseradish peroxidase and methylene blue on the functionalized carbon buckypaper supported by a titanium substrate. Cyclic voltammetry was used to study and optimize the performance of the resulting electrochemical biosensor. The proposed biosensor exhibited high analytical performance towards the quantification of H(2)O(2) at the physiological pH 7.4. Under optimized conditions, the biosensor shows a wide linear response range from 0.1 × 10(-6) to 5 × 10(-4)M concentrations of H(2)O(2). The detection limit was determined to be 7.5 × 10(-8)M (based on S/N=3). Reproducibility and stability of the fabricated biosensor were examined with satisfactory results. The biological relevance of the developed electrochemical biosensor has been further studied by the determination of H(2)O(2) in human urine samples of normal volunteers prior to and following the ingestion of coffee. Increased levels of urinary H(2)O(2) concentration suggest that oxidative stress is induced by coffee drinking in humans. There is considerable interest in oxidative stress as relates to human physiology. The sensitive determination of H(2)O(2) in human urine may serve as a valuable biomarker to effectively elucidate specific levels of oxidative stress in vivo.

A comparison of edge- and basal-plane pyrolytic graphite electrodes towards the sensitive determination of hydrocortisone.

Electrochemical sensor employing edge-plane pyrolytic graphite electrode (EPPGE) for the sensitive detection of hydrocortisone (HC) is delineated for the first time. The electrochemical properties are investigated exercising the cyclic voltammetry and square-wave voltammetry (SWV). When equating with the bare basal-plane pyrolytic graphite electrode (BPPGE), the EPPGE gave better response towards the detection of HC both in terms of sensitivity and detection limit. The voltammetric results indicated that EPPGE remarkably enhances the reduction of HC which leads to considerable amelioration of peak current with shift of peak potential to less negative values. The difference in the surface morphology of two electrodes has been studied. Also, the EPPGE delivered an analytical performance for HC with a sensitivity of 45 nA nM(-1) and limit of detection of 88 nM in the concentration range 100-2000 nM. The method has been utilized for the determination of HC in pharmaceuticals and real samples. The electroanalytical method using EPPGE is the most sensitive method for determination of HC with lowest limit of detection to date. The major metabolites present in blood plasma did not intervene with the present investigation as they did not exhibit reduction peak in the experimental range used. A comparison of results with high performance liquid chromatography (HPLC) signalizes a good agreement.

Electrochemical investigations of corticosteroid isomers--testosterone and epitestosterone and their simultaneous determination in human urine.

Voltammetric investigation of two corticoid isomers--testosterone and epitestosterone has been carried out at bare and single-wall carbon nanotubes (SWNT)-modified edge plane pyrolytic graphite electrode (EPPGE). Square wave voltammetry (OSWV) has been used for the simultaneous determination of isomeric steroids. The reduction of the two isomers occurred in a pH dependent, 2e, 2H+ process and well-defined voltammetric peaks were observed. Under the optimum experimental conditions, linear calibration curves are obtained within the concentration range 5-1000 nM for both the steroids with the limit of detection 2.8 x 10(-9) and 4.1 x 10(-9) M for testosterone and epitestosterone respectively. The developed protocol is successfully implemented for the analysis of both the compounds in the urine samples of normal subjects as well as in patients undergoing treatment with testosterone. The results obtained from the proposed voltammetric method were also compared with HPLC analysis and found to be similar.

A single-wall carbon nanotubes modified edge plane pyrolytic graphite sensor for determination of methylprednisolone in biological fluids.

An electrochemical protocol based on reduction is developed to determine methylprednisolone using single-wall carbon nanotubes (SWNTs) modified edge plane pyrolytic graphite electrode (EPPGE). To obtain a good sensitivity, instrumental variables were studied using Square Wave Voltammetry (SWV). The voltammetric results indicate that SWNTs modified EPPGE remarkably enhances the reduction of methylprednisolone which leads to considerable improvement of peak current with shift of peak potential to less negative values. The voltammetric current showed a linear response for methylprednisolone concentration in the range 5-500 nM with a sensitivity of 98 nA nM(-1). The limit of detection was estimated to be 4.5x10(-9)M. The developed method is used for the determination of methylprednisolone in pharmaceutical dosages and human blood plasma samples of patients undergoing treatment with methylprednisolone. The major metabolites present in blood plasma did not interfere with the present investigation as they did not exhibit reduction peak in the experimental range used. A comparison of results with high performance liquid chromatography (HPLC) indicates a good agreement.

A sensitive voltammetric sensor for determination of synthetic corticosteroid triamcinolone, abused for doping.

Edge plane pyrolytic graphite electrode (EPPGE) modified with single-wall carbon nanotubes (SWNTs) has been used as a sensor to determine triamcinolone, abused by athletes for doping. A comparison of the voltammetric behavior between SWNTs modified EPPGE and fullerene - C(60)-modified EPPGE indicated that SWNTs modified EPPGE is more sensitive. The electrode exhibited an effective catalytic response with good reproducibility and stability. The effect of several parameters such as pH, square wave frequency and steroid concentration were studied. The square wave voltammetric response of the electrode to triamcinolone is linear in the range 0.1-25 nM with a detection limit and sensitivity of 8.9 x 10(-10)M and 2.06 microA nM(-1), respectively. The method was applied for the determination of triamcinolone in several commercially available pharmaceuticals and real urine samples obtained from patients undergoing pharmacological treatment with triamcinolone. A comparison of the observed results with HPLC analysis indicated a good agreement. The product obtained after reduction of triamcinolone was also characterized using (1)H NMR and GC-MS and the site of reduction is found to be carbonyl group at position 20. The method described is rapid, simple and accurate and can be easily applied for detecting cases of doping.

Effect of substrate and embedded metallic impurities of fullerene in the determination of nandrolone.

A comparison of edge plane pyrolytic graphite substrate is made with other substrates like indium tin oxide, glassy carbon, gold and basal plane pyrolytic graphite as a substrate for fullerene modification for the determination of nandrolone by Osteryoung square wave voltammetry (OSWV) in phosphate buffer media. Comparative study of voltammetric response of nandrolone at untreated, purified and super-purified fullerene modified edge plane pyrolytic graphite electrode (EPPGE) is also carried out to determine the role of embedded metallic impurities of fullerene on determination of nandrolone. It is observed that EPPGE serves as best substrate among the studied for casting fullerene. The removal of embedded metals from fullerene shifts the peak potential of nandrolone to more positive potentials and peak current decreases. A linear calibration curve is obtained in the concentration range of 0.01-50 nM with a detection limit and sensitivity of 1.5 x 10(-11) M and 1.838 microA nM(-1), respectively. The developed method was satisfactorily applied to the determination of nandrolone in several commercially available medicinal samples.

Fullerene-C60-modified edge plane pyrolytic graphite electrode for the determination of dexamethasone in pharmaceutical formulations and human biological fluids.

Electrochemical behaviour of dexamethasone at the fullerene-C(60)-modified pyrolytic graphite electrode (PGE) has been investigated using Osteryoung square wave voltammetry (SWV). Compared to a bare PGE and fullerene-C(60)-modified glassy carbon electrode (GCE), the fullerene-C(60)-modified edge plane PGE exhibited an apparent shift of the peak potential to less negative potentials with a marked enhancement in the current response of dexamethasone. The peak potential was linearly dependent on pH with dE(p)/dpH as 59 mV/pH. Calibration plot having good linearity with a correlation coefficient 0.9983 is obtained in the concentration range of 0.05-100 microM and the sensitivity of the method has been found to be 0.685 microA microM(-1). The detection limit is estimated to be 5.5 x 10(-8)M. The electrode showed good sensitivity, stability and reproducibility. The practical analytical utility of the method is illustrated by quantitative determination of dexamethasone in several commercially available pharmaceutical formulations and human blood plasma of patients being treated with dexamethasone. HPLC method was used to compare the results obtained for the quantitative estimation of dexamethasone in biological fluids.

Simultaneous determination of adenosine and inosine using single-wall carbon nanotubes modified pyrolytic graphite electrode.

Voltammetric determination of adenosine and inosine has been carried out at single-wall carbon nanotubes (SWNTs) modified pyrolytic graphite electrode (PGE) at pH 7.2 using Osteryoung square wave voltammetry (OSWV). The modified electrode exhibits remarkable electrocatalytic properties towards adenosine and inosine oxidation with a peak potential of approximately 1229 mV and 1348 mV, respectively. Linear calibration curves are obtained over the concentration range 0.5 microM to 1.0 mM in adenosine and 10 microM to 1.0 mM in inosine with sensitivity of 1.0 microA microM(-1) and 1.9 microA microM(-1) for adenosine and inosine respectively. The limit of detection for adenosine and inosine was found to be 0.51x10(-7) M and 2.04x10(-7) M, respectively. The proposed method was also used to estimate these compounds in human blood plasma and urine samples and the method was validated using HPLC.