rmpM Genosensor for Detection of Human Brain Bacterial Meningitis in Cerebrospinal Fluid

Human brain bacterial meningitis is a life-threatening disease caused mainly by Neisseria meningitidis, lead to damage of the outer membrane covering (meninges) of brain or even death. The usual methods of diagnosis are either time-consuming or have some limitations. The specific rmpM (reduction-modifiable protein M) virulent gene based genosensor is more sensitive, specific, and can detect N. meningitidis directly from the patient cerebrospinal fluid in 30 min including 1-min response time. 5′-Thiol-labeled single-stranded DNA (ssDNA) probe was immobilized onto screen-printed gold electrode (SPGE) and hybridized with denatured (95 °C) single-stranded genomic DNA (ssG-DNA) for 10 min at 25 °C. The electrochemical response was measured by cyclic voltammetry, differential pulse voltammetry (DPV) and electrochemical impedance using redox indicators. The sensitivity of the genosensor was 9.5087?(μA/cm²)/ng with DPV and limit of detection was 3 ng/6 μL ssG-DNA. The immobilization of the ssDNA probe and hybridization with ssG-DNA from N. meningitidis was characterized by atomic force microscopy and Fourier transform infrared spectroscopy. The rmpM genosensor was stable for 6 months at 4 °C with 10 % loss in initial DPV current. The advantage of rmpM genosensor is to detect bacterial meningitis simultaneously in multiple patients using SPGE array during an outbreak of the disease.     

Carbon composite-based DNA sensor for detection of bacterial meningitis caused by Neisseria meningitidis

Carbon/1-octadecanethiol-carboxylated multiwalled carbon nanotubes (cMWCNT) composite was used to construct a DNA sensor for detection of human bacterial meningitis caused by Neisseria meningitidis. The carbon composite electrode was used to covalently immobilize 5′-amine-labeled 19-mer single-stranded DNA (ssDNA) probe, which was hybridized with 1.35?×?10²–3.44?×?10⁴ pM (0.5–128 ng/5 μl) of single-stranded genomic DNA (ssG-DNA) of N. meningitidis for 10 min at room temperature (RT). The surface topography of the DNA sensor was characterized by using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) while electrochemically characterized by electrochemical impedance. The immobilization of ssDNA probe and hybridization with ssG-DNA were detected electrochemically by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at RT in 30 min with a response time of 1 min. The DNA sensor showed high pathogenic specificity and can distinguish among complement, noncomplement, one base mismatch, and triple base mismatch oligomer targets. The limit of detection (LOD) and sensitivity of the sensor were approximately 68 pM and 38.095 (μA/cm²)/nM of ssG-DNA, respectively, using DPV. The improved sensitivity and LOD of the sensor can be attributed to the higher efficiency of probe immobilization due to high surface area-to-volume ratio and good electrical activity of cMWCNT. Figure

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Nanostructured platform for the detection of Neisseria gonorrhoeae using electrochemical impedance spectroscopy and differential pulse voltammetry

We report on a nanocomposite based genosensor for the detection of Neisseria gonorrhoeae, a bacterium causing the sexually transmitted disease gonorrhoea. Amino-labeled probe DNA was covalently immobilized on electrochemically prepared polyaniline and iron oxide (PANI-Fe₃O₄) nanocomposite film on an indium tin oxide (ITO) electrode. Scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) techniques have been employed to characterize surface of the modified electrode. The genosensor has detection limits of 1?×?10^-15 M and 1?×?10^-17 M, respectively, using the EIS and DPV techniques. This biosensor can discriminate a complementary sequence from a single-base mismatch and from non-complementary DNA, and has been utilized for detection of DNA extracted from N. gonorrhoeae culture, and from patient samples with N. gonorrhoeae. It is found to exhibit good specificity for N. gonorrhoeae species and shows no response towards non-gonorrhoeae type of Neisseria species (NgNs) and other gram-negative bacterias (GNBs). The affinity constant for hybridization calculated using the Langmuir adsorption isotherm model is found to be 3.39?×?10⁸ M^-1.

Development of electrochemical genosensor for MYCN oncogene detection using rhodamine B as electroactive label

A novel electrochemical genosensor based on a graphite electrode modified with poly(4-aminophenol) has been constructed for prognostic of neuroblastoma, a malignant tumor originating from embryonic precursor cells of the sympathetic nervous system and associated with the amplification of the MYCN oncogene. The genosensor exhibited distinct electrical and morphological properties using rhodamine B as indicator of DNA hybridization. The detection limit was evaluated to be 0.47 μmol L^?1 (n = 3), and the electrochemical genosensor was selective for the complementary DNA, using serum sample. This DNA sensing platform was successfully applied to detect MYCN, an important biomarker for neuroblastoma.     

Poly(m-ferrocenylaniline) modified carbon nanotubes-paste electrode encapsulated in nafion film for selective and sensitive determination of dopamine and uric acid in the presence of ascorbic acid

A nafion covered carbon nanotubes-paste electrode modified with poly(m-ferrocenylaniline), (Nf/p(FcAni)-CNTsPE), provides a novel voltammetric sensor for the selective determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). We studied the electrochemical activity of Nf/p(FcAni)-CNTsPE toward DA, UA, and AA by differential pulse voltammetry (DPV). DA and UA anodic peaks appear at 0.30 and 0.45 V, respectively while an anodic peak for AA was not observed. DPV oxidation peak values are linearly dependent on DA concentration over the range 1–150 μM (r² = 0.992), and on UA concentration over the range 5–250 μM (r² = 0.997). DA and UA detection limits are estimated to be 0.21 and 0.58 μM, respectively. The modified electrode shows both good selectivity and reproducibility for the selective determination of DA and UA in real samples. Finally, the modified electrode was successfully applied for the determination of DA and UA in pharmaceutical or biological sample fluids.     

Selective determination of L-dopa in the presence of ascorbic acid and uric acid using a 3D graphene foam

Three-dimensional interconnected network graphene foam (GF) was synthesized by chemical vapor deposition. The GF was transferred onto indium tin oxide glass, acting as an electrode for the selective determination of L-dopa in the presence of ascorbic and uric acid. Using differential pulse voltammetry (DPV) method, the oxidation peak current is well linear with L-dopa concentration in the range of 0.05–1 μM with a sensitivity of 2.64 μA μM^?1 and in the range of 1–40 μM with a sensitivity of 1.82 μA μM^?1. The detection limit of this electrode for L-dopa is about 20 nM. The proposed electrode can also effectively avoid the interference of ascorbic acid and uric acid, making the proposed sensor suitable for the accurate determination of L-dopa in human urine fluids. This electrode will have a wide range of potential application prospect in electrochemical detection.     

Electrodeposition of zinc oxide nanoparticles on multiwalled carbon nanotube-modified electrode for determination of caffeine in wastewater effluent

We report on the development of an electrochemical sensor based on electrodepositing zinc oxide on multiwalled carbon nanotube-modified glassy carbon electrode for the detection of caffeine in pharmaceutical wastewater effluents. The measurements were carried out using cyclic voltammetry, electrochemical impedance spectroscopy, chronoamperometry and differential pulse voltammetry (DPV). DPV measurements showed a linear relationship between oxidation peak current and concentration of caffeine in 0.1 M HClO₄ (pH 1.0) over the concentration range 0.00388–4.85 mg/L and a detection limit of 0.00194 mg/L. The diffusion coefficient and Langmuir adsorption constant for caffeine were calculated to be 3.25 × 10^?6 cm² s^?1 and 1.10 × 10³ M^?1, respectively. The sensor showed satisfactory results when applied to the detection of caffeine in wastewater effluents.     

Electrochemical Study of Interaction Between Clozapine and DNA and Its Analytical Application

Abstract

The interaction between clozapine (CLZ) as an orally administrated antipsychotic drug with double stranded calf thymus DNA (dsDNA) was investigated at electrode surface using differential pulse voltammetry (DPV). Activated carbon paste electrode (CPE) was modified with dsDNA and used for monitoring the changes of the characteristics peak of CLZ in 0.05 M acetate buffer (pH 4.3). The adsorptive stripping voltammetry on dsDNA‐modified carbon paste electrode (dsDNA‐CPE) was used for determination of very low concentration of CLZ. Under optimal conditions, the oxidation peak current is proportional to CLZ concentration in the range of 7×10^?9?1.2×10^?6 mol l^?1 with a detection limit of 1.5×10^?9 mol l^?1 for 180 s accumulation time by DPV. The proposed dsDNA‐CPE was successfully used for determination of CLZ in human serum samples with recovery of 97.0±2.5%.     

Electrochemical application of titanium dioxide nanoparticle/gold nanoparticle/multiwalled carbon nanotube nanocomposites for nonenzymatic detection of ascorbic acid

Titanium dioxide nanoparticle/gold nanoparticle/carbon nanotube (TiO₂/Au/CNT) nanocomposites were synthesized, and then characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). A TiO₂/Au/CNT nanocomposite-modified glassy carbon (GC) electrode was prepared using the drop coating method and was investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric current–time response (I-T). The modified material is redox-active. The nonenzymatically detected amount of ascorbic acid (AA) on the TiO₂/Au/CNT electrode showed a linear relationship with the AA concentration, for concentrations from 0.01 to 0.08 μM; the sensitivity was 117,776.36 μA?·?cm^?2?·?(mM)^?1, and the detection limit was 0.01 μM (S/N?=?3). The results indicated that the TiO₂/Au/CNT nanocomposite-modified GC electrode exhibited high electrocatalytic activity toward AA. This paper describes materials consisting of a network of TiO₂, Au, and MWCNTs, and the investigation of their synergistic effects in the detection of AA.     

A new genosensor for meningococcal meningitis diagnosis using biological samples

In this work, a new electrochemical biosensor for DNA detection of bacterial meningitis is proposed. The system is based on specific DNA fragments from the Neisseria meningitidis genome as a probe incorporated on graphite electrodes modified with poly(4-aminophenol). Detection of a complementary oligonucleotide sequence, a specific 710-base pair amplicon, and the genomic DNA of bacteria was carried out by differential pulse voltammetry, using ethidium bromide as an electroactive indicator of hybridization. The complementary oligonucleotide and the genomic DNA of Neisseria meningitidis were quantified by the genosensor, showing detection limits of 0.6 ng μL^?1 and about 6 ng μL^?1, respectively. Morphological differences were observed between hybridized and unhybridized surfaces by atomic force microscopy. The biosensor showed high selectivity, discriminating non-specific targets, and high stability retaining over 98% of its original activity after 120 days of storage. The bioelectrode was effective in discriminating the genomic DNA in samples with human serum without significant interference, proving to be an interesting platform for meningococcal meningitis diagnosis.     

Sol-Gel Imprinted Polymers Based Electrochemical Sensor for Paracetamol Recognition and Detection

Molecular imprinting and sol-gel technique were combined to develop a molecular imprinted polymer (MIP) based electrochemical sensor in this work. With the successive modification of multi-walled carbon nanotubes (MWNTs) and gold nanoparticles (GNPs), a modified glassy carbon electrode (GCE) was immersed in a sol-gel solution in the presence of paracetamol (PR) for the electropolymerization to fabricate an imprinted sensor. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were employed to characterize the constructed sensor. The factors for the sensor preparation, the electropolymerization potential range, the monomer concentration, and the scan rate for the sensor preparation were optimized. The sensor displayed an excellent recognition capacity toward PR compared with other analogues. Additionally, the DPV peak current was linear to the PR concentration in the range from 8.0 × 10^?8 to 5.0 × 10^?5 mol/L, with a detection limit of 4.0 × 10^?8 mol/L. The prepared sensor also showed satisfactory reproducibility and regeneration capacity.     

The use of copper solid amalgam electrodes for determination of the pesticide thiram

The complexes formed between copper and thiram and between mercury and thiram have been electrochemically (voltammetrically) investigated in the present work. Their structure was confirmed using electrospray ionization mass spectrometry. Due to formation of the complex between copper (from copper solid amalgam electrode) and thiram, the concentration of this pesticide can be determined. The voltammetric behavior of thiram was investigated at polished (p-CuSAE) and mercury meniscus modified (m-CuSAE) copper solid amalgam electrodes (inner diameter 1.5 mm) by differential pulse voltammetry (DPV) and by direct current voltammetry (DCV). Optimum conditions for DPV determination of thiram were found in Britton–Robinson buffer. The reaction mechanism was investigated using DCV and elimination voltammetry with linear scan. DPV with optimized parameters was applied for determination of thiram in analyzed solutions. The limits of detection were calculated as 16 nmol?L^?1 (t _acc?=?100 s) for m-CuSAE and 23 nmol?L^?1 (t _acc?=?60 s) for p-CuSAE. The proposed method was successfully applied for thiram determination in real sample solutions.     

Conductometric studies and application of new Schiff base ligand as carbon paste electrode modifier for mercury and cadmium determination

A new chemically modified carbon paste electrode by 2,2?-((pyridine-2,6-diylbis(azanylylidene))bis(methanylylidene))diphenol (L) ligand has been made and used as a sensor for determination of trace mercury and cadmium ions with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. Complexation studies of the ligand with Cu²⁺, Zn²⁺, Hg²⁺, Ni²⁺ and Cd²⁺ ions by conductometric method in acetonitrile–ethanol mixture at 25°C show that the ML complexes have formed. The formation constants of complexes were calculated from the computer fitting of the molar conductance–mole ratio data, and the stability of the resulting complexes varied in order of Cd²⁺ > Hg²⁺ > Cu²⁺ > Zn²⁺ > Ni²⁺. Then a simple and effective chemically modified carbon paste electrode with L was prepared, and the electrochemical properties and applications of the modified electrode were investigated. Under the optimal conditions, the detection limit was 0.0494 μg L^?1 and 0.0782 μg L^?1 for cadmium and mercury ions, respectively, and the linear range for both metal ions were from 1 to 100 μg L^?1. The electrode shows high sensitivity, reproducibility and low cost, and was successfully applied to determination of Cd²⁺ and Hg²⁺ ions in water samples with recovery in the range of 97–101%.     

Indigo Carmine as New Label in PNA Biosensor for Detection of Short Sequence of p53 Tumor Suppressor Gene

A new electrochemical PNA hybridization biosensor for detection of a 15‐mer sequence unique to p53 using indigo carmine (IC) as an electrochemical detector is described in this work. This genosensor is based on the hybridization of target oligonucleotide with its complementary probe immobilized on the gold electrode by self‐assembled monolayer formation. Because this label is electroactive in acidic medium, the interaction between IC and short sequence of p53 is studied by differential pulse voltammety (DPV) in 0.1 M H₂SO₄. The results of electrochemical impedance spectroscopy and cyclic voltammetry in the solution of [Fe(CN)₆]^3?/4? shows no breakage in PNA‐DNA duplex. A decrease in the voltammetric peak currents of IC is observed upon hybridization of the probe with the target DNA. The influence of probe concentration on effective discrimination against non‐complementary oligonucleotides is investigated and a concentration of 10^?7 M is selected. The diagnostic performance of the PNA sensor is described and the detection limit is found to be 4.31×10^?12 M.     

Selective recognition and electrochemical detection of p-nitrophenol based on a macroporous imprinted polymer containing gold nanoparticles

We have combined the molecular imprinting and the layer-by-layer assembly techniques to obtain molecularly imprint polymers (MIPs) for the electrochemical determination of p-nitrophenol (p-NPh). Silica microspheres functionalized with thiol groups and gold nanoparticles (Au-NPs) were assembled on a gold electrode surface layer by layer. The electrode was then immersed into a solution of pyrrole and p-NPh (the template), and electropolymerization led to the creation of a polymer-modified surface. After the removal of the silica spheres and the template, electrochemical impedance spectroscopy and differential pulse voltammetry (DPV) were employed to characterize the surface. The results demonstrated the successful fabrication of macroporous MIPs embedded with Au-NPs on the gold electrode. The effects of monomer concentration and scan rate on the performance of the electrode were optimized. Excellent recognition capacity is found for p-NPh over chemically similar species. The DPV peak current is linearly related to concentration of p-NPh in the 0.1 μM to 1.4 mM range, with a 0.1 μM limit of detection (at S/N?=?3).

Comparison of Boron-Doped Diamond and Glassy Carbon Electrodes for Determination of Terbinafine in Pharmaceuticals Using Differential Pulse and Square Wave Voltammetry

This paper examines the electrochemical oxidation of terbinafine with the boron doped diamond and glassy carbon electrodes. The studies were performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square-wave voltammetry (SWV). The supporting electrolytes, solution pH, the range of potentials, and the scan rates were optimized. Terbinafine was irreversibly oxidized in all electrolytes, yielding well-defined peaks in the positive potential range. The peak potential shifted towards less positive values as the solution pH increased. Voltammetric determination of terbinafine was performed under the optimized conditions. Using the boron doped diamond electrode, a linear relationship between current and concentration was obtained between 5.44 × 10^?7 and 5.18 and 10^?6 mol/L with SWV and between 7.75 · 10^?7 and 8.55 · 10^?6 mol/L by DPV. At the glassy carbon electrode, a linear relationship between 7.75 · 10^?7 and 8.55 · 10^?6 mol/L was obtained by SWV and between 7.75 · 10^?7 and 1.05 · 10^?5 mol/L by DPV. The sensitivity, precision, and selectivity of the procedures were evaluated. In order to check the practical application of the developed methods, the concentration of terbinafine was determined in pharmaceutical preparations.     

Evaluation of a novel composite based on functionalized multi-walled carbon nanotube and iron phthalocyanine for electroanalytical determination of isoniazid

A novel platform for electroanalysis of isoniazid based on graphene-functionalized multi-walled carbon nanotube as support for iron phthalocyanine (FePc/f-MWCNT) has been developed. The FePc/f-MWCNT composite has been dropped on glassy carbon forming FePc/f-MWCNT/GC electrode, which is sensible for isoniazid, decreasing substantially its oxidation potential to +200 mV vs Ag/AgCl. Electrochemical and electroanalytical properties of the FePc/f-MWCNT/GC-modified electrode were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electrochemical microscopy, and amperometry. The sensor presents better performance in 0.1 mol L^?1 phosphate buffer at pH 7.4. Under optimized conditions, a linear response range from 5 to 476 μmol L^?1 was obtained with a limit of detection and sensitivity of 0.56 μmol L^?1 and 0.023 μA L μmol^?1, respectively. The relative standard deviation for 10 determinations of 100 μmol L^?1 isoniazid was 2.5%. The sensor was successfully applied for isoniazid selective determination in simulated body fluids.     

Nickel oxide nanoparticles decorated graphene quantum dot as an effective electrode modifier for electrocatalytic oxidation and analysis of clozapine

In the present work, a novel, simple, and sensitive clozapine (CLZ) sensor was developed based on nickel oxide nanoparticle (NiO)-decorated graphene quantum dot (GQD)-modified glassy carbon electrode (NiO/GQD/GCE). NiO/GQD/GCE was prepared by simple electrodeposition, the electrochemical behavior of CLZ at the surface of the prepared electrode was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), and an improved reversibility and increased peak current with negative shift in the oxidation potential were observed at the proposed electrode. The effect of some experimental parameters has been examined, and based on the results, an electron transfer–chemical reaction–electron transfer mechanism has been proposed for CLZ electrooxidation. The differential pulse voltammetric response of the NiO/GQD/GCE was linear to the concentration of CLZ in the range of 3?×?10^?9 to 1?×?10^?6 M, and the detection limit was found to be 0.55 nM (S/N?=?3). The method has been successfully used for the selective determination of the CLZ amount in the pharmaceutical preparations and human serum samples with good accuracy and precision.     

Immunosensor for electrodetection of the C-reactive protein in serum

Epidemiological studies have demonstrated an association between the risk of cardiovascular events and increasing C-reactive protein (CRP) concentration. This paper reports the development of an immunosensor for the assessment of the cardiovascular process using anti-C-reactive protein antibody immobilized onto a gold-printed screen electrode. Positive and negative human sera were successfully evaluated using electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and atomic force microscopy (AFM). EIS results show that, after the incubation with positive serum for myocardial infarction, the resistance increased about two times in relation to the negative serum. A linear range from 6.25 to 50 μg mL^?1 and detection limit of 0.78 μg mL^?1 using DPV were obtained. The immunosensor developed for the CRP detection using gold electrode revealed efficacy and a potential use for the diagnosis and monitoring of the progression of cardiovascular diseases.     

A Study of Preparation and Performance of a Dichlorvos Electrochemical Sensor Based on Molecularly Imprinted Technique

A new dichlorvos molecularly imprinted electrochemical sensor was prepared. The sensitive membrane sensor was fabricated by electro-polymerizing on an Au electrode surface using o-aminophenol as a monomer and dichlorvos as a template. The 5 mmol/L K₃[Fe(CN)₆] containing 0.1 mol/L KCl was used as the test background solution, while cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to study the properties of the senor. The changes of oxidation peak current versus dichlorvos concentration showed linearity in the range of 0.12–0.42 µmol/L (R ² = 0.9432) and 0.45–15 µmol/L (R ² = 0.9516) with a detection limit of 0.06 µmol/L (S/N = 3). Moreover, the selectivity and repeatability properties of the dichlorvos electrochemical sensor were examined. Results showed that the senor had excellent repeatability (RSD = 3.92%, n = 5), good selectivity to the dichlorvos in detection, and only a ten minute response time. Organophosphorus insecticides have some response signals in the detections.