Surface Of Pencil Graphite Electrode Research Articles

Levan modified patulin specific impedimetric aptasensor with its application in food and biological fluids

In this study, a label-free impedimetric aptasensor was developed for the determination of patulin (PAT) mycotoxin. The pencil graphite electrode (PGE) surface was modified with the levan and then PAT-specific aptamer was immobilized onto the PGE surface. After the interaction of PAT with aptamer EIS measurements were performed. Under optimum conditions, the limit of detection (LOD) in buffer medium was calculated as 0.095 pg/mL in the concentration range of 10−1–105 pg/mL. The selectivity of the developed label-free impedimetric aptasensor was investigated against fumonisin B1 (FB1), ochratoxin A (OTA), and deoxynivalenol (DON) in buffer medium. The implementation of label-free impedimetric aptasensor to patulin determination was performed in apple juice samples as well as in fetal bovine serum (FBS) medium. Accordingly, the LOD of PAT was estimated as 3.27 pg/mL in apple juice and 0.41 pg/mL in the FBS medium. The selectivity of the aptasensor was also investigated in both mediums. It is predicted that the developed aptasensor will have an important place in the fields of food safety and health monitoring in the literature. Also, it is anticipated that the electrochemical determination of mycotoxins, especially in biological fluids, will be a role model for future studies.

Electrochemical investigation of an anticancer drug 5-Fluorouracil in the presence of Theophylline using low-cost and disposable poly(GLY) modified pencil graphite electrode

Herein this study, a facile, efficient and disposable electrochemical sensor has been prepared by electropolymerization of glycine (poly(GLY)) on the surface of pencil graphite electrode (PGE). The surface topology of the equipped poly(GLY) modified pencil graphite electrode (poly(GLY)/PGE) and bare pencil graphite electrode (BPGE) has been characterized by the scanning electron microscopy (SEM) combined with energy dispersive x-ray analysis (EDX) and charge transfer behaviour was measured by electron impedance spectroscopy (EIS) method. The voltammetric behaviour of anticancer, 5-fluorouracil (5-FU) in the presence of theophylline (THP) has been carried out in 0.1 M phosphate buffer solution (PBS) of physiological pH 7.0 using different techniques such as cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). The proposed poly(GLY)/PGE shows augmented peak current for 5-FU at lower potential side over the BPGE due to the electrocatalytic behaviour of modifier layers wrapped on the electrode surface. The kinetic behaviour of 5-FU at modified electrode surface was studied by varying different parameters such as pH, scan rate and concentration study in 0.1 M PBS used as a supporting electrolyte. The limit of detection (LOD) for 5-FU was attained using DPV method with different concentrations (1.0–13.0 μM) and it was found to be 0.012 μM. The possible electrochemical reaction of 5-FU was proposed and it was incorporated by two electrons and two protons mechanism at modified electrode surface. The voltammetric response of poly(GLY)/PGE towards the determination of 5-FU was unaffected in the presence of some excipients in addition to the remarkable stability and reproducibility. The applicability of the proposed sensor has been performed by real sample investigation of 5-FU with a substantial percentage of recovery results in all optimized conditions.

Electrochemical DNA Sensor Designed Using the Pencil Graphite Electrode to Detect Listeria monocytogenes.

In the present work, a novel electrochemical DNA sensor was designed to detect L. monocytogenes. Two different gene fragments were selected for the sensor design. One is a 702bp long fragment of the hlyA gene, encoding the synthesis of listeriolysin O toxin, which is unique only to pathogenic strains of L. monocytogenes and is essential for pathogenicity. The other is a 209bp long fragment of the 16S RNA gene found in all species of the Listeria genus. As the working electrode, the pencil graphite electrode was modified in various ways (activated or covered with polypyrrole), and six different combinations were constituted using three types of the modified working electrode and two different gene fragments. The developed system is based on differential pulse voltammetric transduction of guanine oxidation after hybridization between the selected gene fragment (38µg/mL) and the selected fragment-specific inosine-modified probe (1.8 µmol/L) immobilized on a pencil graphite electrode surface. The comparison of all combinations demonstrates that the best results are obtained with the combination formed from a polypyrrole-coated pencil graphite electrode (prepared at 2 scans) and 702bp fragment of the hlyA gene. The analysis time is less than 1 hour, and the necessary DNA concentrations for the analysis have been determined as 8.2 × 10-11M DNA and 2.7 × 10-10M DNA respectively, for the hlyA gene and 16S RNA gene.

Edge and Basal Plane Anisotropy of a Preanodized Pencil Graphite Electrode Surface Revealed Using Scanning Electrochemical Microscopy and Electrocatalytic Dopamine Oxidation as a Molecular Probe.

Pencil graphite (PGE), an ultralow-cost and ready-to-use disposable-type electrode, has been used for various electrochemical and electroanalytical applications after its surface anodization (PGE*, * means preanodized surface). Indeed, systematic studies on mechanistic and surface features of PGE* have not yet been explored. Herein, we report anodized pencil graphite as a model system to study molecular level insights into the surface using a scanning electrochemical microscopy (SECM) technique and dopamine (DA) electrocatalytic oxidation reaction as a molecular probe. The as-prepared PGE* showed an appreciable electronic conductivity similar to the edge-plane graphitic sites (EPPG) of the highly pyrolytic graphitic electrode (HOPG) but without any surface deterioration that occurs with HOPG due to the instability of the EPPG. Physicochemical characterizations by FESEM, FTIR, Raman, and XPS techniques revealed a flake-like exfoliated PGE* surface with higher contents of carbon-oxygen especially phenolic/alcoholic functional groups than the PGE surface. Based on the chronocoulometric experiment, the number of functional groups formed on the PGE* was calculated as 10.9 × 10-10 mol cm-2. An independent SECM technique using ferricyanide as a redox probe showed the existence of a heterogeneous surface and exhibited an improved electron transfer activity due to the flake-like graphitic island on the PGE* surface. Investigated DA electrochemical oxidation on PGE* yielded about three times enhancement in the peak current signal and about 200 mV reduction in the oxidation potential over the PGE without any serious surface fouling feature that is related to the intermediate polydopamine formation on the basal-plane graphitic surface of the underlying electrode. As an independent electroanalytical study, a prototype electrochemical sensor using PGE* as a working electrode for instant detection of DA-containing pharmaceutical samples in a 1 mL Eppendorf vial has been demonstrated.

Nanocomposite of Electrochemically Reduced Graphene Oxide and Poly (p‐aminobenzenesulfonic acid) Incorporated with Ni (II) Ions as an Electrocatalyst for the Oxidation of Methanol

AbstractA new nanocomposite containing Ni(II) ions, electrochemically reduced graphene oxide (ERGO) and poly (p‐aminobenzenesulfonic acid) (Pp‐ABSA) on pencil graphite electrode (PGE) was prepared using electrochemical deposition coupled with self‐assembly accumulation method and characterized with different techniques. The electrochemical behavior and electrocatalytic activity of modified PGEs were investigated. The Ni/Pp‐ABSA/ERGO/PGE showed a unique electrocatalytic oxidation through an Electrochemical‐Chemical (EC’) pathway for methanol in alkaline media (Jpf=7.04 mA cm−2 and Eonest=0.38 V) compared to Ni/PGE, Ni/Pp‐ABSA/PGE and Ni/ERGO/PGE. The obtained results showed that the self‐assembled incorporation of Ni(II) ions in Pp‐ABSA/ERGO film prepared on PGE surface produced a stable modifier with high electrocatalytic activity towards methanol oxidation. In conclusion, the introduced method for the preparation of Pp‐ABSA/ERGO‐based nanocomposites can open a new, cheap and simple way to design a high‐performance electrocatalyst for direct methanol fuel cell systems.

Coordinated molecularly imprinted-based ratiometric sensor for electrochemical sensing of hazardous ciprofloxacin based on nitrogen and sulfur co-doped porous carbon/silver nanoparticles hybrid

A highly responsive and selective coordinated molecularly imprinted polymer (MIP)-dependent ratiometric electrochemical platform for ciprofloxacin (CIPX) detection was developed. It consists of porous carbon modified with heteroatoms (N, S@C) built on pencil graphite electrode (PGE) surface. The N, S@C/PGE was then modified using silver nanoparticles (AgNPs), which were employed to boost conductivity and surface area of the electrode, as well as an internal reference signal. Molecularly imprinted film was built on AgNPS/N, S@C/PGE surface in the existence of template (CIPX) via electro-deposition of Cu (II)-coordinated pyrrole-3-carboxylic acid. The detection of CIPX is based on the measurement of ICIPX/IAgNPs ratios using differential pulse voltammetry (DPV), which were linearly proportional to CIPX concentration in the range of 0.13–650 nM with LOD (S/N = 3) of 38 pM. The as-fabricated coordinated MIP-dependent ratiometric electrochemical platform exhibited many advantages including low detection limit, long-term stability, detection reliability, and good reproducibility/selectivity. The electrochemical probe was efficiently used for the analysis of CIPX-containing specimens with recoveries % in the range of 97.6–101.6 % with RSDs % in the range of 2.6–3.2 %, proving accuracy of the platform.

Electrochemical testosterone biosensor based on pencil graphite electrode electrodeposited with copper oxide nanoparticles

Accurately monitoring the blood levels of testosterone (TST) in a sensitive, simple, and rapid manner is of paramount importance for the diagnosis and treatment of various medical conditions, as well as for controlling pharmaceutical quality and facilitating doping detection. TST, the primary male sex hormone, plays a crucial role in facilitating human physical performance, protein synthesis, and the development of muscle mass. Consequently, TST and its analogues are frequently abused by athletes as performance-enhancing steroid in order to increase muscle mass and enhance their performance. The use of such steroids is strictly prohibited to guarantee fair play. In this study, we employed a pencil graphite electrode that was electrochemically modified with CuO nanoparticles (CuONPs) for determination of TST. The electrode response was significantly enhanced by approximately fourfold compared to the unmodified pencil graphite electrode (PGE) when electrodeposition CuONPs onto PGE surface was performed at a potential of −0.6 V for 200 s. The success of modification was confirmed through morphological analysis using scanning electron microscopy and energy-dispersive x-ray spectroscopy. Using square wave adsorptive stripping voltammetry analysis in Britton–Robinson buffer at pH 6.0, we demonstrated that the proposed sensor exhibited sensitivity to detect TST within a linear range of 5–200 nM. The detection limit of sensor was calculated 4.6 nM (1.32 ng ml−1). The sensor platform developed for the accurate, sensitive, and specific determination of TST holds tremendous potential for the development of point-of-care devices and their integration into lab-on-a-chip research.

Voltammetric studies and spectroscopic investigations of the interaction of an anticancer drug bevacizumab-DNA and analytical applications of disposable pencil graphite sensor

A sensitive, simple, fast electrochemical biosensor for the DNA interaction of bevacizumab (BEVA), which is used as a targeted drug in cancer treatment, was developed using the differential pulse voltammetry (DPV) technique with pencil graphite electrode (PGE). In the work, PGE was electrochemically activated in a supporting electrolyte medium of +1.4 V/60 s (PBS pH 3.0). Surface characterization of PGE was carried out by SEM, EDX, EIS, and CV techniques. Determination and electrochemical properties of BEVA were examined with CV and DPV techniques. BEVA gave a distinct analytical signal on the PGE surface at a potential of +0.90 V (vs. Ag/AgCl). In the procedure proposed in this study, BEVA gave a linear response on PGE in PBS (pH 3.0 containing 0.02 M NaCl) (0.1 mg mL−1 – 0.7 mg mL−1) with LOD and LOQ values of 0.026 mg mL−1 and 0.086 μg mL−1, respectively. BEVA was reacted with 20 μg mL−1 DNA in PBS for 150 s and analytical peak signals for adenine and guanine bases were evaluated. The interaction between BEVA-DNA was supported by UV–Vis. Absorption spectrometry and the binding constant was determined as 7.3 × 104.

Anti-Kanser İlaç Vinblastin’in Kalem Grafit Elektrot Yüzeyinde Elektrokimyasal Özelliklerinin İncelenmesi Ve Miktar Tayini

Kanser kemoterapisinde kullanılan vinblastin (VNB) antineoplastik bir ilaçtır. Sunulan bu çalışmada, VNB‘nin elektrokimyasal özellikleri tek kullanımlık kalem grafit (PG) elektrot ile geniş bir pH aralığında ve farklı destek elektrolitler ‘’Britton–Robinson (0.04 M BR, pH 2.0-12.0), fosfat (0.04 M PBS, pH 2.0, 3.0, 4.0, 7.4) ve asetat ( 0.04 M ABS, pH 4.8) içinde döngüsel voltametri ‘’CV’’ ve Kare Dalga Voltametri ‘’SWV’’ teknikleriyle incelenmiştir. VNB, +0.993 V gerilim ve 3.844 µA akım değerinde BR (pH 2.0) içinde CV ile tersinmez bir yükseltgenme piki vermiştir. SWV tekniği ile anodik akım sinyali, BR (pH 2.0) içerisinde 11 nM ile 495 nM arasında derişim ile doğrusal bir korelasyon gösterdi ‘’Ip (µA) = 0.0087 C (nM) - 0.3448 (r = 0.993, n = 12)’’ . 11 nM derişim seviyesinde, 2.4 nM gözlenebilme sınırı (LOD) ve % 2.93 göreli standart sapma hesaplandı. Önerilen yöntemin analitik uygulaması ilaç ve idrar örneklerinde pratik edilmiş ve geri kazanımlarla gösterilmiştir.

Zip Nucleic Acid-Based Genomagnetic Assay for Electrochemical Detection of microRNA-34a.

Zip nucleic acid (ZNA)-based genomagnetic assay was developed herein for the electrochemical detection of microRNA-34a (miR-34a), which is related to neurological disorders and cancer. The hybridization between the ZNA probe and miR-34a target was performed in the solution phase; then, the resultant hybrids were immobilized onto the surface of magnetic beads (MBs). After magnetic separation, the hybrids were separated from the surface of MBs and then immobilized on the surface of pencil graphite electrodes (PGEs). In the case of a full-match hybridization, the guanine oxidation signal was measured via the differential pulse voltammetry (DPV) technique. All the experimental parameters that influenced the hybridization efficiency (i.e., hybridization strategy, probe concentration, hybridization temperature, etc.) were optimized. The cross-selectivity of the genomagnetic assay was tested against two different miRNAs, miR-155 and miR-181b, individually as well as in mixture samples. To show the applicability of the ZNA-based genomagnetic assay for miR-34a detection in real samples, a batch of experiments was carried out in this study by using the total RNA samples isolated from the human hepatocellular carcinoma cell line (HUH-7).

HER2 targeted noninvasive immunosensor based on pencil graphite electrode for detection of breast cancer

In the current research, we have fabricated an amperometric immunosensor for the detection of breast cancer using HER2 antibody. The sensor was fabricated by immobilization of anti-HER2 antibody on the surface of pencil graphite electrode (PGE). The techniques used for the characterization of the PGE/anti-HER2 were cyclic voltammetry, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The sensor was optimized in terms of pH, temperature, antigen concentration, response time and antibody concentration. A linear range amidst 1 fgml−1 and 20 ngml−1 was observed. The limit of detection was 1 ​fg/ml. HER2 levels were also determined in sera samples of apparently healthy persons and breast cancer patients. The authentication of the fabricated immunosensor was noticeable due to its good regeneration ability and storage stability.

Voltammetric investigations of functional dyspepsia drug acotiamide at pencil graphite electrode: An eco-friendly and cost effective stripping detection method

First time, the electro-oxidative behaviour and determination of acotiamide at a pencil graphite electrode have been investigated under different experimental conditions using cyclic voltammetry (CV), differential pulse anodic stripping voltammetry (DPASV), and square wave anodic stripping voltammetric (SWASV) techniques. The voltammetric responses of acotiamide have been analyzed at different scan rates, pH and concentrations. Oxidation of acotiamide at the surface of pencil graphite electrode gave two well defined irreversible peaks in the voltammograms in BR buffer of pH 7.0. The oxidation process is completely diffusion controlled. A linear response of peak current has been obtained between 15.5 to 124 μM in non-aqueous media for all the voltammetric techniques. The proposed DPASV and SWASV techniques show limit of detection at 18.58 and 13.36 μM, respectively.

Electrochemical and liquid chromatographic analysis of triamcinolone acetonide in pharmaceutical formulations

Electrochemical reduction of triamcinolone acetonide on pencil graphite electrode surface was firstly investigated by cyclic voltammetry (CV). The dependence of cathodic peak current and peak potential on different pH medium and scan rate were investigated. The adsorption controlled nature of the peak was achieved. During pH optimization, 0.067 M Phosphate (pH 4.50 to pH 7.50), 0.2 M Acetate (pH 3.50 to 5.50) and 0.04 M Britton Robinson (BR; pH 2.00 to 12.00) buffers were employed as supporting electrolytes. Scan rate optimization was investigated in the range 25-1000 mVs-1 (vs. Ag/AgCl). Maximum peak current was observed in the 0.04 M BR buffer (pH 3.50). Peak current increases and shifts to more cathodic values with the increasing scan rate. Curve of logarithm of peak current (log I) versus logarithm of scan rate (log v) showed linear regression with the equation log(Ip/μA) = 0.8395 log(v/mVs-1)-0.8386 and correlation coefficient (R2: 0.9761). This indicated that slope of the logv-logI curve is close to 1.0 and the cathodic electrode reaction was adsorption controlled, as desirable. The linear range was 1×10-7-5×10-5 M, sensitivity was 1,3347 µA M-1, Limit of detection (LOD) and Limit of quantification (LOQ) were 3.18×10-8 M and 1.00×10-7 M, respectively. HPLC-PDA analysis were performed with H2O:MeOH (28:72, v/v) as mobile phases A and B at a flow rate of 1mL/min at 242nm. Method validation studies were conducted in accordance with ICH Q2(R1) guideline and corresponding results were summarized in tables. HPLC-PDA method displayed linearity in 0.1-50µg/mL (2.3×10-7-1.15×10-4 M) concentration range with LOD and LOQ values as 3.992×10-8 and 1.29×10-7M, respectively.

Voltammetric Determination of Oxybutynin Hydrochloride Utilizing Pencil Graphite Electrode Decorated with Gold Nanoparticles

AbstractA novel voltammetric method was successfully applied for the determination of an anticholinergic drug, oxybutynin hydrochloride (OXB). The method is concerned with electrooxidation of the drug on the surface of pencil graphite electrode (PGE). In order to enhance the electrode sensitivity and peak current, the electrode was coated with gold nanoparticles (Au‐NPs) via electrochemical deposition using cyclic voltammetry from gold salt solution. The surface of Au‐NPs modified PGE has been characterized using scanning electron microscopy and X‐ray photoelectron spectroscopy. Various experimental variables were studied and optimized to enhance the sensor's response towards OXB. Quantitative determination of the drug was achieved in phosphate buffer pH 7.5 using differential pulse voltammetry by scanning the potential over range of 0.00 to 2.20 V with scan rate of 40 mV s−1. Validation of the method was achieved according to ICH guidelines. The method was found to be linear over concentration range (2.0×10−7–1.0×10−6 M). The suggested sensor was efficiently developed for the quantitative determination of OXB in pure form, pharmaceutical dosage form and spiked plasma samples.

Diagnostic kit based on halloysite nanoclay-ionic liquid nanocomposite modified electrode for electrochemical determination of cancer biomarker

Nucleic acid hybridization is occurred between the selective single-stranded nucleic acid sequence and its target sequence, which is one of the essential procedure for electrochemical detection of nucleic acid. microRNA-21 (miRNA-21) is known as a biomarker in various cancers. The determination of miRNA-21 was attained through by hybridization of inosine substituted miRNA-21 specific DNA probe (Pinosine) with its target miRNA-21. In this study, the surface of pencil graphite electrode (PGE) was firstly modified with halloysite nanoclay-ionic liquid (HNT/IL) nanocomposite. The characterization of surface was performed by Scanning Electron Microscope (SEM) images and Energy Dispersive X-Ray Analysis (EDX) analysis, and the differences at surface modifications were also shown by electrochemical methods with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). For sensitive and selective determination of miRNA-21, Pinosine and target miRNA concentration, immobilization and hybridization time were optimized by using HNT/IL modified PGE in combination with differential pulse voltammetry (DPV). The detection limit was achieved as 0.17 μg/mL (equals to 23.69 nM) in the linear range of 0.25–2 μg/mL miRNA-21. The selectivity of voltammetric method based on HNT/IL-PGE developed for miRNA-21 was examined in the presence of mismatch (MM) and non-complementary (NC) sequences. Because miRNA-21 is over-expressed in cancer cells, it has been tested in total RNA samples isolated from cancer cell line (breast cancer cell line, MCF-7). In the total RNA samples obtained from MCF-7, the detection limit was calculated as 0.28 μg/mL in the linear range of 1–4 μg/mL. Besides, the healthy cell line (human embryonic kidney cell line, HEK-293) was used as a control group and the results obtained by MCF-7 total RNA samples were compared to the results using HEK-293 total RNA samples in terms of miRNA-21 level.

Development of an ultrasensitive molecularly imprinted poly-(ortho-phenylenediamine) based sensor for the determination of melamine adulteration in milk and infant formula.

A sensitive molecularly imprinted poly‐(ortho‐phenylenediamine) electrochemical sensor was fabricated for selective melamine detection in milk and infant formula. The pencil graphite electrode (PGE) was modified by deposition of Au nanoparticles and reduced graphene oxide (RGO) on its surface. The fabrication of the electrode in various stages was monitored using cyclic voltammetry. The immobilized RGO, MIP, and gold nanoparticles on the PGE surface were morphologically characterized by field‐emission scanning electron microscopy (FESEM). Under the optimized conditions, the linear range and the limit of detection (LOD) were 10–17–10–8 M and 2.64 × 10–16 M (S/N = 3), respectively. The prepared sensor exhibited a good reproducibility and repeatability response. The recovery range of melamine‐spiked milk and infant formula was 92.7%–103.9% and 93.5%–105.8%, respectively. The sensor could apply successfully for melamine determination in milk and infant formula samples.

Investigation of Electrochemical Behavior and Voltammetric Determination of 2-Nitrophenol Using Modified Electrode Prepared by Electropolymerization of 4,4'-Diaminobenzophenone on Pencil Graphite Electrode Surface

Bu çalışmada, 4,4’-diaminobenzofenon (44-DABP) molekülünün grafit kalem uç elektrot (PGE) yüzeyinde elektropolimerleşmesi ile 44-DABP/PGE modifiye elektrodu hazırlanmıştır. Elektropolimerleşme yöntemi ile kaplama işlemi, dönüşümlü voltametri (CV) yöntemi kullanılarak 1×10-4 molL-1 44-DABP çözeltisi içerisinde, 10 çevrim sayısı ile -1,5 V ile +1,5 V arasında 0,1 Vs-1 tarama hızıyla potansiyel taraması yapılarak gerçekleştirilmiştir. Hazırlanan 44-DABP/PGE elektrodu CV ve elektrokimyasal impedans spektroskopisi (EIS) teknikleri kullanılarak elektrokimyasal yöntemlerle karakterize edilmiştir. Ayrıca, 44-DABP/PGE yüzeyinde 2-nitrofenolün (2-NP) elektrokimyasal davranışı CV ve diferansiyel puls voltametrisi (DPV) teknikleri kullanılarak incelenmiş ve ardından DPV tekniği ile voltametrik tayini gerçekleştirildi. 44-DABP/PGE elektrodu ile 2-NP tayini için uygun olan destek elektrolit ve pH gibi optimum çalışma şartları belirlendi. Optimum şartlarda, PGE elektrot yüzeyinin 44-DABP filmi ile modifiye edilmesiyle, 2-NP’nin indirgenme pikinin akım değerinde yaklaşık 20 kat artış olduğu belirlendi. 44-DABP/PGE modifiye elektrot ile 2-NP için çalışma aralığı 0,75–15 µM ve gözlenebilme sınırı (LOD) 0,51 µM olarak belirlendi. 44-DABP/PGE elektrodunun 2-NP tayininde iyi bir tekrarlanabilirliğe sahip olduğu tespit edildi. Son olarak modifiye elektrotla, musluk suyunda standart ekleme yöntemi kullanarak iyi bir geri kazanım ve düşük bağıl standart sapma (BSS) değerleri ile 2-NP tayini başarıyla gerçekleştirilmiştir.

Electrochemical Monitoring of Interaction of Temozolamide with DNA by Graphene Oxide Modified Single-Use Electrodes

Graphene oxide (GO) modified single-use pencil graphite electrodes (PGEs) were used for electrochemical monitoring of surface confined interaction between Temozolamide (TMZ) and calf thymus double stranded DNA (ctdsDNA). First, the PGE surface was activated by EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide) as covalent agents (CA). Then, modification of GO was done onto the surface of chemically activated PGE surface to obtain CA-GO-PGEs. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy studies were used to establish the interfacial electron transfer of the electrodes. The optimization of experimental conditions was carried out via CV technique followed by electrochemical examination of the interaction of TMZ with ctdsDNA.

Detection of Senecionine in Dietary Sources by Single-Use Electrochemical Sensor.

Pyrrolizidine alkaloids (PAs) are produced by plants as secondary compounds that are the most widely distributed natural toxins. There have been many cases of human toxicity caused by consumption of toxic plant species, as herbal teas and grain or grain products contaminated with PA-containing seeds have been reported. Companies that produce dried spices and tea leaves should examine the PA level in their products. For the first time in the literature, a simple and inexpensive electrochemical assay based on a single-use sensor was introduced for quantitative determination of senecionine (SEN) in the most frequently contaminated food sources. SEN was immobilized on a pencil graphite electrode surface by the passive adsorption technique. Differential pulse voltammetry (DPV) was used to evaluate the oxidation signal of SEN, which was observed to be around +0.95 V. The oxidation signal was specific to the SEN in the sample, and the current value was proportional to its concentration. The selectivity of our assay was also tested in the presence of other similar PAs such as intermedine, lycopsamine, and heliotrine. The detection limit is calculated by developed assay and found to be 5.45 µg/mL, which is an acceptable concentration value of SEN occurring at toxic levels for consumers. As an application of the developed sensor in food products, the electrochemical detection of SEN was successfully performed in flour and herbal tea products.

Thiophene Functionalized Porphyrin for Electrochemical Carbon Dioxide Reduction

The production of catalysts that display strong efficiencies in aqueous media for the electrochemical carbon dioxide reduction reaction (CO2RR) is essential both for a healthy world and for realistic application of energy waste to generate value-added fuels. In this study, thiophene functionalized metal-free (poly-H2Por) and cobalt porphyrin-based (poly-CoPor) organometallic catalysts were easily attached on the pencil graphite electrode surface via electrochemical polymerization method and these, porphyrin coated, pencil graphite electrodes (PGE) were used as electrocatalysts for electrochemical CO2 reduction for the first time in the literature. To reveal the electrochemical activity of CO2RR, the electropolymerized catalysts were investigated with linear sweep voltammetry in 0.1 M KHCO3 solution. The results showed that, the electrode which is modified with poly-CoPor decreased the overpotential of CO2RR, according to bare pencil graphite electrode, from −1.35 V to −0.63 V.