Electrochemical Oxidation of Bioactive Carbamazepine and Its Interaction with DNA

Comparison of signal enhancement strategies for carbamazepine detection in undiluted human saliva using an electrochemical sensor with stencil-printed carbon electrodes

Carbamazepine (CBZ), a drug prescribed to prevent seizures in people with epilepsy, has a narrow therapeutic range such that patients would greatly benefit from personalized drug dosage recommendations. Saliva is an excellent sample for personalized monitoring of CBZ levels because saliva CBZ concentration correlates with the free concentration of CBZ in blood, and can be collected non-invasively. CBZ level quantification using electrochemical detection has been demonstrated in a variety of electrode systems and samples, however, human saliva presents a particular challenge in terms of its complex composition that can result in signal interference via a high background current at the potentials of interest for CBZ detection. Previous demonstrations of electrochemical detection of CBZ in saliva have included rigorous pre-treatment of the sample using centrifugation and high levels of dilution, which is not compatible with lower-resource field settings for patient monitoring of CBZ levels. In this work, we systematically investigate several strategies to improve the detection of CBZ in a background of undiluted human saliva using polymeric laminate-based devices with stencil-printed carbon electrodes; (i) adding the anionic surfactant sodium dodecyl sulfate to the saliva, (ii) filtering saliva to remove larger molecular weight species, (iii) plasma pretreatment of the device electrodes, and (iv) incubation of the sample on the electrodes. These methods enabled the quantification of therapeutically-relevant concentrations of CBZ in a background of human saliva without the need for saliva preprocessing like dilution.

Nano optical and electrochemical sensors and biosensors for detection of narrow therapeutic index drugs

For the first time, a comprehensive review is presented on the quantitative determination of narrow therapeutic index drugs (NTIDs) by nano optical and electrochemical sensors and biosensors. NTIDs have a narrow index between their effective doses and those at which they produce adverse toxic effects. Therefore, accurate determination of these drugs is very important for clinicians to provide a clear judgment about drug therapy for patients. Routine analytical techniques have limitations such as being expensive, laborious, and time-consuming, and need a skilled user and therefore  the nano/(bio)sensing technology leads to high interest.

Simultaneous opto-electrochemical monitoring of carbamazepine and its electro-oxidation by-products in wastewater

The growing human impact on aquatic environments deriving from the extensive use of pharmaceuticals and the release of persistent pollutants necessitates the implementation of new, widespread methods for characterising and quantifying such contaminants and their related degradation products. Carbamazepine, 5 H-dibenzo[b,f]azepine-5-carboxamide, (CBZ) is a widely used anti-epileptic drug characterised by limited removal by conventional wastewater treatments and high persistency in the environment. In this work, CBZ detection and quantification was performed in phosphate buffer, as well as in samples of complex matrix-like landfill leachates and treated wastewater originating from a medical facility, and simultaneously by optical and electrochemical methods using a novel transparent carbon-based nanostructured electrode. Coupling electrochemical (differential pulse voltammetry) with optical (UV-visible spectroscopy) methods, it has been possible to reach the limit of detection (LOD) for CBZ at the levels of 4.7 μM for the electrochemical method, 10.3 μM for the spectroscopic method, and 3.6 μM for the opto-electrochemical method. Raman spectroscopy and ultra-high performance liquid chromatography coupled with tandem mass spectrometry techniques were employed to support and validate the combined technique. The novel developed technique showed high selectivity to carbamazepine and its by-products, even in environmental samples. Thus, this environmentally friendly, fast and accurate detection method is believed to be successfully implementable in investigating other pharmaceutical and chemical contaminates of concern.

Carbon based nanomaterials for the detection of narrow therapeutic index pharmaceuticals

Precise detection of important pharmaceuticals with narrow therapeutic index (NTI) is very critical as there is a small window between their effective dose and the doses at which the adverse reactions are very likely to appear. Regarding the fact that various pharmacokinetics will be plausible while considering pharmacogenetic factors and also differences between generic and brand name drugs, accurate detection of NTI will be more important. Current routine analytical techniques suffer from many drawbacks while using novel biosensors can bring up many advantages including fast detection, accuracy, low cost with simple and repeatable measurements. Recently the well-known carbon Nano-allotropes including carbon nanotubes and graphenes have been widely used for development of different Nano-biosensors for a diverse list of analytes because of their great physiochemical features such as high tensile strength, ultra-light weight, unique electronic construction, high thermo-chemical stability, and an appropriate capacity for electron transfer. Because of these exceptional properties, scientists have developed an immense interest in these nanomaterials. In this case, there are important reports to show the effective Nano-carbon based biosensors in the detection of NTI drugs and the present review will critically summarize the available data in this field.

Single-Molecule Sensing of DNA Intercalating Drugs in Water

The occurrence of pharmaceutical residues in surface water is raising environmental concern. To accompany the evolution of measures for natural resources protection, sensing methods enabling sensitive and rapid water quality monitoring are needed. We recently managed the parallelization of the Tethered Particle Motion (TPM), a single molecule technique, sensitive to the conformational changes of DNA. Here, we investigate the capacity of high throughput TPM (htTPM) to detect drugs that intercalate into DNA. As a proof-of-concept we analyze the htTPM signal for two DNA intercalating dyes, namely, YOYO-1 and SYTOX orange. The efficient detection of intercalating drugs is then demonstrated with doxorubicin. We further evaluate the possibility to detect carbamazepine, an antiepileptic massively prescribed and persistent in water, which had been described to interact with DNA through intercalation. Our results corroborated by other techniques show that, in fact, carbamazepine is not a DNA intercalator. The comparison of the results obtained with different aqueous buffers and solutions allows us to identify optimal conditions for the monitoring of intercalation compounds by htTPM.

Simultaneous determination of acetaminophen, pramipexole and carbamazepine by ZSM-5 nanozeolite and TiO2 nanoparticles modified carbon paste electrode

In this present paper, a simple voltammetric method has been reported for the simultaneous determination of acetaminophen (AC), pramipexole (PRX) and carbamazepine (CBZ) using ZSM-5 nanozeolite-TiO₂ nanoparticles composite modified carbon paste electrode (ZSM-5/TiO₂/CPE). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and N₂ adsorption-desorption isotherm were used to characterize the structure of synthesized ZSM-5 nanozeolite. Also, cyclic voltammetry (CV), choronoamperometry and differential pulse voltammetry (DPV) were used to investigate the performance of the modified electrode. The oxidation peak currents of AC, PRX and CBZ at the surface of ZSM-5/TiO₂/CPE were increased dramatically against CPE and their overpotentials decreased. Also, DPV method was used for the simultaneous determination of three drugs in ternary mixture. The effects of modifier amount, pH and scan rate were investigated on the electrochemical response of AC, PRX and CBZ oxidation. The diffusion coefficient, D, and the catalytic rate constant, k_cat, were estimated for the oxidation of AC, PRX and CBZ at the surface of modified electrode. Under the optimized experimental conditions, AC, PRX and CBZ give linear response over the range of 2.5-110, 0.6-105 and 6.0-97 μM, respectively. The detection limits were found to be 0.58, 0.38 and 1.04 μM (S/N = 3) for AC, PRX and CBZ, respectively. The fabricated electrode showed good stability, reproducibility and repeatability as well as high recovery. The practical application of the modified electrode was demonstrated by measuring the concentration of spiked AC, PRX and CBZ in human plasma as real sample. The proposed method is simple, rapid and inexpensive and can be utilized as a valuable analytical tool in quality control of the pharmaceutical industry.

Anodic Voltammetric Behavior of Lincomycin and its Electroanalytical Determination in Pharmaceutical Dosage form and Urine at Gold Electrode

The anodic voltammetric behavior of an antibiotic drug, lincomycin hydrochloride (LIN) at gold electrode (GE) has been investigated using cyclic and linear sweep voltammetry. The dependence of the current on pH, concentration and scan rate were investigated to optimize the experimental conditions for the determination of lincomycin. The anodic peak was characterized and the process was adsorption-controlled. The number of electrons transferred in the oxidation process was calculated. In the range of 8.0×10−6 to 1.0×10−4 M, the current measured by linear sweep voltammetry presents a good linear property as a function of the concentration of lincomycin with a detection limit of 1.7×10−7 M with good selectivity and sensitivity. The proposed method was successfully applied to lincomycin determination in pharmaceutical dosage form and in urine as a real sample. This method can be employed in clinical analysis, quality control and routine determination of drugs in pharmaceutical formulations.

A novel disposable electrochemical sensor for determination of carbamazepine based on Fe doped SnO2 nanoparticles modified screen-printed carbon electrode

An effective strategy to fabricate a novel disposable screen printing carbon electrode modified by iron doped tin dioxide nanoparticles for carbamazepine (CBZ) detection has been developed. Fe-SnO2 (Fe=0 to 5 wt.%) NPs were synthesized by a simple microwave irradiation method and assessed for their structural and morphological changes due to Fe doping into SnO2 matrix by X-ray diffraction and scanning and transmission electron microscopy. The electrochemical behaviour of carbamazepine at the Fe-SnO2 modified screen printed carbon electrode (SPCE) was investigated by cyclic voltammetry and square wave voltammetry. Electron transfer coefficient α (0.63) and electron transfer rate constant ks (0.69 s(-1)) values of the 5 wt.% Fe-SnO2 modified SPCE indicate that the diffusion controlled process takes place on the electrode surface. The fabricated sensor displayed a good electrooxidation response towards the detection of CBZ at a lower oxidation potential of 0.8 V in phosphate buffer solution at pH7.0. Under the optimal conditions, the sensor showed fast and sensitive current response to CBZ over a wide linear range of 0.5-100 μM with a low detection limit of 92 nM. Furthermore, the practical application of the modified electrode has been investigated by the determination of CBZ in pharmaceutical products using standard addition method.

Online Investigation of Aqueous-Phase Electrochemical Reactions by Desorption Electrospray Ionization Mass Spectrometry

Electrochemistry (EC) combined with mass spectrometry (MS) is a powerful tool for elucidation of electrochemical reaction mechanisms. However, direct online analysis of electrochemical reaction in aqueous phase was rarely explored. This paper presents the online investigation of several electrochemical reactions with biological relevance in the aqueous phase, such as nitrosothiol reduction, carbohydrate oxidation, and carbamazepine oxidation using desorption electrospray ionization mass spectrometry (DESI-MS). It was found that electroreduction of nitrosothiols [e.g., nitrosylated insulin B (13-23)] leads to free thiols by loss of NO, as confirmed by online MS analysis for the first time. The characteristic mass shift of 29 Da and the reduced intensity provide a quick way to identify nitrosylated species. Equally importantly, upon collision-induced dissociation (CID), the reduced peptide ion produces more fragment ions than its nitrosylated precursor ion (presumably the backbone fragmentation cannot compete with the facile NO loss for the precursor ion), thus facilitating peptide sequencing. In the case of saccharide oxidation, it was found that glucose undergoes electro-oxidation to produce gluconic acid at alkaline pH, but not at neutral and acidic pHs. Such a pH-dependent electrochemical behavior was also observed for disaccharides such as maltose and cellobiose. Upon electrochemical oxidation, carbamazepine was found to undergo ring contraction and amide bond cleavage, which parallels the oxidative metabolism observed for this drug in leucocytes. The mechanistic information of these redox reactions revealed by EC/DESI-MS would be of value in nitroso-proteome research and carbohydrate/drug metabolic studies.

Oxidizing capacity of periodate activated with iron-based bimetallic nanoparticles

Nanosized zerovalent iron (nFe0) loaded with a secondary metal such as Ni or Cu on its surface was demonstrated to effectively activate periodate (IO4-) and degrade selected organic compounds at neutral pH. The degradation was accompanied by a stoichiometric conversion of IO4- to iodate (IO3-). nFe0 without bimetallic loading led to similar IO4- reduction but no organic degradation, suggesting the production of reactive iodine intermediate only when IO4- is activated by bimetallic nFe0 (e.g., nFe0-Ni and nFe0-Cu). The organic degradation kinetics in the nFe0-Ni(or Cu)/IO4- system was substrate dependent: 4-chlorophenol, phenol, and bisphenol A were effectively degraded, whereas little or no degradation was observed with benzoic acid, carbamazepine, and 2,4,6-trichlorophenol. The substrate specificity, further confirmed by little kinetic inhibition with background organic matter, implies the selective nature of oxidant in the nFe0-Ni(or Cu)/IO4- system. The comparison with the photoactivated IO4- system, in which iodyl radical (IO3•) is a predominant oxidant in the presence of methanol, suggests IO3• also as primary oxidant in the nFe0-Ni(or Cu)/IO4- system.