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Background: Electrochemical methods in drug analysis have a lot of advantages, including simplicity, speed, low-cost instrumentation, informing about the drug mechanism, and nonaffection by excipients in dosage forms. Electrochemical techniques utilize the advantages of nanomaterials to increase sensitivity and, in some cases, selectivity. Among these nanomaterials, metal oxide nanoparticles are also preferred by researchers because of their unique properties such as biocompatibility, stability, non-toxicity, and catalytic characteristic. Objective: This review provided brief information about metal oxide nanoparticles used in electrochemical sensors and summarized applications for drug analysis with these sensors in tables showing the studies in the literature during the last decade. Results: In the last decade, metal oxides are frequently used in electrochemical drug analysis as electrode modifier individually and with other nanomaterials especially carbon-based ones. All these studies showed that metal oxide nanoparticles increase the active surface area of the electrode and the catalytic activity. Conclusion: When metal oxide nanoparticles and carbon-based nanomaterials are used together, they create a synergistic effect that further increases catalytic activity and thus lowers detection limits to be obtained in nM even pM levels.

© 2022 Elsevier B.V.This study examines the interaction between pyrimidine nucleoside analogue azacytidine, an anti-leukemic drug, and DNA by employing electrochemical, UV–vis spectroscopy, fluorescence spectroscopy and molecular docking techniques. In the electrochemical technique, azacytidine and dsDNA interaction was investigated in two different ways: (1) in solution and (2) with a biosensor using differential pulse voltammetry (DPV) at a glassy carbon electrode. The interaction between azacytidine and dsDNA at increasing interaction times was investigated in line with the changes in adenine and guanine oxidation signals. In addition, interaction studies of polyguanine-azacytidine and polyadenine-azacytidine were performed with DPV. The binding constant values were calculated as 2.420 × 104 M−1 and 3.266 × 104 M−1 at 25 °C using UV and fluorescence spectroscopy, respectively. In conclusion, based on electrochemical and spectroscopic methods as well as molecular docking studies, it was predicted that azacytidine can bind to dsDNA via groove binding.

This paper demonstrates a Schiff base i. e. 5-(diethylamino)-2-((2,6-diethylphenylimino)methyl)phenol (5-DDMP) that was sensed by DNA biosensor. dsDNA was immobilized onto GCE modified with functionalized multi-walled carbon nanotubes to prepare a biosensor. The efficiency of dsDNA biosensor was determined and binding of 5-DDMP with dsDNA was searched by UV-vis spectrophotometry and differential pulse voltammetry. Molecular docking simulations between 5-DDMP and dsDNA were explored and as a result, a hydrogen bond and a pi-pi contact were observed between 5-DDMP and deoxyguanosine base (dG22) of the strand B, deoxyadenosine base (dA5) of the strand A, respectively. These studies could be useful for new anticancer drug design and development.

Oxymetazoline, a nasal decongestant drug was investigated by a sensitive, simple and reproducible electrochemical method using Titania (TiO2) nanoparticles and carboxyl group functionalized multi-walled carbon nanotubes fabricated on glassy carbon electrode using cyclic voltammetry and differential pulse voltammetry. The possible electro-oxidation mechanism of this drug was also studied in detail. The performance of designed method was determined by electrochemical impedance spectroscopy, cyclic voltammetry and anodic stripping differential pulse voltammetry. The obtained results revealed enhanced electrochemical behavior of oxymetazoline as compared to bare glassy carbon electrode. Under optimum conditions i.e. buffer pH; pH 7.0 phosphate buffer solution, accumulation potential; 0 V, and accumulation time; 180 s, the differential pulse voltammetric response of oxymetazoline was probed between the linear concentration range of 0.12 μM to 1.5 μM in aqueous medium containing pH 7.0 PBS and 20% methanol. The limit of detection of oxymetazoline was evaluated as 4.40 nM. Moreover, the developed sensing method was validated for its practical application in nasal spray with excellent recovery.

Background: Nanomaterials have a significant role in improving the performance of electrochemical sensing systems. Unique physical and chemical properties have extended the application of nanomaterials in the fields of engineering, materials and biomedical science. In the last few years, these materials with unique properties have been preferred in the design of experimental approaches for the analysis of metal ions, proteins, biomarkers and pharmaceutical compounds. This paper reports preparation, characterization of two different nanomaterials and their electrochemical application on doublestranded calf-thymus DNA signals. Methods: The multi-walled carbon nanotubes were functionalized with amine groups (MWCNTs-NH2) by employing the dielectric barrier discharge plasma treatment and then applied as MWCNTs- NH2/glassy carbon electrode. Moreover, the synthesized mesoporous silica MCM-41 was chemically amine functionalized and used as MCM-41-NH2/carbon paste electrode. For biosensor preparation, a thin layer of calf thymus double stranded deoxyribonucleic acid (ct-dsDNA) was immobilized over the modified electrodes. Results: The influence of dsDNA immobilized substrate was investigated based on the electrochemical signals. While dsDNA/MCM-41-NH2/carbon paste biosensor showed a selective effect for guanine signals, the dsDNA/MWCNTs-NH2/glassy carbon biosensor presented electrocatalytic effect for dsDNA signals. Both dsDNA modified electrodes were employed to explore the interaction between the dsDNA and the anticancer drug etoposide (ETP) in aqueous solution through voltammetric techniques. By increasing the interaction time with ETP, the adenine peak current was quenched in the presence of MWCNTs-NH2 based glassy carbon electrode. Whereas, in the presence of MCM-41-NH2 based CP electrode, selective interaction with guanine occurred and oxidation peak intensity was diminished. Conclusion: The selective effect of MCM-41-NH2 can be used when the studied substances give a signal with the same potential of adenine.

The voltammetric behavior of the vardenafil was investigated by means of square wave stripping voltammetry (SWSV), differential pulse stripping voltammetry (DPSV) and cyclic voltammetry (CV) on the modified electrodes constructed by graphite, metal oxide and functionalized multi-walled carbon nanotubes (MWCNT).Different experimental conditions were optimized such as pH and electrolyte type, accumulation potential and accumulation time for both techniques and step potential, pulse amplitude and frequency for SWSV. In the optimum conditions a linear relationship has been constructed in the concentration range of 0.02 to 1.0 mg/L and 0.01 to 0.5 mg/L for SWSV and DPSV in pH 3.0 phosphate buffer solution, respectively. Limit of detection (LOD) values for vardenafil determinations were13.6 mu g/L and 4.38 mu g/L for SWSV and DPSV, respectively. Quantifications were performed on commercial pharmaceutical tablets and synthetic blood serum using both techniques. The relative errors were +5.0% and -3.0% for SWSV and DPSV, respectively in the determination of vardenafil active ingredient in Levitra (R) tablet. SWS and DPS voltammetric determination of synthetic blood serum spiked with 50.0 mu g/L vardenafil exhibited 100.8% and 104.4% recovery, respectively. Interference effects of some organic species such as ascorbic acid, uric acid, dopamine, glucose have also been investigated.

Biosensors are very popular systems in several fields including medical, clinical, environment, food-agriculture, security, and forensic sciences. They also require interdisciplinary work that combines biology, analytical chemistry, physics, and bioelectronics. A biosensor is a device that includes a biological recognition element connected or integrated into a transducer. Although different methods are used as transducers, electrochemical techniques are often preferred as good alternative due to their simplicity, low cost, fast response time, and miniaturization. Nanotechnology is used to make more sensitive analysis with electrochemical methods. Many nanomaterials are integrated with electrochemical transducers and one of the most current among these is quantum dots, which are nanometer-sized semiconductor crystals. The final part of the “Electroanalytical Applications of Quantum Dot Based Biosensors” book summarizes the importance of quantum dots for electrochemical biosensors in terms of synthesis, integration into electrochemical techniques, and usage with other materials and also explains the near future expectations for quantum dots.

Quantum dots (QDs) are nanostructural objects used in various fields of chemistry. Because of their electrical properties and wide possibilities of surface modification, they are increasingly used in electrochemistry and electroanalysis. Our study concerns the applications of QDs for the construction of sensors for electrochemical determinations. The sensor design uses both the electrical properties of QDs that can act as the conductive phase and the ability to modify the QDs’ surface, which allows electron transfer mediators with specific properties to be obtained. QDs are applied to both chemical sensors and biosensors design. This study describes the current state of knowledge regarding the electrochemistry of QDs itself and examples of sensors built on solid electrodes using QDs.

Citalopram (CIT) and its S-enantiomer, escitalopram (ESC), are antidepressants belonging to the class called selective serotonin reuptake inhibitors and have many different pharmacological and biological properties. Understanding the interaction mechanism of small drug molecules with DNA both helps in the development of new DNA-targeted drugs and provides more in-depth knowledge for controlling gene expression. In this study, the interaction of CIT and ESC with double-stranded calf thymus DNA (ct-dsDNA) was investigated for the first time. Spectrofluorometric, liquid chromatographic, and voltammetric response profiles of drugs and ct-dsDNA at different concentrations showed DNA-drug complex formation. Calculated binding constants were greater with all three techniques for ESC compared to CIT and were of the order of 103-104, which is in accordance with those of well-known groove binders. The results also showed the significant effect of chirality on complex formation. The thermodynamic parameters, including free energy change (ΔG < 0) and enthalpy change (ΔH < 0) obtained at different temperatures, indicated that complex formation was mainly driven by hydrogen bonding and van der Waals forces for both drugs. The results of this study may enhance the understanding of the interaction between CIT or ESC and ct-dsDNA and can be considered as the pioneer for future studies to uncover possible hidden phenotypes of these compounds.

Liquid chromatography (LC) coupled to an electrochemical (EC) detector is a complementary analytical tool compared to LC coupled with optical or mass spectrometry detectors (LC-MS). LC-EC can be applied to the determination of molecules difficult to be analyzed by other commercially available detectors. New EC detector design and new working electrode material have extended the scope of application in the field of pharmaceutical compounds analysis. Combining EC with LC-MS offers additional advantages compared to optical detectors in terms of drug stability and drug metabolism mimicry studies. Selected literature devoted to pharmacologically active compounds in their dosage forms, herbal drugs in natural products, drug residues in feed and/or in biological samples are reported in this review.

In this study, clopidogrel (CLP), which is an antiplatelet agent widely used in the prevention of ischemic stroke, was analyzed using functionalized multi-walled carbon nanotubes (fMWCNTs) and CdSe quantum dots (QDs) modified glassy carbon electrode. The dependence of intensities of currents and potential on pH, concentration, scan rate, nature of the buffer was further investigated. The oxidation process exhibited mixed diffusion under adsorption controlled process depending on pH. For the analytical application, adsorptive stripping differential pulse voltammetric (AdSDPV) technique was used and all operational parameters were optimized. The plot of peak current vs CLP concentration consisted of a linear segment in the concentration range between 2.0 × 10−6 M and 4.0 × 10−5 M and the detection limit (3σ) was obtained 7.55 × 10−8 M in pH 2.14 phosphate buffer solution. Moreover, in order to evaluate the analytical applicability of the proposed method, it was applied to the determination of CLP in serum samples with linear range of 2.5 × 10−6–1.5 × 10−5 M and the detection limit value of 2.99 × 10−7 M. Determination of CLP in tablet dosage form Atervix® was also proposed with acceptable recovery values.

A biomarker is an indicator or molecular signature that is observed in normal bodily biological processes or disease conditions. Biomarkers exist in various forms, such as proteins, peptides, antibodies, cells, metabolites, hormones, lipids, and enzymes. Developing sensitive methods for the detection of diseases at an earlier stage via these structures is essential in terms of better treatment options. Therefore, researchers have recently become interested in designing nanosensors by integrating nano-scale materials with optical, mechanical, electrical, and magnetic sensors. The use of nanostructures, such as nanotubes, nanofibers, quantum dots, and nanowires, contributes to the development of cheaper, faster, and smaller sensors, which increase sensitivity as well as enhance the detection limit and response time. This chapter examines the contributions of nanotechnology in detecting and determining biomarkers and the significance of this process in the diagnosis and treatment of diseases. Moreover, the methods of biomarker detection are analyzed via different studies as presented in the literature.

In this study, we report the development of a sensitive label-free impedimetric sensor based on molecularly imprinted polymer (MIP) as biomimetic receptor coupled with screen-printed electrodes (SPEs) for the detection of vascular endothelial growth factor (VEGF). Firstly, electropolymerization of o-phenylenediamine (o-PD) in the presence of VEGF molecule by cyclic voltammetry was performed onto graphite screen-printed electrodes. The solvent extraction of the target was then carried out. The MIP based sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Using optimized experimental conditions, the single-use MIP-based sensor showed a good analytical performance for VEGF detection from 20 to 200 pg mL(-1) with limit of detection of 0.08 pg mL(-1). Finally, the developed MIP-based sensor in human serum samples was also tested.

Studying the process of interaction between DNA and drugs became widespread in last more than ten years. In this regard, designing electrochemical DNA biosensors contributed to the development of more selective and sensitive electrochemical methods for the detection of specific DNA binding. This paper is based on the researches in the last years (between 2004 and 2015) focusing on the studies on electroanalytical interactions between dsDNA and drugs. Normal pulse, cyclic, differential pulse and square wave voltammetric methods were generally employed for analyzing drug and dsDNA oxidation signals through using various sensors and nanosensors. The researches on these fields are summarized as tables providing information about pH and medium of the study, sensor/nanosensor type, modes of mechanism and binding constant of drug-dsDNA interaction, the results expressed in the concentration range and also detection limits.

The i-E oxidation curves, obtained using a boron doped diamond electrode, for studies of oxidations of two piperazine derivatives ARIP (I) and PIRI (II), resulted in a sharp increase of current in the range of the oxidation potentials. After reaching a value, depending on concentration of I or II, the current remains practically constant up to +1.6 V. Such limiting currents i1 are a linear function of concentrations and depend on the v1/2. Hence it is diffusion controlled, shifts of the oxidation potentials indicate, that the monoprotonated forms are oxidized. At more negative potentials a limiting current i2 occurs, due to the oxidation of the diprotonated form. Current i2 increases with decreasing pH in a shape of a part of a dissociation curve. Diffusion control reflects the large size of molecules I and II. The two-electron oxidations yield a C=N bond in the piperazine ring. It seems to be the first reported diffusion controlled oxidation curves obtained on a stationary solid electrode.

Foodborne diseases have become a major public health problem worldwide in recent years and are generally caused by the consumption of food or drink contaminated with pathogens or toxins. Common foodborne bacterial pathogens include Escherichia coli O157:H7, Shiga-toxin producing E. coli, Campylobacter jejuni, Clostridium perfringens, Salmonella enterica, Bacillus cereus, Listeria monocytogenes, and Yersinia. Early screening for foodborne pathogens plays an important role in preventing and controlling outbreaks of foodborne diseases. For this reason, a lot of effort has been directed into the study and development of rapid testing methods for foodborne pathogens. There are a lot of conventional methods for the determination of foodborne pathogens such as culture-based methods, immunological-based reactions, and polymerase chain reaction. These conventional methods are time consuming, exhaustive, and expensive. Biosensor design is an important foodborne pathogen detection method that is sensitive, rapid, and low-cost. This study is focused on the methods used to immobilize biological components to generate biosensors, applications of the most commonly used electrochemical and optical biosensors, and recent prospects for foodborne pathogen detection and determination.

A carbon paste electrode modified by –COOH functionalized multiwalled carbon nanotubes and Fe2O3 nanoparticles was prepared for the determination of antiparkinson drug ropinirole using adsorptive stripping differential pulse and square wave voltammetric methods. The results showed that the modified electrode significantly enhanced the oxidation peak current of ropinirole. Effects of pH, scan rate, and electrolyte type on the determination of ropinirole were analyzed. Ropinirole gave two irreversible anodic peaks at modified electrode in pH 6.0 phosphate buffer solution; studies were realized for the peak which was more positive potential (peak 2). Limit of detection values were 1.30 × 10−3 μg mL−1 and 4.08 × 10−4 μg mL−1 for peak 2 with adsorptive stripping differential pulse and square wave voltammetric methods, respectively. The proposed methods were applied to analysis of pharmaceutical dosage form containing ropinirole. The recovery studies with values of 105.50 and 100.88 % showed the accuracy of these methods. The number of transferred electrons was investigated.

After oral administration, drug absorption from solid dosage forms depends on the release of the drug active compounds from the dosage form, the dissolution or solubilization of the drug under physiological conditions, and the permeability across the gastrointestinal tract. Dissolution testing is an essential part of designing more effective solid dosage forms in pharmaceutical industry. Moreover, dissolution testing contributes to the selection of appropriate formulation excipients for improving the dosage form efficiency. This study aims to analyze in-vitro drug dissolution testing in solid dosage forms since 2010 in order to present a comprehensive outlook of recent trends. In doing that the previous studies in the literature are summarized in the form of a table to demonstrate the apparatuses used for dissolution testing, the media in which the solid dosage form is dissolved, the method preferred for analysis from dissolution media, the conditions of analyses and the results obtained.

The electro-oxidation mechanism of lapatinib (LPT) at a glassy carbon electrode (GCE) was studied using various voltammetric techniques. The effects of pH and scan rate on LPT signal were determined in detail by cyclic voltammetry; as a result, the first and the second peaks were found diffusion and adsorption controlled, respectively. LPT exhibited three anodic peaks at 0.76 V, 0.95 V and 1.22 V by differential pulse voltammetry and two electrons were transferred for each peak. The oxidation of LPT was compared with some model compounds which contained aromatic amine structures. The possible electrooxidation pathway was also proposed. The electrochemical biosensor was designed in order to show the interaction between ct-dsDNA and LPT. For better understanding of the interaction mechanism between LPT and ct-dsDNA, spectroscopic techniques were performed. The binding constant (K) between LPT and DNA was calculated as 6.03 × 105 M−1, 4.20 × 105 M−1 and 3.50 × 104 M−1 for electrochemical, UV–vis spectrophotometric and fluorescence spectroscopic techniques, respectively. Ultimately, based on electrochemical and spectroscopic methods, it was confirmed that LPT could intercalate into the dsDNA helix.

A simple, sensitive and reproducible silver nanoparticle/multi walled carbon nanotubes modified glassy carbon electrode was developed as a sensor for the voltammetric determination of zolmitriptan with good accuracy and precision. The electrochemical behavior of zolmitriptan was investigated in detail using the proposed modified glassy carbon electrode. The results showed that the modified electrode significantly enhanced the oxidation peak current of zolmitriptan. Experimental conditions, such as pH, scan rate, accumulation time and potential, amount of silver nanoparticle and functionalized multi walled carbon nanotubes on the glassy carbon electrode were optimized for zolmitriptan assay. Under optimum conditions, the voltammetric determination of zolmitriptan was performed between the linear range of 1.00 × 10 −8 and 8.00 × 10 −7 M with a detection limit of 1.47 × 10 −9 M. The developed method was successfully applied to the determination of the drug in tablets and human urine samples with good recoveries. The detection limit was found as 2.08 × 10 −9 M for zolmitriptan in urine samples with a linear range of 1.00 × 10 −8 to 1.00 × 10 −7 M. No electroactive interferences from the tablet excipients and endogenous substances from biological material were found. The possible electrooxidation pathway and the number of transferred electrons were investigated in detail. Also, controlled potential coulometric experiments were carried out.

Valganciclovir hydrochloride (VAL) is an antiviral drug active compound which is used for the treatment of the cytomegalovirus infections. The voltammetric oxidation of VAL was investigated at multi-walled carbon nanotubes modified glassy carbon electrode using cyclic and differential pulse voltammetry over a wide pH range. The results revealed that the oxidation of VAL is an irreversible pH-dependent process in an adsorption-controlled mechanism. The results show that the oxidation signal was remarkably enhanced to provide down to the ultra trace levels. Operational parameters have been optimized. The calibration curve was linear in the concentration range of 7.50 × 10 −9 –1.00 × 10 −6 M with the detection limit of 1.52 × 10 −9 M. The reproducibility of the peak current was found 2.07% ( n = 5) relative standard deviation (RSD) value in pH 4.0 Britton-Robinson (BR) buffer for the modified electrode. The modified electrode showed good stability and reproducibility, and also it was successfully applied to the sensitive and selective determination of VAL in its dosage forms.

Simple, rapid, sensitive, and reproducible methods were developed for the assay of paroxetine in tablets. The electrooxidative behavior and determination of paroxetine on boron-doped diamond and edge plane graphite electrodes were investigated as details using cyclic, differential pulse, and square wave voltammetric methods. The oxidation process was irreversible and exhibited mixed diffusion-adsorption controlled process depending on pH. The dependence of the peak current and peak potentials on pH, nature of the buffer, and scan rate studies were examined as details. The linear responses have been obtained in the range from 7.0 × 10?7 M to 3.5 × 10?6 M with 6.95 × 10?9 M detection limit for the boron-doped diamond electrode and from 1.0 × 10?8 M to 5.0 × 10?6 M with 1.03 × 10?9 M detection limit for the edge plane graphite electrode. The possible electrooxidation mechanism of paroxetine was investigated by means of model compounds of tamsulosin and mebeverine. It can be suggested that alkoxybenzene moiety may be the responsible group for the oxidation of paroxetine (PRX). The developed methods have been successfully applied for the determination of paroxetine in pharmaceutical dosage form. © 2015, Springer-Verlag Berlin Heidelberg.