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Procaine hydrochloride (P.HCl) is one of the earliest and most well-established local anesthetic drugs used in medicine. Though it is employed frequently for effective clinical nerve blocks during surgeries, its immoderate administration has often shown reports of systemic toxicity. To prevent such repercussions, developing a sensor for the drug is crucial to enable real-time monitoring of the drug and assist in quality control procedures during its industrial preparations. Thus, in this work, we have fabricated a simple yet highly selective and sensitive amperometric sensor for P.HCl detection based on a Barium-oxide multi-wall carbon nanotube-modified carbon paste electrode (BaO-MWCNT/CPE). Herein, we have adopted a novel approach devoid of sophisticated procedures and pretreatments for rapidly determining P.HCl. Furthermore, experimental conditions, including supporting electrolytes, pH, and scan rate, were optimized to achieve a well-defined P.HCl anodic peak current at 631 mV, which is lower than the previously reported peak potentials, indicating an advantage of reduced overpotential. Besides, a striking 66-fold rise in current responsiveness to P.HCl was achieved upon modification with BaO-MWCNT. Such an intense signal enhancement upon electrode modification compared to bare CPE was due to the strong electrocatalytic feature of BaO-MWCNT, which was verified using surface morphology studies with scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Additionally, the charge transfer kinetics analyzed via electrochemical impedance spectroscopy (EIS) justified the enhancement of electrocatalytic activity upon electrode modification. The developed sensor exhibited a remarkable analytical performance over a wide linear dynamic range of 2.0-100.0 µM with a detection limit of 0.14 µM. Moreover, a significant merit of this sensor is its excellent selectivity towards P.HCl even in the presence of various common interferants. Finally, the versatility of the sensor was further validated by implementing it for the trace analysis of urine and blood serum real samples.

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The leading cause of gynecological cancer-related morbidity and mortality is ovarian cancer (OC), which is dubbed a silent killer. Currently, OC is a target of intense biomarker research, because it is often not discovered until the disease is advanced. The goal of OC research is to develop effective tests using biomarkers that can detect the disease at the earliest stages, which would eventually decrease the mortality, thereby preventing recurrence. Therefore, there is a pressing need to revisit the existing biomarkers to recognize the potential biomarkers that can lead to efficient predictors for the OC diagnosis. This Perspective covers an update on the currently available biomarkers used in the triaging of OC to gain certain insights into the potential role of these biomarkers and their estimation that are crucial to the understanding of neoplasm progression, diagnostics, and therapy.

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The use of the herbicide aminotriazole (3-ATA) in agriculture poses rising concerns about global water-borne contamination. Due to its toxicity which is known to cause cancer and thyroid dysfunction, 3-ATA is considered an important analytical target. Environmental protection agencies worldwide have introduced several directives that set concentration limits for chemicals to combat water pollution. Hence, to evaluate the presence of 3-ATA in water and limit their impact on ecosystems and human health, the development of an efficient real-time monitoring device is the key. The as-synthesized copper oxide decorated multiwall carbon nanotubes at 400 °C (CuO-MWCNT@400) showed remarkable efficiency as modifiers. Under optimal conditions, we explored the direct oxidation of 3-ATA at CuO-MWCNT@400 modified carbon paste electrode (MCPE). With its distinguishing synergistic features like high levels of porosity, stability, and surface area, this structure favoured greater detection, selectivity, and sensitivity. The amperometric i-t curve technique was adopted for the first time for 3-ATA quantification. This technique rendered a good detection sensitivity of 1.65 × 10-8 mol L-1 and anti-interference characteristics for several interferent species, including fungicides, fertilizers, herbicides, inorganic ions, and carbohydrates. Finally, the proof-of-concept was yielded by selective and sensitive detection of 3-ATA from two different samples of spiked water. We believe this work will enhance awareness and garner appreciation of the electrochemical sensor's analytical performance in protecting our environment and water resources.

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Diabetes mellitus is a physiological and metabolic disorder affecting millions of people worldwide, associated with global morbidity, mortality, and financial expenses. Long-term complications can be avoided by frequent, continuous self-monitoring of blood glucose. Therefore, this review summarizes the current state-of-art glycemic control regimes involving measurement approaches and basic concepts. Following an introduction to the significance of continuous glucose sensing, we have tracked the evolution of glucose monitoring devices from minimally invasive to non-invasive methods to present an overview of the spectrum of continuous glucose monitoring (CGM) technologies. The conveniences, accuracy, and cost-effectiveness of the real-time CGM systems (rt-CGMs) are the factors considered for discussion. Transdermal biosensing and drug delivery routes have recently emerged as an innovative approach to substitute hypodermal needles. This work reviews skin-patchable glucose monitoring sensors for the first time, providing specifics of all the major findings in the past 6 years. Skin patch sensors and their progressive form, i.e., microneedle (MN) array sensory and delivery systems, are elaborated, covering self-powered, enzymatic, and non-enzymatic devices. The critical aspects reviewed are material design and assembly techniques focusing on flexibility, sensitivity, selectivity, biocompatibility, and user-end comfort. The review highlights the advantages of patchable MNs' multi-sensor technology designed to maintain precise blood glucose levels and administer diabetes drugs or insulin through a "sense and act" feedback loop. Subsequently, the limitations and potential challenges encountered from the MN array as rt-CGMs are listed. Furthermore, the current statuses of working prototype glucose-responsive "closed-loop" insulin delivery systems are discussed. Finally, the expected future developments and outlooks in clinical applications are discussed.

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Health care monitoring is an extremely important aspect of human life that can be accomplished using wearable skin-patchable sensors. Upon interfacing with the skin or epidermal surface of the body, the sensing patches can monitor the movements of human parts such joints, legs, and fingers as well as tiny vibrations caused by respiration, blood flow, and heart beat. Wearable skin patches have shown improved promise in monitoring the body temperature and fever in addition to quick measurement of blood pressure and pulse rate along with breathing rate. Sensors can also analyze the sweat contents when in contact with the skin as well as other analytes such as diabetes-based volatile organic compounds (VOCs) and organophosphate nerve stimulating agents. Hence, the sensors can be of immense help in the early prediction of malfunctions of the body organs such as heart and lungs, leading to timely and effective treatment. This review covers different important aspects of skin-patchable sensors including mechanical strength and flexibility, sensitivity, transparency, self-healing, self-cleaning, and self-powering ability as well as their latest applications in medical technology.

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The application of Propyl Paraben (PP) as a chemical preservative has expanded and diversified. Widespread use of products containing PP has resulted in its ubiquitous occurrence in environment and biological fluids among the general population. Several in-vivo studies have associated PP with estrogenic activity and malfunctioning of reproductive organs. In this work, we have developed a highly sensitive voltammetric sensor for PP detection based on polyaniline-zinc-oxide nano-composite modified carbon paste electrode (PANI/ZnO/MCPE). The synthesized nano-composite was characterized using spectroscopic techniques. Experimental conditions such as supporting electrolyte, their pH and scan rate were optimized to attain a well defined PP anodic peak current at 690 mV. Our experiments indicate a strong synergistic interaction between ZnO and PANI, resulting in the magnification of PP current with a declined over-potential, compared to bare CPE. We have proposed a mechanism of π-π interaction between PP and PANI/ZnO/MCPE. The electrode process was characterized to be irreversible; diffusion controlled and proceeds with an exchange of 1e- and H+. Noteworthy analytical performance over wide linear range from 100.0 to 1.0 µM, with a detection limit of 0.13 µM and anti-interference characteristics were ascertained. A significant advantage of this sensor is its inability to detect micro molar concentrations of ascorbic acid (AA) while PP is detected at micro levels in the presence of high concentrations of AA. The versatility of this sensor was demonstrated by efficaciously applying it to trace analysis of complex real samples such as pharmaceutical formulations, biological samples and lake water with good recoveries.

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Due to the enforcement of regulatory restrictions to prevent risk to human health from Bisphenol A (BPA), its structural analogue Bisphenol F (BPF) has been introduced into the market as an alternative. But however recent studies describe BPF as an effectual endocrine disruptor. Hence, there is an indispensible need for research concerning BPF human and environmental exposure level. In this work, we have elicited the development of an economical electrochemical sensor, to quantify and investigate in detail the electrochemical behavior of BPF using carbon paste electrode (CPE) modified with zinc oxide reduced graphene nanocomposite (ZnO/G) and cetyltrimethylammonium bromide (CTAB). The ZnO/G was synthesized using Hummers method and characterized by spectroscopic techniques. Under optimal conditions, conductive and biocompatible ZnO/G/CTAB/MCPE offered ultra sensitivity for BPF recognition by Differential Pulse Voltammetry (DPV), with a detection limit of 0.06 µM. Lowering of activation energy for electro-oxidation of BPF and absence of peak for interfering molecule Ascorbic acid (AA) makes it an unique sensor for the detection of BPF with significant analytical advantage over other electrodes reported in literature. Versatility of the electrode was demonstrated by applying it to real time analysis of human body fluids, canned beverage and different water samples fortified with BPF. The satisfactory recoveries obtained, consequently authenticates the practicality of the proposed sensor.

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The fabrication of differential pulse voltametry (DPV) sensor for the effective detection of Quercetin (QR) was achieved by modifying carbon paste electrode (CPE) with Iron decorated multi walled carbon nano tubes (Fe-MWCNTs) followed by drop casting of hexadecyltrimethylammonium bromide onto the surface for optimal results. Cyclic voltammetry and DPV techniques were used for qualitative and quantitative analysis of QR (Quercetin) respectively. The sensor revealed impressive electro-catalytic behavior towards oxidation of QR with almost 6.4 times increase in current compared to bare carbon paste electrode CPE and also decrease in the energetics. Under optimum conditions, a wide linear dynamic range of 0.06 to 3000µM, with a lower limit of detection, 1.20nM with S/N=3 was observed. Absence of peak for the interfering molecules such as Folic acid and Ascorbic acid makes it a unique sensor with significant analytical advantage. The quantification of QR at this sensor was not affected by the presence of 1000 fold Uric Acid implying that the sensor is capable of specifically identifying QR in a mixture of interfering molecules. In this paper, we demonstrate that with minimal use of modifiers and simple procedures of fabrication, the fabricated sensor exhibits excellent stability, reproducibility and swift responses. Application of the developed electrode was demonstrated by detecting QR in wine and coconut water samples with satisfactory recoveries.

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Free radicals are formed as byproducts of metabolism, and are highly unstable due to the presence of unpaired electrons. They readily react with other important cellular components such as DNA causing them damage. Antioxidants such as (+)-catechin (CAT), neutralize free radicals in the blood stream. Hence there is a need for detection and quantification of catechin concentration in various food sources and beverages. Electro-oxidative properties of catechin were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). A carbon paste working electrode modified by electropolymerizing methylene blue (MB) was fabricated. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) techniques were used to study the surface morphology of the electrode. Quasi-reversible electron transfer reaction occurred at +0.260V through a diffusion controlled process. In comparison to the bare carbon paste electrode (CPE), there was a significant 5.3 times increment in anodic current sensitivity at the modified electrode at physiological pH. Our findings indicate that for the electro-oxidation of CAT, CPE is a better base material for electropolymerization of MB compared to glassy carbon electrode (GCE). Nyquist plot followed the theoretical shape, indicating low interfacial charge transfer resistance of 0.095kΩ at the modified electrode. Calibration plots obtained by DPV were linear in two ranges of 1.0×10-3 to 1.0×10-6 and 1.0×10-7 to 0.1×10-8M. The limit of detection (LOD) and limit of quantification (LOQ) was 4.9nM and 14nM respectively. Application of the developed electrode was demonstrated by detecting catechin in green tea and spiked fruit juice with satisfactory recoveries. The sensor was stable, sensitive, selective and reproducible.

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Iron nanoparticles decorated multi-wall carbon nanotubes modified carbon paste electrode (Fe-MWCNTs/MCPE) was prepared by bulk-modification method. The electrochemical impedance spectroscopy (EIS) suggests least charge transfer resistance at the modified electrode. The electrochemical behavior of UA was studied in 0.1M phosphate buffer solution (PBS) of pH3.0 using cyclic voltammetry (CV) while differential pulse voltammetry (DPV) was used for quantification. The spectroelectrochemial study of oxidation of UA at Fe-MWCNTs/MCPE showed a decrease in the absorbance of two peaks with time, which are ascribed to π to π(⁎) and n to π(⁎) transitions. Under optimum condition, the DPV response offered two linear dynamic ranges for UA in the concentration range 7.0×10(-8)M-1.0×10(-6)M and 2.0×10(-6)M-1.0×10(-5)M with detection limit (4.80±0.35)×10(-8)M (S/N=3). The practical analytical application of this sensor was successfully evaluated by determination of spiked UA in clinical samples, such as human blood serum and urine with good percentage recovery. The proposed electrochemical sensor offers a simple, reliable, rapid, reproducible and cost effective analysis of a quaternary mixture of biomolecules containing AA, DA, UA and Tyr which was free from mutual interferences.

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A oxidação eletrocatalítica de paracetamol, acompanhada ou não pela eletropolimerização do próprio, sobre poli(azul da anilina) foi descrita matematicamente (usando a teoria de estabilidade linear e análise de bifurcações). Para o comportamento do composto foi sugerido o mecanismo que concorda com os dados experimentais e com os cálculos teóricos. Foi investigada também a dependência do desempenho do polímero e do comportamento do composto do pH.

The electrocatalytic paracetamol oxidation over poly(aniline blue), accompanied or not by its electropolymerization, has been described mathematically (using the linear stability theory and bifurcation analysis). For the compound' s behavior a mechanism, according with the experimental data and theoretical calculations, has been suggested. Also the pH-dependence of the work of the polymer and the compound' s behavior has been investigated.

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An amperometric sensor for the determination of epinephrine (EP) was fabricated by modifying the carbon paste electrode (CPE) with pristine multi-walled carbon nanotubes (pMWCNTs) using bulk modification followed by drop casting of sodium dodecyl sulfate (SDS) onto the surface for its optimal potential application. The modified electrode showed an excellent electrocatalytic activity towards EP by decreasing the overpotential and greatly enhancing the current sensitivity. FE-SEM images confirmed the dispersion of pMWCNTs in the CPE matrix. EDX analysis ensured the surface coverage of SDS. A comparative study of pMWCNTs with those of oxidized MWCNTs (MWCNTsOX) modified electrodes reveals that the former is the best base material for the construction of the sensor with advantages of lower oxidation overpotential and the least background current. The performance of the modified electrode was impressive in terms of the least charge transfer resistance (Rct), highest values for diffusion coefficient (DEP) and standard heterogeneous electron transfer rate constant (k°). Analytical characterization of the modified electrode exhibited two linear dynamic ranges from 1.0×10(-7) to 1.0×10(-6)M and 1.0×10(-6) to 1.0×10(-4)M with a detection limit of (4.5±0.18)×10(-8)M. A 100-fold excess of serotonin, acetaminophen, folic acid, uric acid, tryptophan, tyrosine and cysteine, 10-fold excess of ascorbic acid and twofold excess of dopamine do not interfere in the quantification of EP at this electrode. The analytical applications of the modified electrode were demonstrated by determining EP in spiked blood serum and adrenaline tartrate injection. The modified electrode involves a simple fabrication procedure, minimum usage of the modifier, quick response, excellent stability, reproducibility and anti-fouling effects.

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A modified carbon paste electrode (CPE) for the selective detection of dopamine (DA) in presence of large excess of ascorbic acid (AA) and uric acid (UA) at physiological pH has been fabricated by bulk modification of CPE with multi-walled carbon nanotubes (MWCNTs) followed by electropolymerization of glycine (Gly). The surface morphology is compared using SEM images. The presence of nitrogen was confirmed by the energy dispersion X-ray spectroscopy (EDS) indicating the polymerization of Gly on the surface of the modified electrode. The impedance study indicates a better charge transfer kinetics for DA at CPE modified with MWCNT/polyglycine electrode. The presence of MWCNTs in carbon paste matrix triggers the extent of electropolymerization of Gly and imparts more selectivity towards DA by electrochemically not sensing AA below a concentration of 3.1×10(-4)M. Due to the exclusion of the signal for AA, the interference of AA in the determination of DA is totally ruled out by DPV method which is used for its detection at lower concentrations. Large peak separation, good sensitivity, reproducibility and stability allow this modified electrode to analyze DA individually and simultaneously along with AA and UA. Detection limit of DA was determined from differential pulse voltammetric (DPV) study and found to be 1.2×10(-8)M with a linear dynamic range of 5.0×10(-7)M to 4.0×10(-5)M. The practical analytical application of this electrode was demonstrated by measurement of DA content in dopamine hydrochloride injection and human blood serum.

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An electrochemical sensor for the amperometric determination of L-tryptophan (Trp) was fabricated by modifying the carbon paste electrode (CPE) with multi-walled carbon nanotubes (MWCNTs) using drop cast method. 4.0 µL of the dispersion containing 2.0 mg of MWCNTs in 1.0 mL of ethanol was drop cast onto the electrode surface and dried in hot air oven to form a stable layer of MWCNTs. The electro-catalytic activity of the modified electrode towards the oxidation of Trp was thoroughly investigated. The modification with MWCNTs has greatly improved the current sensitivity of CPE for the oxidation of Trp. A very minimal amount of the modifier was required to achieve such a high sensitivity. The field emission scanning electron microscopy (FESEM) images revealed a uniform coverage of the surface of CPE by MWCNTs. Nyquist plots revealed the least charge transfer resistance for the modified electrode. The analytical performance of the modified electrode was examined using amperometry under hydro-dynamic conditions. The two linear dynamic ranges observed for Trp were 0.6-9.0 µM and 10.0-100.0 µM. The amperometric determination of Trp did not suffer any interference from other biomolecules. The detection limit of Trp at modified electrode was (3.30±0.37)×10(-8)M (S/N=3). The analytical applications of the modified electrode were demonstrated by estimating Trp in the spiked milk and biological fluid such as blood serum. The modified electrode showed good reproducibility, long-term stability and anti-fouling effects.

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A biocompatible electrochemical sensor for selective detection of epinephrine (EP) in the presence of 1000-fold excess of ascorbic acid (AA) and uric acid (UA) was fabricated by modifying the carbon paste electrode (CPE) with multi-walled carbon nanotubes (MWCNTs) using a casting method. The electro-catalytic activity of the modified electrode for the oxidation of EP was investigated. The current sensitivity of EP was enhanced to about five times upon modification. A very minimum amount of modifier was used for modification. The voltammetric response of EP was well resolved from the responses of AA and UA. The electrochemical impedance spectroscopic (EIS) studies reveal the least charge transfer resistance for the modified electrode. The AA peak that is completely resolved from that of EP at higher concentrations of AA and the inability of the sensor to give an electrochemical response for AA below a concentration of 3.0×10(-4)M makes it a unique electrochemical sensor for the detection of EP which is 100% free from the interference of AA. Two linear dynamic ranges of 1.0×10(-4)-1.0×10(-5) and 1.0×10(-5)-5.0×10(-7)M with a detection limit of 2.9×10(-8)M were observed for EP at modified electrode. The practical utility of this modified electrode was demonstrated by detecting EP in spiked human blood serum and EP injection. The modified electrode is highly reproducible and stable with anti fouling effects.

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An electrochemical sensor for sensitive detection of acetaminophen (AAP) was developed by electropolymerizing Patton and Reeder's reagent at carbon paste electrode (CPE). Modification improves the redox kinetics of AAP with increased current sensitivity. A similar modification at multiwall carbon nanotube (MWCNT) modified CPE did not result in an impressive charge transfer. Electrochemical impedance spectroscopy (EIS) of the bare and modified electrodes investigated imply a least charge transfer resistance at Patton and Reeder's reagent modified carbon paste electrode (MCPE/PR) as compared to bare CPE and MWCNT modified electrode. Differential pulse voltammetric (DPV) study at MCPE/PR electrode did not suffer any interference from its hydrolytic degradation product 4-aminophenol (4-AP) even in 1000-fold excess of its concentration and enables its detection simultaneously. A linear dynamic range of 0.7-100 µM with detection limit (S/N=3) of 0.53 µM was obtained for AAP. This modified electrode is easy to prepare, cheap, and having good reproducibility and stability. The analytical performance of the modified electrode is assessed by successfully applying it for the estimation of acetaminophen in different pharmaceutical samples and spiked biological fluid.

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A wax-impregnated carbon paste electrode with mercury oxalate as the bulk modifier is found to be suitable for the determination of heavy metal ions by differential pulse anodic stripping voltammetry. The contents of binder and modifier have been optimized, until they showed low background current and easy renewability. The bulk-modified electrode is applied for the simultaneous determination of Zn, Cd, Pb and Cu in medicinal plants and Ayurvedic tablets (Liv 52). The results obtained have been validated with HMDE and AAS and are found to be comparable.

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