Square-wave voltammetric determination of hydroxychloroquine in pharmaceutical and synthetic urine samples using a cathodically pretreated boron-doped diamond electrode

Determination of phenytoin at trace levels in domestic wastewater and synthetic urine samples by gas chromatography-mass spectrometry after its preconcentration by simple liquid-phase microextraction

This work presents a sensitive and accurate analytical method for the determination of phenytoin at trace levels in domestic wastewater and synthetic urine samples by gas chromatography-mass spectrometry (GC-MS) after the metal sieve-linked double syringe liquid-phase microextraction (MSLDS-LPME) method. A metal sieve was produced in our laboratory in order to disperse water-immiscible extraction solvents into aqueous media. Univariate optimization studies for the selection of proper extraction solvent, extraction solvent volume, mixing cycle, and initial sample volume were carried out. Under the optimum MSLDS-LPME conditions, mass-based dynamic range, limit of quantitation (LOQ), limit of detection (LOD), and percent relative standard deviation (%RSD) for the lowest concentration in calibration plot were figured out to be 100.5-10964.2 μg kg-1, 150.6 μg kg-1, 45.2 μg kg-1, and 9.4%, respectively. Detection power was improved as 187.7-folds by the developed MSLDS-LPME-GC-MS system while enhancement in calibration sensitivity was recorded as 188.0-folds. In the final step of this study, the accuracy and applicability of the proposed system were tested by matrix matching calibration strategy. Percent recovery results for domestic wastewater and synthetic urine samples were calculated as 95.6-110.3% and 91.7-106.6%, respectively. These results proved the accuracy and applicability of the proposed preconcentration method, and the obtained analytical results showed the efficiency of the lab-made metal sieve apparatus.

Fluorometric and colorimetric platforms for rapid and sensitive hydroxychloroquine detection in aqueous samples

The detection of pharmaceuticals has been an active area of research with numerous application areas ranging from therapeutic and environmental monitoring to pharmaceutical manufacturing and diagnostics. And, the emergence of COVID-19 pandemic has increased the demand for detection of certain active pharmaceutical ingredients such as Hydroxychloroquine (HCQ) mainly due to their increased manufacturing and usage. In this study, we present two optical, fluorometric and colorimetric, detection platforms for the rapid and sensitive detection of HCQ. These platforms take advantage of the interactions between the highly fluorescent dye Thioflavin T (ThT) and Tel24 G-quadruplex (G4) DNA structure, as well as the salt-induced aggregation behavior of negatively charged citrate-capped silver nanoparticles (Cit-AgNPs) in the presence of HCQ. In the fluorometric method, the addition of HCQ led to a significant and rapid decrease in the fluorescence signal of the ThT + Tel24 probe. In the colorimetric method, HCQ induced the aggregation of Cit-AgNPs in the presence of NaCl, resulting in a noticeable color change from yellowish-gray to colorless. Under the optimized conditions, the colorimetric platform exhibited a linear range of 18.0-240.0 nM and a detection limit of 9.2 nM, while the fluorometric platform showed a linear range of 0.24-5.17 μM and a detection limit of 120 nM. The selectivity of the proposed optical methods towards the target analyte was demonstrated by evaluating the response to other structurally similar small molecules. Finally, the practical applicability of both detection systems was confirmed by analyzing HCQ-spiked human urine samples that yielded average recoveries ranging from 75.4 to 110.2 % for the fluorometric platform and 86.9-98.2 % for the colorimetric platform. These results indicate the potential of the developed methods for HCQ detection in complex matrices.

Quality-by-design ecofriendly potentiometric sensor for rapid monitoring of hydroxychloroquine purity in the presence of toxic impurities

Hydroxychloroquine (HCQ) is prescribed to treat malaria and certain autoimmune diseases. Recent studies questioned its efficiency in relieving COVID-19 symptoms and improving clinical outcomes. This work presents a quality-by-design approach to develop, optimize, and validate a potentiometric sensor for the selective analysis of HCQ in the presence of its toxic impurities (key starting materials), namely 4,7-Dichloroquinoline (DCQ) and hydroxynovaldiamine (HND). The study employed a custom experimental design of 16 sensors with different ion exchangers, plasticizers, and ionophores. We observed the Nernstian slopes, correlation coefficients, quantification limit, response time, and selectivity coefficient for DCQ and HND. The computer software constructed a prediction model for each response. The predicted responses strongly correlate to the experimental ones, indicating model fitness. The optimized sensor achieved 93.8% desirability. It proved a slope of 30.57 mV/decade, a correlation coefficient of 0.9931, a quantification limit of 1.07 × 10-6 M, a detection limit of 2.18 × 10-7 M, and a fast response of 6.5 s within the pH range of 2.5-8.5. The sensor was successfully used to determine HCQ purity in its raw material. The sensor represents a potential tool for rapid, sensitive, and selective monitoring of HCQ purity during industrial production from its starting materials.

New approaches in antibiotics detection: The use of square wave voltammetry

Antibiotics belongs to a class of pharmaceutical compounds widely used due to their effectiveness against bacterial infections. However, if consumed or inappropriately disposed of in the environment can results in environmental and public health problems, because they are considered emerging contaminants and their residues represent damage, whether in the long or short term, to different terrestrial ecosystems, in addition to bringing potential risks to agricultural sectors, such as livestock and fish farming. For this, the development of analytical methods for low-concentration detection and identification of antibiotics in natural waters, wastewaters, soil, foods, and biological fluids is necessary. This review shows the applicability of square wave voltammetry for the analytical determination of antibiotics from different chemical classes and covers a variety of samples and working electrodes that are used as voltammetric sensors. The review involved the analysis of scientific publications from the Science Direct® and Scopus® databases, with scientific manuscripts covering the period between January 2012 and May 2023. Various manuscripts were discussed indicating the applicability of square wave voltammetry in antibiotics detection in urine, blood, natural waters, milk, among other complex samples.

A simple, fast, portable and selective system using carbon nanotubes films and a 3D-printed device for monitoring hydroxychloroquine in environmental samples

In this work, an electrochemical method was developed for rapid and sensitive detection of hydroxychloroquine (HCQ), an ineffective candidate drug for COVID-19 treatment however widely consumed during the pandemic, in aqueous samples using a multi-walled carbon nanotubes (MWCNT) film produced through the interfacial method on the indium tin oxide electrode (ITO). According to Raman spectroscopy, X-ray diffraction, UV-vis spectroscopy, Energy-dispersive X-ray spectroscopy, scanning electron microscopy, and atomic force microscopy, the interfacial method produces homogeneous thin films of carbon nanotubes on the substrate surface, which keep connected to the surface forming a three-dimensional microporous structure. The electrochemical behavior and oxidation kinetics of HCQ were also investigated in the MWCNT film. The sensor showed a 7 times higher oxidation current for (69.88 μA) for HCQ than the ITO electrode (9.33 μA) due to the electrocatalytic properties MWCNTs. The ITO-modified electrode was assembled on a portable 3D-printed batch-injection cell for the amperometric detection of HCQ. The oxidation peak current of HCQ is linearly proportional to the concentrations of HCQ ranging from 1.0 to 100.0 μmol L^-1, with a limit of detection of 0.27 μmol L^-1. Water samples (river and tap water) were spiked with HCQ, without the need for dispendious pretreatment (except filtration), and analyzed by the portable system, revealing the detection of HCQ with the recovery of 92.0%-99.8%, which suggested the great potential for real environmental monitoring application.

NiFe-based Prussian blue analogue nanopolygons hybridized with functionalized glyoxal polymer as a voltammetric platform for the determination of amisulpride in biological samples

A novel voltammetric platform based on pencil graphite electrode (PGE) modification has been proposed, containing bimetallic (NiFe) Prussian blue analogue nanopolygons decorated with electro-polymerized glyoxal polymer nanocomposites (p-DPG NCs@NiFe PBA Ns/PGE). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave voltammetry (SWV) were utilized to investigate the electrochemical performance of the proposed sensor. The analytical response of p-DPG NCs@NiFe PBA Ns/PGE was evaluated through the quantity of amisulpride (AMS), one of the most common antipsychotic drugs. Under the optimized experimental and instrumental conditions, the method showed linearity over the range from 0.5 to 15 × 10-8 mol L-1 with a good correlation coefficient (R = 0.9995) and a low detection limit (LOD) reached, 1.5 nmol L-1, with excellent relative standard deviation for human plasma and urine samples. The interference effect of some potentially interfering substances was negligible, and the sensing platform demonstrated an outstanding reproducibility, stability, and reusability. As a first trial, the proposed electrode aimed to shed light on the AMS oxidation mechanism, where the oxidation mechanism was monitored and elucidated using the FTIR technique. It was also found that the prepared p-DPG NCs@NiFe PBA Ns/PGE platform had promising applications for the simultaneous determination of AMS in the presence of some co-administered COVID-19 drugs, which could be attributed to the large active surface area, and high conductivity of bimetallic nanopolygons.

Electrochemical sensor based on a ZnO-doped graphitized carbon for the electrocatalytic detection of the antibiotic hydroxychloroquine. Application: tap water and human urine

Abstract

In December 2019, the world experienced a new coronavirus, SARS-CoV-2, causing coronavirus disease 2019 originating from Wuhan.The virus has crossed national borders and now affects more than 200 countries and territories. Hydroxychloroquine has been considered as a drug capable of treating COVID-19. The objective of this work is to establish a simple platform for electrocatalytic detection of hydroxychloroquine in human urine samples and pharmaceutical samples (tablets) using a ZnO@CPE sensor constructed by simple and inexpensive hydrothermal methods using a square wave voltammetry method. The best results are obtained in a PBS electrolyte with irreversible behavior of the hydroxychloroquine complement and controlled by diffusion coupled with absorption phenomena. The ZnO@CPE shifts the oxidation potential of hydroxychloroquine with the formation of a single very intense peak at the position of Epa = 0.5 V/(vs Ag/AgCl) with a shift is ΔEp = 0.1 V(vs Ag/AgCl) compared to the unmodified electrode. The obtained ZnO@CPE hybrid nanocomposite was characterized by different techniques and showed excellent electrocatalytic activity and higher active surface area compared to the bare carbon paste electrode. Under the optimized experimental conditions, the ZnO@CPE sensor showed good analytical performance for the determination of trace amounts of hydroxychloroquine, a wide linearity range from 10^-3 M to 0.8 × 10^-6 M with a very low detection limit in the range of 1.33 × 10^-7 M, satisfactory selectivity, acceptable repeatability and reproducibility. The calculated recovery and coefficient of variation for the two samples analyzed are very satisfactory, ranging from 97.6 to 102% and 1.2 to 2.3% respectively. The proposed applied method and the fabricated sensor offer the possibility to analyze traces of hydroxychloroquine in real human urine and water samples.

Graphical abstract

Strategy for the electro-oxidation reaction of hydroxychloroquine on the electro-catalytic surface of the ZnO@Carbon graphite electrode and real-time detection of hydroxychloroquine.

Structural growth of zinc oxide nanograins on carbon cloth as flexible electrochemical platform for hydroxychloroquine detection

Pharmaceutical pollution that imposes a health threat worldwide is making accurate and rapid detection crucial to prevent adverse effects. Herein, binder-free zinc oxide nanograins on carbon cloth (ZnO NGs@CC) have been synthesized hydrothermally and employed to fabricate a flexible electrochemical sensor for the quantification of hydroxychloroquine (HCQ) that is typical pharmaceutical pollution. The characteristics of ZnO NGs@CC were investigated by various in-depth electron microscopic, spectroscopic and electroanalytical approaches. Compared with the pristine CC platform, the ZnO NGs@CC platform exhibits superior electrochemical performance in detecting HCQ with a large oxidation current at a low over-potential of +0.92 V with respect to the Ag/AgCl (Sat. KCl) reference electrode. With the support of desirable characteristics, the fabricated ZnO NGs@CC-based electrochemical sensor for HCQ detection displays good performances in terms of wide sensing range (0.5-116 μM), low detection limit (0.09 μM), high sensitivity (0.279 μA μM^-1 cm^-2), and strong selectivity. By the resulting 3D hierarchical nanoarchitecture, ZnO NGs@CC has progressive structural advantages that led to its excellent electrochemical performance in sensing applications. Furthermore, the electrochemical sensor is employed to detect HCQ in biological and environmental samples and also achieves good recovery rates. Thus, the designed ZnO NGs@CC demonstrates admirable electrochemical activity toward HCQ real-time monitoring and would be an excellent electrochemical platform for HCQ sensing.

Additively manufactured electrodes for the electrochemical detection of hydroxychloroquine

Although studies have demonstrated the inactivity of hydroxychloroquine (HCQ) towards SARS-CoV-2, this compound was one of the most prescribed by medical organizations for the treatment of hospitalized patients during the coronavirus pandemic. As a result of it, HCQ has been considered as a potential emerging contaminant in aquatic environments. In this context, we propose a complete electrochemical device comprising cell and working electrode fabricated by the additive manufacture (3D-printing) technology for HCQ monitoring. For this, a 3D-printed working electrode made of a conductive PLA containing carbon black assembled in a 3D-printed cell was associated with square wave voltammetry (SWV) for the fast and sensitive determination of HCQ. After a simple surface activation procedure, the proposed 3D-printed sensor showed a linear response towards HCQ detection (0.4-7.5 μmol L^-1) with a limit of detection of 0.04 μmol L^-1 and precision of 2.4% (n = 10). The applicability of this device was shown to the analysis of pharmaceutical and water samples. Recovery values between 99 and 112% were achieved for tap water samples and, in addition, the obtained concentration values for pharmaceutical tablets agreed with the values obtained by spectrophotometry (UV region) at a 95% confidence level. The proposed device combined with portable instrumentation is promising for on-site HCQ detection.

A simple and efficient derivatization strategy combined with switchable solvent liquid-liquid microextraction hydroxychloroquine methyl acetate-d3 -based quadruple isotope dilution gas chromatography mass spectrometry for the determination of hydroxychloroquine sulfate in biological fluids

RATIONALE

A derivatization switchable solvent liquid-liquid microextraction quadruple isotope dilution gas chromatography mass spectrometry (D-SS-LLME-ID⁴ -GC/MS) method is presented for the determination of hydroxychloroquine sulfate in human biofluids.

METHODS

While mixing type/period and concentration of NaOH were optimized via a univariate optimization approach, a multivariate optimization approach was used to determine optimum values for relatively more important parameters such as volumes of derivatization agent (acetic anhydride), NaOH and switchable solvent.

RESULTS

Under the optimum experimental conditions, limit of detection and limit of quantification were calculated as 0.03 and 0.09 mg/kg (mass based), respectively. An isotopically labelled material (hydroxychloroquine methyl acetate-d₃ ) was firstly synthesized to be used in ID⁴ experiments which give highly accurate and precise recovery results. After the application of D-SS-LLME-ID⁴ , superior percent recovery results were recorded as 99.9 ± 1.6-101.3 ± 1.2 for human serum, 99.9 ± 1.7-99.8 ± 1.8 for urine and 99.6 ± 1.5-101.0 ± 1.1 for saliva samples.

CONCLUSIONS

The developed D-SS-LLME-ID⁴ -GC/MS method compensates the complicated matrix effects of human biofluids and provides highly accurate quantification of an analyte with precise results.

Quantitative analysis of favipiravir and hydroxychloroquine as FDA-approved drugs for treatment of COVID-19 using synchronous spectrofluorimetry: application to pharmaceutical formulations and biological fluids

Coronavirus disease 2019 (COVID-19) is a contagious viral infection caused by coronavirus 2 (SARS-CoV-2) that causes severe acute respiratory syndrome. It has ravaged several countries and burdened many healthcare systems. As the process of authorizing a novel treatment for human use is extensive and involves multiple phases to obtain safety information and identify potential concerns. Therefore, the fastest and easiest choice was to use United States Food and Drug Administration (US FDA)-approved drugs such as favipiravir and hydroxychloroquine. For the simultaneous estimation of both medications, a simple synchronous spectrofluorimetric approach was established in which both drugs were measured at 372 and 323 nm, respectively in the presence of each other without interference at Δλ 60 nm. The effect of various experimental conditions on synchronous fluorescence intensities were thoroughly investigated and optimized. The maximum synchronous fluorescence intensities were obtained at pH 5.4 using acetate buffer (0.2 M, 0.5 ml) and ethanol as a diluent. Excellent linearity ranges were obtained using 1.0-18.0 ng/ml and 10.0-120.0 ng/ml for favipiravir and hydroxychloroquine, respectively. The approach exhibited high sensitivity with detection limits down to 0.25 ng/ml and 1.52 ng/ml and quantitation limits down to 0.77 ng/ml and 4.62 ng/ml, respectively. Spiking human plasma samples with the studied drugs yielded high % recoveries, allowing a significant bioanalytical application. Moreover, the method was validated according to International Conference on Harmonization guidelines and further applied to commercial pharmaceutical preparations with good results.

Electrocatalytic Determination of Hydroxychloroquine Using Sodium Dodecyl Sulphate Modified Carbon Nanotube Paste Electrode

Selective, sensitive, easy, and fast voltammetric techniques were developed for the analysis of Hydroxychloroquine (HCQ). These analysis were carried out at sodium dodecyl sulphate modified carbon nanotube paste electrode (SDSMCNTPE) using an aqueous 0.2 M phosphate buffer solution as supporting electrolyte. The field emission-scanning electron microscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy were used for material characterization. A minute quantity of the SDS surfactant was sufficient to convey an outstanding electrocatalytic action to the electrochemical oxidation nature of HCQ. The HCQ molecule parades only electrochemical oxidation (irreversible) with the transfer of two electrons. The detection of HCQ was carried out through CV method at SDSMCNTPE and bare carbon nanotube paste electrode (BCNTPE). The corresponding analytical curve offered a decent linear nature in the considered HCQ concentration range (10-40 µM) and the detection limit was found to be 0.85 µM. The significant peak to peak split-up was observed between HCQ and interferents with a decent sensitivity and stability. The SDSMCNTPE to be an approachable electrode for the usage in the examination of HCQ independently and in the presence of paracetamol (PC) and ascorbic acid (AA). Thus, they were used to determine HCQ in pharmaceutical formulations and the results that showed good agreement with comparative methods. Furthermore, a mechanism for HCQ electro-oxidation was proposed.

Upconversion-nanoparticle-functionalized Janus micromotors for efficient detection of uric acid

We report enzyme-powered upconversion-nanoparticle-functionalized Janus micromotors, which are prepared by immobilizing uricase asymmetrically onto the surface of silicon particles, to actively and rapidly detect uric acid. The asymmetric distribution of uricase on silicon particles allows the Janus micromotors to display efficient motion in urine under the propulsion of biocatalytic decomposition of uric acid and simultaneously detect uric acid based on the luminescence quenching effect of the UCNPs modified on the other side of SiO₂. The efficient motion of the motors greatly enhances the interaction between UCNPs and the quenching substrate and improves the uric acid detection efficiency. Overall, such a platform using uric acid simultaneously as the detected substrate and motion fuel offers considerable promise for developing multifunctional micro/nanomotors for a variety of bioassay and biomedical applications.

Electrochemical sensor based on a chitosan-molybdenum vanadate nanocomposite for detection of hydroxychloroquine in biological samples

In this study, we firstly introduce an ultra-high sensitive V_3.6Mo_2.4O₁₆-chitosan (MV-CHT) nanocomposite for electrochemical hydroxychloroquine sulfate (HCQ) monitoring toward paracetamol (PCM) and pantoprazole (PPZ) in environmental and clinical diagnostics. The single-phase MV nanostructures are prepared via the sol-gel pechini route, followed by engineering maleic acid as a structure-directing agent. The stabilization of the MV electro-catalysts is adopted by varying critical factors such as calcination temperature, different chelating ligands, chelating molality and cross-linker concentration. The structural and morphological characterizations, namely, ordered active sites, structural integrity, porous network and dispersibility on the cationic polymer are confirmed by physicochemical analyses. Also, analytical nature of the MV-CHT modified carbon paste electrode (MV-CHT/CPE) is constructed via electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) techniques. As a result, the nano-MV-CHT/CPE platforms with 10% of polymeric matrixes delivered the boosted analytical performance in terms of linear ranges (0.0019-194.0 µM), lower detection limit (LOD = 0.224 nM), together with excellent sensitivity and selectivity. The novel combination of MV nanoparticles and CHT provide the fluent channels for rapid charge transport and effective surface area. Such results illustrate the synergistic and interaction capability of MV-CHT-based sensing catalysts with bioactive molecules, which make them as superior drug monitoring devices.

A Versatile Strategy to Coat Individual Cell with Fully/Partially Covered Shell for Preparation of Self-Propelling Living Cells

Coating living cells with a functional shell has been regarded as an effective way to protect them against environmental stress, regulate their biological behaviors, or extend their functionalities. Here, we reported a facile method to prepare fully or partially coated shells on an individual yeast cell surface by visible light-induced graft polymerization. In this strategy, yeast cells that were surface-absorbed with polyethylenimine (PEI) were deposited on the negatively charged glass slide to form a single layer by electrostatic interaction. Then, surface-initiated graft polymerization of poly(ethylene glycol) diacrylate (PEGDA) on yeast cells under visible light irradiation was carried out to generate cross-linked shells on the cells. The process of surface modification had negligible influence on the viability of yeast cells due to the mild reaction condition. Additionally, compared to the native yeast cells, a 17.5 h of delay in division was observed when the graft polymerization was performed under 15 mW/cm² irradiation for 30 min. Introducing artificial shell endowed yeast cells with significant resistance against lyticase, and the protection can be enhanced by increasing the thickness of shell. Moreover, the partially coated yeast cells would be prepared by simply adjusting the reaction condition such as irradiation density and time. By immobilizing urease on the functional patch, the asymmetrically modified yeast cells exhibited self-propelling capability, and the speed of directional movement reached 4 μm/s in the presence of 200 mM urea. This tunable coating individual cell strategy with varying functionality has great potential applications in fields of cell-based drug delivery, cell therapy, biocatalysis, and tissue engineering.

One step derivatization and dispersive liquid-liquid microextraction of hydroxychloroquine sulfate for its sensitive and accurate determination using GC-MS

In the present study, a novel analytical method for the determination of hydroxychloroquine sulfate in human serum and urine samples was established. One step derivatization and dispersive liquid-liquid microextraction (DLLME) was developed for quantitative determination of hydroxychloroquine sulfate in aqueous samples. Hydroxychloroquine sulfate was first hydrolyzed and converted to its benzoate derivative by adding benzoyl chloride in chloroform which also served as extraction solvent. Significant parameters such as type/volume of extraction and dispersive solvents, concentration/volume of sodium hydroxide, type/period of mixing and concentration of derivatizing agent were carefully optimized by one variable at a time approach. Under the optimum DLLME conditions, limit of detection (LOD), quantitation (LOQ) and dynamic range were calculated as 35.2, 117.2 and 96-1980 μg/kg (ppb), respectively. Recovery studies were conducted by spiked human serum and urine samples and the results were ranged between 93 and 107% with low standard deviations. Developed method can be easily used in hydroxychloroquine sulfate based SARS-CoV-2 and malaria treatment studies.

A Novel Electrochemical Sensor Based on Reduced Graphene Oxide–TiO2 Nanocomposites with High Selectivity for the Determination of Hydroxychloroquine

A simply sensitive sensor based on a reduced graphene oxide–TiO₂ nanocomposite modified glassy carbon electrode (RGO–TiO₂/GCE) was developed for the electrochemical determination of an antimalarial drug, hydroxychloroquine (HCQ). The modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Electrochemical test showed that the RGO–TiO₂ electrode had stronger electrochemical activity and higher effective real surface area than that of TiO₂ electrode and bare electrode. The electrochemical response of RGO–TiO₂ nanocomposite modified electrode toward HCQ oxidation was studied by CV, chronoamperometry (CHA), chronocoulometry (CHC) and square-wave voltammetry (SWV). Interestingly, RGO–TiO₂/GCE indicated an excellent electrocatalytic activity for HCQ. Under the optimal experimental conditions, a linear relationship between the peak current and the concentration was obtained, ranging from 0.25 to 500 μM, with the detection limit (S/N = 3) of 12.5 nM and quantification limit (S/N = 10) of 0.97 μM. Furthermore, the proposed sensor was successfully applied to the determination of HCQ in pharmaceutical (tablets) samples. In summary, the developed sensor was low cost and efficient, making it potentially attractive for practical sample analysis application of HCQ.

Green Composite Sensor for Monitoring Hydroxychloroquine in Different Water Matrix

Hydroxychloroquine (HCQ), a derivative of 4-aminoquinolone, is prescribed as an antimalarial prevention drug and to treat diseases such as rheumatoid arthritis, and systemic lupus erythematosus. Recently, Coronavirus (COVID-19) treatment was authorized by national and international medical organizations by chloroquine and hydroxychloroquine in certain hospitalized patients. However, it is considered as an unproven hypothesis for treating COVID-19 which even itself must be investigated. Consequently, the high risk of natural water contamination due to the large production and utilization of HCQ is a key issue to overcome urgently. In fact, in Brazil, the COVID-19 kit (hydroxychloroquine and/or ivermectin) has been indicated as pre-treatment, and consequently, several people have used these drugs, for longer periods, converting them in emerging water pollutants when these are excreted and released to aquatic environments. For this reason, the development of tools for monitoring HCQ concentration in water and the treatment of polluted effluents is needed to minimize its hazardous effects. Then, in this study, an electrochemical measuring device for its environmental application on HCQ control was developed. A raw cork–graphite electrochemical sensor was prepared and a simple differential pulse voltammetric (DPV) method was used for the quantitative determination of HCQ. Results indicated that the electrochemical device exhibited a clear current response, allowing one to quantify the analyte in the 5–65 µM range. The effectiveness of the electrochemical sensor was tested in different water matrices (in synthetic and real) and lower HCQ concentrations were detected. When comparing electrochemical determinations and spectrophotometric measurements, no significant differences were observed (mean accuracy 3.0%), highlighting the potential use of this sensor in different environmental applications.

Accurate and sensitive determination of hydroxychloroquine sulfate used on COVID-19 patients in human urine, serum and saliva samples by GC-MS

A rapid, accurate, and sensitive analytical method, ultrasonication-assisted spraying based fine droplet formation-liquid phase microextraction-gas chromatography-mass spectrometry (UA-SFDF-LPME-GC-MS), was proposed for the determination of trace amounts of hydroxychloroquine sulfate in human serum, urine, and saliva samples. To determine the best extraction strategy, several liquid and solid phase extraction methods were investigated for their efficiencies in isolation and preconcentration of hydroxychloroquine sulfate from biological matrices. The UA-SFDF-LPME method was determined to be the best extraction method as it was operationally simple and provided accurate results. Variables such as the extraction solvent, spraying number, sodium hydroxide concentration and volume, sample volume, mixing method, and mixing period were optimized for the proposed method using the one-variable-at-a-time approach. In addition, Tukey's method based on a post hoc comparison test was employed to evaluate the significant difference between the parameters inspected. After the optimization studies, the limit of detection (LOD) and limit of quantification (LOQ) were determined to be 0.7 and 2.4 μg/kg, respectively. The sensitivity of the GC-MS system based on the LOD was enhanced approximately 440-fold when the UA-SFDF-LPME method was employed. Spiking experiments were also conducted for the human serum, urine, and saliva samples to determine the applicability and accuracy of the proposed method. Recoveries for the human serum, urine, and saliva samples were found to be in the ranges of 93.9%-101.7%, 95.2%-105.0%, and 93.1%-102.3%, respectively. These results were satisfactory and indicated that the hydroxychloroquine sulfate level in the above biological samples could be analyzed using the proposed method.

Dimensionally Stable Anode Based Sensor for Urea Determination via Linear Sweep Voltammetry

Urea is an added value chemical with wide applications in the industry and agriculture. The release of urea waste to the environment affects ecosystem health despite its low toxicity. Online monitoring of urea for industrial applications and environmental health is an unaddressed challenge. Electroanalytical techniques can be a smart integrated solution for online monitoring if sensors can overcome the major barrier associated with long-term stability. Mixed metal oxides have shown excellent stability in environmental conditions with long lasting operational lives. However, these materials have been barely explored for sensing applications. This work presents a proof of concept that demonstrates the applicability of an indirect electroanalytical quantification method of urea. The use of Ti/RuO₂-TiO₂-SnO₂ dimensional stable anode (DSA^®) can provide accurate and sensitive quantification of urea in aqueous samples exploiting the excellent catalytic properties of DSA^® on the electrogeneration of active chlorine species. The cathodic reduction of accumulated HClO/ClO⁻ from anodic electrogeneration presented a direct relationship with urea concentration. This novel method can allow urea quantification with a competitive LOD of 1.83 × 10⁻⁶ mol L⁻¹ within a linear range of 6.66 × 10⁻⁶ to 3.33 × 10⁻⁴ mol L⁻¹ of urea concentration.

Cyclodextrin-mediated gold nanoparticles as multisensing probe for the selective detection of hydroxychloroquine drug

β-Cyclodextrin (β-CD) modified gold nanoparticles (AuNP) were rapidly synthesized using microwave assisted procedure. Parameters, such as time, pH and concentrations of β-CD and gold, were optimized for the synthesis of β-CD-AuNP. The addition of enantiomers and racemic mixture of hydroxychloroquine (R-HCQ, S-HCQ and RS-HCQ) drugs and their interaction with β-CD led to a red shift in the surface plasmon resonance of β-CD-AuNP. The changes associated with the introduction of HCQ in β-CD-AuNP were studied using various characterization techniques such as UV-vis, FT-IR, XRD, dynamic light scattering, zeta potential, transmission electron microscopy, fluorescence spectroscopy and electrochemical techniques. The host-guest interaction of β-cyclodextrin with S-HCQ, R-HCQ and RS-HCQ resulted in the aggregation of gold nanoparticles. The surface plasmon resonance at 521 nm for β-CD-AuNP was shifted to 600, 620 and 670 nm on the addition of S-HCQ, R-HCQ and RS-HCQ, respectively, with a color change from pink to blue. The selectivity and sensitivity of the developed system for RS-HCQ were investigated and the limit of detection (LOD=3 s/m) was found to be 2.61, 0.15, and 0.85 nM for optical, fluorescence and electrochemical methods, respectively. The successful monitoring of RS-HCQ drug in pharmaceutical samples is possible with these techniques.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s11814-020-0719-7 and is accessible for authorized users.

Facile one pot sonochemical synthesis of layered nanostructure of ZnS NPs/rGO nanosheets for simultaneous analysis of daclatasvir and hydroxychloroquine

In this study, zinc sulfide nanoparticles were loaded on reduced graphene oxide (ZnS NPs/rGO) using simple sonochemical method. The nanocomposite was characterized using different morphological and electrochemical techniques such as TEM, SEM, PXRD, EDX, Raman spectroscopy, FTIR, N₂-adsorption-desorption, CV, and EIS. The ZnS NPs/rGO modified glassy carbon electrode (GCE) was used to simultaneously estimate hydroxychloroquine (HCQ) and daclatasvir (DAC) in a binary mixture for the first time. The modified nanocomposite exhibited good catalytic activity towards HCQ and DAC detection. In addition, it showed higher sensitivity, good selectivity and stability; and high reproducibility towards HCQ and DAC analysis. The activity of the modified electrode was noticeably improved due to synergism between ZnS NPs and rGO. Under optimum conditions of DPV measurements, the anodic peak currents (Ipa) were obviously increased with the increase of HCQ and DAC amounts with linear ranges of 5.0-65.0 and 7.0-65.0 nM with LODs of 0.456 and 0.498 nM for HCQ and DAC, respectively. The ZnS NPs/ rGO modified GCE was used to quantify HCQ and DAC in biological fluids with recoveries of 98.7-102.7% and 96.9-104.5% and RSDs of 1.89-3.57% and 1.91-3.70%, respectively.

Boron-Doped Diamond Electrodes: Recent Developments and Advances in View of Electrochemical Drug Sensors

Conductive boron-doped diamond (BDD), in addition to its superior material properties, offers many important advantages that make it an interesting material for electroanalytical studies. It has been considered as an excellent electrode material for electrooxidation of drug active compounds in their dosage forms or in biological materials due to its good physical and chemical properties. It contains not only the largest solvent working potential window compared to other electrode materials, but also it has low background and capacitive currents; lower problems with passivation and it has the ability to withstand extreme potentials, corrosive, and high temperature/pressure environments. The aim of this review is not only to provide a state-of-the-art of diamond electrochemistry but also to serve as a reference point for any researcher wishing to commence work with diamond electrodes and understand electrochemical data. Therefore, it is focused on the carbon-based materials, electrochemical properties of the BDD film electrode, its fundamental research, and its electrochemical pretreatment process are discussed in detail. In this case, there are important studies to show the effective BDD drug sensors for the detection and determination of drugs and the present review critically summarizes the available data in this field between 2015 and 2020.

Development of a portable electroanalytical method using nickel modified screen-printed carbon electrode for ethinylestradiol determination in organic fertilizers

Urine and struvite are organic fertilizers that have all nutritional requirements for the growth of a plant. However, these fertilizers may contain some emerging organic contaminants, such as ethinylestradiol, which is one of the most common hormones found in aquatic environments and can cause several changes in living organisms. Thus, the present study developed a fast, sensitive, inexpensive, and portable method for determining ethinylestradiol in urine and struvite, using square wave voltammetry (SWV) and screen-printed carbon electrodes modified with electrodeposited nickel film (SPCE-Ni). The electrodeposition of the nickel film on the screen-printed electrode was performed by cyclic voltammetry and optimized using complete factorial design 2³ and central composite design. The parameters optimized for SPCE-Ni were: number of cycles (1000); scan rate (5 V s^-1) and Ni²⁺ concentration (9.4 mmol L^-1). The operational parameters of the SWV for ethinylestradiol analysis were also optimized by experimental designs and obtained the following optimal values: step potential (10 mV), modulation amplitude (40 mV), and frequency (20 Hz). The method used 0.1 mol L^-1 BR buffer (pH 8.0) as support electrolyte and presented a limit of detection of 0.052 µmol L^-1 (R² = 0.996). Ethinylestradiol recovery test in struvite, human urine, synthetic urine, and pharmaceutical tablets ranged from 93.9% to 107.5%, indicating that there is no matrix effect. Furthermore, an interference test was performed with several drugs did not show any significant changes in the ethinylestradiol analytical signal, guaranteeing a greater precision of the method. These results reinforce the possibility of applying the proposed method in loco with a practical and fast way, without the need to use significant amounts of sample.

Simultaneous electrochemical detection of azithromycin and hydroxychloroquine based on VS2 QDs embedded N, S @graphene aerogel/cCNTs 3D nanostructure

In this research paper, an innovative electrochemical sensor was suggested for simultaneous voltammetric analysis of azithromycin (AZM) and hydroxychloroquine (HCQ) for the first time. The sensor based on hydrothermal synthesis of vanadium disulfide quantum dots (VS₂ QDs) and insertion within 3D N, S graphene aerogel (3D N, S @ GNA) and carbon nanotubes nanaostructure as a new and widely group of carbon nanomaterials. The nanocomposites were characterized morphologically using different techniques. In addition, the nanomaterials were characterized electrochemically using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The proposed electrochemical sensor showed wide dynamic linear ranges of 0.28–30 × 10⁻⁸ M and 0.84–22.5 × 10⁻⁸ M for analysis of AZM and HCQ, respectively. The limits of detection (LODs) based on signal to noise (S/N) 3:1 were found to be 0.091 × 10⁻⁸ M and 0.277 × 10⁻⁸ M for AZM and HCQ, respectively. Briefly, the electrochemical sensor had good stability, selectivity, reproducibility and feasibility for simultaneous detection of AZM and HCQ in presence of different interfering species.

Enzyme-powered Janus platelet cell robots for active and targeted drug delivery

Transforming natural cells into functional biocompatible robots capable of active movement is expected to enhance the functions of the cells and revolutionize the development of synthetic micromotors. However, present cell-based micromotor systems commonly require the propulsion capabilities of rigid motors, external fields, or harsh conditions, which may compromise biocompatibility and require complex actuation equipment. Here, we report on an endogenous enzyme-powered Janus platelet micromotor (JPL-motor) system prepared by immobilizing urease asymmetrically onto the surface of natural platelet cells. This Janus distribution of urease on platelet cells enables uneven decomposition of urea in biofluids to generate enhanced chemophoretic motion. The cell surface engineering with urease has negligible impact on the functional surface proteins of platelets, and hence, the resulting JPL-motors preserve the intrinsic biofunctionalities of platelets, including effective targeting of cancer cells and bacteria. The efficient propulsion of JPL-motors in the presence of the urea fuel greatly enhances their binding efficiency with these biological targets and improves their therapeutic efficacy when loaded with model anticancer or antibiotic drugs. Overall, asymmetric enzyme immobilization on the platelet surface leads to a biogenic microrobotic system capable of autonomous movement using biological fuel. The ability to impart self-propulsion onto biological cells, such as platelets, and to load these cellular robots with a variety of functional components holds considerable promise for developing multifunctional cell-based micromotors for a variety of biomedical applications.

Fabrication of a magnetic metal–organic framework molecularly imprinted polymer for extraction of anti-malaria agent hydroxychloroquine

A new magnetic metal–organic framework molecularly imprinted polymer was synthesized by the sol–gel method for the determination of hydroxychloroquine sulfate.

Amperometric Determination of Hydrogen Peroxide in Whitening Gels Using Boron-doped Diamond Electrode

The aim of this work was to develop an electrochemical cell and a methodology based on an amperometric determination of hydrogen peroxide in whitening gel samples under a boron-doped diamond electrode using flow injection analysis. Different parameters were evaluated to obtain the best conditions of analysis: among them, the flow of electrolyte at 2.8 mL min^-1, the loop sampling 175 μL (28.5 cm), an analytical length of 159 μL (25 cm) and an applied potential of +0.60 V vs. Ag/AgCl_(sat). The proposed method was suitable in terms of precision of results (RSD <10%); the accuracy was confirmed in the analysis of the gels through addition and recovery studies with results between 74 and 107%. The method was then applied to the analysis of tooth-whitening gel samples, acquired in different cities of the region. Regarding the results, a medium concentration value of 2.39% (w/w) was observed.

Taking advantage of CTAB micelles for the simultaneous electrochemical quantification of diclofenac and acetaminophen in aqueous media

Cetyltrimethylammonium bromide hemimicelles, formed on the surfaces of a carbon paste electrode, selectively adsorbed diclofenac molecules from a neutral aqueous solution containing acetaminophen, allowing simultaneous quantification of both drugs.

Fast quantification of α-lipoic acid in biological samples and dietary supplements using batch injection analysis with amperometric detection

Batch injection analysis (BIA) with amperometric detection, using a pyrolytic graphite electrode modified with cobalt phthalocyanine (PG/CoPc), was employed for determination of α-lipoic acid (ALA) in pharmaceutical product and in synthetic urine samples. The proposed BIA method is based on the application of a potential of +0.9V vs. Ag/AgCl, KCl sat, enabling quantification of ALA over a concentration range from 1.3×10(-6) to 1.0×10(-4)molL(-1), with a detection limit of 1.5×10(-8)molL(-1). A sampling rate of 180 injections per hour was attained and measurements of the reproducibility of successive injections (100µmolL(-1) ALA on the same electrode) showed a RSD of 2.11% for 40 successive injections. The new sensor was utilised for ALA quantification in a dietary pharmaceutical supplement and in synthetic urine and the results obtained for both samples were compared with parallel analysis using high performance liquid chromatography (HPLC), the method recommended by the United States Pharmacopeia. The results obtained were similar (at a 95% confidence level) and in the case of the synthetic urine sample (prepared with a known amount of ALA) the recovery was situated between 98.0% and 102.6%.

Multiwall carbon nanotube-modified electrode as a nanosensor for electrochemical studies and stripping voltammetric determination of an antimalarial drug

MWCNTs/CPE exhibited excellent effect towards the oxidation of hydroxychloroquine.