Analysis and electroanalysis of perchlorate in water and food samples: a critical review.

Perchlorate, ClO4-, with diverse applications, has become one of the major contaminants in surface and groundwater sources. This highly soluble and stable anion poses a considerable threat to human health given that it contaminates drinking water, vegetables, milk, and other contaminated food products. ClO4- can impair the thyroid function; thus, drinking water with high levels of this anion is a severe problem worldwide. However, due to the high solubility, stability, and mobility of ClO4-, its remediation and monitoring remain a major challenge. Considering the various analytical methods, including electrochemistry, each method has advantages and disadvantages in terms of detection sensitivity, selectivity, analysis time, and cost. Also, sample preconcentration and clean-up must be performed for the analysis of more complex matrices such as food and biological samples to ensure a low detection limit and selectivity. Both ion chromatography (IC) and capillary electrophoresis (CE) coupled with electrochemical detection, in addition to liquid chromatography (LC)-mass spectrometry (MS), are expected to play key roles due to their lower detection limit with excellent sensitivities and selectivity. Herein, we also discuss the perspective on various electrode materials for the detection of ClO4- regarding whether ClO4- can be measured at the lowest levels with the highest selectivity.

Development of Capillary Zone Electrophoresis Method for the Simultaneous Separation and Quantification of Metformin and Pioglitazone in Dosage Forms; and Comparison with HPLC Method.

A capillary zone electrophoretic (CZE) method was developed, validated, and applied for the assay of metformin (MET) and pioglitazone (PIO) in pharmaceutical formulations. The optimum running buffer composition was found to be 75 mmol/L phosphate buffer containing 30% acetonitrile (ACN) at pH 4.0. The optimum instrumental conditions were found to be injection time, 10 s; applied voltage, 25 kV; hydrodynamic injection pressure, 0.5 psi for 10 s, capillary temperature, 25 °C; and the detection wavelength, 210 nm. The quantifications were calculated based on the ratio of the peak areas of analytes to atenolol as an internal standard. The CZE method was validated in terms of accuracy (98.21-104.81%), intra- and inter-day precision of migration time and peak area (relative standard deviation ≤ 5%), linearity (correlation coefficients ≥ 0.9985), limit of detection (≤0.277 µg/mL), and limit of quantitation (≤0.315 µg/mL). The proposed method was applied for the analysis of PIO and MET both individually and in a combined dosage tablet formulation. All electrophoretic parameters were calculated and evaluated. A previously reported high-performance liquid chromatographic (HPLC) method was also applied to the same samples. A comprehensive comparison was then carried out for the analytical features of both methods CZE and HPLC. Comparable results were obtained with the advantage of reagent consumption and separation efficiency of CZE over HPLC and shorter analysis time by HPLC compared with CZE.

Important Roles and Potential Uses of Natural and Synthetic Antimicrobial Peptides (AMPs) in Oral Diseases: Cavity, Periodontal Disease, and Thrush.

Numerous epithelial cells and sometimes leukocytes release AMPs as their first line of defense. AMPs encompass cationic histatins, defensins, and cathelicidin to encounter oral pathogens with minimal resistance. However, their concentrations are significantly below the effective levels and AMPs are unstable under physiological conditions due to proteolysis, acid hydrolysis, and salt effects. In parallel to a search for more effective AMPs from natural sources, considerable efforts have focused on synthetic stable and low-cytotoxicy AMPs with significant activities against microorganisms. Using natural AMP templates, various attempts have been used to synthesize sAMPs with different charges, hydrophobicity, chain length, amino acid sequence, and amphipathicity. Thus far, sAMPs have been designed to target Streptococcus mutans and other common oral pathogens. Apart from sAMPs with antifungal activities against Candida albicans, future endeavors should focus on sAMPs with capabilities to promote remineralization and antibacterial adhesion. Delivery systems using nanomaterials and biomolecules are promising to stabilize, reduce cytotoxicity, and improve the antimicrobial activities of AMPs against oral pathogens. Nanostructured AMPs will soon become a viable alternative to antibiotics due to their antimicrobial mechanisms, broad-spectrum antimicrobial activity, low drug residue, and ease of synthesis and modification.

Perspectives on electrochemical biosensing of COVID-19.

Rapid detection of human coronavirus disease 2019, termed as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or COVID-19 infection, is urgently needed for containment strategy owing to its unprecedented spreading. Novel biosensors can be deployed in remote clinical settings without central facilities for infection screening. Electrochemical biosensors serve as analytical tools for rapid detection of viral structure proteins, mainly spike (S) and nucleocapsid (N) proteins, human immune responses, reactive oxygen species, viral ribonucleic acid, polymerase chain reaction by-products, and other potential biomarkers. The development of point-of-care testing devices is challenging due to the requirement of extensive validation, a time-consuming and expensive step. Together with specific biorecognition molecules, nanomaterial-based biosensors have emerged for the fast detection of early viral infections.

Isoquinolinequinone N-oxides as anticancer agents effective against drug resistant cell lines.

The isoquinolinequinone (IQQ) pharmacophore is a privileged framework in known cytotoxic natural product families, caulibugulones and mansouramycins. Exploiting both families as a chemical starting point, we report on the structured development of an IQQ N-oxide anticancer framework which exhibits growth inhibition in the nM range across melanoma, ovarian and leukaemia cancer cell lines. A new lead compound (16, R6 = benzyl, R7 = H) exhibits nM GI50 values against 31/57 human tumour cell lines screened as part of the NCI60 panel and shows activity against doxorubicin resistant tumour cell lines. An electrochemical study highlights a correlation between electropositivity of the IQQ N-oxide framework and cytotoxicity. Adduct binding to sulfur based biological nucleophiles glutathione and cysteine was observed in vitro. This new framework possesses significant anticancer potential.

Profiling of phenolic flavorings using core-shell reversed-phase liquid chromatography with electrochemical detection at a boron-doped diamond electrode.

A high-performance liquid chromatography (HPLC) method equipped with a boron-doped diamond (BDD) electrode was established for the simultaneous determination of phenol, 4-ethylphenol (4-EP), guaiacol, 4-ethylguaiacol (4-EG), 4-vinylguaiacol (4-VG), eugenol, and o-, m- and p-cresol. The separation was performed on a reversed-phase HALO C18 core-shell column (3.0 × 50 mm, 2.7 µm) with a mobile phase comprising 10 mM formate, pH 3, and 15% acetonitrile (ACN) (v/v), a flow rate of 1.5 mL/min, corresponding to a total run time of 9 min. The electrochemical detection (ECD) was set at +1.5 V vs. Pd/H2 in oxidative mode. Under optimized operating conditions, good linearity was obtained for the nine phenolics with corresponding coefficients of determination (R2) above 0.998. The limits of detection (LODs, S/N = 3) were 10 nM-1 µM, with an 80-fold increase in sensitivity for guaiacol achieved with ECD over ultraviolet (UV) detection. The sensitive and selective HPLC-ECD method was successfully applied for the identification and quantification of the nine phenolics in Islay, Irish, Scotch, and Highland whiskey samples, with significantly higher concentrations of the flavorings determined in Islay whiskey.

Captavidin as a regenerable biorecognition element on boron-doped diamond for biotin sensing.

Captavidin, a nitrated avidin with moderate affinity with biotin, irreversibly adsorbs on carboxymethylcellulose to form a regenerable biorecognition element for biotin. This layer was retained and stabilized on a boron-doped diamond electrode by a Nafion film for repeated impedance analyses of biotin down to below 1 nM. The labeless electrochemical sensing scheme was then demonstrated for the analysis of biotin in blood plasma. The incorporation of captavidin confers detection specificity and regenerability, whereas the Nafion and carboxymethylcellulose layers circumvent the diffusion of endogenous electroactive species. The biosensing layer is simply regenerated by applying oxidation of +2 V for 1 min instead of its submersion in carbonate buffer for 10 min.

Electrochemical Sensing of Biotin Using Nafion-Modified Boron-Doped Diamond Electrode.

Nafion formed on the surface of a boron-doped diamond electrode allows for a chemosensing system for biotin. The modified electrode is capable of oxidizing biotin and offers a detection limit of 5 nM, the average normal level of biotin in blood plasma. The developed method was successfully applied to determine biotin in human plasma samples and a popular health product as two popular models.

Rapid Electrochemical Detection of Pseudomonas aeruginosa Signaling Molecules by Boron-Doped Diamond Electrode.

As the leading cause of morbidity and mortality of cystic fibrosis (CF) patients, early detection of Pseudomonas aeruginosa (PA) is critical in the clinical management of this pathogen. Herein, we describe rapid and sensitive electroanalytical methods using differential pulse voltammetry (DPV) at a boron-doped diamond (BDD) electrode for the detection of PA signaling biomolecules. Monitoring the production of key signaling molecules in bacterial cultures of P. aeruginosa PA14 over 8 h is described, involving sample pretreatment by liquid-liquid and solid-phase extraction. In addition, direct electrochemical detection approach of PA signaling molecules is also reported in conjunction with hexadecyltrimethylammonium bromide (CTAB) to disrupt the bacterial membrane.

Synthesis and electrochemical detection of a thiazolyl-indole natural product isolated from the nosocomial pathogen Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen, capable of surviving in a broad range of natural environments and quickly acquiring resistance. It is associated with hospital-acquired infections, particularly in patients with compromised immunity, and is the primary cause of morbidity and mortality in cystic fibrosis (CF) patients. P. aeruginosa is also of nosocomial importance on dairy farms and veterinary hospitals, where it is a key morbidity factor in bovine mastitis. P. aeruginosa uses a cell-cell communication system consisting of signalling molecules to coordinate bacterial secondary metabolites, biofilm formation, and virulence. Simple and sensitive methods for the detection of biomolecules as indicators of P. aeruginosa infection would be of great clinical importance. Here, we report the synthesis of the P. aeruginosa natural product, barakacin, which was recently isolated from the bovine ruminal strain ZIO. A simple and sensitive electrochemical method was used for barakacin detection using a boron-doped diamond (BDD) and glassy carbon (GC) electrodes, based on cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The influence of electrolyte pH on the peak potential and peak currents was also investigated. At pH 2.0, the peak current was linearly dependent on barakacin concentration (in the range used, 1-10 µM), with correlation coefficients greater than 0.98 on both electrodes. The detection limit (S/N = 3) on the BDD electrode was 100-fold lower than that obtained on the GC electrode. The optimized method using the BDD electrode was extended to bovine (cow feces) and human (sputum of a CF patient) samples. Spiked barakacin was easily detected in these matrices at a limit of 0.5 and 0.05 µM, respectively. Graphical abstract Electrochemical detection of barakacin.

Molecular Signature of Pseudomonas aeruginosa with Simultaneous Nanomolar Detection of Quorum Sensing Signaling Molecules at a Boron-Doped Diamond Electrode.

Electroanalysis was performed using a boron-doped diamond (BDD) electrode for the simultaneous detection of 2-heptyl-3-hydroxy-4-quinolone (PQS), 2-heptyl-4-hydroxyquinoline (HHQ) and pyocyanin (PYO). PQS and its precursor HHQ are two important signal molecules produced by Pseudomonas aeruginosa, while PYO is a redox active toxin involved in virulence and pathogenesis. This Gram-negative and opportunistic human pathogen is associated with a hospital-acquired infection particularly in patients with compromised immunity and is the primary cause of morbidity and mortality in cystic fibrosis (CF) patients. Early detection is crucial in the clinical management of this pathogen, with established infections entering a biofilm lifestyle that is refractory to conventional antibiotic therapies. Herein, a detection procedure was optimized and proven for the simultaneous detection of PYO, HHQ and PQS in standard mixtures, biological samples, and P. aeruginosa spiked CF sputum samples with remarkable sensitivity, down to nanomolar levels. Differential pulse voltammetry (DPV) scans were also applicable for monitoring the production of PYO, HHQ and PQS in P. aeruginosa PA14 over 8 h of cultivation. The simultaneous detection of these three compounds represents a molecular signature specific to this pathogen.

One step preparation and electrochemical analysis of IQS, a cell-cell communication signal in the nosocomial pathogen Pseudomonas aeruginosa.

Pseudomonas aeruginosa uses a hierarchical cell-cell communication system consisting of a number of regulatory elements to coordinate the expression of bacterial virulence genes. Sensitive detection of quorum sensing (QS) molecules has the potential for early identification of P. aeruginosa facilitating early medical intervention. A recently isolated cell-cell communication molecule, a thiazole termed IQS, can bypass the las QS system of P. aeruginosa under times of stress, activating a subset of QS-controlled genes. This compound offers a new target for pathogen detection and has been prepared in a one step protocol. A simple electrochemical strategy was employed for its sensitive detection using boron-doped diamond and glassy carbon electrodes by cyclic voltammetry and amperometry.