Selection of a new aptamer targeting amoxicillin for utilization in a label-free electrochemical biosensor.

Pharmaceutical pollution has received considerable attention because of the harmful effects of pharmaceutical compounds on human health, even in trace amounts. Amoxicillin is one of the frequently used antibiotics that was included in the list of emerging water pollutants. Therefore, a highly selective and rapid technique for amoxicillin detection is required. In this work, a new aptamer was selected for amoxicillin and utilized for the development of a label-free electrochemical aptasensor. Aptamer selection was performed using the systematic evolution of ligands by exponential enrichment. The selected aptamer showed good specificity against other antibiotics, including the structurally related antibiotics: ampicillin and ciprofloxacin. Among the selected aptamers, Amx3 exhibited the lowest dissociation constant value of 112.9 nM. An aptasensor was developed by immobilization of thiolated Amx3 aptamer onto gold screen-printed electrodes via self-assembly, which was characterized using cyclic voltammetry and electrochemical impedance spectroscopy. The detection was realized by monitoring the change in the differential pulse voltammetry peak current in the ferro/ferricyanide redox couple upon binding of the aptasensor to amoxicillin. The aptasensor showed very good sensitivity with an ultralow limit of detection of 0.097 nM. When the aptasensor was tested using actual spiked milk samples, excellent recovery percentages were observed. The label-free electrochemical aptasensor developed herein is a promising tool for the selective and sensitive detection of amoxicillin in environmental samples.

Electrochemical sensor based on gum Arabic nanoparticles for rapid and in-situ detection of different heavy metals in real samples.

The key solution to combat trace metal pollution and keep the environment, ecosystem, animals, and humans safe is earlier and rapid trace metal detection. For all these reasons, we propose in this work the design of a simple electrochemical sensor functionalized with green nanoparticles for electrochemical detection of the fourth most dangerous heavy metal ions namely copper, zinc, lead, and mercury. The green nanoparticles are fabricated by a one-step, consisting of reducing platinum nanoparticles by a natural gum Arabic polymer. To guarantee the success of these nanoparticles' design, the nanoparticles have been characterized by Fourier-transform infrared spectroscopy FTIR, and thermogravimetric TGA techniques. While, for the electrochemical characterization, we have adopted cyclic voltammetry CV and electrochemical impedance spectroscopy EIS to control different steps of surface modification, and the differential pulse anodic stripping DPAS was monitored to follow up the electrochemical detection of different heavy metals. Results: have confirmed the good chemical and physical properties of the elaborated nanoparticles. As, the developed sensor showed a specific electrochemical response toward the heavy metal ions separately, with a lower limit of detection lower LOD than that recommended by the World Health Organization, in order of 9.6 ppb for Cu2+, 1.9 ppb for Zn2+, 0.9 ppb for Hg2+, and 4.2 ppb for Pb2+. Impressively, the elaborated sensor has demonstrated also high stability, outstanding sensitivity, and excellent analytical performance.In addition, the elaborated analytical tool has been successfully applied to the determination of various heavy metal ions in real samples, reflecting then its promising prospect in practical application.

An Electrochemical Sensor for Sulfadiazine Determination Based on a Copper Nanoparticles/Molecularly Imprinted Overoxidized Polypyrrole Composite.

To protect consumers from risks related to overexposure to sulfadiazine, total residues of this antibacterial agent in animal-origin foodstuffs not exceed international regulations. To this end, a new electrochemical sensor based on a molecularly imprinted polymer nanocomposite using overoxidized polypyrrole and copper nanoparticles for the detection of sulfadiazine is elaborated. After optimization of the preparation of the electrochemical sensors, their differential pulse voltammetric signal exhibits an excellent stability and reproducibility at 1.05 V, with a large linear range between 10-9 and 10-5 mol L-1 and a low detection limit of 3.1 × 10-10 mol L-1. The produced sulfadiazine sensor was successfully tested in real milk samples. The combination of the properties of the electrical conduction of copper nanoparticles with the properties of the preconcentration of the molecularly imprinted overoxidized polypyrrole allows for the highly sensitive detection of sulfadiazine, even in real milk samples. This strategy is new and leads to the lowest detection limit yet achieved, compared to those of the previously published sulfadiazine electrochemical sensors.

In Silico and In Vitro Studies for Benzimidazole Anthelmintics Repurposing as VEGFR-2 Antagonists: Novel Mebendazole-Loaded Mixed Micelles with Enhanced Dissolution and Anticancer Activity.

Cancer is a leading cause of death worldwide and its incidence is unfortunately anticipated to rise in the next years. On the other hand, vascular endothelial growth factor receptor 2 (VEGFR-2) is highly expressed in tumor-associated endothelial cells, where it affects tumor-promoting angiogenesis. Therefore, VEGFR-2 is considered one of the most promising therapeutic targets for cancer treatment. Furthermore, some FDA-approved benzimidazole anthelmintics have already shown potential anticancer activities. Therefore, repurposing them against VEGFR-2 can provide a rapid and effective alternative that can be implicated safely for cancer treatment. Hence, 13 benzimidazole anthelmintic drugs were subjected to molecular docking against the VEGFR-2 receptor. Among the tested compounds, fenbendazole (FBZ, 1), mebendazole (MBZ, 2), and albendazole (ABZ, 3) were proposed as potential VEGFR-2 antagonists. Furthermore, molecular dynamics simulations were carried out at 200 ns, giving more information on their thermodynamic and dynamic properties. Besides, the anticancer activity of the aforementioned drugs was tested in vitro against three different cancer cell lines, including liver cancer (HUH7), lung cancer (A549), and breast cancer (MCF7) cell lines. The results depicted potential cytotoxic activity especially against both HUH7 and A549 cell lines. Furthermore, to improve the aqueous solubility of MBZ, it was formulated in the form of mixed micelles (MMs) which showed an enhanced drug release with better promising cytotoxicity results compared to the crude MBZ. Finally, an in vitro quantification for VEGFR-2 concentration in treated HUH7 cells has been conducted based on the enzyme-linked immunosorbent assay. The results disclosed that FBZ, MBZ, and ABZ significantly (p < 0.001) reduced the concentration of VEGFR-2, while the lowest inhibition was achieved in MBZ-loaded MMs, which was even much better than the reference drug sorafenib. Collectively, the investigated benzimidazole anthelmintics could be encountered as lead compounds for further structural modifications and thus better anticancer activity, and that was accomplished through studying their structure-activity relationships.

Coronavirus Disease (COVID-19) Control between Drug Repurposing and Vaccination: A Comprehensive Overview.

Respiratory viruses represent a major public health concern, as they are highly mutated, resulting in new strains emerging with high pathogenicity. Currently, the world is suffering from the newly evolving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus is the cause of coronavirus disease 2019 (COVID-19), a mild-to-severe respiratory tract infection with frequent ability to give rise to fatal pneumonia in humans. The overwhelming outbreak of SARS-CoV-2 continues to unfold all over the world, urging scientists to put an end to this global pandemic through biological and pharmaceutical interventions. Currently, there is no specific treatment option that is capable of COVID-19 pandemic eradication, so several repurposed drugs and newly conditionally approved vaccines are in use and heavily applied to control the COVID-19 pandemic. The emergence of new variants of the virus that partially or totally escape from the immune response elicited by the approved vaccines requires continuous monitoring of the emerging variants to update the content of the developed vaccines or modify them totally to match the new variants. Herein, we discuss the potential therapeutic and prophylactic interventions including repurposed drugs and the newly developed/approved vaccines, highlighting the impact of virus evolution on the immune evasion of the virus from currently licensed vaccines for COVID-19.

Trifluoromethylated Flavonoid-Based Isoxazoles as Antidiabetic and Anti-Obesity Agents: Synthesis, In Vitro α-Amylase Inhibitory Activity, Molecular Docking and Structure-Activity Relationship Analysis.

Diabetes mellitus is a major health problem globally. The management of carbohydrate digestion provides an alternative treatment. Flavonoids constitute the largest group of polyphenolic compounds, produced by plants widely consumed as food and/or used for therapeutic purposes. As such, isoxazoles have attracted the attention of medicinal chemists by dint of their considerable bioactivity. Thus, the main goal of this work was to discover new hybrid molecules with properties of both flavonoids and isoxazoles in order to control carbohydrate digestion. Moreover, the trifluoromethyl group is a key entity in drug development, due to its strong lipophilicity and metabolic stability. Therefore, the present work describes the condensation of a previously synthesized trifluoromethylated flavonol with different aryl nitrile oxides, affording 13 hybrid molecules indicated as trifluoromethylated flavonoid-based isoxazoles. The structures of the obtained compounds were deduced from by 1H NMR, 13C NMR, and HRMS analysis. The 15 newly synthesized compounds inhibited the activity of α-amylase with an efficacy ranging from 64.5 ± 0.7% to 94.7 ± 1.2% at a concentration of 50 µM, and with IC50 values of 12.6 ± 0.2 µM-27.6 ± 1.1 µM. The most effective compounds in terms of efficacy and potency were 3b, 3h, 3j, and 3m. Among the new trifluoromethylated flavonoid-based isoxazoles, the compound 3b was the most effective inhibitor of α-amylase activity (PI = 94.7 ± 1.2% at 50 µM), with a potency (IC50 = 12.6 ± 0.2 µM) similar to that of the positive control acarbose (IC50 = 12.4 ± 0.1 µM). The study of the structure-activity relationship based on the molecular docking analysis showed a low binding energy, a correct mode of interaction in the active pocket of the target enzyme, and an ability to interact with the key residues of glycosidic cleavage (GLU-230 and ASP-206), explaining the inhibitory effects of α-amylase established by several derivatives.

Strong Inhibitory Activity and Action Modes of Synthetic Maslinic Acid Derivative on Highly Pathogenic Coronaviruses: COVID-19 Drug Candidate.

In late December 2019, a novel coronavirus, namely severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), escaped the animal-human interface and emerged as an ongoing global pandemic with severe flu-like illness, commonly known as coronavirus disease 2019 (COVID-19). In this study, a molecular docking study was carried out for seventeen (17) structural analogues prepared from natural maslinic and oleanolic acids, screened against SARS-CoV-2 main protease. Furthermore, we experimentally validated the virtual data by measuring the half-maximal cytotoxic and inhibitory concentrations of each compound. Interestingly, the chlorinated isoxazole linked maslinic acid (compound 17) showed promising antiviral activity at micromolar non-toxic concentrations. Thoughtfully, we showed that compound 17 mainly impairs the viral replication of SARS-CoV-2. Furthermore, a very promising SAR study for the examined compounds was concluded, which could be used by medicinal chemists in the near future for the design and synthesis of potential anti-SARS-CoV-2 candidates. Our results could be very promising for performing further additional in vitro and in vivo studies on the tested compound (17) before further licensing for COVID-19 treatment.

ß-Blockers bearing hydroxyethylamine and hydroxyethylene as potential SARS-CoV-2 Mpro inhibitors: rational based design, in silico, in vitro, and SAR studies for lead optimization.

The global COVID-19 pandemic became more threatening especially after the introduction of the second and third waves with the current large expectations for a fourth one as well. This urged scientists to rapidly develop a new effective therapy to combat SARS-CoV-2. Based on the structures of ß-adrenergic blockers having the same hydroxyethylamine and hydroxyethylene moieties present in the HIV-1 protease inhibitors which were found previously to inhibit the replication of SARS-CoV, we suggested that they may decrease the SARS-CoV-2 entry into the host cell through their ability to decrease the activity of RAAS and ACE2 as well. Herein, molecular docking of twenty FDA-approved ß-blockers was performed targeting SARS-CoV-2 Mpro. Results showed promising inhibitory activities especially for Carvedilol (CAR) and Nebivolol (NEB) members. Moreover, these two drugs together with Bisoprolol (BIS) as an example from the lower active ones were subjected to molecular dynamics simulations at 100 ns. Great stability across the whole 100 ns timeframe was observed for the top docked ligands, CAR and NEB, over BIS. Conformational analysis of the examined drugs and hydrogen bond investigation with the pocket's crucial residues confirm the great affinity and confinement of CAR and NEB within the Mpro binding site. Moreover, the binding-free energy analysis and residue-wise contribution analysis highlight the nature of ligand-protein interaction and provide guidance for lead development and optimization. Furthermore, the examined three drugs were tested for their in vitro inhibitory activities towards SARS-CoV-2. It is worth mentioning that NEB achieved the most potential anti-SARS-CoV-2 activity with an IC50 value of 0.030 µg ml-1. Besides, CAR was found to have a promising inhibitory activity with an IC50 of 0.350 µg ml-1. Also, the IC50 value of BIS was found to be as low as 15.917 µg ml-1. Finally, the SARS-CoV-2 Mpro assay was performed to evaluate and confirm the inhibitory effects of the tested compounds (BIS, CAR, and NEB) towards the SARS-CoV-2 Mpro enzyme. The obtained results showed very promising SARS-CoV-2 Mpro inhibitory activities of BIS, CAR, and NEB (IC50 = 118.50, 204.60, and 60.20 µg ml-1, respectively) compared to lopinavir (IC50 = 73.68 µg ml-1) as a reference standard.

An Acetylcholinesterase Inhibition-Based Biosensor for Aflatoxin B1 Detection Using Sodium Alginate as an Immobilization Matrix.

In this study, we investigated a novel aflatoxin biosensor based on acetylcholinesterase (AChE) inhibition by aflatoxin B1 (AFB1) and developed electrochemical biosensors based on a sodium alginate biopolymer as a new matrix for acetylcholinesterase immobilization. Electrochemical impedance spectroscopy was performed as a convenient transduction method to evaluate the AChE activity through the oxidation of the metabolic product, thiocholine. Satisfactory analytical performances in terms of high sensitivity, good repeatability, and long-term storage stability were obtained with a linear dynamic range from 0.1 to 100 ng/mL and a low detection limit of 0.1 ng/mL, which is below the recommended level of AFB1 (2 µg/L). The suitability of the proposed method was evaluated using the samples of rice supplemented with AFB1 (0.5 ng/mL). The selectivity of the AChE-biosensor for aflatoxins relative to other sets of toxic substances (OTA, AFM 1) was also investigated.

Experimental and theoretical study of CO2 adsorption by activated clay using statistical physics modeling.

The objective of this paper was to study CO2 adsorption on activated clay in the framework of geological storage. The activation of clay was characterized via scanning electron microscopy, N2 adsorption-desorption isotherms, and X-ray diffraction. The adsorption isotherms were generated at different temperatures, namely, 298 K, 323 K, and 353 K. Based on the experimental result, a new model was simulated and interpreted using a multi-layer model with two interaction energies. The physicochemical parameters that described the CO2 adsorption process were determined by physical statistical formalism. The characteristic parameters of the CO2 adsorption isotherm such as the number of carbon dioxide molecules per site (n), the receptor site densities (NM), and the energetic parameters were investigated. In addition, the thermodynamic functions that governed the adsorption process such as the internal energy, entropy, and Gibbs free energy were determined by a statistical physics model. Thus, the results showed that CO2 adsorption on activated clay was spontaneous and exothermic in nature.

Aflatoxin B1 Detection Using a Highly-Sensitive Molecularly-Imprinted Electrochemical Sensor Based on an Electropolymerized Metal Organic Framework.

A sensitive electrochemical molecularly-imprinted sensor was developed for the detection of aflatoxin B1 (AFB1), by electropolymerization of p-aminothiophenol-functionalized gold nanoparticles in the presence of AFB1 as a template molecule. The extraction of the template leads to the formation of cavities that are able to specifically recognize and bind AFB1 through π-π interactions between AFB1 molecules and aniline moities. The performance of the developed sensor for the detection of AFB1 was investigated by linear sweep voltammetry using a hexacyanoferrate/hexacyanoferrite solution as a redox probe, the electron transfer rate increasing when the concentration of AFB1 increases, due to a p-doping effect. The molecularly-imprinted sensor exhibits a broad linear range, between 3.2 fM and 3.2 µM, and a quantification limit of 3 fM. Compared to the non-imprinted sensor, the imprinting factor was found to be 10. Selectivity studies were also performed towards the binding of other aflatoxins and ochratoxin A, proving good selectivity.

Electrochemical impedance immunosensor for rapid detection of stressed pathogenic Staphylococcus aureus bacteria.

In this work, we report the adaptation of bacteria to stress conditions that induce instability of their cultural, morphological, and enzymatic characters, on which the identification of pathogenic bacteria is based. These can raise serious issues during the characterization of bacteria. The timely detection of pathogens is also a subject of great importance. For this reason, our objective is oriented towards developing an immunosensing system for rapid detection and quantification of Staphylococcus aureus. Polyclonal anti-S. aureus are immobilized onto modified gold electrode by self-assembled molecular monolayer (SAM) method. The electrochemical performances of the developed immunosensor were evaluated by impedance spectroscopy through the monitoring of the charge transfer resistance at the modified solid/liquid interface using ferri-/ferrocyanide as redox probe. The developed immunosensor was applied to detect stressed and resuscitate bacteria. As a result, a stable and reproducible immunosensor with sensitivity of 15 kΩ/decade and a detection limit of 10 CFU/mL was obtained for the S. aureus concentrations ranging from 10(1) to 10(7) CFU/mL. A low deviation in the immunosensor response (±10 %) was signed when it is exposed to stressed and not stressed bacteria.

An Electrochemical Immunosensor for Detection of Staphylococcus aureus Bacteria Based on Immobilization of Antibodies on Self-Assembled Monolayers-Functionalized Gold Electrode.

The detection of pathogenic bacteria remains a challenge for the struggle against biological weapons, nosocomial diseases, and for food safety. In this research, our aim was to develop an easy-to-use electrochemical immunosensor for the detection of pathogenic Staphylococcus aureus ATCC25923. The biosensor was elaborated by the immobilization of anti-S. aureus antibodies using a self-assembled monolayer (SAMs) of 3-Mercaptopropionic acid (MPA). These molecular assemblies were spontaneously formed by the immersion of the substrate in an organic solvent containing the SAMs that can covalently bond to the gold surface. The functionalization of the immunosensor was characterized using two electrochemical techniques: cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Here, the analysis was performed in phosphate buffer with ferro/ferricyanide as the redox probe. The EIS technique was used for affinity assays: antibody-cell binding. A linear relationship between the increment in the electron transfer resistance (RCT) and the logarithmic value of S. aureus concentration was observed between 10 and 106 CFU/mL. The limit of detection (LOD) was observed at 10 CFU/mL, and the reproducibility was calculated to 8%. Finally, a good selectivity versus E. coli and S. epidermidis was obtained for our developed immunosensor demonstrating its specificity towards only S. aureus.