An alginate-based eutectogel impregnated with polyvinylpyrrolidone/benzoic acid deep eutectic solvent and magnetic carboxylated multiwalled carbon nanotubes: Evaluated as sorbent in green microextraction of pesticides.

This article presents the synthesis and application of a novel magnetic eutectogel constituting a polymeric deep eutectic solvent (PDES), carboxylated multiwall carbon nanotube (MWCNT-COOH), and super-dispersible/super-paramagnetic polyvinylpyrrolidone coated-Fe3O4 nanocrystals incorporated in alginate gel. Different methods were used for the characterization of novel polymeric based DES gel including FT-NMR, ATR-FTIR, and SEM were used. The novel DES eutectogel was used for the extraction of pesticides from honey. The modified eutectogel with PDES, MWCNT, and PDES-MWCNT showed 1.8-, 1.4-, and 2.5-fold enhancement in the sorption efficiency under green magnetic micro-solid-phase extraction (MSPE) method before GC-MS analysis. Important factors including the acidity of the samples, adsorption and desorption conditions, and the ionic strength of the preparation solution were investigated. The matrix effect, specificity, the quantification limits (0.023-1.023 µg kg-1), linear dynamic range (0.023-500 µg kg-1 with R2 of 0.9845-0.9986), relative standard deviations (<8.4%), were evaluated. In addition, the method was used to analyze 12 pesticides in four samples of honey. In the spiked concentration range of 0.1 to 10 µg kg-, the obtained recoveries were between 73.2 and 110.8% (RSD% = 8.1%, n = 3).

Synthesis of a magnetic micro-eutectogel based on a deep eutectic solvent gel immobilized in calcium alginate: Application for green analysis of melamine in milk and dairy products.

A new three-component magnetic eutectogel composed of a crosslinked copolymeric deep eutectic solvent (DES) and polyvinylpyrrolidone-coated Fe3O4 nano-powder impregnated in calcium alginate gel was synthesized and applied as a sorbent material in a green alternative micro solid-phase extraction of melamine in milk and dairy products. The analyses were performed using the HPLC-UV technique. The copolymeric DES was prepared through thermally-induced free-radical polymerization of [2-hydroxyethyl methacrylate]:[thymol] DES (1:1 mol ratio) as functional monomer, azobisisobutyronitrile (as initiator), and ethylene glycol dimethacrylate (as crosslinker). The sorbent was characterized using ATR-FTIR, 1H & 13C FT-NMR, SEM, VSM, and BET techniques. The stability of the eutectogel in water and its effect on the pH of the aqueous solution was studied. A one-at-a-time approach was applied to optimize the impact of significant factors influencing sample preparation efficiency (sorbent mass, desorption conditions, adsorption time, pH, and ionic strength). The method validation was performed by evaluating matrix-matched calibration linearity (2-300 µg kg-1, r2 = 0.9902), precision, system suitability, specificity, enrichment factor, and matrix effect. The obtained limit of quantification (0.38 µg kg-1) was lower than the established maximum level for melamine by Food and Drug Administration (FDA) (0.25 mg kg-1), Food and Agriculture Organization (FAO) (0.5 & 2.5 mg kg-1), and The European Union (EU) (2.5 mg kg-1) in milk and dairy products. The optimized procedure was applied for the analysis of melamine in bovine milk, yogurt, cream, cheese, and ice cream. The obtained normalized recoveries of 77.4-105.3% (RSD% <7.0%) were acceptable regarding the practical default range set by the European Commission (70-120%, RSD≤20%). The sustainability and green aspects of the procedure were evaluated by the Analytical Greenness Metric Approach (0.6/1.0) and the Analytical Eco-Scale tool (73/100). This paper presents the first-time synthesis and application of this micro-eutectogel for the analysis of melamine in milk and milk-based dairy products.

Green vortex-assisted emulsification microextraction using a ternary deep eutectic solvent for extraction of tetracyclines in infant formulas.

A novel green alternative vortex-assisted emulsification liquid-liquid microextraction based on a new hydrophobic deep eutectic solvent (DES) was developed to extract tetracyclines in infant formulas. Five new ternary DESs were synthesized and tested in this regard. Among them [thymol]:[ethylene glycol]:[benzyl alcohol] (2:2:1) DES demonstrated the highest extraction efficiency. The analyzes were performed by HPLC. The DES was characterized by attenuated total reflectance-FTIR, nuclear magnetic resonance spectroscopy, and octanol-water partition coefficient. The effect of type, mole ratio, and volume of DES, dispersing agent, pH, and ionic strength was studied. The limits of quantification and linear range were 3-9.32 and 3-500 µg kg-1, respectively. The method was applied to detect tetracyclines in infant formulas, and the recoveries were obtained as 68.9-102.0 % with relative standard deviations < 9 %. The procedure greenness was assessed using the Analytical Eco-Scale. This paper represents the first application of a novel ternary DES to analyze tetracyclines in infant formulas.

A green alternative QuEChERS developed based on green deep eutectic solvents coupled with gas chromatography-mass spectrometry for the analysis of pesticides in tea samples.

A novel green modified QuEChERS based on green deep eutectic solvents (DES) followed by GC-MS was developed to analyze pesticides in tea samples. Among different tested DESs for the extraction of analytes, ChCl:PEG (1:4) DES showed the highest efficiency. Three-dimensional magnetic graphene was functionalized by ChCl:urea (1:2) natural DES, characterized and used as sorbent in the in-syringe dispersive micro-SPE to cleanup tea extract. Under optimized conditions, linear range was 0.70-500 µg kg-1. The limits of quantification (0.70-1.90 µg kg-1) were lower than the maximum residue levels established by the European Union for pesticides in tea (0.015-0.1 mg kg-1). The method was applied to detect pesticides in green and black teas, and the recoveries were 70.2-105.2%. This work represents the first application of ChCl:PEG DES and 3DGA-Fe3O4/ChCl:urea in extraction of pesticides and tea sample cleanup, respectively. The greenness of procedure was evaluated by Analytical Eco-Scale and Complementary Green Analytical Procedure Index.

Natural thymol-based ternary deep eutectic solvents: Application in air-bubble assisted-dispersive liquid-liquid microextraction for the analysis of tetracyclines in water.

Four new thymol-based ternary deep eutectic solvents were prepared and evaluated as the extractive phase in air-bubbles assisted dispersive liquid-liquid microextraction for extraction of tetracycline, doxycycline, and oxytetracycline from the water before high-performance liquid chromatography. The maximum extraction efficiencies were obtained using 400 µL of [choline chloride]:[thymol]:[nonanoic acid] in the molar ratio of 1:2:2 at pH = 5. The solvent was characterized by FTIR and NMR spectroscopy. The hydrophobicity of the deep eutectic solvent and its effect on the pH of water samples after mixing was also studied. Besides, the extraction efficiency of the ternary deep eutectic solvent was compared with that of two binary thymol-based deep eutectic solvents, including [choline chloride]:[thymol] and [thymol]:[nonanoic acid] at the same conditions. Under optimal conditions, limits of detection and quantification were 1.2-8.0 and 3.8-26.6 µg/L, respectively. The linear ranges were 18.2-500 µg/L for oxytetracycline, 26.6-500 µg/L for tetracycline, and 3.8-500 µg/L for doxycycline with the determination coefficients > 0.9912. Intra- and inter-day relative standard deviations were 1.2-3.8 and 7.7-11.2%, respectively. The developed method was applied to the analysis of tetracyclines in unspiked and spiked environmental water samples, and the obtained recoveries were 74.5-95.4% with relative standard deviations of 1.2-4.0%.

Deep eutectic solvent-based clean-up/vortex-assisted emulsification liquid-liquid microextraction: Application for multi-residue analysis of 16 pesticides in olive oils.

A new hydrophobic deep eutectic solvent (DES) composed of thymol and vanillin (1:1) was prepared and used as the extraction solvent in vortex-assisted emulsification liquid-liquid microextraction of 16 pesticides in olive oil before GC-µECD analysis. Due to the complexity of oil samples, a DES-based liquid-liquid solvent system (n-hexane/acetonitrile/DES) was developed to achieve an effective clean-up. Among the four examined hydrophilic DESs, [choline chloride]:[urea] led to improved sensitivity, and clean chromatograms with low noise and drift from the sample matrix. Besides, the effect of the significant factors such as extraction solvent volume, pH, ionic strength, and vortex time was investigated. At the optimized conditions, the validation parameters such as linear range 0.04-250 µg kg-1, the limits of detection of 0.01-0.08 µg kg-1, intra-day, and inter-day relative standard deviations (RSDs) < 6.8 and < 9.7%, were obtained. This method was followed by GC-µECD and applied to determine pesticides in five olive oil samples. The relative recoveries were in the range of 63.1-119.4%.

Sleep-Wake Cycle in Young and Older Mice.

Sleep plays a key role in multiple cognitive functions and sleep pattern changes with aging. Human studies revealed that aging decreases sleep efficiency and reduces the total sleep time, the time spent in slow-wave sleep (SWS), and the delta power (1-4 Hz) during sleep; however, some studies of sleep and aging in mice reported opposing results. The aim of our work is to estimate how features of sleep-wake state in mice during aging could correspond to age-dependent changes observed in human. In this study, we investigated the sleep/wake cycle in young (3 months old) and older (12 months old) C57BL/6 mice using local-field potentials (LFPs). We found that older adult mice sleep more than young ones but only during the dark phase of sleep-wake cycle. Sleep fragmentation and sleep during the active phase (dark phase of cycle), homologous to naps, were higher in older mice. Older mice show a higher delta power in frontal cortex, which was accompanied with similar trend for age differences in slow wave density. We also investigated regional specificity of sleep-wake electrographic activities and found that globally posterior regions of the cortex show more rapid eye movement (REM) sleep whereas somatosensory cortex displays more often SWS patterns. Our results indicate that the effects of aging on the sleep-wake activities in mice occur mainly during the dark phase and the electrode location strongly influence the state detection. Despite some differences in sleep-wake cycle during aging between human and mice, some features of mice sleep share similarity with human sleep during aging.

Slow wave detection in sleeping mice: Comparison of traditional and machine learning methods.

BACKGROUND: During slow-wave sleep the electroencephalographic (EEG) and local field potential (LFP) recordings reveal the presence of large amplitude slow waves. Systematic extraction of individual slow waves is not trivial. NEW METHOD: In this study, we used the neural network pattern recognition to detect individual slow waves in LFP recorded from mice as well as other commonly used methods that are based on fast frequencies modulation, amplitude, or duration. RESULTS: The number and quality of events detected as slow waves depended on the chosen method of detection, level of thresholds, or on combination of methods. Each individual method yields some false-positive and false-negative detections. Typically, the fast frequency-method has a higher false discovery rate, but almost no missing waves; amplitude-based method has relatively high false-positive and false-negative rates; duration-based method has low false-negative rates; neural network pattern recognition approach has the lowest false-positive rate among individual methods, often rejecting waves that were falsely detected by other approaches. Combining all 4 detection methods practically eliminated false-positive errors, but a large number of slow waves remained undetected. CONCLUSIONS: The use of a particular method of slow wave detection needs to be adjusted to the objectives of a given study: to detect all slow waves, but also numerous false positives can be achieved using the fast frequency approach. Neural network pattern recognition method alone can detect slow waves with the lowest false-positive rate, that can be further minimized with the use of combination of other methods.

UV-Vis, FTIR, 1H, 13C NMR spectra and thermal studies of charge transfer complexes formed in the reaction of Gliclazide with π- and σ-electron acceptors.

Charge transfer interactions (CT) between a gliclazide (GLC) donor and a picric acid (PA) π acceptor or iodine σ acceptor, were studied in a chloroform solution and in the solid state. UV-vis spectroscopy elucidated the formation of the complexes, and allowed determination of the stoichiometry, stability constants (K), and thermodynamic quantities (ΔG°, ΔH°, and ΔS°), and spectroscopic properties such as the molar extinction coefficient (εCT), oscillator strength (f), transition dipole moment (µEN), and ionization potential (Ip). Beer's law was obeyed over the 2-8 and 4-12 µg mL-1 concentration ranges for GLC with PA (method A) and I2 (method B), respectively, with correlation coefficients of 0.9986 and 0.9989. The limits of detection (LOD) and limits of quantification (LOQ) have also been reported. The 1:1 stoichiometric CT complexes were synthesized and characterized by FTIR, 1H, and 13C NMR spectroscopy. The results indicated a favorable proton migration from PA to the donor molecule, and an interaction between the NH of GLC and iodine. Thermogravimetric analysis techniques (TGA/DTA) and differential scanning calorimetry (DSC) were used to determine the thermal stability of the synthesized CT complex. The kinetic parameters (ΔG*, ΔH*, and ΔS*) were calculated from thermal decomposition data using the Coats-Redfern method.

Cellular and neurochemical basis of sleep stages in the thalamocortical network.

The link between the combined action of neuromodulators in the brain and global brain states remains a mystery. In this study, using biophysically realistic models of the thalamocortical network, we identified the critical intrinsic and synaptic mechanisms, associated with the putative action of acetylcholine (ACh), GABA and monoamines, which lead to transitions between primary brain vigilance states (waking, non-rapid eye movement sleep [NREM] and REM sleep) within an ultradian cycle. Using ECoG recordings from humans and LFP recordings from cats and mice, we found that during NREM sleep the power of spindle and delta oscillations is negatively correlated in humans and positively correlated in animal recordings. We explained this discrepancy by the differences in the relative level of ACh. Overall, our study revealed the critical intrinsic and synaptic mechanisms through which different neuromodulators acting in combination result in characteristic brain EEG rhythms and transitions between sleep stages.

In vivo models of cortical acquired epilepsy.

The neocortex is the site of origin of several forms of acquired epilepsy. Here we provide a brief review of experimental models that were recently developed to study neocortical epileptogenesis as well as some major results obtained with these methods. Most of neocortical seizures appear to be nocturnal and it is known that neuronal activities reveal high levels of synchrony during slow-wave sleep. Therefore, we start the review with a description of mechanisms of neuronal synchronization and major forms of synchronized normal and pathological activities. Then, we describe three experimental models of seizures and epileptogenesis: ketamine-xylazine anesthesia as feline seizure triggered factor, cortical undercut as cortical penetrating wound model and neocortical kindling. Besides specific technical details describing these models we also provide major features of pathological brain activities recorded during epileptogenesis and seizures. The most common feature of all models of neocortical epileptogenesis is the increased duration of network silent states that up-regulates neuronal excitability and eventually leads to epilepsy.

Neocortical focus: experimental view.

All brain normal or pathological activities occur in one of the states of vigilance: wake, slow-wave sleep, or REM sleep. Neocortical seizures preferentially occur during slow-wave sleep. We provide a description of neuronal behavior and mechanisms mediating such a behavior within neocortex taking place in natural states of vigilance as well as during seizures pointing to similarities and differences exhibited during sleep and seizures. A concept of epileptic focus is described using a model of cortical undercut, because in that model, the borders of the focus are well defined. In this model, as in other models of acquired epilepsy, the main factor altering excitability is deafferentation, which upregulates neuronal excitability that promotes generation of seizures. Periods of disfacilitation recorded during slow-wave sleep further upregulate neuronal excitability. It appears that the state of neurons and neuronal network in the epileptic focus produced by deafferentation are such that seizures cannot be generated there. Instead, seizures always start around the perimeter of the undercut cortex. Therefore, we define these areas as the seizure focus. In this zone, neuronal connectivity and excitability are moderately enhanced, lowering the threshold for seizure generation.

Involvement of the dorsal hippocampal GABA-A receptors in histamine-induced facilitation of memory in the Morris water maze.

Several types of learning and memory processes are regulated by the hippocampus which is an important subcortical structure in the mammalians' brain. Previous investigations have shown that different receptor systems in the CA1 region of hippocampus are involved in learning and memory functions. Investigating the possible influence of dorsal hippocampal GABA-A receptors on histamine-induced spatial facilitation in adult male Wistar rats was the focus of the current study. Rats were bilaterally implanted with dorsal hippocampal (CA1) cannulae, recovered from surgery and then trained in Morris water maze (MWM) for 4 consecutive days. A block of four trials was given each day. All drugs were injected into CA1 regions, 5min before training. Pre-training intra-CA1 microinjection of muscimol, a GABA-A receptor agonist, at the dose of 0.01 or 0.02µg/rat, increased the traveled distance or the escape latency and traveled distance to the hidden platform, respectively, indicating a water maze spatial acquisition impairment. Intra-CA1 administration of bicuculline, a GABA-A receptor antagonist however, significantly decreased the escape latency and traveled distance to the hidden platform, suggesting a spatial learning facilitation. On the other hand, pre-training intra-CA1 microinjection of the subthreshold dose of muscimol plus different doses of histamine (0.025, 0.05 and 0.1µg/rat) did not alter the histamine response. Meanwhile, the co-administration of the ineffective dose of bicuculline together with histamine potentiated the spatial learning. Moreover, bilateral infusion of histamine (0.025, 0.05 and 0.1µg/rat) by itself, facilitated the spatial learning. Notably, the drug injections had no effect on swimming speed during the MWM training sessions. Our results suggest that the dorsal hippocampal (CA1) GABA-A mechanism(s) may influence the histamine-induced facilitation of spatial acquisition.