Multivariate analysis applied to X-ray fluorescence to assess soil contamination pathways: case studies of mass magnetic susceptibility in soils near abandoned coal and W/Sn mines.

Determining the origin and pathways of contaminants in the natural environment is key to informing any mitigation process. The mass magnetic susceptibility of soils allows a rapid method to measure the concentration of magnetic minerals, derived from anthropogenic activities such as mining or industrial processes, i.e., smelting metals (technogenic origin), or from the local bedrock (of geogenic origin). This is especially effective when combined with rapid geochemical analyses of soils. The use of multivariate analysis (MVA) elucidates complex multiple-component relationships between soil geochemistry and magnetic susceptibility. In the case of soil mining sites, X-ray fluorescence (XRF) spectroscopic data of soils contaminated by mine waste shows statistically significant relationships between magnetic susceptibility and some base metal species (e.g., Fe, Pb, Zn, etc.). Here, we show how qualitative and quantitative MVA methodologies can be used to assess soil contamination pathways using mass magnetic susceptibility and XRF spectra of soils near abandoned coal and W/Sn mines (NW Portugal). Principal component analysis (PCA) showed how the first two primary components (PC-1 + PC-2) explained 94% of the sample variability, grouped them according to their geochemistry and magnetic susceptibility in to geogenic and technogenic groups. Regression analyses showed a strong positive correlation (R2 > 0.95) between soil geochemistry and magnetic properties at the local scale. These parameters provided an insight into the multi-element variables that control magnetic susceptibility and indicated the possibility of efficient assessment of potentially contaminated sites through mass-specific soil magnetism.

Electrostatic-Gated Kinetics of Rapid Ion Transfers at a Nano-liquid/Liquid Interface.

Charge (ion and electron)-transfer reactions at a liquid/liquid interface are critical processes in many important biological and chemical systems. An ion-transfer (IT) process is usually very fast, making it difficult to accurately measure its kinetic parameters. Nano-liquid/liquid interfaces supported at nanopipettes are advantageous approaches to study the kinetics of such ultrafast IT processes due to their high mass transport rate. However, correct measurements of IT kinetic parameters at nanointerfaces supported at nanopipettes are inhibited by a lack of knowledge of the nanometer-sized interface geometry, influence of the electric double layer, wall charge polarity, etc. Herein, we propose a new electrochemical characterization equation for nanopipettes and make a suggestion on the shape of a nano-water/1,2-dichloroethane (nano-W/DCE) interface based on the characterization and calculation results. A theoretical model based on the Poisson-Nernst-Planck equation was applied to systematically study how the electric double layer influences the IT process of cations (TMA+, TEA+, TPrA+, ACh+) and anions (ClO4-, SCN-, PF6-, BF4-) at the nano-W/DCE interface. The relationships between the wall charge conditions and distribution of concentration and potential inside the nanopipette revealed that the measured standard rate constant (k0) was enhanced when the polarity of the ionic species was opposite to the pipette wall charge and reduced when the same. This work lays the right foundation to obtain the kinetics at the nano-liquid/liquid interfaces.

Molecularly Imprinted Methyl-Modified Hollow TiO2 Microspheres.

The possibility of generating organically modified hollow TiO2 microspheres via a simple sol-gel synthesis was demonstrated for the first time in this work. A mixture of titania precursors, including an organically modified precursor, was used to obtain methyl-modified hollow TiO2 microspheres selective for bilirubin by the molecular imprinting technique (Methyl-HTM-MIM). Methyl-HTM-MIM were prepared by a sol-gel method using titanium (IV) isopropoxide (TTIP), and methyltitanium triisopropoxide (MTTIP) as precursors. Two ratios of titania precursors were tested (1/6 and 1/30 molMTTIP/molTTIP). With the characterization results obtained by the SEM and ATR-FTIR techniques, it was possible to establish that only the 1/30 molMTTIP/molTTIP ratio allowed for the preparation of hollow spheres with a reasonably homogeneous methylated-TiO2 shell. It was possible to obtain a certain degree of organization of the hybrid network, which increased with calcination temperatures. By adjusting isothermal adsorption models, imprinting parameters were determined, indicating that the new methylated microspheres presented greater selectivity for bilirubin than the totally inorganic hollow TiO2 microspheres. The effectiveness of the molecular imprinting technique was proven for the first time in an organically modified titania material, with imprinting factor values greater than 1.4, corresponding to a significant increase in the maximum adsorption capacity of the template represented by the molecularly imprinted microspheres. In summary, the results obtained with the new methyl-HTM-MIM open the possibility of exploring the application of these microspheres for selective sorption (separation or sensing, for example) or perhaps even for selective photocatalysis, particularly for the degradation of organic compounds.

Electrochemistry-Assisted Surface Plasmon Resonance Biosensor for Detection of CA 15-3.

In this work, we describe an innovative methodology based on combined surface plasmon resonance (SPR) and electrochemical responses (eSPR) in the same immunoassay for screening CA 15-3 cancer biomarker with high sensitivity (and selectivity), in a very simple, label-free, accurate, and fully automated manner. Detection was achieved by performing two simple steps. In the first step, direct SPR was used to monitor CA 15-3 interaction with surface immobilized antibody. Two linear response ranges were obtained and the detection limit achieved is poor (LOD of 21 U mL-1). However, in the second detection step, electrochemical measurements at the SPR gold surface were performed to measure the decrease of redox probe peak current upon antigen-antibody interaction, providing a suitable amplification strategy to lower detection levels of CA 15-3 (LOD of 0.0998 U mL-1), without the need of additional complex and/or expensive amplification steps to enhance the sensitivity. Moreover, selectivity studies were performed against other common cancer biomarkers and the results showed that the eSPR immunosensor is selective for the CA 15-3 protein. Finally, the clinical applicability of the developed eSPR biosensing methodology was successfully applied to detect CA 15-3 in human serum samples at clinically relevant levels due to the high sensitivity of electrochemical readout. The same concept may be further extended to other proteins of interest.

An Atomic-Level Perspective of HMG-CoA-Reductase: The Target Enzyme to Treat Hypercholesterolemia.

This review provides an updated atomic-level perspective regarding the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoAR), linking the more recent data on this enzyme with a structure/function interpretation. This enzyme catalyzes one of the most important steps in cholesterol biosynthesis and is regarded as one of the most important drug targets in the treatment of hypercholesterolemia. Taking this into consideration, we review in the present article several aspects of this enzyme, including its structure and biochemistry, its catalytic mechanism and different reported and proposed approaches for inhibiting this enzyme, including the commercially available statins or the possibility of using dimerization inhibitors.

Electrochemical Behavior of a Mitochondria-Targeted Antioxidant at an Interface between Two Immiscible Electrolyte Solutions: An Alternative Approach to Study Lipophilicity.

In this work, we report for the first time the accumulation activity by energized rat heart mitochondria and the ionic transfer process at a liquid-liquid interface of a novel mitochondria-targeted antioxidant, named as AntiOxCIN4, which is structurally based on a hydroxycinnamic acid. Lipophilicity studies conducted at the water/1,6-dichlorohexane (DCH) interface allowed the building up of an ionic partition diagram of AntiOxCIN4 in accordance with the electrochemical data obtained. The partition coefficients of both positively charged (-2.3) and zwitterionic (0.2) forms of the antioxidant were determined. This study contributed to gaining an insight about the ability of the synthesized antioxidants to cross biomembrane barriers by using an interface between two immiscible electrolyte solutions (ITIES) as a model system.

Cationic imprinting of Pb(II) within composite networks based on bovine or fish chondroitin sulfate.

Imprinting chondroitin sulfate (CS)/silica composites with Pb(II) and Cu(II) cations was explored with CS of bovine and different fish species origin. The process was based on the assumption that particular arrangements of the linear CS chains in aqueous solution, induced so as to accommodate cross complexation with the cations, would be embodied into a tridimensional matrix created through an organoalkoxysilane sol-gel scheme. The presence of Cu(II) in the synthesis of the composites did not result in the production of significantly stronger Cu(II)-oriented binding arrangements, and therefore, the imprinting was not successful. Inversely, for Pb(II), the materials obtained exhibited a "memory" effect for the Pb(II) ions, expressed in the observation of stronger (13%-44%) binding as compared to the nonimprinted counterparts, and increased selectivity (1.5-2 folds) against Cd(II). The imprinting features observed were dependent on the CS source. However, it was not possible to identify, among a set of their properties (carboxylate and sulfate abundance, percent of disulfated units, 4S/6S ratio, and molecular weight), any that correlated directly with the observed imprinting features. The augmented selectivity provided by the cation-imprinting process may be advantageous in areas such as analytical separation, remediation, purification, sensing, and others, particularly in those cases where a certain cation is of special interest within a mixture of them.

Influence of the anion on the properties of ionic liquid mixtures: a molecular dynamics study.

Mixing of ionic liquids provides new opportunities for their tuning, enabling the applications of ionic liquid mixtures to expand. At the same time, the genesis of the fundamental properties of ionic liquid mixtures is still poorly understood. In this study we carried out a molecular dynamics simulation of binary mixtures of 1-buthyl-3-methylimidazolium hexafluorophosphate, 1-buthyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-buthyl-3-methylimidazolium tris(perfluoroethyl)trifluorophosphate ([C4mim][PF6] + [C4mim][NTf2], [C4mim][PF6] + [C4mim][FAP], [C4mim][FAP] + [C4mim][NTf2]) in a wide concentration range at 303.15 K and complemented it with quantum mechanical calculations. Three pure ionic liquids underwent the same kind of analysis for comparison purposes. We found that the addition of the [FAP]--anion to a mixture enhances the segregation of non-polar domains and weakens the hydrogen-bond network. The H-bonds in the studied mixtures are rather weak, as follows from QTAIM analysis, with the rarest occurrence for the [FAP]--anion. The competition of two anions in the mixtures for the most acidic hydrogen of the 1-butyl-3-methylimidazolium cation is reported. In most of the cases, the smaller anion ([PF6]- or [NTf2]-) with stronger charge concentration displaces the bigger one ([NTf2]- or [FAP]-) from the preferred coordination site. The existing nano-segregation in some mixtures notably slows down ion diffusion. Our results show that the differences in anion size, shape and nature are the main reasons for nano-segregation and the non-ideal behavior of ionic liquid mixtures.

On the thickness of the double layer in ionic liquids.

In this study, we examined the thickness of the electrical double layer (EDL) in ionic liquids using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. We focused on BF4- anion adsorption from the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) ionic liquid on the Au(111) surface. At both DFT and MD levels, we evaluated the capacitance-potential dependence for the Helmholtz model of the interface. Using MD simulations, we also explored a more realistic, multilayer EDL model accounting for the ion layering. Concurrent analysis of the DFT and MD results provides a ground for thinking whether the electrical double layer in ionic liquids is one- or multi-ionic-layer thick.

Interactions in the ionic liquid [EMIM][FAP]: a coupled experimental and computational analysis.

Gas-phase electronic and structural properties of the room temperature ionic liquid 1-ethyl-3-methylimidazolium tris(perfluoroethyl)trifluorophosphate ([EMIM][FAP]) were studied using density functional theory, and confirmed with results from infrared spectroscopy. A conformational analysis allowed the identification of several plausible conformers of the ion pairs. For the detected conformers, the infrared spectra were predicted and their thermodynamic properties were evaluated. The topology of the electronic density of the most stable conformers of [EMIM][FAP] ion pairs were characterised using the quantum theory of atoms in molecules. A number of possible hydrogen bonds between the cations and anions of the ionic liquid were identified. Excellent correspondence was found between the predicted spectra of gas-phase [EMIM][FAP] conformers and the experimental infrared spectrum, which in turn allowed a clear attribution of the vibration modes of [EMIM][FAP]. Finally, the contribution of the various conformers of both isomers of the [FAP](-) anion to the ionic liquid macro-properties is shown.

Voltammetric studies of topotecan transfer across liquid/liquid interfaces and sensing applications.

An amperometric ion sensor featuring a microhole supported water/organic gel interface was developed for the quantitative analysis of a water-soluble anticancer drug species, namely, topotecan, which has been used for ovarian and lung cancer treatments. Voltammetric responses associated with topotecan transfer across a polarized water/1,2-dichloroethane (1,2-DCE) interface were first investigated at different aqueous pH values to provide information on a topotecan partition diagram for understanding the lipophilicity of the topotecan drug species. The well-defined voltammetric characteristics for topotecan transfer in pH 4.0 buffer was then employed in conjunction with a microhole supported water/polyvinyl chloride-2-nitrophenyloctyl ether (PVC-NPOE) gel interface to develop a topotecan sensor. Current responses due to the direct transfer of topotecan molecules across the microhole interface increased linearly with respect to topotecan concentration when using cyclic voltammetry and differential pulse stripping voltammetry (DPSV). Improvements in sensitivity were obtained using DPSV and preconcentrating topotecan in the gel layer by holding the transferring potential at 1 V (vs Ag/AgCl) for 30 s followed by stripping of the drug. The topotecan drug sensor shows a low detectable concentration of 0.1 µM with a good selectivity over other anticancer drug molecules and interfering reagents. As a practical demonstration, the sensing platform was applied for the analysis of topotecan in a diluted serum sample. The results were also compared to those using high performance liquid chromatography (HPLC).

Natural compounds-based nanomedicines for cancer treatment: Future directions and challenges.

Several efforts have been extensively accomplished for the amelioration of the cancer treatments using different types of new drugs and less invasives therapies in comparison with the traditional therapeutic modalities, which are widely associated with numerous drawbacks, such as drug resistance, non-selectivity and high costs, restraining their clinical response. The application of natural compounds for the prevention and treatment of different cancer cells has attracted significant attention from the pharmaceuticals and scientific communities over the past decades. Although the use of nanotechnology in cancer therapy is still in the preliminary stages, the application of nanotherapeutics has demonstrated to decrease the various limitations related to the use of natural compounds, such as physical/chemical instability, poor aqueous solubility, and low bioavailability. Despite the nanotechnology has emerged as a promise to improve the bioavailability of the natural compounds, there are still limited clinical trials performed for their application with various challenges required for the pre-clinical and clinical trials, such as production at an industrial level, assurance of nanotherapeutics long-term stability, physiological barriers and safety and regulatory issues. This review highlights the most recent advances in the nanocarriers for natural compounds secreted from plants, bacteria, fungi, and marine organisms, as well as their role on cell signaling pathways for anticancer treatments. Additionally, the clinical status and the main challenges regarding the natural compounds loaded in nanocarriers for clinical applications were also discussed.

Electrochemical immunosensor for point-of-care detection of soybean Gly m TI allergen in foods.

Soybean is a legume with high technological functionality, commonly used by the food industry as an ingredient in different products. However, soybean is an allergenic food whose undeclared presence in processed foods may represent a public health risk. In this work, it was developed an efficient electrochemical immunosensor, targeting the soybean trypsin inhibitor (Gly m TI) allergen using commercial anti-Gly m TI IgG, aiming at detecting/quantifying minute amounts of soybean in different food formulations. For this purpose, model mixtures of different foods (sausages, cooked-hams, biscuits) were prepared to contain known amounts of soybean protein isolate (100,000-0.1 mg kg-1) and submitted to specific thermal treatments (autoclaving, oven-cooking, baking). The electrochemical immunosensor allowed quantifying down to 0.1 mg kg-1 of soybean in the three food matrices, raw and processed (0.0012 mg of Gly m TI/kg of matrix). Accordingly, the immunosensor is suitable for detecting traces of soybean in raw, processed, and complex foods, thus protecting 99 % of soybean-allergic patients.

Boosting Supercapacitor Efficiency with Amorphous Biomass-Derived C@TiO2 Composites.

Carbon materials are readily available and are essential in energy storage. One of the routes used to enhance their surface area and activity is the decoration of carbons with semiconductors, such as amorphous TiO2, for application in energy storage devices.

Marine waste derived carbon materials for use as sulfur hosts for Lithium-Sulfur batteries.

Lithium-sulfur batteries are a promising alternative to lithium-ion batteries as they can potentially offer significantly increased capacities and energy densities. The ever-increasing global battery market demonstrates that there will be an ongoing demand for cost effective battery electrode materials. Materials derived from waste products can simultaneously address two of the greatest challenges of today, i.e., waste management and the requirement to develop sustainable materials. In this study, we detail the carbonisation of gelatin from blue shark and chitin from prawns, both of which are currently considered as waste biproducts of the seafood industry. The chemical and physical properties of the resulting carbons are compared through a correlation of results from structural characterisation techniques, including electron imaging, X-ray diffraction, Raman spectroscopy and nitrogen gas adsorption. We investigated the application of the resulting carbons as sulfur-hosting electrode materials for use in lithium-sulfur batteries. Through comprehensive electrochemical characterisation, we demonstrate that value added porous carbons, derived from marine waste are promising electrode materials for lithium-sulfur batteries. Both samples demonstrated impressive capacity retention when galvanostatically cycled at a rate of C/5 for 500 cycles. This study highlights the importance of looking towards waste products as sustainable feeds for battery material production.

Electrochemical study of the anticancer drug daunorubicin at a water/oil interface: drug lipophilicity and quantification.

In this work, the ion transfer mechanism of the anticancer drug daunorubicin (DNR) at a liquid/liquid interface has been studied for the first time. This study was carried out using electrochemical techniques, namely cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The lipophilicity of DNR was investigated at the water/1,6-dichlorohexane (DCH) interface, and the results obtained were presented in the form of an ionic partition diagram. The partition coefficients of both neutral and ionic forms of the drug were determined. The analytical parameter for the detection of DNR was also investigated in this work. An electrochemical DNR sensor is proposed by means of simple ion transfer at the water/DCH interface, using DPV as the quantification technique. Experimental conditions for the analytical determination of DNR were established, and a detection limit of 0.80 µM was obtained.

Microparticles as BDMDAC (Quaternary Ammonium Compound) Carriers for Water Disinfection: A Layer-by-Layer Approach without Biocide Release.

This work studies the antimicrobial activity of benzyldimethyldodecyl ammonium chloride (BDMDAC)-coated microparticles with distinct morphological structures. Functionalized microparticles were prepared by the layer-by-layer (LbL) self-assembly technique on hydroxyapatite (Hap), calcium carbonate (CaCO3) and glass beads (GB) cores. All particles were characterized, before and after functionalization, by Fourier-Transform Infrared Spectroscopy (FTIR), Brunner-Emmett-Teller (BET) and Scanning Electron Microscopy (SEM) analyses. Antimicrobial activity was tested against planktonic Pseudomonas fluorescens. Planktonic bacteria were exposed to 100 mg/L, 200 mg/L and 400 mg/L of BDMDAC-coated microparticles for 240 min. This strategy promoted a complete bacteria reduction at 200 mg/L for Hap microparticles after 240 min. No release of biocide was detected through HPLC analyses during 2 weeks, suggesting that bacteria inactivation may be attributed to a contact killing mechanism.

Imprinted Hydrogel Nanoparticles for Protein Biosensing: A Review.

Over the past decade, molecular imprinting (MI) technology has made tremendous progress, and the advancements in nanotechnology have been the major driving force behind the improvement of MI technology. The preparation of nanoscale imprinted materials, i.e., molecularly imprinted polymer nanoparticles (MIP NPs, also commonly called nanoMIPs), opened new horizons in terms of practical applications, including in the field of sensors. Currently, hydrogels are very promising for applications in bioanalytical assays and sensors due to their high biocompatibility and possibility to tune chemical composition, size (microgels, nanogels, etc.), and format (nanostructures, MIP film, fibers, etc.) to prepare optimized analyte-responsive imprinted materials. This review aims to highlight the recent progress on the use of hydrogel MIP NPs for biosensing purposes over the past decade, mainly focusing on their incorporation on sensing devices for detection of a fundamental class of biomolecules, the peptides and proteins. The review begins by directing its focus on the ability of MIPs to replace biological antibodies in (bio)analytical assays and highlight their great potential to face the current demands of chemical sensing in several fields, such as disease diagnosis, food safety, environmental monitoring, among others. After that, we address the general advantages of nanosized MIPs over macro/micro-MIP materials, such as higher affinity toward target analytes and improved binding kinetics. Then, we provide a general overview on hydrogel properties and their great advantages for applications in the field of Sensors, followed by a brief description on current popular routes for synthesis of imprinted hydrogel nanospheres targeting large biomolecules, namely precipitation polymerization and solid-phase synthesis, along with fruitful combination with epitope imprinting as reliable approaches for developing optimized protein-imprinted materials. In the second part of the review, we have provided the state of the art on the application of MIP nanogels for screening macromolecules with sensors having different transduction modes (optical, electrochemical, thermal, etc.) and design formats for single use, reusable, continuous monitoring, and even multiple analyte detection in specialized laboratories or in situ using mobile technology. Finally, we explore aspects about the development of this technology and its applications and discuss areas of future growth.

Plasmonic genosensor for detecting hazelnut Cor a 14-encoding gene for food allergen monitoring.

A plasmonic nanostructure was constructed as a biorecognition element coupled to an optical sensing platform in sandwich format, targeting the hazelnut Cor a 14 allergen-encoding gene. The analytical performance of the genosensor presented a linear dynamic range between 100 amol L-1 and 1 nmol L-1, a limit of detection (LOD) < 19.9 amol L-1, and a sensitivity of 13.4 ± 0.6 m°. The genosensor was successfully hybridized with hazelnut PCR products, tested with model foods, and further validated by real-time PCR. It reached a LOD <0.001% (10 mg kg-1) of hazelnut in wheat material (corresponding to 1.6 mg kg-1 of protein) and a sensitivity of -17.2 ± 0.5 m° for a linear range of 0.001%-1%. Herein, a new genosensing approach is proposed as a highly sensitive and specific alternative tool with potential application in monitoring hazelnut as an allergenic food, protecting the health of sensitized/allergic individuals.

Post grafted gallic acid to chitosan-Ag hybrid nanoparticles via free radical-induced grafting reactions.

The present study proposes two unique systems using free radical-induced grafting reactions to combine Ag, chitosan (CS) and gallic acid (GA) into a single particulate nanostructure. GA-grafted-CS (GA-g-CS) was used to reduce Ag+ to Ag0, and producing Ag-GA-g-CSNPs (hybrid NPs I). Also, GA was grafted into CS-AgNPs, to form GA-g-CS AgNPs (hybrid NPs II). Although there were previous attempts to graft GA into CS, this is first time to graft GA into CS-AgNPs. The study aimed to enhance biocompatibility, antibacterial and antioxidant properties of CS-AgNPs via grafted GA. Grafting GA into CS-AgNPs was confirmed by UV-Vis, DLS, DSC/TGA, XRD, EDX and FTIR. The morphology and size of NPs were studied by TEM and SEM. The decrease of ζ-potential from +50 mV in CS-Ag NPs to +33 and + 29 mV, in the presented 2 nanoforms hybrid NPs I and II, respectively, is an indication for the successful GA graft. Among all samples, hybrid NPs II showed lower toxicity, higher antioxidant and antibacterial activity. The obtained results revealed that grafting GA to CS-AgNPs, as a new method to combine Ag, CS and GA in a uniparticulate structure, is a unique process which may deserve a more future consideration.