Unveiling the Collaborative Effect at the Cucurbit [8] uril-MoS2 Hybrid Interface for Electrochemical Melatonin Determination.

Invited for the cover of this issue are two collaborating groups: one at the Universidad Autónoma de Madrid and the other at the Instituto de Ciencia de Materiales de Madrid. The image depicts Cucurbit[8]uril adsorbed on a transition metal dichalcogenide surface letting the cavity open for complex formation with melatonin and allowing efficient electrochemical sensing. Read the full text of the article at 10.1002/chem.202203244.

Unveiling the Collaborative Effect at the Cucurbit[8]uril-MoS2 Hybrid Interface for Electrochemical Melatonin Determination.

Host-guest interactions are of paramount importance in supramolecular chemistry and in a wide range of applications. Particularly well known is the ability of cucurbit[n]urils (CB[n]) to selectively host small molecules. We show that the charge transfer and complexation capabilities of CB[n] are retained on the surface of 2D transition metal dichalcogenides (TMDs), allowing the development of efficient electrochemical sensing platforms. We unveil the mechanisms of host-guest recognition between the MoS2 -CB[8] hybrid interface and melatonin (MLT), an important molecular regulator of vital constants in vertebrates. We find that CB[8] on MoS2 organizes the receptor portals perpendicularly to the surface, facilitating MLT complexation. This advantageous adsorption geometry is specific to TMDs and favours MLT electro-oxidation, as opposed to other 2D platforms like graphene, where one receptor portal is closed. This study rationalises the cooperative interaction in 2D hybrid systems to improve the efficiency and selectivity of electrochemical sensing platforms.

Differential pulse voltammetric determination of the carcinogenic diamine 4,4'-oxydianiline by electrochemical preconcentration on a MoS2 based sensor.

An electrochemical sensor for the carcinogen 4,4'-oxydianiline (Oxy) is described. The method is based on the ability of MoS2 nanosheets to preconcentrate Oxy. A glassy carbon electrode (GCE) was covered, by drop-casting, with MoS2 nanosheets that were obtained by exfoliation. X-Ray photoemission spectroscopy indicates that Oxy accumulates on the MoS2 nanosheets through an electropolymerization process similar to that reported for aniline. Both electrochemical impedance spectroscopy and atomic force microscopy were used to characterize the electrode surface at the different stages of device fabrication. Employing the current measured at +0.27 V vs. Ag/AgCl after Oxy adsorption, the modified GCE enables the voltammetric detection of Oxy at 80 nM levels with relative errors and relative standard deviations of <8.3 and <5.6%, respectively, at all the concentrations studied. The method was applied to the selective determination of Oxy in spiked river water samples. Very good selectivity and recoveries of around 95% in average are found. Graphical abstractSchematic representation of 4,4-oxydianiline electrochemical polymerization and preconcentration onto molybdenum disulfide nanosheets for the diamine determination in river waters.

Synergistic effect of MoS2 and diamond nanoparticles in electrochemical sensors: determination of the anticonvulsant drug valproic acid.

The authors describe an electrochemical sensor based on the use of diamond nanoparticles (DNPs) and molybdenum disulfide (MoS2) platelets. The sensor was applied to the voltammetric determination of the anticonvulsant valproic acid which was previously derivatized with ferrocene. The MoS2 platelets were obtained by an exfoliation method, and the DNPs were directly dispersed in water and subsequently deposited on a glassy carbon electrode (GCE). The sensor response was optimized in terms of the solvent employed for dispersing the MoS2 nanomaterial and the method for modifying the GCE. Sensors consisting of a first layer of MoS2 dispersed in ethanol/water and a second layer of DNPs give better response. The single steps of sensor construction were characterized by atomic force microscopy and electrochemical impedance spectroscopy. The differential pulse voltammetric response of the GCE (measured at +0.18 V vs. Ag/AgCl) was compared to that of sensors incorporating only one of the nanomateriales (DNPs or MoS2). The formation of a hybrid MoS2-DNP structure clearly improves performance. The GCE containing both nanomaterials exhibits high sensitivity (740 µA ⋅ mM-1 ⋅ cm-2), a 0.27 µM detection limit, and an 8% reproducibility (RSD). The sensor retained 99% of its initial response after 45 days of storage. Graphical abstract Electrochemical sensor by co-immobilization of MoS2 and diamond nanoparticles (DNP). The formation of a hybrid MoS2-DNP structure enhances the performance of the sensor towards valproic acid derivatized with a ferrocene group, when compared with sensors incorporating only DNP or MoS2.

Evaluating the impact of medication cabinets in patients' rooms on a medical-surgical telemetry unit.

Results of a pre-post survey study designed to evaluate the impact of medication cabinets in patients' rooms on nurses' satisfaction with medication administration, medication charge accuracy, and errors are described.

Enhanced Electrochemical Detection of Nonelectroactive Compounds Based on Surface Supramolecular Interactions on Chevron-like Graphene Nanoribbons Modified through Click Chemistry.

In this study, we have developed a nanostructured electrochemical sensor based on modified graphene nanoribbons tailored for the analysis of nonelectroactive compounds via a surface competitive assay. Stigmasterol, a nonelectroactive phytosterol, was selected as a representative case. Chevron-like graphene nanoribbons, chemically synthesized, were immobilized onto glassy carbon electrodes and covalently functionalized to allow the on-surface formation of a supramolecular complex. To this end, the nanoribbons were first modified through a diazotization process by electrochemical reduction of a 4-azidoaniline diazonium salt, leaving the electrode surface with azide groups exposed to solution. Next, the incorporation of a ferrocene group, as a redox probe, was carried out by a click chemistry reaction between ethynylferrocene and these azide groups. Finally, the recognition event leads to the formation of a supramolecular complex between ferrocene and a macrocyclic receptor on the electrode surface. To this end, the receptors cucurbit[7]uril, cucurbit[8]uril, and ß-cyclodextrin were evaluated, with the better results obtained with ß-cyclodextrin. Atomic force microscopy and scanning electron microscopy measurements were performed for the morphological characterization of the resulting electrochemical platform surface. The ability of ß-cyclodextrin to form an inclusion complex with ferrocene or with stigmasterol allows to perform a competitive assay, which translates into the decrease and recovery of the ferrocene electrochemical signal. For stigmasterol determination, a linear concentration range between 200 and 750 µM and a detection limit of 60 µM were obtained, with relative errors and relative standard deviations less than 7.1 and 9.8%, respectively.

Harnessing two-dimensional nanomaterials for diagnosis and therapy in neurodegenerative diseases: Advances, challenges and prospects.

Neurodegenerative diseases (NDDs) are specific brain disorders characterized by the progressive deterioration of different motor activities as well as several cognitive functions. Current conventional therapeutic options for NDDs are limited in addressing underlying causes, delivering drugs to specific neuronal targets, and promoting tissue repair following brain injury. Due to the paucity of plausible theranostic options for NDDs, nanobiotechnology has emerged as a promising field, offering an interdisciplinary approach to create nanomaterials with high diagnostic and therapeutic efficacy for these diseases. Recently, two-dimensional nanomaterials (2D-NMs) have gained significant attention in biomedical and pharmaceutical applications due to their precise drug-loading capabilities, controlled release mechanisms, enhanced stability, improved biodegradability, and reduced cell toxicity. Although various studies have explored the diagnostic and therapeutic potential of different nanomaterials in NDDs, there is a lack of comprehensive review addressing the theranostic applications of 2D-NMs in these neuronal disorders. Therefore, this concise review aims to provide a state-of-the-art understanding of the need for these ultrathin 2D-NMs and their potential applications in biosensing and bioimaging, targeted drug delivery, tissue engineering, and regenerative medicine for NDDs.

Enhanced Electrocatalysis on Copper Nanostructures: Role of the Oxidation State in Sulfite Oxidation.

The influence of surface morphology and the oxidation state on the electrocatalytic activity of nanostructured electrodes is well recognized, yet disentangling their individual roles in specific reactions remains challenging. Here, we investigated the electrooxidation of sulfite ions in an alkaline environment using cyclic voltammetry on copper oxide nanostructured electrodes with different oxidation states and morphologies but with similar active areas. To this aim, we synthesized nanostructured Cu films made of nanoparticles or nanorods on top of glassy carbon electrodes. Our findings showed an enhanced sensitivity and a lower detection threshold when utilizing Cu(I) over Cu(II). Density functional theory-based thermochemical analysis revealed the underlying oxidation mechanism, indicating that while the energy gain associated with the process is comparable for both oxide surfaces, the desorption energy barrier for the resulting sulfate molecules is three times higher on Cu(II). This becomes the limiting step of the reaction kinetics and diminishes the overall electrooxidation efficiency. Our proposed mechanism relies on the tautomerization of hydroxyl groups confined on the surface of Cu-based electrodes. This mechanism might be applicable to electrochemical reactions involving other sulfur compounds that hold technological significance.

Synergistic effect of manganese (II) phosphate & diamond nanoparticles in electrochemical sensors for reactive oxygen species determination in seminal plasma.

In this work, we explore the ability of manganese (II) phosphate (MnP) as a catalytic element for the determination of reactive oxygen species (ROS) in seminal plasma, when MnP is employed as modifier of a glassy carbon electrode. The electrochemical response of the manganese (II) phosphate-modified electrode shows a wave at around +0.65 V due to the oxidation of Mn2+ to MnO2+, which is clearly enhanced after addition of superoxide, the molecule considered as the mother of ROS. Once proved the suitability of manganese (II) phosphate as catalyst, we evaluate the effect of including a 0D (diamond nanoparticles) or a 2D (ReS2) nanomaterial in the sensor design. The system consisting of manganese (II) phosphate and diamond nanoparticles yielded the largest improvement of the response. The morphological characterization of the sensor surface was performed by scanning electron microscopy and atomic force microscopy, while cyclic and differential pulse voltammetry were employed for the electrochemical characterization of the sensor. After optimizing the sensor construction, calibration procedures by chronoamperometry were performed, leading to a linear relation between peak intensity and the superoxide concentration in the range of 1.1 10-4 M - 1.0 10-3 M with a limit of detection of 3.2 10-5 M. Seminal plasma samples were analysed by the standard addition method. Moreover, the analysis of samples fortified with superoxide at the µM level leads to recoveries of 95%.

2D-ReS2 & diamond nanoparticles-based sensor for the simultaneous determination of sunset yellow and tartrazine in a multiple-pulse amperometry FIA system.

We present a flow injection system with a multiple pulse amperometric detection (FIA-MPA)-based methodology for the simultaneous analysis of sunset yellow and tartrazine. As transducer, we have developed a novel electrochemical sensor based on the synergistic effect of ReS2 nanosheets and diamond nanoparticles (DNPs). Among several transition dichalcogenides for the sensor development, we have selected ReS2 nanosheets since it yields a better response towards both colourants. Scanning probe microscopy characterization shows that the surface sensor is composed by scattered and stacked ReS2 flakes and large aggregates of DNPs. With this system, the gap between the oxidation potential values of sunset yellow and tartrazine is wide enough to allow the simultaneous determination of both dyes. Under the optimum potential pulse conditions (0.8 and 1.2 V) during 250 ms, a flow rate of 3 mL/min and a volume injection of 250 µL, detection limits of 3.51 × 10-7 M and 2.39 × 10-7 M for sunset yellow and tartrazine, respectively, were obtained. This method exhibits good accuracy and precision with Er minor than 13% and RSD lower than 8% with a sampling frequency of 66 samples per hour. Pineapple jelly samples were analyzed by the standard addition method, obtaining 53.7 mg/kg and 29.0 mg/kg of sunset yellow and tartrazine, respectively. From the analysis of fortified samples, recoveries of 94% and 105% were obtained.

MoS2 quantum dots-based optical sensing platform for the analysis of synthetic colorants. Application to quinoline yellow determination.

In this work, a novel fluorescence sensor has been designed to solve the actual need of new fast and inexpensive sensing platforms for the analysis of synthetic colorants. It is based on MoS2 quantum dots obtained by a hydrothermal method and incorporated as fluorophore into the matrix of PVC membranes, which are deposited on quartz substrates by spin-coating. It was proven, as in these conditions, MoS2 quantum dots maintain the fluorescent properties that they present in solution. Experiments carried out in solution displayed a maximum emission when they were excited under 310 nm. This initial fluorescence decreases linearly in presence of increasing concentrations of various synthetic colorants namely quinoline yellow, tartrazine, sunset yellow, allura red, ponceau 4R and carmoisine. The two possible mechanisms that can explain this quenching effect, colorants absorbing photons emitted by quantum dots and/or competing with the nanomaterial for photons coming from the excitation source, were evaluated. The most pronounced effect was observed with quinoline yellow, as a result of a mixed mechanism. The optimized methodology developed for the determination of quinoline yellow showed a linear concentration range between 5.4 and 55.0 µg with a limit of detection of 1.6 µg. The sensor was applied to the determination of quinoline yellow in a food colour paste obtaining results in good agreement with those obtained by HPLC-UV-vis measurements.

Electrochemical sensor based on the synergy between Cucurbit[8]uril and 2D-MoS2 for enhanced melatonin quantification.

We present the development of an electrochemical sensor towards melatonin determination based on the synergistic effect between MoS2 nanosheets and cucurbit[8]uril. For the sensor construction cucurbit[8]uril suspensions were prepared in water, and MoS2 nanosheets were obtained by liquid exfoliation in ethanol:water. The sensing platform was topographically characterized by Atomic Force Microscopy. Electrochemical Impedance Spectroscopy experiments allowed us to study the charge transfer process during melatonin oxidation. Moreover, stoichiometry of the resulting complex has also been determined. After the optimization of the sensor construction and the experimental variables involved in the Differential Pulse Voltammetric response of melatonin, detection limit of 3.80 × 10-7 M, relative errors minor than 3.8% and relative standard deviation lower than 4.4% were obtained. The proposed sensor has been successfully applied to melatonin determination in pharmaceutical and biological samples as human urine and serum, with very good recoveries ranging from 90 to 102%.

New supramolecular interactions for electrochemical sensors development: different cucurbit[8]uril sensing platform designs.

Three different strategies for cucurbit[8]uril immobilization on a glassy carbon electrode have been assayed. The electrochemical properties of the resulting modified electrodes in solutions containing neutral, positively and negatively charged potential cucurbit[8]uril guests were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The comparison of the electrochemical behaviour exhibited by the unmodified electrodes against various probes, with respect to that of each modified electrode, resulted in an appropriate method to choose among different strategies for the development of electrochemical sensors. These sensors are based on the incorporation of the cucurbit[8]uril molecular selection properties that depend on the chemical characteristics of the potential analytes. Furthermore, atomic force microscopy was employed for the characterization of the different surfaces developed.

Lactate biosensing based on covalent immobilization of lactate oxidase onto chevron-like graphene nanoribbons via diazotization-coupling reaction.

We have designed and prepared an electrochemical biosensor for lactate determination. Through a diazotation process, the enzyme lactate oxidase (LOx) is anchored onto chevron-like graphene nanoribbons (GNR), previously synthesized by a solution-based chemical route, and used as modifiers of glassy carbon electrodes. In a first step, we have performed the grafting of a 4-carboxyphenyl film, by electrochemical reduction of the corresponding 4-carboxyphenyl diazonium salt, on the GNR-modified electrode surface. In this way, the carboxylic groups are exposed to the solution, enabling the covalent immobilization of the enzyme through the formation of an amide bond between these carboxylic groups and the amine groups of the enzyme. The biosensor design was optimized through the morphological and electrochemical characterization of each construction step by atomic force microscopy, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy.The cyclic voltammetric response of the biosensor in a solution of hydroxymethylferrocene in presence of l-lactate evidenced a clear electrocatalytic effect powered by the specific design of the biosensing platform with LOx covalently attached to the GNR layer. From the calibration procedures employed for l-lactate determination, a linear concentration range of 3.4 · 10-5- 2.8 · 10-4 M and a detection limit of 11 µM were obtained, with relative errors and relative standard deviations less than 6.0% and 8.4%, respectively. The applicability of the biosensor was tested by determining lactate in apple juices, leading to results that are in good agreement with those obtained with a well-established enzymatic spectrophotometric assay kit.

Skin cancer prevalence in farm workers in Spain

Background: Solar ultraviolet radiation (UVR) is one of the main risk factors for non-melanoma skin cancer. In Spain, 11% of the population are outdoor workers. Farmers are among the outdoor workers with the highest levels of chronic sun exposure. Objectives: To study the prevalence of skin cancer in farmers and evaluate their photoprotection habits. Materials & Methods: We performed an observational cross-sectional prospective study of farmers who completed a validated questionnaire on UVR exposure and protective behaviour and underwent a skin examination and skin colorimetry overseen by a dermatologist. Results: The study population consisted of 215 farm workers (84.4% male; mean age: 65.8 ± 14 years; mean years working: 45 ± 18). Actinic keratosis (AK) was detected in 41.4%, basal cell carcinoma (BCC) in 9.8%, and squamous cell carcinoma (SCC) in 1.4%. The most frequent photoprotection measure was the shade (69.3%). Photoaging type was significantly associated with the presence of AK and BCC, and Olson Grade II and III AK lesions correlated with SCC. The number of nevi on the lower extremities was the only predictor of the appearance of BCC. Conclusion: Photoprotection measures were not regularly used by most farm workers and the prevalence of skin cancer lesions was high. The findings underscore the need to improve photoprotection habits and early detection of skin cancer in this population.

Evaluation of Cost-Benefit and Measures During the COVID-19 Pandemic for Incoming Travelers Through Tests in Origin in Spain.

Background: The World Health Organization has promoted preventive measures for reducing the impact of the pandemic. One of these measures was tests in origin for travelers. Testing strategies for COVID-19 facilitate the overall public health response to the pandemic and contributes to minimize the infection among the population COVID-19. Goal: In this work, we assess the efficiency of diagnostic testing of incoming travelers in the Canary Islands, Spain, during a period of 4 months, with a focus on the economic impact for the regional government. We study the cost-benefit of this measure as well as the potential influence on the number of positive cases in the population. Methods: We processed the real data in the Canary Islands of pre-flight PCR and antigen tests that were required to the residents when traveling back to the Canaries from anywhere in Spain in a period of 4 months, from 14 December, 2020 to 4 April, 2021. As a result, we calculated the economic impact of doing those tests and compare them with the estimated costs of passengers under the hypothesis of entering the islands without testing. The cost-benefit was obtained for different scenarios, where the incoming passengers generated hospitalization and intensive care unit (ICU) costs directly and via transmissions. Results: The incoming testing funded by the government, if applied during the bad evolution of the pandemic with 1.2 ratio of transmission, clearly saved money to the public health system. In addition to the economic impact of this measure, we estimated the potential influence on the number of positive cases in the population according to different scenarios of the propagation of the pandemic. At the beginning of February 2021, the savings were about €130.551,47, with a 95% confidence interval (CI) of €24.677,94-236.425,00. By the end of April 2021, the savings were above €2,000,000 (€2.284.788,50 on average and 95% CI of €2.092.914,84-2.476.662,16) and the savings increased as the pandemic evolved. At the end of the period, the savings were twice the expenses. Conclusions: Testing in origin has proved to be a good measure that helped to mitigate COVID-19 spread among regions. Our results confirm that the free PCR or rapid antigen tests produce relevant savings to the public budget. We studied 61.990 reported data during 2020 and 2021 from the travelers from national flights, against 346.449 of total incoming travelers to the Canary Islands in this period. The measure pursued by the Government of the Canary Islands of providing free tests for residents showed a clear benefit for both, limiting the propagation of COVID-19 and reducing the costs of the hospitalizations and ICU admissions. It should be noted that the free testing measure in this period was before starting the vaccination campaigns. As measure of public health in the airports, testing helped to control and make the mobility of travelers secure.

Could a dysfunction of ferritin be a determinant factor in the aetiology of some neurodegenerative diseases?

BACKGROUND: The concentration of iron in the brain increases with aging. Furthermore, it has also been observed that patients suffering from neurological diseases (e.g. Parkinson, Alzheimer...) accumulate iron in the brain regions affected by the disease. Nevertheless, it is still not clear whether this accumulation is the initial cause or a secondary consequence of the disease. Free iron excess may be an oxidative stress source causing cell damage if it is not correctly stored in ferritin cores as a ferric iron oxide redox-inert form. SCOPE: Both, the composition of ferritin cores and their location at subcellular level have been studied using analytical transmission electron microscopy in brain tissues from progressive supranuclear palsy (PSP) and Alzheimer disease (AD) patients. MAJOR CONCLUSIONS: Ferritin has been mainly found in oligodendrocytes and in dystrophic myelinated axons from the neuropili in AD. In relation to the biomineralization of iron inside the ferritin shell, several different crystalline structures have been observed in the study of physiological and pathological ferritin. Two cubic mixed ferric-ferrous iron oxides are the major components of pathological ferritins whereas ferrihydrite, a hexagonal ferric iron oxide, is the major component of physiological ferritin. We hypothesize a dysfunction of ferritin in its ferroxidase activity. GENERAL SIGNIFICANCE: The different mineralization of iron inside ferritin may be related to oxidative stress in olygodendrocites, which could affect myelination processes with the consequent perturbation of information transference.

A supramolecular hybrid sensor based on cucurbit[8]uril, 2D-molibdenum disulphide and diamond nanoparticles towards methyl viologen analysis.

We develop an electrochemical sensor by using 2D-transition metal dichalcogenides (TMD), specifically MoS2, and nanoparticles stabilized with cucurbit[8]uril (CB[8]) incorporated together with them. Two different nanoparticles are assayed: diamond nanoparticles (DNPs) and gold nanoparticles (AuNp). 0D materials, together with TMD, provide increased conductivity and active surface while the macrocycle CB[8] affords selectivity towards the guest methyl viologen (MV2+), also named paraquat. Glassy Carbon (GC) electrodes are modified by drop-casting of suspensions of MoS2, followed by either a CB[8]-DNPs hybrid dispersion or a CB[8]-AuNp suspension. Atomic force microscopy is employed for the morphological characterization of the electrochemical sensor surface while cyclic voltammetry and electrochemical impedance spectroscopy techniques allow the electrochemical characterization of the sensor. The well-stablished signals of CB[8]-encapsulated MV2+ arise in voltammetric measurements when the macrocycle modifies the 0D-materials. Once the sensor construction and differential pulse voltammetry parameters have been optimized for quantification purposes, calibration procedures are performed with the platform GC/MoS2/CB[8]-DNPs. This sensing platform shows linear relations between peak intensity and the MV2+ concentration in the linear concentration range of (0.73-8.0) · 10-6 M with a limit of detection of 2.2 · 10-7 M. Analyses of river water samples fortified with MV2+ at the µM level shows recoveries of 100% with RSD values of 6.4% (n = 3).

MoS2 quantum dots for on-line fluorescence determination of the food additive allura red.

This work presents an on-line fluorescence method for the allura red (AR) determination. The method is based on the fluorescence quenching of dots of MoS2 because of their interaction with the non-fluorescence dye. MoS2-dots were synthetized and characterized by spectroscopic techniques and High Resolution Transmission Electronic Microscopy (HR-TEM). The simultaneous injection of the nanomaterial and the dye in a flow injection analysis system allows the determination of allura red at 1.7 × 10-6 M concentration level with a very good accuracy and precision (Er minor than 10% and RSD lower than 8%) and a sampling frequency of 180 samples per hour. Moreover, the interaction fluorophore-quencher results a dynamic inhibition mechanism. The proposed methodology was applied to the AR analysis in soft beverages and powders for gelatine preparation. Colourant concentrations of 63 ± 2 mg/L (n = 3) and 0.30 ± 0.01 mg/g (n = 3) were found, respectively. These results were validated by high performance liquid chromatography technique.

Iron speciation study in Hfe knockout mice tissues: magnetic and ultrastructural characterisation.

Liver, spleen and heart tissues of DBA/2 Hfe knockout mice have been characterised by low temperature AC magnetic susceptibility measurements together with Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction in order to investigate the chemical iron speciation in a murine model of iron overload diseases. With emphasis on ferritin-like species, the temperature dependent in-phase and out-of-phase susceptibility profiles agree with the elemental analysis in that, in this model, iron accumulation takes place in the hepatic tissue while in the spleen and heart tissues no differences have been observed between knockout and wild type animals. The comparison of the magnetic properties between perfused and non-perfused liver tissues has made it possible to estimate the magnetic contribution of usually present blood remains. The TEM observations reveal that, besides the isolated ferritins and ferritin-containing lysosomes-siderosomes present in the hepatocytes, other iron deposits, of heterogeneous size, morphology and crystalline structure (haematite and/or goethite), are present in the cytoplasm, near the membrane, and in extracellular spaces.