Bipolar Electrochemiluminescence Imaging: A Way to Investigate the Passivation of Silicon Surfaces.

This work depicts the original combination of electrochemiluminescence (ECL) and bipolar electrochemistry (BPE) to map in real-time the oxidation of silicon in microchannels. We fabricated model silicon-PDMS microfluidic chips, optionally containing a restriction, and monitored the evolution of the surface reactivity using ECL. BPE was used to remotely promote ECL at the silicon surface inside microfluidic channels. The effects of the fluidic design, the applied potential and the resistance of the channel (controlled by the fluidic configuration) on the silicon polarization and oxide formation were investigated. A potential difference down to 6 V was sufficient to induce ECL, which is two orders of magnitude less than in classical BPE configurations. Increasing the resistance of the channel led to an increase in the current passing through the silicon and boosted the intensity of ECL signals. Finally, the possibility of achieving electrochemical reactions at predetermined locations on the microfluidic chip was investigated using a patterning of the silicon oxide surface by etched micrometric squares. This ECL imaging approach opens exciting perspectives for the precise understanding and implementation of electrochemical functionalization on passivating materials. In addition, it may help the development and the design of fully integrated microfluidic biochips paving the way for development of original bioanalytical applications.

Mapping Solvent Entrapment in Multiphase Systems by Electrogenerated Chemiluminescence.

The interfacial properties of multiphase systems are often difficult to quantify. We describe the observation and quantification of immiscible solvent entrapment on a carbonaceous electrode surface using microscopy-coupled electrogenerated chemiluminescence (ECL). As aqueous microdroplets suspended in 1,2-dichloroethane collide with a glassy carbon electrode surface, small volumes of the solvent become entrapped between the electrode and aqueous phase, resulting in an overestimation of the true microdroplet/electrode contact area. To quantify the contribution of solvent entrapment decreasing the microdroplet contact area, we drive an ECL reaction within the microdroplet phase using tris(bipyridine)ruthenium(II) chloride ([Ru(bpy)3]Cl2) as the ECL luminophore and sodium oxalate (Na2C2O4) as the co-reactant. Importantly, the hydrophilicity of sodium oxalate ensures that the reaction proceeds in the aqueous phase, permitting a clear contrast between the aqueous and 1,2-dichloroethane present at the electrode interface. With the contrast provided by ECL imaging, we quantify the microdroplet radius, apparent microdroplet contact area (aqueous + entrapped 1,2-dichloroethane), entrapped solvent contact area, and the number of entrapped solvent pockets per droplet. These data permit the extraction of the true microdroplet/electrode contact area for a given droplet, as well as a statistical assessment regarding the probability of solvent entrapment based on microdroplet size.

Low adherence to traditional dietary pattern and food preferences of low-income preschool children with food neophobia.

OBJECTIVE: To associate dietary patterns and food neophobia in low-income preschoolers. DESIGN: This was a cross-sectional study using a semi-structured questionnaire for socio-demographic data, birth conditions and breast-feeding history. Food neophobia was assessed using an adapted version of the Child Food Neophobia Scale. Children's nutritional status was assessed using BMI-for-age and height-for-age Z-scores. Dietary patterns were estimated using a semi-quantitative FFQ through exploratory factor analysis. Multiple linear regression was used to test for an association between food neophobia and dietary pattern adherence. SETTING: Philanthropic childhood education schools in Aracaju, an urban community in northeastern Brazil, between July and December 2017. PARTICIPANTS: Two hundred fourteen children aged 3-6 years and their parents. RESULTS: The percentages of low/medium and high food neophobia among preschoolers were 85·9 % and 11·2 %, respectively. Children with high food neophobia more frequently consumed ultra-processed foods rich in sugars (snacks, filled and unfilled cookies and sweets), as well as protein-rich foods (white meat, cheese and yogurt). Three dietary patterns were identified (traditional, snacks and school snacks). Children with a high level of neophobia had lower adherence to traditional dietary patterns. CONCLUSIONS: A high level of food neophobia among socially vulnerable preschoolers is an eating behaviour related to unhealthy eating and is associated with the poorest diet in typical foods.

Harvesting rainwater for food security: farmers' perceptions of the Boardwalk Cisterns Program in Alagoas, Brazil.

INTRODUCTION: Boardwalk Cisterns is a government program that aims to attend a population with precarious access to water in Brazil. Developed as part of the Zero Hunger strategy, it intends to increase food security and contribute to the realization of the human right to food. The objective of this study was to assess farmers' perceptions of the Boardwalk Cisterns program and its impact on the food security situation of beneficiary households. METHODS: Data were collected through a descriptive cross-sectional quali-quantitative survey. Questionnaires were applied to farming families selected from two municipalities in the state of Alagoas (Northeast Brazil), containing questions on sociodemographic characteristics, production methods, and food security status. The Free Evocation Technique for social representation, analyzed through the software Ensemble of Programs Permettant L'analyze des Évocations, was used to ascertain farmers' perceptions of the program. RESULTS: The study showed a positive perception of the interviewees in relation to the boardwalk cisterns. The program brought some improvement in the agricultural production conditions and, consequently, in the food security situation of the households. Corn, beans and cassava were the most common crops, with almost half of this production (48.3%) destined for consumption by the families themselves. Farmers also reported having more water, allowing them to plant more fruit trees, as well as medicinal and ornamental plants. Nevertheless, 79.1% of the households interviewed were still in a situation of food insecurity, of which 28.1% were classified as mild food insecurity, 26% as moderate food insecurity, and 25% as severe food insecurity. CONCLUSION: Farmers were correct in their perception that the Boardwalk Cisterns program improved their food security situation. The program resulted in greater access to water, and greater production and consumption of food. However, by itself, the Boardwalk Cisterns program was not enough to raise beneficiary families above their food-insecure status. The program alleviated the problem of food insecurity, but other complementary government interventions are needed to guarantee the food security of families living in extreme poverty.

Photophysics, Electrochemistry and Efficient Electrochemiluminescence of Trigonal Truxene-Core Dyes.

We synthesized and characterized a series of dyes built from a spirofluorene or truxene core. The quadrupolar spirofluorene system is the initial building unit for the design and preparation of more complex star-shaped dyes consisting of a truxene core bearing three di- or triphenylamine moieties with or without a thiophene connector. Their photophysical, electrochemical, and electrochemiluminescence (ECL) properties were first investigated in solution. Structure/activity relationships were derived and rationalized by comparing the quadrupolar system and trigonal truxene-core derivatives using computational studies. The photophysical and redox characteristics are drastically tuned by the introduction of a thiophene bridge and electron-donor substituents at their terminal branches. These comparative studies show the essential role of the stability of both radical cations and anions to obtain efficient ECL dyes. The stabilization of the radicals is directly related to the charge delocalization due to the π-conjugation by the thiophene bridge. The brightest ECL is achieved by annihilation and coreactant (benzoyl peroxide) pathways with the blue-emitting truxene dye, which is 2- and 4.5-times greater than that of the quadrupolar compound and reference [Ru(bpy)3 ]2+ emitter, respectively. Such an extensive study on these extended π-conjugated molecules presenting different core structures may guide the design and synthesis of new ECL dyes with a strong efficiency.

Electrochemiluminescence reaction pathways in nanofluidic devices.

Nanofluidic electrochemical devices confine the volume of chemical reactions to femtoliters. When employed for light generation by electrochemiluminescence (ECL), nanofluidic confinement yields enhanced intensity and robust luminescence. Here, we investigate different ECL pathways, namely coreactant and annihilation ECL in a single nanochannel and compare light emission profiles. By high-resolution imaging of electrode areas, we show that different reaction schemes produce very different emission profiles in the unique confined geometry of a nanochannel. The confrontation of experimental results with finite element simulation gives further insight into the exact reaction ECL pathways. We find that emission strongly depends on depletion, geometric exclusion, and recycling of reactants in the nanofluidic device.

Multiplexed Remote SPR Detection of Biological Interactions through Optical Fiber Bundles.

The development of sensitive methods for in situ detection of biomarkers is a real challenge to bring medical diagnosis a step forward. The proof-of-concept of a remote multiplexed biomolecular interaction detection through a plasmonic optical fiber bundle is demonstrated here. The strategy relies on a fiber optic biosensor designed from a 300 µm diameter bundle composed of 6000 individual optical fibers. When appropriately etched and metallized, each optical fiber exhibits specific plasmonic properties. The surface plasmon resonance phenomenon occurring at the surface of each fiber enables to measure biomolecular interactions, through the changes of the retro-reflected light intensity due to light/plasmon coupling variations. The functionalization of the microstructured bundle by multiple protein probes was performed using new polymeric 3D-printed microcantilevers. Such soft cantilevers allow for immobilizing the probes in micro spots, without damaging the optical microstructures nor the gold layer. We show here the potential of this device to perform the multiplexed detection of two different antibodies with limits of detection down to a few tenths of nanomoles per liter. This tool, adapted for multiparametric, real-time, and label free monitoring is minimally invasive and could then provide a useful platform for in vivo targeted molecular analysis.

Influence of Various Model Compounds on the Rheological Properties of Zein-Based Gels.

The controlled release of a compound entrapped in a biocompatible formulation is a sought-after goal in modern pharmaceutical technology. Zein is a hydrophobic protein which has several advantageous properties that make it suitable for use as a biocompatible and degradable material under physiological conditions. It is, therefore, proposed for different biomedical and pharmaceutical applications. In particular, due to its gelling properties, it can be used to form a polymeric network able to preserve biomolecules from harsh environments. The current study was designed to investigate the influence of different probes on the rheological properties of gels made up of zein, in order to characterize the systems as a function of the polymer concentration. Four model compounds characterized by different physico-chemical properties were entrapped in zein gels, and different behaviors (viscoelastic or pronounced solid-like characteristics) of the systems were observed. Zein-based gels showed various release profiles of the encapsulated compounds, suggesting that there are different interaction rates between the probes and the polymeric matrix.

Enhanced Bipolar Electrochemistry at Solid-State Micropores: Demonstration by Wireless Electrochemiluminescence Imaging.

Bipolar electrochemistry (BPE) is a powerful method based on the wireless polarization of a conductive object that induces the asymmetric electroactivity at its two extremities. A key physical limitation of BPE is the size of the conductive object because the shorter the object, the larger is the potential necessary for sufficient polarization. Micrometric and nanometric objects are thus extremely difficult to address by BPE due to the very high potentials required, in the order of tens of kV or more. Herein, the synergetic actions of BPE and of planar micropores integrated in a microfluidic device lead to the spatial confinement of the potential drop at the level of the solid-state micropore, and thus to a locally enhanced polarization of a bipolar electrode. Electrochemiluminescence (ECL) is emitted in half of the electroactive micropore and reveals the asymmetric polarization in this spatial restriction. Micrometric deoxidized silicon electrodes located in the micropore are polarized at a very low potential (7 V), which is more than 2 orders of magnitude lower compared to the classic bipolar configurations. This behavior is intrinsically associated with the unique properties of the micropores, where the sharp potential drop is focused. The presented approach offers exciting perspectives for BPE of micro/nano-objects, such as dynamic BPE with objects passing through the pores or wireless ECL-emitting micropores.

Highly parallel remote SPR detection of DNA hybridization by micropillar optical arrays.

Remote detection by surface plasmon resonance (SPR) is demonstrated through microstructured optical arrays of conical nanotips or micropillars. Both geometries were fabricated by controlled wet chemical etching of bundles comprising several thousands of individual optical fibers. Their surface was coated by a thin gold layer in order to confer SPR properties. The sensitivity and resolution of both shapes were evaluated as a function of global optical index changes in remote detection mode performed by imaging through the etched optical fiber bundle itself. With optimized geometry of micropillar arrays, resolution was increased up to 10-4 refractive index units. The gold-coated micropillar arrays were functionalized with DNA and were able to monitor remotely the kinetics of DNA hybridization with complementary strands. We demonstrate for the first time highly parallel remote SPR detection of DNA via microstructured optical arrays. The obtained SPR sensitivity combined with the remote intrinsic properties of the optical fiber bundles should find promising applications in biosensing, remote SPR imaging, a lab-on-fiber platform dedicated to biomolecular analysis, and in vivo endoscopic diagnosis. Graphical abstract We present a single fabrication step to structure simultaneously all the individual cores of an optical fiber bundle composed of thousands of fibers. The resulting sensor is optimized for reflection mode (compatible with in vivo applications) and is used to perform for the first time highly parallel remote SPR detection of DNA via several thousands of individual optical fiber SPR sensors paving the way for multiplexed biological detection.

Circularly-Polarized Electrochemiluminescence from a Chiral Bispyrene Organic Macrocycle.

The first observation of circular polarization of electrochemiluminescence (ECL) from a purely organic derivative is reported. A bispyrene scaffold mounted on a constrained polyether macrocycle displaying intense excimer fluorescence and highly circularly-polarized (CP) photoluminescence has been selected for this purpose. The compound displays an ECL dissymmetry factor of about |8×10-3 |, which is in good agreement with the corresponding photoluminescence value. This observation is the first step towards the molecular engineering of tailored dyes that can act as both ECL and CP-ECL reporters for (bio)analysis by bringing a new level of information when dealing with chiral environments. Additionally, it provides an extra dimension to the ECL phenomenon and opens the way to chiral detection and discrimination.

Surface-Confined Electrochemiluminescence Microscopy of Cell Membranes.

Herein is reported a surface-confined microscopy based on electrochemiluminescence (ECL) that allows to image the plasma membrane of single cells at the interface with an electrode. By analyzing photoluminescence (PL), ECL and AFM images of mammalian CHO cells, we demonstrate that, in contrast to the wide-field fluorescence, ECL emission is confined to the immediate vicinity of the electrode surface and only the basal membrane of the cell becomes luminescent. The resulting ECL microscopy reveals details that are not resolved by classic fluorescence microscopy, without any light irradiation and specific setup. The thickness of the ECL-emitting regions is ∼500 nm due to the unique ECL mechanism that involves short-lifetime electrogenerated radicals. In addition, the reported ECL microscopy is a dynamic technique that reflects the transport properties through the cell membranes and not only the specific labeling of the membranes. Finally, disposable transparent carbon nanotube (CNT)-based electrodes inkjet-printed on classic microscope glass coverslips were used to image cells in both reflection and transmission configurations. Therefore, our approach opens new avenues for ECL as a surface-confined microscopy to develop single cell assays and to image the dynamics of biological entities in cells or in membranes.

C-Functionalized Cationic Diazaoxatriangulenes: Late-Stage Synthesis and Tuning of Physicochemical Properties.

A series of nine C-functionalized cationic diazaoxatriangulene (DAOTA) dyes have been successfully synthesized and fully characterized, including X-ray structural analysis of four derivatives. The introduction of electron-withdrawing or -donating functions enables the tuning of both electro- and photochemical properties with, for instance, two consecutive (reversible) reductions or oxidations observed for nitro or amino derivatives, respectively. The substituents also impacted on the optical properties, with absorption maxima varying from λ=528 to 640 nm and fluorescence being shifted from the yellow to the red range, up to λ=656 nm.

Femtoliter oil droplets act as CO2 micropumps for uninterrupted electrochemiluminescence at the water|oil interface.

Interfacial effects are well-known to significantly alter chemical reactivity, especially in confined environments, where the surface to volume ratio increases. Here, we observed an inhomogeneity in the electrogenerated chemiluminescence (ECL) intensity decrease over time in a multiphasic system composed of femtoliter water droplets entrapping femtoliter volumes of the 1,2-dichloroethane (DCE) continuous phase. In usual electrochemiluminescence (ECL) reactions involving an ECL chromophore and oxalate ([C2O4]2-), the build-up of CO2 diminishes the ECL signal with time because of bubble formation. We hypothesised that relative solubilities of chemical species in these environments play a dramatic role in interfacial reactivity. Water droplets, loaded with the ECL luminophore [Ru(bpy)3]2+ and the coreactant [C2O4]2- were allowed to stochastically collide and adsorb at the surface of a glassy carbon macroelectrode. When water droplets coalesce on the surface, they leave behind femtoliter droplets of the DCE phase (inclusions). We report the surprising finding that the addition of multiple interfaces, due to the presence of continuous phase's femtoliter inclusions, allows sustained ECL over time after successive potential applications at the triple-phase boundary between water droplet|electrode|DCE inclusion. When femtoliter droplets of DCE form on the electrode surface, bright rings of ECL are observed during the simultaneous oxidation of [Ru(bpy)3]2+ and [C2O4]2-. Control experiments and finite element modelling allowed us to propose that these rings arise because CO2 that is generated near the 1,2-dichloroethane droplet partitions in due to relative solubility of CO2 in 1,2-dichloroethane and builds up and/or is expelled at the top of the droplet. The small droplets of the DCE phase act as micropumps, pumping away carbon dioxide from the interface. These results highlight the unexpected point that confined microenvironments and their geometry can tune chemical reactions of industrial importance and fundamental interest.

Lipid- and polymer-based formulations containing TNF-α inhibitors for the treatment of inflammatory bowel diseases.

Monoclonal antibodies inhibiting tumor necrosis factor-alpha (iTNF-α) have revolutionized the therapeutic regimen of inflammatory bowel disease, but their main drawback is the parenteral route of administration they require. An alternative approach lies in the delivery of these molecules to the area involved in the inflammatory process by means of innovative formulations able to promote their localization in affected tissues while also decreasing the number of administrations required. This review describes the advantages deriving from the use of lipid- and polymer-based systems containing iTNF-α, focusing on their physicochemical and technological properties and discussing the preclinical results obtained in vivo using rodent models of colitis.

DIFUCOSIN: DIclofenac sodium salt loaded FUCOidan-SericIN nanoparticles for the management of chronic inflammatory diseases.

The current investigation emphasizes the use of fucoidan and sericin as dual-role biomaterials for obtaining novel nanohybrid systems for the delivery of diclofenac sodium (DS) and the potential treatment of chronic inflammatory diseases. The innovative formulations containing 4 mg/ml of fucoidan and 3 mg/ml of sericin showed an average diameter of about 200 nm, a low polydispersity index (0.17) and a negative surface charge. The hybrid nanosystems demonstrated high stability at various pHs and temperatures, as well as in both saline and glucose solutions. The Rose Bengal assay evidenced that fucoidan is the primary modulator of relative surface hydrophobicity with a two-fold increase of this parameter when compared to sericin nanoparticles. The interaction between the drug and the nanohybrids was confirmed through FT-IR analysis. Moreover, the release profile of DS from the colloidal systems showed a prolonged and constant drug leakage over time both at pH 5 and 7. The DS-loaded nanohybrids (DIFUCOSIN) induced a significant decrease of IL-6 and IL-1ß with respect to the active compound in human chondrocytes evidencing a synergistic action of the individual components of nanosystems and the drug and demonstrating the potential application of the proposed nanomedicine for the treatment of inflammation.

Rutin-loaded zein gel as a green biocompatible formulation for wound healing application.

Wound healing is a challenging clinical problem and efficient wound management is essential to prevent infection. This is best done by utilizing biocompatible materials in order to complete the healing in a rapid manner, with functional and esthetic outcomes. In this context, the zein protein fulfills the criteria of the ideal wound dressing which include non-toxicity and non-inflammatory stimulation. Zein gels containing rutin were prepared without any chemical refinement or addition of gelling agents in order to obtain a natural formulation characterized by antioxidant and anti-inflammatory properties to be proposed for the treatment of burns and sores. In vitro scratch assay showed that the proposed gel formulations promoted cell migration and a rapid gap closure within 24 h (~90 %). In addition, the in vivo activities of rutin-loaded zein gel showed a greater therapeutic efficacy in Wistar rats, with a decrease of the wound area of about 90 % at day 10 with respect to the free form of the bioactive and to DuoDERM®. The evaluation of various markers (TNF-α, IL-1ß, IL-6, IL-10) confirmed the anti-inflammatory effect of the proposed formulation. The results illustrate the feasibility of exploiting the peculiar features of rutin-loaded zein gels for wound-healing purposes.

An Electrochemical Perspective on the Interfacial Width between Two Immiscible Liquid Phases.

Molecular dynamics simulations and vibrational sum-frequency spectroscopy are historically the main techniques applied to the description of the molecular structure and dynamics of the immiscible liquid/liquid interface. A molecular sharpness is estimated for oil/water interfaces, with an interfacial width that extends from hundreds of Å to 1 nm. However, electrochemical studies have elucidated a deeper liquid/liquid interface on the order of several micrometers. The breaking down of single-entity electrochemistry to simpler systems and the combination of high-resolution microscopies is confirming a larger extension of the interface. What can be the role of the electrochemist in clarifying this fundamental question? We try to give a suggestion at the end of a brief historical overview of the liquid/liquid interface studies.

Abiotic microcompartments form when neighbouring droplets fuse: an electrochemiluminescence investigation.

Many studies have shown chemistry proceeds differently in small volumes compared to bulk phases. However, few studies exist elucidating spontaneous means by which small volumes can form in Nature. Such studies are critical in understanding the formation of life in microcompartments. In this study, we track in real-time the coalescence of two or more water microdroplets adsorbed on an electrified surface in a 1,2-dichloroethane continuous phase by electrogenerated chemiluminescence (ECL) imaging, uncovering the spontaneous generation of multiple emulsions inside the resulting water droplets. During the fusion of adsorbed water droplets with each other on the electrode surface, volumes of organic and water phases are entrapped in between and detected respectively as ECL not-emitting and emitting regions. The diameter of those confined environments inside the water droplets can be less than a micrometer, as described by scanning electron microscopy data. This study adds a new mechanism for the generation of micro- and nano-emulsions and provides insight into confinement techniques under abiotic conditions as well as new potential strategies in microfluidic devices.

Correction: Abiotic microcompartments form when neighbouring droplets fuse: an electrochemiluminescence investigation.

[This corrects the article DOI: 10.1039/D2SC06553C.].