Aqueous Layer Research Articles

Changes in tear film function in patients after pterygium excision surgery done under topical anaesthesia with and without conjunctival autograft – A protocol for a randomized interventional study

Background: Pterygium is an extra-ocular disorder related to progressive subepithelial growth of degenerative conjunctival tissue over the cornea. There are multifactorial causes that lead to the growth of pterygium. The tear film becomes unstable due to the degenerative growth of the conjunctiva. The tear film is divided into three different layers. The lipid layer is secreted by the meibomian gland, which is the exterior layer exposed to the environment and prevents tears from drying out too rapidly. The lacrimal gland releases the middle layer, the aqueous layer, which provides oxygen to the corneal epithelial layer. The goblet cells secrete mucus, the innermost layer that makes the corneal epithelium hydrophilic. Due to uneven wettability brought on by the progression of pterygium, the tear film becomes unstable and may damage the ocular surface. It has been found that pterygium excision increases tear film stability. According to a study, the incidence of pterygium in central rural India is 12.9%. Incidence increases with age, gender, and occupation. Methods: The patients with pterygium will be divided into two groups for the pterygium excision surgery: Group 1 consists of patients in which conjunctival autograft will not be done after pterygium excision, and Group 2 consists of patients in which conjunctival autograft will be done after pterygium excision. Preoperatively and postoperatively, visual acuity was assessed in all the patients on day 1, 4 weeks, and 8 weeks on follow-up. Tear film evaluation was done through Tear film Break Up Time (T-BUT) and Schirmer’s Test in patients preoperatively and postoperatively on day 1, 4 weeks, and 8 weeks follow up. CTRI Registration: REF/2023/07/071130 (30/07/2023) Protocol version: v1 dated 7/08/2023

Revisiting the pKa-Flux method for determining intrinsic membrane permeability

Intrinsic membrane permeability is one of several factors that critically determine the intestinal absorption of a chemical. The intrinsic membrane permeability of a chemical is usually extracted from transwell experiments with Caco-2 or MDCK cells, preferably by the pKa-Flux method, which is considered the method of choice when aqueous boundary layer effects need to be excluded. The pKa-Flux method has two variants, the iso-pH method, where apical and basolateral pH are equal, and the gradient-pH method, where apical and basolateral pH are different. The most commonly used method is the gradient-pH method, as it is intended to reflect the pH-conditions in the gastrointestinal tract. However, concentration-shift effects caused by the applied pH-difference between apical and basolateral compartment in the gradient-pH method have not been considered in the evaluation of the experimental data in the past. Consequently, incorrect intrinsic membrane permeabilities have been determined. In this work, we present a revised method for extracting the intrinsic membrane permeability from gradient-pH data that considers concentration-shift effects in the basolateral aqueous boundary layer and filter as well as in the cytosol. Furthermore, we propose the use of the iso-pH method, where only concentration-shift effects in the cytosol need to be considered, as an alternative to the gradient-pH method. We use the five lipophilic bases amantadine, chloroquine, propranolol, venlafaxine and verapamil as examples to compare gradient-pH method and iso-pH method with regard to the extractability of the intrinsic membrane permeability. For lipophilic bases, the iso-pH method proves to be advantageous. All intrinsic membrane permeabilities determined in this work were substantially higher than the intrinsic membrane permeabilities reported in literature.

Nanovesicular-Mediated Intranasal Drug Therapy for Neurodegenerative Disease.

Numerous neurodegenerative conditions, such as Alzheimer's, Huntington's, Parkinson's, amyotrophic lateral sclerosis, and glioblastoma multiform are now becoming significant concerns of global health. Formulation-related issues, physiological and anatomical barriers, post-administration obstacles, physical challenges, regulatory limitations, environmental hurdles, and health and safety issues have all hindered successful delivery and effective outcomes despite a variety of treatment options. In the current review, we covered the intranasal route, an alternative strategic route targeting brain for improved delivery across the BBB. The trans-nasal pathway is non-invasive, directing therapeutics directly towards brain, circumventing the barrier and reducing peripheral exposure. The delivery of nanosized vesicles loaded with drugs was also covered in the review. Nanovesicle systems are organised in concentric bilayered lipid membranes separated with aqueous layers. These carriers surmount the disadvantages posed by intranasal delivery of rapid mucociliary clearance and enzymatic degradation, and enhance retention of drug to reach the site of target. In conclusion, the review covers in-depth conclusions on numerous aspects of formulation of drug-loaded vesicular system delivery across BBB, current marketed nasal devices, significant jeopardies, potential therapeutic aids, and current advancements followed by future perspectives.

Remote Measurements of Tear Electrolyte Concentrations on Both Sides of an Inserted Contact Lens.

In this paper, a method is described to perform ion concentration measurements on both sides of an inserted contact lens, without physical contact with the eye or the contact lens. The outer surface of an eye is covered with a tear film that has multiple layers. The central aqueous layer contains electrolytes and proteins. When a contact lens is inserted, it becomes localized in the central layer, which creates two layers known as the pre-lens tear film (PLTF) and the post-lens tear film (PoLTF). The PoLTF is in direct contact with the sensitive corneal epithelial cells which control electrolyte concentrations in tears. It is difficult to measure the overall electrolyte concentration in tears because of the small 7 μL volume of bulk tears. No methods are known, and no method has been proposed, to selectively measure the concentrations of electrolytes in the smaller volumes of the PLTF and the PoLTF. In this paper, we demonstrate the ability to localize fluorophores on each side of a contact lens without probe mixing or diffusion across the lens. We measured the concentration of sodium in the region of the PoLTF using a sodium-sensitive fluorophore positioned on the inner surface of a contact lens. The fluorescence measurements do not require physical contact and are mostly independent of eye motion and fluorophore concentration. The method is generic and can be combined with ion-sensitive fluorophores for the other electrolytes in tears. Instrumentation for non-contact measurements is likely to be inexpensive with modern opto-electronic devices. We expect these lenses to be used for measurements of other ions in the PLTF and the PoLTF, and thus become useful for both research and in the diagnosis of infections, keratitis and biomarkers for diseases.

Microscopic Analysis of E-Cigarette Vapors Effects on the Eyes

Recently, e-cigarettes or VAPE have become a new trend among smokers. Known as a modern cigarette with a wide selection of flavors and aromas such as vanilla, raspberry and spearmint as well as abundant steam, making vaping a favorite activity among teenagers. This research is a literature study on various medical research journal databases such as PubMed, Science Direct, Cochrane and Google Scholar. Based on research results, it is known that the vapor from vaping causes dryness, thickening and even damage to the cornea. The occurrence of lipid peroxidation by free radicals contained in vaping vapor causes the eye protective layer "tear film" consisting of lipid, aqueous, and mucin layers to be damaged. Dry eye syndrome and damage to the eye epithelium are characterized by a decrease in the number of goblet cells and inflammation of the corneal tissue, even an increased of potential for cataracts can occur either by direct exposure or by inhalation of vapors which causes a systemic increase in oxidant levels.

The mechanism of NaTi2(PO4)3 aqueous electrochemical degradation revisited

NASICON structure type materials are attracting increasing attention as electrode active materials for ion insertion batteries and deionization devices. NaTi2(PO4)3 due to its favorable potential is among the most suitable negative electrodes for various applications in aqueous electrolytes. However, various parasitic processes limit its Coulombic efficiency, self-discharge characteristics, and capacity retention. Understanding and mitigation of these processes are essential in order to fully utilize the potential of such and similar materials. In this study, the degradation mechanisms of NaTi2(PO4)3 in aqueous electrolytes is studied in great detail. The results indicate that, to a different extent, both hydrogen evolution and oxygen reduction reactions are taking place during NaTi2(PO4)3 electrochemical cycling and contribute to pH increase. The latter reaction due to the presence of Ti(III) species is found to be prevalent in aerated electrolytes. There is virtually no degradation and capacity loss observed at pH 7, but it becomes significant at pH 10 even in oxygen-free electrolytes. Contrary to previous studies, this work shows that capacity loss is actually slower at lower C-rates. The post mortem X-ray diffraction analysis shows that only a fraction of capacity loss could be directly attributed to NaTi2(PO4)3 decomposition and even less to its dissolution into electrolyte. Therefore, most of the observed capacity fade during cycling is related to contact loss in the electrode structure which most likely comes from the formation of electron blocking aqueous interphasial layer.

Numerical simulation of buoyancy–driven flow in a human stomach geometry: Comparison of SPH and FVM models

The primary functions of the stomach, including mixing, digestion, and emptying, are affected by the spatial distribution of content properties, and how this distribution changes in response to gravity and wall contraction forces. One aspect that is not well studied is the buoyancy effects that result from content with heterogenous density. A buoyancy–driven flow in a non–deforming stomach is simulated using the Smoothed Particle Hydrodynamics (SPH) and Finite Volume Method (FVM). An aqueous liquid layer is initially placed above a fatty layer of the same volume. The buoyancy effect driven by gravity and strongly influenced by the stomach shape, causes the fat to rise to the top layer and the aqueous liquid to sink to the bottom. Rayleigh–Taylor Instability (RTI) is well–captured in the SPH model in the initial interface flow development. Some detailed flow behaviours are slightly different between the two models once the bulk turnover flow is established, but both models show that the separation process happens rapidly (within 6 s) in the curved geometry of the stomach. The final phase separation is more complete in the FVM compared with the SPH. Sensitivity analysis is conducted in both models to examine the solution accuracy. This work suggests that buoyancy driven flow effects, which have not been investigated previously, occur on a much shorter timescale (6 s) than peristaltic (20 – 60 s) and digestion timescales (hours). This result may help basic understanding of digestive processes and be used to guide food and drug design.

A surfactant-based quasi-hydrophobic deep eutectic solvent for dispersive liquid-liquid microextraction of gliflozins from environmental water samples using UHPLC/fluorescence detection

Despite the anticipated exceptional properties of deep eutectic solvents (DES) in microextraction techniques, their self-aggregation behaviour has only been sporadically studied in the previous literature. In the presented study, a novel surfactant-based quasi-hydrophobic deep eutectic solvent (DES) is synthesized and utilized in dispersive liquid-liquid microextraction (DLLME) of three gliflozins in environmental water samples as a proof-of-concept examples. The synthesized DES is composed of benzalkonium chloride (BZKCl) as a hydrogen bond acceptor and octanol (Oct) as a hydrogen bond donor. A full optimization of the extraction conditions was carried out including molar ratio and composition of DES, volume of DES, volume of water samples, extraction time and type of diluting solvent. Moreover, the extraction mechanism was thoroughly investigated, and it was established that the extraction of the target analytes is attributed to the analytes' incorporation into the micelles’ cores that facilitates mass transfer from the aqueous layer into DES layer. Furthermore, micelles formed by surfactant-based DES will provide adequate dispersion of extractant phase within water samples, which consequently improves the extraction efficiency. Micelles formation was confirmed by transmission electron microscopy (TEM). Furthermore, 1H NMR spectra verifies that the synthesized DES keeps its integrity even after extraction, which excludes any decomposition of DES after DLLME procedure. The extraction recovery is in an excellent agreement with the hydrophobicity of the investigated drugs, being the highest for the most hydrophobic one. The extracted analytes were separated by UHPLC coupled with fluorescence detection. Under the optimized experimental conditions, the method exhibits excellent linearity and a high detection sensitivity with a limit of detection of 0.5, 2.0 and 0.1 ng mL−1 for EMP (empagliflozin), DAP (dapagliflozin) and CAN (canagliflozin), respectively. The greenness of the developed microextraction approach was assessed by different greenness metrics such as Complex GAPI and AGREE tools. The developed method shows excellent greenness of synthetic procedure for preparation of DES, the environmentally benign nature of DLLME procedure as well as the greenness of the developed UHPLC approach.

Long-term high fructose intake promotes lacrimal gland dysfunction by inducing gut dysbiosis in mice

The lacrimal gland is essential for maintaining ocular surface health through the secretion of the aqueous layer of the tear film. It is therefore important to explore the intrinsic and extrinsic factors that affect the structure and function of the lacrimal gland and the mechanisms underlying them. With the prevalence of Westernized diets characterized by high sugar and fat content, the susceptibility to many diseases, including ocular diseases, is increased by inducing dysbiosis of the gut microbiome. Here, we found that the composition, abundance, and diversity of the gut microbiome was significantly altered in mice by drinking 15% high fructose water for one month, as determined by 16S rRNA sequencing. This was accompanied by a significant increase in lipid deposition and inflammatory cell infiltration in the extraorbital lacrimal glands (ELGs) of mice. Transcriptome analysis based on bulk RNA-sequencing revealed abnormal activation of some of several metabolic and immune-related pathways. In addition, the secretory response to stimulation with the cholinergic receptor agonist pilocarpine was significantly reduced. However, when the composition and diversity of the gut microbiome of high fructose intake (HFI)-treated mice were improved by transplanting feces from normal young healthy mice, the pathological alterations in ELG structure, inflammatory cell infiltration, secretory function and transcriptome analysis described above were significantly reversed compared to age-matched control mice. In conclusion, our data suggest that prolonged HFI may cause pathological damage to the structure and function of the ELG through the induction of gut dysbiosis. Restoration of intestinal dysbiosis in HFI-treated mice by fecal transplantation has a potential role in ameliorating these pathological impairments.

Thermo-Osmosis in Charged Nanochannels: Effects of Surface Charge and Ionic Strength.

Thermo-osmosis refers to fluid migration due to the temperature gradient. The mechanistic understanding of thermo-osmosis in charged nano-porous media is still incomplete, while it is important for several environmental and energy applications, such as low-grade waste heat recovery, wastewater recovery, fuel cells, and nuclear waste storage. This paper presents results from a series of molecular dynamics simulations of thermo-osmosis in charged silica nanochannels that advance the understanding of the phenomenon. Simulations with pure water and water with dissolved NaCl are considered. First, the effect of surface charge on the sign and magnitude of the thermo-osmotic coefficient is quantified. This effect was found to be mainly linked to the structural modifications of an aqueous electrical double layer (EDL) caused by the nanoconfinement and surface charges. In addition, the results illustrate that the surface charges reduce the self-diffusivity and thermo-osmosis of interfacial liquid. The thermo-osmosis was found to change direction when the surface charge density exceeds -0.03C · m-2. It was found that the thermo-osmotic flow and self-diffusivity increase with the concentration of NaCl. The fluxes of solvent and solute are decoupled by considering the Ludwig-Soret effect of NaCl ions to identify the main mechanisms controlling the behavior. In addition to the advance in microscopic quantification and mechanistic understanding of thermo-osmosis, the work provides approaches to investigate a broader category of coupled heat and mass transfer problems in nanoscale space.

Isoquinoline alkaloids isolated from Glaucium corniculatum var. corniculatum and Glaucium grandiflorum subsp. refractum var. torquatum with bioactivity studies

Context The genus Glaucium Mill., one of the important Papaveraceae family plants, is rich in isoquinoline alkaloids and distributed worldwide. Objective Isolation and identification of bioactive alkaloids from Glaucium grandiflorum Boiss. & Huet. subsp. refractum (Nabelek) Mory var. torquatum (Cullen) Mory and G. corniculatum (L.) Rudolph var. corniculatum (Aslan 2012), and investigation of their antioxidant and anticholinesterase activities. Materials and methods The aerial parts of each plant were dried, powdered, and percolated with methanol, then each extract was fractionated between 50% aqueous acetic acid and petroleum. Their aqueous acidic layer was adjusted to pH 7–8 with NH4OH and extracted with chloroform, the extract was subjected to CC separation and isolation. Structures of the isolated alkaloids were elucidated by 1D and 2D-NMR and mass spectral analyses. The alkaloid extracts and their pure alkaloids were tested for anti-cholinesterase (AChE and BuChE) and antioxidant (ABTS, CUPRAC, β-carotene linoleic acid tests) activities in vitro. Results Methanol extracts of Glaucium grandiflorum subsp. refractum var. torquatum and G. corniculatum var. corniculatum afforded a novel compound glauciumoline and seven known isoquinoline alkaloids three of which have an aporphine-type and the other five have a protopine-type skeleton. Among them, trans-protopinium (7) and cis-protopinium (8) were isolated from a Glaucium species for the first time. Tertiary amine extracts (TAEs) of both plants showed very strong acetylcholinesterase inhibitory activity. The TAE of the plants also showed strong antioxidant activity while the isolated alkaloids showed no meaningful activity in the anticholinesterase and antioxidant tests. Discussion and conclusions Glaucium species are considered promising therapeutic agents in the treatment of Alzheimer’s disease.

Environmental factors strongly influence the leaching of di(2-ethylhexyl) phthalate from polyvinyl chloride microplastics

Phthalic acid esters (phthalates) are an important group of additives (plasticizers) to ensure the flexibility and stability especially of polyvinyl chloride (PVC) and to enable its processing. However, phthalates like di(2-ethylhexyl) phthalate (DEHP) are harmful for aquatic organisms due to their endocrine disrupting effects and toxicity. For the assessment of exposure concentrations, thorough understanding of leaching kinetics of phthalates from PVC (micro-) plastics into aqueous environments is necessary. This study investigates how environmental factors influence the leaching of phthalates from PVC microplastics into aquatic systems. The leaching of phthalates from PVC microplastics into aqueous media is limited by aqueous boundary layer diffusion (ABLD) and thus, process-specific parameters can be affected by environmental factors such as salinity and the flow conditions. We conducted batch leaching experiments to assess the influence of salinity and flow conditions (turbulence) on the leaching of DEHP from PVC microplastics into aqueous media. DEHP is salted out with increasing salinity of the solution and a salting-out coefficient for DEHP of 0.46 was determined. The partitioning coefficient of DEHP between PVC and water KPVC/W increased with increasing salinity from 108.52 L kg−1 in a 1 mM KCl solution to 108.75 L kg−1 in artificial seawater thereby slowing down leaching. Increasing flow velocities led to higher leaching rates because the ABL thickness decreased from 1315 µm at 0 rpm shaking speed (no-flow conditions) to 38.4 µm at 125 rpm (turbulent conditions). Compared to salinity, turbulence had a more pronounced effect on leaching. Increasing the flow velocity led to a 35-fold decrease in the leaching rate, while increasing salinity led to a 2-fold increase. By calculating specific leaching times, that is, leaching half-lives (t1/2), time frames for leaching in different aquatic systems such as rivers and the ocean were determined. Given ABLD-limited leaching, DEHP is leached faster from PVC microplastics in rivers (t1/2 > 49 years) than in the ocean (t1/2 > 398 years). In both systems, PVC microplastics are a long-term source of phthalates.

Sub-500 nm patterned synthesis of corrosion resistant SnO2 and Pt@SnO2 using metal-organic precursor

In this study, a thin film of transparent conducting metal oxide, SnO2, is obtained using a novel metal-organic precursor, Sn-TOABr complex. The precursor is synthesized by phase-transferring tin from the aqueous layer to the liquid-liquid interface. The formed precursor is used for depositing SnO2 thin films over arbitrary and even large substrates via the modified atmospheric pressure chemical vapor deposition (MAPCVD) method in a simple furnace at 450 °C. The vapor-deposited SnO2 thin films are crystalline, semiconducting, highly transparent with excellent mechanical robustness against scratch and scotch tape tests, and resistant towards corrosive media. The obtained robust thin films via this MAPCVD technology expand applications towards protective coatings for arbitrary substrates. Using a simple direct micromolding technique, sub-500 nm patterns of SnO2 and Pt@SnO2 were obtained. This single-step soft lithography patterning technique, besides being cost-effective, offers a large throughput.

Flexible and conductive core-sheath fiber using multifunctional merocyanine as a smart electrolyte for a high-performance fibrous visible light sensor

Flexible conductive fibers have attracted significant attention in the wearable electronics field because of light weight, small size, and easy shape morphing. To date, there are few reports on multifunctional flexible conductive fibers. Finding a facile and effective solution for large-scale production of flexible conductive fibers is still a challenge. In this work, a flexible core-sheath fiber with excellent electrical conductivity (24.71 Ω·m) and visible light sensing is fabricated, which contains a merocyanine diol (MC(OH)2)/CrCl3·6H2O/ethanol aqueous solution core layer and a silicon rubber outer layer. The synthesized MC(OH)2 is an intelligent molecular switch with a visible light response that can reversibly convert from open-form MC(OH)2 to closed-form spiropyran diol (SP(OH)2) after short visible light irradiation. In the reverse process, the transition from SP(OH)2 to MC(OH)2 can occur gradually in the dark. This can be used to sense visible light in addition to electrical conductivity. The reversible change in the electrical resistance of the MC(OH)2/CrCl3·6H2O/ethanol aqueous solution reaches 15.59%. This fiber shows excellent electrical conductivity, good flexibility, a sensitive visible light response, good photochromism, a simple structure, low cost, easy preparation, and suitability for industrial large-scale production, offering promise for applications in the fields of flexible and wearable electronics.

ОСОБЕННОСТИ ПОСТРОЕНИЯ МОДЕЛИ ЗЕРКАЛЬНОЙ АНТЕННЫ С УЧЕТОМ ВЛИЯНИЯ МЕТЕОРОЛОГИЧЕСКИХ ФАКТОРОВ

An electrodynamic model of a millimeter-range single-mirror antenna with a puddle in the reflector is given. As a justification for the need for a model, the influence of rainfall on the design of millimeter-range mirror antennas was assessed. The aim of the study was to create a model of the parabolic reflector of a mirror antenna with an aqueous precipitation layer, with parameters chosen for the climatic region in which the antenna is located. An analysis of known models of single mirror antennas with a layer of precipitation has been carried out. It has been shown that the known models do not describe the operation of a millimeter-range mirror antenna with a reflector in which a puddle of water has formed. It is suggested that the influence of this layer on the directional characteristics of the antenna be assessed with the aperture method used for mirror antennas with reflector profile defects. The results of the modelling of the directivity pattern of a mirror antenna with a puddle of water in the reflector are presented. It is shown that the appearance of a puddle leads to an asymmetric change in the height of the first side lobes of the directivity pattern in the vertical plane. In the horizontal plane, changes are observed in the growth level of each side lobe, except for the first one. The lobes' symmetry is not affected. Research focus: The process of emitting a millimeter electromagnetic wave using a single mirror antenna with a layer of water in the reflector. Subject of the study: "Mirror antenna reflector with water precipitation layer - millimeter wavelength electromagnetic wave" system. Methods: Electromagnetic meteorological method, modified aperture method, modified Ruze method, statistical meteorological method. Main result: A wireless communication system using the magnetic component of the electromagnetic field has been developed. Practical relevance: The results of this research may be useful in the design of millimeter-range mirror antennas to assess the influence of meteorological precipitation on the directivity characteristics. The work was presented at the VIII All-Russian Microwave Conference "Microwave week 2022" in Moscow.

Solid-contact polymeric membrane ion-selective electrodes using a covalent organic framework@reduced graphene oxide composite as ion-to-electron transducer.

A solid-contact ion-selective electrode (SC-ISE) based on a covalent organic framework@reduced graphene oxide (rGO) composite is proposed. The composite can be synthesized through the polycondensation of 1,3,5-triformylphloroglucinol (TFP) and 2,6-diaminoanthraquinone (DAAQ) on the rGO nanosheets, which shows high capacitance and good redox-active properties. By applying Cd2+-ISE as a model, the electrode exhibits a Nernstian slope of 29.7±0.4 mV/decade in the activity range of 1.0×10-7 - 7.9×10-4M and the limit of detection is 6.8×10-8M. Particularly, the electrode based on DAAQ-TFP@rGO exhibits a low potential drift of 1.2±0.2μV/h over 70h due to the large capacitance of 2.0mF. Moreover, the DAAQ-TFP@rGO-based Cd2+-ISE shows good reproducibility and the standard deviations of the standard potentials for single batch and batch-to-batch are 0.28 (n=4) and 0.30mV (n=4), respectively. The developed SC-Cd2+-ISE is not disturbed by light or gas and no aqueous layer occurs between the sensing membrane and DAAQ-TFP@rGO layer. The DAAQ-TFP@rGO composite is highly promising for construction of calibration-free SC-ISEs.

One-Pot, Three-Phase Recycling of Metals from Li-Ion Batteries in Rotating, Concentric-Liquid Reactors.

Efficient recycling of spent lithium-ion batteries, LIBs, is essential for making their numerous applications sustainable. Hydrometallurgy-based separation methods are an indispensable part of the recycling process but remain limited by the extraction efficiency and selectivity, and typically require numerous binary liquid-liquid extraction steps in which the capacity of the extracting organic phase or partition coefficient of extracted metals become an overall bottleneck. In this paper, we describe rotating reactors in which aqueous feed, organic extractant, and aqueous acceptor phases are all present in the same, rotating vessel and can be vigorously stirred and emulsified without the coalescence of aqueous layers. In this arrangement, the extractant molecules are not equilibrated with the feed and, instead, "shuttle" between the feed/extractant and the extractant/acceptor interfaces multiple times, with each such molecule ultimately transferring ∼10 metal ions. This shuttling allows for using extractant concentrations much lower than in previous designs even for extremely concentrated feeds and, simultaneously, ensures unprecedented speed and selectivity of the one-pot processes. These experimental results are accompanied by theoretical considerations of the selectivity versus speed trends as well as discussion of parameters essential for system's upscaling. This article is protected by copyright. All rights reserved.

Tear film lipid layer and corneal oxygenation: a new function?

The classic model of tear film is composed of mucin layer, aqueous layer and the outermost tear film lipid layer (TFLL). The complex mixture of different classes of lipids, mainly secreted by meibomian glands, gives the TFLL unique physicochemical properties. Based on these properties, several functions of TFLL have been found and/or proposed such as the resistance to evaporation and facilitating the formation of a thin film. However, the role of TFLL in the oxygenation of the cornea, a transparent avascular tissue, has never been discussed in the literature. The continuous metabolic activity of the corneal surface and the replenishment of atmospheric gas creates an O2 gradient in the tear film. The molecules of O2 must therefore be transferred from the gas phase to the liquid phase through the TFLL. This process is a function of the diffusion and solubility of the lipid layer as well as interface transfer, which is influenced by alterations in the physical state and lipid composition. In the absence of research on TFLL, the present paper aims to bring the topic into the spotlight for the first time based on existing knowledge on O2 permeability of the lipid membranes and evaporation resistance of the lipid layers. The oxidative stress generated in perturbed lipid layers and the consequent adverse effects are also covered. The function of the TFLL proposed here intends to encourage future research in both basic and clinical sciences, e.g., opening new avenues for the diagnosis and treatment of ocular surface conditions.

Regulating the Polypyrrole Ion-Selective Membrane and Au Solid Contact Layer to Improve the Performance of Nitrate All-Solid Ion-Selective Electrodes.

With polymerization duration and Au3+ concentration of the electrolyte regulated, a desirable nitrate-doped polypyrrole ion-selective membrane (PPy(NO3-)-ISM) and Au solid contact layer of anticipate surface morphology were obtained, and the performance of nitrate all-solid ion-selective electrodes (NS ISEs) was improved. It was found that the roughest PPy(NO3-)-ISM remarkably increases the actual contact surface area of the PPy(NO3-)-ISMs with nitrate solution, which leads to better adsorption of NO3- ions upon the PPy(NO3-)-ISMs, and produces a larger number of electrons. The most hydrophobic Au solid contact layer avoids the formation of the aqueous layer at the interface between the PPy(NO3-)-ISM and Au solid contact layer, and ensures unimpeded transporting of the produced electrons. The PPy-Au-NS ISE for polymerization duration 1800 s and at Au3+ concentration 2.5 mM of the electrolyte displays an optimal nitrate potential response, including a Nernstian slope of 54.0 mV/dec, LOD of 1.1 × 10-4 M, rapid average response time less than 1.9 s, and long-term stability of more than 5 weeks. This indicates that the PPy-Au-NS ISE is an effective working electrode for the electrochemical determination of NO3- concentration.

Highly stable ammonium ion-selective electrodes based on one-pot synthesized gold nanoparticle-reduced graphene oxide as ion-to-electron transducers

An effective transducer for all-solid-state ion-selective electrodes (SC-ISEs) was developed based on gold nanoparticle-reduced graphene oxide (AuNP-rGO) hybrid material. The AuNP-rGO composite was synthesized via a simple, eco-friendly, and one-pot method with sodium citrate as the reducing agent and the stabilizer. The nanocomposite was deposited on the GC substrate via the drop-casting method and then covered with an ammonium ion-selective membrane (NH4+-ISM) to form the potentiometric electrode. The AuNP-rGO layer possessed a large surface area, high capacitance, and good hydrophobicity; thereby effectively enhancing the potential stability of the electrode without the formation of an aqueous layer. The electrode also exhibited a rapid potential response (<10 s) to NH4+ ions, an excellent Nernstian response with a slope of 56.94 (±1.57) mV/decade, a detection range of 10-5 − 10-2 M, and a detection limit of 3.80 × 10-6 M. The proposed electrode also exhibited outstanding properties including insensitivity to interferences (light, oxygen, carbon dioxide, and redox species), good reproducibility, and long operating life. The electrode has been successfully applied for NH4+ detection in real water samples, which makes it a promising alternative for developing effective and robust SC-ISEs.