Advanced metal deposition and microfabrication techniques enable preparation of metal surfaces with high precision and excellent control over their size and shape with subnanometer resolution. Thin metal films of different types and functions can be found in many analytical instruments. Surfaces with high optical quality serve as mirrors, beam splitters, antireflective coatings etc. Smooth metal coating is crucial in electron microscopy. Unique properties of the thin metal films are widely used in optical systems, as tools for sample manipulation but also for chemical sensing and detection. While some of the applications are widespread and belong to the basic curriculum in analytical chemistry, the newer or less common uses of thin metal films are well known only to the experts in the field. The purpose of this critical review is to highlight the role of thin metal films in bioanalysis and summarize some of their main applications in current bioanalytical instrumentation.
- MeSH
- Biosensing Techniques instrumentation methods MeSH
- Electrochemical Techniques instrumentation methods MeSH
- Metals chemistry MeSH
- Humans MeSH
- Microfluidics instrumentation methods MeSH
- Nucleic Acids analysis MeSH
- Proteins analysis MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
PURPOSE: Fluid-bed coating processes make it possible to manufacture pharmaceutical products with tuneable properties. The choice of polymer type and coating thickness provides control over the drug release characteristics, and multi-layer pellet coatings can combine several active ingredients or achieve tailored drug release profiles. However, the fluid-bed coating is a parametrically sensitive process due to the simultaneous occurrence of polymer solution spraying and solvent evaporation. Designing a robust fluid-bed coating process requires the knowledge of thin film drying kinetics, which in turn critically depends on an accurate description of concentration-dependent solvent diffusion in the polymer. METHODS: This work presents a mathematical model of thin film drying as an enabling tool for fluid-bed process design. A custom-built benchtop drying cell able to record and evaluate the drying kinetics of a chosen polymeric excipient has been constructed, validated, and used for data collection. RESULTS: A semi-empirical mathematical model combining heat transfer, mass transfer, and film thickness evolution was formulated and used for estimating the solvent diffusion coefficient and solvent distribution in the polymer layer. The combined experimental and computational methodology was then used for analysing the drying kinetics of common polymeric excipients: poly(vinylpyrrolidone) and two grades of hydroxypropyl methylcellulose. CONCLUSIONS: The experimental setup together with the mathematical model represents a valuable tool for predictive modeling of pharmaceutical coating processes.
- MeSH
- Hypromellose Derivatives MeSH
- Kinetics MeSH
- Polymers * MeSH
- Excipients * MeSH
- Solvents MeSH
- Publication type
- Journal Article MeSH
The mercury bioaccumulation by common carp (Cyprinus carpio L.) tissues (gills, skin, eyes, scales, muscle, brain, kidneys, liver, and spleen) and the capability of the diffusive gradient in thin film (DGT) technique to predict bioavailability of mercury for individual carp's tissues were evaluated. Carp and DGT units were exposed to increasing concentrations of mercury (Hg2+: 0 μg L-1, 0.5 μg L-1, 1.5 μg L-1and 3.0 μg L-1) in fish tanks for 14 days. In the uncontaminated fish group, the highest mercury concentration was determined in the muscle tissues and, in fish groups exposed to mercury, the highest mercury concentration was determined in the detoxification (kidneys) and input (gills) organs. A strong and positive correlation between the rate of mercury uptake by the DGT technique and the rate of mercury accumulation by fish tissues (gills, skin, scales, and eyes) was observed.
- MeSH
- Biological Availability MeSH
- Diffusion MeSH
- Carps metabolism MeSH
- Kinetics MeSH
- Kidney chemistry metabolism MeSH
- Mercury analysis pharmacokinetics MeSH
- Muscles chemistry metabolism MeSH
- Gills chemistry metabolism MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
We assessed the relationship between the diffusive gradient in thin film (DGT) technique using the new ion-exchange resin Ambersep GT74 and the uptake of mercury (Hg) by a model plant cultivated on metal-contaminated agricultural soils under greenhouse conditions. Based on the total Hg content, 0.37 to 1.17% of the Hg passed to the soil porewater from the solid phase, and 2.18 to 9.18% of the Hg is DGT-available. These results were confirmed by calculating the R value (the ratio of the concentrations of bioavailable Hg measured by DGT and soil solution), which illustrated the strong bonding of Hg to the solid phase of soil and its extremely low mobility. Only inorganic Hg2+ species were found in the metal-contaminated agricultural soils, as determined by a high-performance liquid chromatography-cold vapor atomic fluorescence spectrometry speciation analysis. The Hg was distributed in Miscanthus × giganteus organs in the following order for all sampling sites: roots (55-82%) > leaves (8-27%) > stems (7-16%) > rhizomes (4-7%). Environ Toxicol Chem 2019;38:321-328. © 2018 SETAC.
- MeSH
- Biological Availability MeSH
- Models, Biological MeSH
- Biological Transport MeSH
- Ion Exchange Resins chemistry MeSH
- Soil Pollutants analysis metabolism MeSH
- Poaceae metabolism MeSH
- Environmental Monitoring methods MeSH
- Soil chemistry MeSH
- Mercury analysis metabolism MeSH
- Chromatography, High Pressure Liquid MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- MeSH
- Cytotoxicity Tests, Immunologic methods MeSH
- Hydroxyapatites administration & dosage adverse effects therapeutic use MeSH
- Ceramics administration & dosage therapeutic use radiation effects MeSH
- Lasers MeSH
- Lymphocytes cytology MeSH
- In Vitro Techniques MeSH
- Titanium administration & dosage adverse effects therapeutic use MeSH
- Dental Implants administration & dosage MeSH
The tear film at the ocular surface is covered by a thin layer of lipids. This oily phase stabilizes the film by decreasing its surface tension and improving its viscoelastic properties. Clinically, destabilization and rupture of the tear film are related to dry eye disease and are accompanied by changes in the quality and quantity of tear film lipids. In dry eye, eye drops containing oil-in-water emulsions are used for the supplementation of lipids and surface-active components to the tear film. We explore in detail the biophysical aspects of interactions of specific surface-active compounds, cetalkonium chloride and poloxamer 188, which are present in oil-in-water emulsions, with tear lipids. The aim is to better understand the macroscopically observed eye drops-tear film interactions by rationalizing them at the molecular level. To this end, we employ a multi-scale approach combining experiments on human meibomian lipid extracts, measurements using synthetic lipid films, and in silico molecular dynamics simulations. By combining these methods, we demonstrate that the studied compounds specifically interact with the tear lipid film enhancing its structure, surfactant properties, and elasticity. The observed effects are cooperative and can be further modulated by material packing at the tear-air interface.
- MeSH
- Motion Pictures * MeSH
- Microscopy, Fluorescence methods MeSH
- Quaternary Ammonium Compounds chemistry MeSH
- Humans MeSH
- Lipids chemistry MeSH
- Fatty Alcohols chemistry MeSH
- Meibomian Glands metabolism MeSH
- Poloxamer chemistry MeSH
- Molecular Dynamics Simulation * MeSH
- Models, Theoretical MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
