Surface properties of glass micropipettes and their effect on biological studies

In this paper, an investigation on surface properties of glass micropipettes and their effect on biological applications is reported. Pipettes were pulled under different pulling conditions and the effect of each pulling parameter was analyzed. SEM stereoscopic technique was used to reveal the surface roughness properties of pipette tip and pipette inner wall in 3D. More than 20 pipettes were reconstructed. Pipette heads were split open using focused ion beam (FIB) milling for access to the inner walls. It is found that surface roughness parameters are strongly related on the tip size. Bigger pipettes have higher average surface roughness and lower developed interfacial area ratio. Furthermore, the autocorrelation of roughness model of the inner surface shows that the inner surface does not have any tendency of orientation and is not affected by pulling direction. To investigate the effect of surface roughness properties on biological applications, patch-clamping tests were carried out by conventional and FIB-polished pipettes. The results of the experiments show that polished pipettes make significantly better seals. The results of this work are of important reference value for achieving pipettes with desired surface properties and can be used to explain biological phenomenon such as giga-seal formation.     

Preparation of voltammetric biosensor for tryptophan using multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were grown by chemical vapor deposition. The effect of the composition of carbon paste electrode on its voltammograms was evaluated in basic solution with 5.0×10⁻⁵ M tryptophan (Trp). It was found that addition of MWCNTs to the carbon paste would generate the peak current of Trp because of its catalytic effect on the redox process. The pH strongly affects the peak potential of Trp. The best analytical response was obtained at pH 13.0. The anodic peak currents were proportional to Trp concentrations in the range of 1.0×10⁻⁹−1.0×10⁻⁴ M under the optimized experimental conditions. The detection limit was 2.2×10⁻¹⁰ M. The effect of potential scan rate on the peak potential and peak current of tryptophan was investigated. The correlation of the peak currents against v^1/2 (v is the scan rate) is linear, which is very similar to a diffusion-controlled process. The proposed biosensor was applied to the determination of Trp in pharmaceuticals formulations successfully.     

Direct Growth and Photoluminescence of SiO<Subscript>x</Subscript> Nanowires and Aligned Nanocakes by Simple Carbothermal Evaporation

The growth of SiO_x nanowires and nanocakes on an Au-coated n-type-Silicon (100) substrate was achieved via carbothermal evaporation. The effects of the Au layer thickness and the rapid heating rate on the morphology of obtained SiO_x nanowires were investigated. A broad emission band from 290 to 600 nm was observed in the photoluminescence (PL) spectrum of these nanowires. There are four PL peaks: one blue emission peak 485 nm (2.56 eV) two green bands centered at 502 nm (2.47 eV) and 524 nm (2.37 eV) for nanocakes and one ultraviolet emission peak at 350 nm (3.54 eV) and a hemisphere curve over the bluish green area taken for SiO_x nanowires. These emissions may be related to the various oxygen defects and twofold coordinated silicon lone pair centers.     

Electrophoretic deposition of titanium nitride coatings

Electrophoretic deposition of the titanium nitride (TiN) coatings from suspensions prepared by dispersion of TiN particles in triethanolamine (TEA) containing butanol medium was studied. Effects of the TiN particles concentration (C_TiN) on the weight of the deposited coatings, triethanolamine concentration (C_TEA=0.25, 0.5, 0.75, and 1 mL/L) on the Zeta potential of the TiN particles, suspension electrical conductivity and pH, as well as effects of the deposition voltage (V_d=60, 90, and 120 V) and time (t_d =1, 2, and 3 minutes) on the microstructure and thickness of the deposited coatings were investigated. Variations in deposition current density, effective deposition voltage, electrical resistance, and deposited coating weight versus deposition time were recorded. The morphology of the as‐dried coatings was studied using Scanning Electron Microscope (SEM). The results indicated that by increasing the C_TiN the weight of deposits increases linearly up to 40 g/L. For suspensions containing C_TiN=40 g/L, the optimum C_TEA is obtained to be 0.5 mL/L leading to Zeta potential of 43.25 mV. Uniform and crack‐free as‐dried coatings obtained at V_d and t_d of 90 V and 2 minutes, respectively.     

The synergistic cooperation between MCM-41 and azithromycin: a pH responsive system for drug adsorption and release

The capability of MCM-41 silica for accepting and delivering poorly soluble azithromycin (AZT) in water is reported as robust drug delivery system. This property has been evidenced by using two MCM-41 samples with different pore sizes as hosts of AZT. The choice of this macrolide antibiotic is due not only to its low bioavailability but also to its molecular size which lies in the range of pore diameter of MCM-41s. The drug was loaded inside the pore voids of the mesoporous when MCM-41 was stirred at AZT solution, based on XRD, Nitrogen adsorption–desorption isotherms, TGA analysis data and FT-IR spectroscopy. The amount of AZT stored inside the pores of MCM-41 s was between 22 and 25 wt%. The loaded drug was released in different rates from the particles by changing the pH (1.7 and 7.4) to give a smart pH-responsive carrier system. The drug release kinetics was fitted to Korsmeyer–Peppas and Higuchi models which indicated that the rate of drug release was controlled by the diffusion of the drug. The result of the present study confirms that the controlled adsorption and liberation of AZT may improve the oral bioavailability of poor water soluble AZT. This study demonstrates the feasibility of designing reliable drug delivery systems by appropriate choice of the matrix and the organic molecule. In general, MCM-41 is a promising matrix for AZT adsorption with different application from drug delivery to wastewater filtration.     

Pretreatment of wool/polyester blended fabrics to enhance titanium dioxide nanoparticle adsorption and self‐cleaning properties

This research aims to enhance the self‐cleaning properties of fibre‐blended fabric using surface pretreatment prior to the application of titanium dioxide nanoparticles. To this end, the polyester/wool fabric was modified, in that the wool fibres were oxidised with potassium permanganate and the polyester fibres were hydrolysed with lipase before nano processing. Butane tetracarboxylic acid was also used to enhance the adsorption of the nanoparticles and also to stabilise them on the fabric surface. The self‐cleaning properties of the fabric were examined through staining of the fabric with CI Basic Blue 9 and then discolouring by exposing to ultraviolet and daylight irradiation. Some other properties of the treated fabrics, such as water drop absorption, crease recovery angle and bending were investigated and are discussed in detail. The colour changes of different samples indicated an appropriate discoloration on the titanium dioxide‐treated fabrics after ultraviolet and daylight irradiation. Overall, the surface pretreatment of the wool and polyester fibres improved the self‐cleaning properties of the fabric significantly.     

Synthesis of high surface area nanocrystalline MgO by pluronic P123 triblock copolymer surfactant

Nanocrystalline magnesium oxide with high surface area was prepared by a simple precipitation method using pluronic P123 triblock copolymer (Poly(ethylene glycol)-block, Poly(propylene glycol)-block, Poly(ethylene glycol)) as surfactant. The prepared samples were characterized by X-ray Diffraction (XRD), N₂ adsorption (BET), Fourier transform infrared spectroscopy (FTIR), Thermal, differential thermal gravimetric and differential thermal analyses (TG/DTG/DTA) and Scanning electron microscopy (SEM). The obtained results revealed that the addition of surfactant is effective to prepare magnesium oxide with high surface area and affects the morphology of the prepared samples. The results showed that the magnesium oxide calcined at different temperatures ranging from 600 to 800 °C possessed a high surface area in the range of 133.9–78.1 m² g^?1. In addition, the magnesium oxide prepared with the addition of surfactant showed a narrower pore size distribution compared to the sample prepared without the addition of a surfactant.     

Delignification of intact biomass and cellulosic coproduct of acid‐catalyzed hydrolysis

The kinetics of acid‐catalyzed hemicellulose removal and also alkaline delignification of oat hull biomass were investigated. All three operational parameters namely, catalyst concentration (0.10–0.55 N H₂SO₄), temperature (110–130°C), and residence time (up to 150 min) affected the efficiency of hemicellulose removal, with 100% of hemicellulose removed by appropriate selection of process parameters. Analysis of delignification kinetics (in the temperature range of 30–100°C) indicated that it can be expressed very well by a two‐phase model for the crude biomass and also for the hemicellulose‐prehydrolyzed material. The application of acid‐catalyzed prehydrolysis improved the capacity of lignin dissolution especially at lower temperatures (30 and 65°C) and accelerated the dissolution of lignin. This acceleration of delignification by prehydrolysis was possible at all levels of temperature in the bulk phase; however, results were more significant at the lower temperatures in the terminal phase. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1783–1791, 2015