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Downscaling of microfluidic cell culture and detection devices for electrochemical monitoring has mostly focused on miniaturization of the microfluidic chips which are often designed for specific applications and therefore lack functional flexibility. We present a compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection, enabling complete cell based assays comprising on-line electrode cleaning, sterilization, surface functionalization, cell seeding, cultivationand electrochemical real-time monitoring of cellular dynamics. To demonstrate the versatility and multifunctionality of the platform, we explored amperometric monitoring of intracellular redox activity in yeast (Saccharomyces cerevisiae) and detection of exocytotically released dopamine from rat pheochromocytoma cells (PC12). Electrochemical impedance spectroscopy was used in bothapplications for monitoring cell sedimentation and adhesion as well as proliferation in the case of PC12 cells. The influence of flow rate on the signal amplitude in the detection of redox metabolism as well as the effect of mechanical stimulation on dopamine release were demonstrated using the programmable fluid handling capability. The here presented platform is aimed at applications utilizing cell based assays, ranging from e.g. monitoring of drug effects in pharmacological studies, characterization of neural stem cell differentiation, and screening of genetically modified microorganisms to environmental monitoring.

Mono- and multiparticulate nanostructured silica films were prepared by the Langmuir–Blodgett (LB) technique both from hydrophilic and hydrophobic Stober silica nanospheres of 92 and 107 nm diameters. The effective refractive index and the film thickness were determined from the transmission spectra (300–1200 nm) by evaluating interference peaks and parameter fitting. The spectra were notably different depending on particle sizes, number of layers transferred, and particle hydrophobicity. The monolayers showed expressed antireflection properties. From the film thickness values obtained for multiparticulate LB films we came to the conclusion that the particles arrange themselves in a close-packed array during the preparation of LB films.

Stober silica particles having diameters of ca. 100 and ca. 200 nm were prepared and silylated using trimethylsilyl N,N-dimethylcarbamate, achieving a range of surface coverage by trimethylsilyl groups by varying the amounts of silylating agent used. The efficacy of silylation was characterized in terms of hydrophobicity of the particles which was assessed by film balance investigations at water−air interfaces and additionally by imaging the long- and short-range structures of silica particulate layers at water−air interfaces and on mica supports by using Brewster-angle and atomic force microscopies.

The influence of calcium and zinc ions on the corrosion inhibition effect of 1‐hydroxyethane‐1,1‐diphosphonic acid (HEDP) on carbon steel has been investigated by electrochemical techniques, X‐ray photoelectron spectroscopy, and atomic force microscopy. Addition of calcium or zinc ions greatly increased the inhibition efficiency of HEDP in a synergistic manner. The highest inhibition effect was obtained for molar ratios of Ca/HEDP = 0.5 and Zn/HEDP = 3 for . The corrosion inhibition mechanism in the presence of these additives proved to be different from that with HEDP alone and was related to the formation of different complex species between HEDP and cation additives. The frequency response of the studied system was described by a transfer function containing two relaxation time constants corresponding to the charge‐transfer process and the porous oxide layer. Higher zinc and phosphorous content in the inhibitor layer and a continuous change in the O‒Fe and HO‒Fe ratio were achieved by increasing zinc concentration in the solution (in the range Zn/HEDP = 0.5–3) as supported by XPS measurements. Changes in the chemical structure were established in the oxide‐hydroxide layer developed spontaneously on the steel surface. The synergistic effect of inhibitor compounds appeared also in surface morphology, leading to the development of smooth, i.e., dense, protective layers as revealed by atomic force microscopy. © 1999 The Electrochemical Society. All rights reserved.

A possible sink for divalent lead in the environment is clays such as montmorillonite that have cation exchange capacities. To assess the reaction, a calcium–montmorillonite was mixed with lead perchlorate solutions of varying concentrations and at various pH's. The recovered solids were studied by a variety of techniques (X-ray photoelectron and infrared spectroscopy, scanning electron microscopy, and atomic force microscopy) to determine what, if any, alterations occurred. The ion exchange of lead for calcium reduced the hydrated water in the clay, and evidence for proton–lead ion exchange at the edges of the sheets was observed. Evidence for a second, unexpected, reaction was also observed. Small spots (0.2 to 1 μm) of lead enrichment were observed on the surface of clay particles. They were also observed on clays recovered from the sediment of a Hungarian lake. The results show that lead ions are adsorbed onto montmorillonite by two processes: cation exchange and nano- and microparticle production. Cation exchange leads to the even distribution of the ions, while the production of spots causes the enrichment of lead ions. The production of these particles is not expected from the thermodynamic properties of the solution and cannot be observed in the absence of clay.

By decreasing the volume of the cryoprotective solution, we were able to dramatically increase the freezing speed and decrease the toxicity and osmotic side effects of the cryoprotectants (CP). Several carriers have been developed successfully (Vajta G et al. 1998 Mol. Reprod. Dev. 51, 53–58; Liebermann J et al. 2002 Reprod. Biomed. Online 4, 146–150; Park SP et al. 1999 Hum. Reprod. 15, 1787–1790; Chung HM et al. 2000 Fertil. Steril. 73, 545–551; Kuwayama M and Kato O 2000 Fertil. Steril. 74(Suppl. 3), S49 O-127; Matsumoto H et al. 2001 Cryobiology 42, 139–144; Lane M et al. 1999 Fertil. Steril. 72, 1073–1078; Dinnyés A et al. 2000 Biol. Reprod. 63, 513–518). The objective of our study was to vitrify Day 3 cleavage stage mouse embryos with the Vitroloop™ (Vitrolife, Kungsbacka, Sweden) cryopreservation technology. Vitrification was carried out in RapidVit™ Cleave (Vitrolife) solutions (holding, equilibration, and vitrification medium). Embryos were exposed to a 2-step loading of CP, ethylene glycol (EG), and propylene glycol (PG), before being placed in a small loop attached to the lid of a cryo-vial and rapidly submerged into liquid nitrogen (LN). First, the embryos were transferred from the G-MOPS holding medium to the equilibration medium containing 8% EG for 2 min. Then, embryos were transferred into a 20-μL drop of vitrification medium containing 16% EG, 16% PG, 10 mg mL–1 Ficoll 400, and 0.65 m sucrose for 30 s. After that, the embryos (maximum of 2 at a time) were transferred onto the loop, which was quickly sealed in a cryo-vial of LN and stored. After storage in LN, embryos were warmed by a 3-step dilution of the CP with sucrose (RapidWarmCleave™, Vitrolife) carried out at 37°C. First, the loop with the embryos was quickly immersed in 37°C warming medium 1 (0.65 m sucrose) for 20 s. Then, the embryos were transferred into warming medium 2 (0.25 m sucrose) for 1 min, then into warming medium 3 (0.125 m sucrose) for 2 min, and finally into warming medium 4 (G-MOPS medium) for 5 min. Following warming, embryos were cultured in G1 medium (Vitrolife) at 37°C with 6.5% CO2 and maximum humidity in air. Embryo viability was assessed by 48 h in vitro culture; the survival of embryos was based on morphological appearance in vitro after thawing and continued development to expanded blastocysts upon subsequent culture. The control embryos were treated likewise except that they were not vitrified. A total of 229 cleavage-stage embryos were vitrified and warmed; out of these, 11 were lost (11/229; 4.8%). Of the remaining 218 embryo, 202 survived vitrification (202/218; 92.7%) and 180 developed further to expanded blastocysts during in vitro culture (180/202; 82.6%). In the control group, 91.4% of the embryos developed to expanded blastocysts (75/82) indicating that the solutions used were not toxic. Our data show that a high percentage of cleavage-stage mouse embryos survived vitrification in the mixture of EG and PG combined with the use of cryoloop and developed normally in vitro after thawing. To our knowledge, this is the first report of the successful use of the Vitroloop™ vitrification procedure with cleavage-stage mouse embryos. The authors thank Vitrolife Ltd. (Kungsbacka, Sweden) and FertiCad Ltd. (Budapest, Hungary) for providing the solutions. The 3-month fellowship for Phillip Klambauer was provided by CEEPUS.

A versatile microfluidic, multichamber cell culture and analysis system with an integrated electrode array and potentiostat suitable for electrochemical detection and microscopic imaging is presented in this paper. The system, which allows on-line electrode cleaning and modification, was developed for real-time monitoring of cellular dynamics, exemplified in this work by monitoring of redox metabolism inside living yeast cells and dopamine release from PC12 cells.