Assessment of cytotoxicity using electric cell-substrate impedance sensing: concentration and time response function approach

This paper describes a simple and convenient method to measure the concentration and time response function f (C,t) of cells exposed to a toxicant by electric cell-substrate impedance sensing. Attachment and spreading of fibroblastic V79 cells cultured on small gold electrodes precoated with fibronectin were detected as electrical resistance changes. With this method, chemical cytotoxicity was easily screened by observing the response function of attached cells in the presence of inhibitor. The cytotoxicities of three test models, cadmium chloride, sodium arsenate, and benzalkonium chloride, were quantified by measuring the percentage inhibition as a function of the inhibitor concentration. The half-inhibition concentration, the required concentration to achieve 50% inhibition, derived from the response function agreed well with the results obtained using the standard neutral red assay.     

Real-time monitoring primary cardiomyocyte adhesion based on electrochemical impedance spectroscopy and electrical cell-substrate impedance sensing

The cell-substrate distance is a direct indicator of cell adhesion to extracellular matrix which is indispensable in cell culture. A real-time monitoring approach can provide a detailed profile of cell adhesion, so that enables the detecting of adhesion-related cell behavior. In this work, we report a novel real-time impedance-based method to record the adhesion profile of cardiomyocyte, overcoming its inscrutability due to the primary culture. Microfabricated biosensors are applied in cardiomyocyte culture after characterizing the cell-free system. Cyclic frequency scanning data of cell-related impedance are generated and automatically fit into the equivalent circuit model, which is established using electrochemical impedance spectroscopy. The data are displayed as the alteration of normalized cell-substrate distance and the essential parameters for manual electric cell-substrate impedance sensing calibration of absolute distance. The time course displays a significant decline in the equivalent cell-substrate distance, from 155.8 to 60.2 nm in the first 20 h of cardiomyocyte culture. Furthermore, the cardiomyocytes cultured in long-term medium and short-term medium (ACCT) for 10 h exhibit distinct difference in adhesion rate as well as cell-substrate distance (72 vs 68 nm).     

An in-depth study of accidents involving collisions with utility poles

This paper summarizes the objectives, methodology, findings, and recommendations of a large-scale study of automobile crashes involving utility poles. In an 8-month survey of accidents, information on site characteristics and accident severity was obtained for a sample of 879 crashes. Randomly-selected samples of 795 sites and 627 vehicles provided control information. An accident-predictor model which identifies accident risk on the basis of site measurements has been derived. The model reveals a range of relative risks in the population of exposed poles of the order of 1000:1, and enables the identification of the relatively small proportion of poles which account for the majority of accidents. The model was used in conjunction with estimates of the costs of accidents to show that a number of remedial treatments are warranted. The hazardous effects of low tyre tread depths and improper tyre inflation pressures are also demonstrated.     

Monitoring motility, spreading, and mortality of adherent insect cells using an impedance sensor

An emerging sensor technology referred to as electric cell-substrate impedance sensing (ECIS) has been extended for monitoring the behavior of insect cells including attachment, motility, and mortality. In ECIS, adherent cells were cultured on an array of eight small gold electrodes deposited on the bottom of tissue culture wells and immersed in a culture medium. Upon the attachment and spreading of cells on the gold electrode, the impedance increased because the cells acted as insulating particles to restrict the current flow. Experimental data revealed that insect cells interacted differently with various proteins used to precoat the gold electrode with concanavalin A as the best promoter to accelerate the rate of cell attachment. After the cells were fully spread, the measured impedance continued to fluctuate to reflect the constant motion and metabolic activity of the cells. As the cell behavior was sensitive to external chemicals, the applicability of ECIS for inhibition assays was demonstrated with HgCl2, trinitrotoluene, trinitrobenzene (TNB), and 2-amino-4,6-dinitrotoluene as model systems. Unlike conventional assays, the quantitative data obtained in this study are taken in real time and in a continuous fashion to depict cell motility and mortality.     

In vitro real-time characterization of cell attachment and spreading

A method based on the piezoelectric quartz crystal microbalance (QCM) technique for in vitro real-time characterization of cell attachment and spreading on surfaces has been developed. The method simultaneously measures the resonant frequency, f, and the dissipation energy, D, of the oscillating system. The QCM responses are sensitive to very small amounts (a few hundreds) of cells and highly specific to surface chemical properties. The first results from deposition of cells on two polystyrene surfaces of different wettability in serum-containing medium are reported. It has previously been shown that a decrease in f is related to the degree of cell spreading. In our data it appears that the extent or quality of cell attachment is reflected in an increase in D caused by adhering cells. The combined information from f and D measured by this technique might therefore be useful to probe cell–surface interactions for biomaterials. © 1998 Kluwer Academic Publishers     

An in-depth analysis of government funding and international collaboration in scientific research

Scientometrics - Based on publications indexed in the Web of Science, the current study focused on internationally collaborated publications and publications acknowledging government funding of...     

Effect of calcium,zinc and magnesium on the attachment and spreading of osteoblast like cells onto ceramic matrices

Calcium phosphate ceramic has been widely used as bone substitute materials. Neumerours approaches have been investigated to develop tissue-engineered scaffold from hydroxyapatite because of its advantages like osteoconduction. We have developed porous ceramic matrices from nanoparticles of calcium phosphate containing zinc and magnesium. Mimicking the grain size of natural bone enhances the bone forming function of cells. Osteoblast-like MG63 cells were cultured on to these porous ceramic matrices. Cell adhesion and spreading onto these matrices were studied for 24 h and 5 days in vitro. It was observed that on calcium phosphate matrix, containing a combination of zinc and magnesium, the osteoblast adhesion and spreading was significant on 5th day. This appeared to be comparable to the hydroxyapatite control. This makes it a promising candidate as a bone tissue-engineering scaffold.     

An in-depth analysis of Raman and near-infrared chemical images of common pharmaceutical tablets

This study reports on the application of Raman and near-infrared (NIR) imaging techniques for determining the spatial distribution of all (five) components in a common type of pharmaceutical tablet manufactured in two different ways. Multivariate chemical images were produced as principal component (PC) scores, while univariate images were produced by using the most unique spectra selected by the orthogonal projection approach (OPA), a searching algorithm. Multivariate Raman images were obtained for all five components in both tablets, while only two or three components could be imaged with the NIR instrument. Very interesting PC results are reported that in effect cast doubt on the effectiveness of the established criteria for determining signal-related PCs in the Raman data. PCA has been found to be indispensable for imaging the minor components using the Raman data. Significant similarity between the multivariate and univariate chemical images has been noted despite there being considerable spectral overlap within the Raman and, especially, within the NIR mapping data sets. Gray-scale images are carefully thresholded, which allowed for quantitative comparison of the obtained binarized images. A thorough discussion is given on the problems and approximations needed for producing composite images.     

Analytical electric field and sensitivity analysis for two microfluidic impedance cytometer designs

Microfabricated impedance cytometers have been developed to measure the electrical impedance of single biological particles at high speed. A general approach to analytically solve the electric field distributions for two different designs of cytometers: parallel facing electrodes and coplanar electrodes, using the Schwarz-Christoffel Mapping method is presented. Compared to previous analytical solutions, our derivations are more systematic and solutions are more straightforward. The solutions have been validated by comparison with numerical simulations performed using the finite element method. The influences on the electric field distribution due to the variations in the geometry of the devices have been discussed. A simple method is used to determine the impedance sensitivity of the system and to compare the two electrode designs. For identical geometrical parameters, we conclude that the parallel electrodes design is more sensitive than the coplanar electrodes.     

Cell attachment and spreading processes monitored by the thickness shear-mode quartz sensor

Kinetics of attachment and spreading processes of adherent living cells are investigated using the thickness shear-mode quartz-crystal sensor technique. Within the framework of the transmission line representation and its variant the lumped element model, experimental results of the shear electrical motional resistance derived from the Butterworth-Van Dyke equivalent circuit in the vicinity of the sensor mechanical resonant frequency have shown that the increase of this parameter is strongly correlated with the evolving surface coverage during attachment and spreading of the adherent living cells on the quartz sensor surface. Both the dependence of the shear electrical motional resistance on the cell concentration and the contribution of the extracellular matrix proteins on the shear acoustical response of the thickness shear-mode quartz sensor are analyzed. Shear acoustical results are further correlated to both optical microscopic observation and cell counting technique. Finally, the ability of the thickness shear-mode quartz resonator technique to monitor specific cell-substrate interactions is discussed.     

An impedance study of the electrophoretic deposition from yttrium silicate suspensions

Yttrium silicate powders were prepared according to a modified Pechini method. The powders were dispersed in isopropanol and the conditions of electrophoretic deposition from these suspensions were optimized. Well adhering coatings were obtained. Impedance spectroscopy was applied to characterize the solvent and the suspension as well as to study the causes for the rapid current decay recorded during constant voltage deposition. Specific conductivity and dielectric constants of solvent and suspension were extracted as well as the resistance of the deposit. Results indicate that mainly mass transport processes through the deposited layer are responsible for the current decay, and to a much lesser extent the resistance of the deposit.     

The attachment,spreading and growth of baby hamster kidney cells on collagen,chemically modified collagen and collagen-composite substrata

Various replicates of collagen substrata were prepared to study the attachment, growth and spreading of baby hamster kidney (BHK) cells. Cell attachment was measured in both the presence and absence of serum. Spreading and growth did not occur in the absence of serum. Attachment to fibrous collagen was less than that found with glass, rat-tail tendon collagen or films prepared from pepsin-solubilized collagen (PS-collagen). Incorporation of hyaluronate, heparin and protamine sulphate into the fibrous collagen and the acetylation of fibrous collagen had little effect. However, incorporation of chondroitin sulphate or chemical modification of fibrous collagen by either methylation or succinylation increased BHK cell attachment. In the absence of serum, the attachment to collagen, acetylated collagen and collagen composites was reduced. The reduction in attachment was marked with fibrous collagen and gelatin films, but less so with collagen composites, acetylated collagen, rat-tail tendon and PS-collagen films. Interestingly, attachment to succinylated collagen and methylated collagen was largely unaffected by the absence of serum, and possible reasons for this are discussed. Cell shape measurements showed decreased spreading of BHK cells on chemically modified collagen films, especially on gelatin films and dried PS-collagen gels. Cell shape and spreading on PS-collagen, rat-tail tendon collagen and collagen-composite films was found to be similar to that on fibrous collagen. BHK cell growth on fibrous collagen, chemically modified collagens, collagen composites, rat-tail tendon and PS-collagen films was similar to that found on plastic tissue culture substrate. Denaturation of fibrous collagen resulted in decreased growth, and BHK cell growth was markedly reduced on PS-collagen gels and dried gels.     

An electrochemical impedance spectroscopy study of polymer electrolyte membrane fuel cells electrocatalyst single wall carbon nanohorns-supported

Electrochemical impedance spectroscopy (EIS) was used to study the polymer electrolyte membrane fuel cells (PEMFC) performance when using single wall carbon nanohorns (SWNH) to support Pt nanoparticles. Additionally, as-prepared and oxidized SWNH Pt-supports were compared with conventional carbon black. Two different oxidizing treatments were considered: oxygen flow at 500 degrees C and reflux in an acid solution at 85 degrees C. Both oxidizing treatments increased SWNH surface area; oxygen treatment increased surface area 4 times while acid treatment increased 2.6 times. The increase in surface area should be related to the opening access to the inner tube of SWNH. Acid treatment of SWNH increased chemical fragility and decreased electrocatalyst load in comparison with as-prepared SWNH. On the other hand, the oxygen treated SWNH sample allowed to obtain the highest electrocatalyst load. The use of as-prepared and oxygen treated SWNH showed in both cases catalytic activities 60% higher than using conventional carbon black as electrocatalyst support in PEMFC. Moreover, EIS analysis indicated that the major improvement in performance is related to the cathode kinetics in the as-prepared SWNH sample, while concerning the oxidized SWNH sample, the improvements are related to the electrokinetics in both anode and cathode electrodes. These improvements should be related with differences in the hydrophobic character between SWNH and carbon black.     

Electrode microchamber for noninvasive perturbation of mammalian cells with nanosecond pulsed electric fields

Nanosecond pulsed electric fields can pass through the external membrane of biological cells and disturb fast-responding intracellular structures and processes. To enable real-time imaging and investigation of these phenomena, a microchamber with integral electrodes and optical path for observing individual cells exposed to ultrashort electric pulses was designed and fabricated utilizing photolithographic and microelectronic methods. SU-8 photoresist was patterned to form straight sidewalls from 10 to 30 /spl mu/m in height, with gold film deposited on the top and sidewalls for conductive, nonreactive electrodes and a uniform electric field. Channel dimensions (10-30 /spl mu/m/spl times/100 /spl mu/m/spl times/12000 /spl mu/m) are suitable for observations of mammalian cells during nanosecond, megavolt-per-meter pulsed electric field exposure. Experimental studies utilizing the electrode microchamber include live-cell imaging of nanoelectropulse-induced intracellular calcium bursts and membrane phospholipid translocation.     

A functional for the input impedance of thin electric vibrator

A functional for the input impedance of electric vibrator is derived for the variation of the distribution of vibrator current. Using the approximation of sinusoidal current distribution, a simple approximate formula for the input impedance of a symmetric electric vibrator is derived. The active and reactive components of impedance are calculated versus the ratio of the length of vibrator arm to wavelength for three values of the vibrator diameter.     

染料敏化太阳能电池电极界面特性的电化学阻抗谱研究

电化学阻抗谱(EIS)是研究染料敏化太阳能电池内部电子和离子输运过程的重要技术之一,测试了不同的聚乙二醇4000(PEG)添加量、不同静置时间和不同光照强度的DSSCs的EIS,利用等效电路对阻抗谱的各个部分进行拟合,讨论了TiO2/电解质界面的复合反应速率常数、电子寿命、扩散系数、电子传递电阻和电子在薄膜中的传输电阻等参数,探讨了实验条件对电池电极的界面特性的影响。     

Selected area and in-depth auger analysis of thin films

Auger electron spectroscopy (AES) has rapidly developed from a purely research oriented technique into an extremely versatile analytical method with unique features for qualitative and quantitative materials characterization. The low escape depth (5–10 Å) of the emitted Auger electrons makes it ideal for surface analysis and for depth profile impurity distribution analysis when combined with in situ ion sputtering.Both surface and depth profile analysis can be accomplished on a selected area by the use of optical or primary electron beam scanning techniques. Results are presented which illustrate the significance of the analytical capabilities of AES in the qualitative and quantitative analysis of thin film electronic materials used in the fabrication of precision thin film resistors, capacitors and conductors.     

Application of femtosecond laser ablation time-of-flight mass spectrometry to in-depth multilayer analysis

A femtosecond laser system was used in combination with a time-of-flight mass spectrometer (TOF-MS) for in-depth profiling of semiconductor and metal samples. The semiconductor sample was a Co-implanted (10(17) ions/cm3) silicon wafer that had been carefully characterized by other established techniques. The total depth of the shallow implanted layer was 150 nm. As a second sample, a thin film metal standard had been used (NIST 2135c). This standard consisted of a silicon wafer with nine alternating Cr and Ni layers, each having a thickness of 56 and 57 nm, respectively. An orthogonal TOF-MS setup was implemented. This configuration was optimized until a sufficient mass resolution of 300 (m/delta m) and sensitivity was achieved. The experiments revealed that femtosecond-laser ablation TOF-MS is capable of resolving the depth profiles of these demanding samples. The poor precision of the measurements is discussed, and it is shown that this is due to pulse-to-pulse stability of the current laser system. Femtosecond-laser ablation TOF-MS is shown to be a promising technique for rapid in-depth profiling with a good lateral resolution of various multilayer thin film samples.     

Nanoflow low pressure high peak capacity single dimension LC-MS/MS platform for high-throughput, in-depth analysis of mammalian proteomes

The use of narrow bore LC capillaries operated at ultralow flow rates coupled with mass spectrometry provides a desirable convergence of figures of merit to support high-performance LC-MS/MS analysis. This configuration provides a viable means to achieve in-depth protein sequence coverage while maintaining a high rate of data production. Here we explore potential performance improvements afforded by use of 25 μm × 100 cm columns fabricated with 5 μm diameter reversed phase particles and integrated electrospray emitter tips. These columns achieve a separation peak capacity of ≈750 in a 600-min gradient, with average chromatographic peak widths of less than 1 min. At room temperature, a pressure drop of only ≈1500 psi is sufficient to maintain an effluent flow rate of ≤10 nL/min. Using mouse embryonic stem cells as a model for complex mammalian proteomes, we reproducibly identify over 4000 proteins across duplicate 600 min LC-MS/MS analyses.