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Fractal analysis has been widely used to determine the complexity of irregular shapes of various natural objects including biological systems. Here we report an investigation into the nature of the cell boundary nanostructure (less than 200 nm in thickness) in an aqueous environment using atomic force microscopy. The box-counting method revealed the fractal nature of detailed contours of cells cultured on a solid substratum. The fractal dimensions (Df) of individual cells of the human epithelial cell line MCF10A converged on a narrow range (Df = 1.352 ± 0.044) despite their morphological diversity. Treatment with cytochalasin D, an inhibitor of actin polymerization, was shown to decrease both the ruggedness and the Df of cell boundaries. These findings suggest that the Df value is a useful parameter for describing the complexity of cellular ultrastructure dependent on the actin cytoskeleton.

Although retinoic acid (RA) is well known to inhibit the differentiation of 3T3-L1 cells into adipocytes both in vivo and in vitro, its molecular mechanism is not fully understood. In this report, we investigate the inhibitory mechanism of adipocyte differentiation by RA in 3T3-L1 cells. Because both RA and Wnt are known to inhibit adipogenesis at a common step involving the inhibition of PPAR-γ expression, we focused on the crosstalk between these two signaling pathways. We found that RA treatment resulted in a dramatic inhibition of adipogenesis, especially at an early phase of differentiation, and led to increased β-catenin protein expression. Moreover, RA enhances the transcriptional activity of β-catenin as well as Wnt gene expression during adipogenesis. Taken together, the present study demonstrated that Wnt/β-catenin signaling may be associated with the RA-induced suppression of adipogenesis and may cooperatively inhibit adipocyte differentiation.

Prohibitin (PHB) is a multifunctional protein conserved in eukaryotic systems and shows various expression levels in tumor cells. However, regulation of PHB is not clearly understood. Here, we focused on the regulation of PHB expression by Wnt signaling, one of dominant regulatory signals in various leukemic cells. High mRNA levels of PHB were found in half of clinical leukemia samples. PHB expression was increased by inhibition of the MAPK pathway and decreased by activation of EGF signal. Although cell proliferating signals downregulated the transcription of PHB, treatment with lithium chloride, an analog of the Wnt signal, induced PHB level in various cell types. We identified the TCF-4/LEF-1 binding motif, CATCTG, in the promoter region of PHB by site-directed mutagenesis and ChIP assay. This β-catenin-mediated activation of PHB expression was independent of c‑MYC activation, a product of Wnt signaling. These data indicate that PHB is a direct target of β-catenin and the increased level of PHB in leukemia can be regulated by Wnt signaling.

The vibrational spectral differences of normal and lung cancer cells were studied for the development of effective cancer cell screening by means of attenuated total reflection infrared spectroscopy. The phosphate monoester symmetric stretching nu(s)(PO3(2-)) band intensity at ~970 cm(-1) and the phosphodiester symmetric stretching nu(s)(PO2(-)) band intensity at approximately 1,085 cm(-1) in nucleic acids and phospholipids appeared to be significantly strengthened in lung cancer cells with respect to the other vibrational bands compared to normal cells. This finding suggests that more extensive phosphorylation occur in cancer cells. These results demonstrate that lung cancer cells may be prescreened using infrared spectroscopy tools.

A methodology for modeling and simulating the electro-thermal behavior of an enclosed electronic package is presented and validated. The electro-thermal model is constructed using system dynamics. The system model, in which the electrical and the thermal domain are combined, is presented. The developed model describes the dynamic thermal behavior system that was an electronic device in the test enclosure. An effective way to identify the thermal parameters of the system, especially the thermal contact resistance, is suggested. In detail, the new method for thermal resistance identification is based on the temperature difference behavior between the component and the air temperature inside the enclosure. Based on the proposed model, either the variation of the heat source or the ambient temperature can be estimated. Simulated results were in good agreement with the measured temperature in the transient state accompanying with the variation of the environment.

A valveless micropump, actuated by a PZT disk bonded to a glass plate, can generate positive flow. In order to estimate flow characteristics of micropumps, it is necessary to theoretically analyze the radial expansion (more specifically, the equivalent moment) of the PZT disk according to the voltage input. Using the equivalent moment, deflection equations are derived for the tri-layer disk (PZT, epoxy bonder and glass plate) and are confirmed to match well with experiments. The flow rate of the valveless micropump is also theoretically and experimentally investigated in terms of input voltage and oscillation frequency. The flow increased at a rate of 0.1 μL/min/V, and the maximum flow rate was obtained at the driving frequency of around 225 Hz.

A novel micropump with fixed-geometry valves was designed and tested with a leakage barrier to reduce leakage flow. Conventional micropumps with fixed-geometry valves have achieved net positive fluid flow from different fluid resistances in diffuser/nozzle channels. However, those micropumps are susceptible to leakage flow even at low pressure differences between the inlet and the outlet because the channels remain normally open state when the pumps are not in operation. Therefore, a leakage barrier in the chamber was designed to reduce leakage flow without interfering with the net positive fluid flow of the diffuser/nozzle channels. The diffuser/nozzle channels, the chamber and the leakage barrier were fabricated on the silicon substrate by KOH etching and the silicon substrate was anodically bonded with a Pyrex glass plate. A PZT disk was bonded on the glass plate by epoxy and was actuated to oscillate the glass diaphragm for flow generation. When the micropump is not operating, the leakage barrier removes most of the gap between the glass plate and the bottom of the chamber. It was experimentally confirmed that the leakage barrier reduced the leakage flow by 96% compared to the case of no leakage barrier at a pressure difference of −400 Pa. Moreover, by applying the holding dc voltage to the PZT disk, a smaller gap can be obtained reducing the leakage flow further down to 0.043 µL min−1 at a holding dc voltage of 100 V. The maximum flow rate was 3.9 µL min−1 at a peak-to-peak driving voltage of 150 V at 20 Hz with a maximum back pressure of around 800 Pa. The approximate device size was 18 × 25 mm2.

A piezoresistive silicon pressure sensor with bipolar on-chip signal conditioning circuits permits offset voltage, full scale span and temperature coefficient of offset voltage and full scale span to be calibrated from a trimming ion-implanted resistors. The ion-implanted resistors with temperature coefficient of 1700 ppm/°C or 4700 ppm/°C were fabricated by the same process as that used for the base and piezoresistors. The fabricated sensor exhibits a sensitivity of 40.5 mV/kPa and temperature coefficient of 46 ppm/°C at the temperature range of −10 to 70°C.

A new micro catalytic gas sensor for detecting inflammable gases was fabricated on a Si wafer by thin film deposition and Si anisotropic etching. The size of the fabricated sensor was 3.25×2.20 mm 2 . The sensor was designed to consist of a catalyst with high surface area and a heater with high temperature coefficient of resistance (TCR) in order to acquire high sensitivity to gases of interest. The TCR of the sensor was found to be 3844 ppm °C −1 . Sensitivities to methane and butane gases were 2.2 mV 1000 ppm −1 and 8.9 mV 1000 ppm −1 , respectively. The optimum applied Wheatstone bridge power was varied in the range from 350 to 400 mW, being much smaller than those of commercial pellistors. It was also found that sensitivities to methane and butane gas were decreased by increasing humidity.

In this paper, we demonstrate a new single-cell optoporation and transfection technique using a femtosecond Gaussian laser beam and optical tweezers. Tightly focused near-infrared (NIR) femtosecond laser pulse was employed to transiently perforate the cellular membrane at a single point in MCF-7 cancer cells. A distinct technique was developed by trapping the microparticle using optical tweezers to focus the femtosecond laser precisely on the cell membrane to puncture it. Subsequently, an external gene was introduced in the cell by trapping and inserting the same plasmid-coated microparticle into the optoporated cell using optical tweezers. Various experimental parameters such as femtosecond laser exposure power, exposure time, puncture hole size, exact focusing of the femtosecond laser on the cell membrane, and cell healing time were closely analyzed to create the optimal conditions for cell viability. Following the insertion of plasmid-coated microparticles in the cell, the targeted cells exhibited green fluorescent protein (GFP) under the fluorescent microscope, hence confirming successful transfection into the cell. This new optoporation and transfection technique maximizes the level of selectivity and control over the targeted cell, and this may be a breakthrough method through which to induce controllable genetic changes in the cell. (C) 2013 Optical Society of America

A photonic crystal fiber (PCF) based dual-color nonlinear microscope that combines coherent anti-Stokes Raman scattering (CARS) microscopy and two-photon excitation fluorescence (TPEF) microscopy was developed and applied to imaging of polystyrene beads, lily pollens, and live breast cancer cells using a femtosecond laser.

In this paper, frequency response (dynamic compression and recovery) is suggested as a new physical marker to differentiate between breast cancer cells (MCF7) and normal cells (MCF10A). A single cell is placed on the laminated piezoelectric actuator and a piezoresistive microcantilever is placed on the upper surface of the cell at a specified preload displacement (or an equivalent force). The piezoelectric actuator excites the single cell in a sinusoidal fashion and its dynamic deformation is then evaluated from the displacement converted by measuring the voltage output through a piezoresistor in the microcantilever. The microcantilever has a flat contact surface with no sharp tip, making it possible to measure the overall properties of the cell rather than the local properties. These results indicate that the MCF7 cells are more deformable in quasi-static conditions compared with MCF10A cells, consistent with known characteristics. Under conditions of high frequency of over 50 Hz at a 1 μm preload displacement, 1 Hz at a 2 μm preload displacement, and all frequency ranges tested at a 3 μm preload displacement, MCF7 cells showed smaller deformation than MCF10A cells. MCF7 cells have higher absorption than MCF10A cells such that MCF7 cells appear to have higher deformability according to increasing frequency. Moreover, larger preload and higher frequencies are shown to enhance the differences in cell deformability between the MCF7 cells and MCF10A cells, which can be used as a physical marker for differentiating between MCF10A cells and MCF7 cells, even for high-speed screening devices.

A novel and simplest polarization microscope by single polarization modulation method to visualize cytoskeletal structure in bio-cells have been developed. The polarization microscope visualizes cytoskeletal structure based on birefringence characteristics of cells. In the polarization microscope, a series of intensity images according to single modulation of rotating linear polarizer were obtained to visualize cytoskeletal structure. Phase retardation and principal axis orientation were calculated by analytic data processing from the acquired intensity images. Phase retardation and principal axis orientation of breast cancer cells, MCF 7 and MDA MB 231 were measured and visualized as their birefringence characteristics by the polarization microscope. Phase retardation sensitivity of the polarization microscope system also was measured in this paper.

A micro-plasma generator for the detection of heavy metals in the water has been fabricated and evaluated. As for the new type of a plasma source, the micro-plasma generator based on water electrode has been proposed. This type of device features simple device structure that doesnpsilat require nebulizer for water samples. Water sample is isolated from a metal electrode by glass substrate, eliminating unexpected side effects such as electrophoresis and electrochemical reaction between a metal electrode and ions in water. This configuration prevents metal electrodes from erosion, which will lead to high detection reliability for water contaminants. The lead (Pb) in nitric acid solution (0.1 M) was detected using the fabricated micro-plasma generator and a fiber optic spectrometer. Two atomic emission lines of the lead (at 368 nm, 405 nm) were clearly observed. 10 ppm of Pb ions in nitric acid solution was measured using the proposed micro-plasma generator based on water electrode.

Fourier-transform infrared (FT-IR) spectroscopy, a non-destructive, label-free, and high sensitive and specific analytical method is a vibrational technique that gives information on the chemical composition of a sample of biological specimens. It is also a powerful approach to detect changes in the protein composition and structure of intact living cells. To determine a cellular function or change of biological materials (cells, tissues, microorganisms, etc.), we have studied the amide I band of protein by using both FT-IR spectra based on attenuated total reflection (ATR) and their second derivative spectra. we have performed the breast cancer cells and the pathogenic microorganisms exposed to anticancer and antibiotic drugs, respectively. Based on these studies, we found that the potential to use this technique for the detection and quantification of the protein secondary structure components of biological specimens under drug application

A coherent anti-Stokes Raman scattering (CARS) microspectroscopy imaging system was developed using a femtosecond laser and a photonic crystal fiber (PCF). We separated resonant and non-resonant CARS signals in the time domain by the chirp of the PCF, and applied this system to compare live human breast normal and cancer cells. The CARS image and spectrum at C–H stretch vibration in lipid droplets could subsequently be used to differentiate cancer cells from normal cells, thereby confirming the potential of the CARS microspectroscopy imaging system as a diagnostic tool that allows the high-sensitivity, high-resolution, and fast detection of breast cancer.

In this paper, we describe a cantilever-type electrode (CE) array-based high-throughput sorting platform, which is a tool used to separate microparticles using gravitation and negative dielectrophoretic (n-DEP) force. This platform consists of meso-size channels and a CE array, which is designed to separate a large number of target particles by differences in their dielectric material properties (DMP) and the weight of the particles. We employ a two-step separation process, with sedimentation as the first step and n-DEP as the second step. In order to differentiate the weight and the DMP of each particle, we employ the sedimentation phenomena in a vertical channel and the CE-based n-DEP in an inclined channel. By using three kinds of polystyrene beads with diameters of 10, 25 and 50 µm, the optimal population (107 beads ml−1) of particles and the appropriate length (25 mm) of the vertical channel for high performance were determined experimentally. Conclusively, by combining sedimentation and n-DEP schemes, we achieve 74.5, 94.7 and 100% separation efficiency for sorting microparticles with a diameter of 10, 25 and 50 µm, respectively.

We propose a new, simple theory-based, accurate polarization microscope for birefringence imaging of cytoskeletal structures of biological cells. The new theory lets us calculate very easily the phase retardation and the orientation of the principal axis of a particular area of a biological living cell in media by simply measuring the intensity variation of a pixel of a CCD camera while rotating a single polarizer. Just from the measured intensity maxima and minima, the amount of phase retardation delta between the fast and the slow axis of the sample area is obtained with an accuracy of 5.010+/-0.798x10(-3) rad. The orientation of the principal axis is calculated from the angle of the polarizer for the intensity maximum. We have compared our microscopes with two previously reported polarization microscopes for birefringence imaging of cytoskeletal structures and demonstrated the utility of our microscope with the phase retardation and orientation images of weakly invasive MCF7 and highly invasive MDA MB 231 human breast cancer cells as an example.

Time‐resolved scanning acoustic microscopy (SAM) equipped with time‐resolved signal analysis offers unique possibilities for studying the mechanical properties of cells in vitro. The method is nondestructive and noninvasive on a cellular level, which enables real‐time measurements on living cells. The ultrasonic attenuation coefficients and sound speeds of MCF 10A normal breast cells and MCF 7 weakly invasive cancerous cells were measured and compared using a time‐resolved SAM operating at 0.86 GHz center frequency and with 5 ns pulse duration. The attenuation coefficients of MCF 10A and MCF 7 cells were found to be 126 ± 67 and 443 ± 129 dB, respectively, while the sound speeds of the same cells were 1583 ± 24 and 1736 ± 61 m/s, respectively. Both the attenuation coefficient and sound speed of MCF 7 cells were higher than those of MCF 10A cells. In particular, the difference in the attenuation coefficients was pronounced. The relative differences in sound speed and attenuation coefficient could be utilized to differentiate normal cells from cancerous cells. [Weiss et al. IEEE Trans. Ultrasonics, Ferroeletrics, and Freq. Contrl. 54, 2257–2271 (2007)] [Work supported by Korean Science and Engineering Foundation.]

A thin film micro heat-flux sensor using thermopile, which can measure the heat flow, was fabricated by a complementary-metal-oxide-semiconductor-compatible process. The combination of a ten-junction polysilicon and aluminum thermoelectric sensor with an ultralow noise preamplifier and low pass Butterworth filter has enabled the resolution of 3.4μW power and shows the sensitivity of 2.43mV∕μW. In order to estimate the heat generation of samples from the output measurement of a micro heat-flux sensor, a methodology for modeling and simulating electro-thermal behavior in a micro heat-flux sensor with integrated electronic circuit is presented and validated. The electro-thermal model was constructed by using system dynamics, particularly the bond graph methodology. The electro-thermal system model, where the thermal domain and the electrical domain are coupled, expresses the behavior that the heat generation of samples converts thermal input to electrical output through the system model. The proposed electro...

A thermally reflowed glass microlens array was fabricated on a Si substrate. Glass lenses are more durable and scratch-resistant than plastic lenses made by the same, simple thermal reflow process. The microlens was designed using the ray tracing technique and optimized by controlling the nominal diameter and height of glass cylinders. The glass cylinders were formed by wet etching a glass plate in a HF (49%) solution and reflowed to form a semi-spherical lens shape at 850 °C (glass transition temperature Tg = 820 °C) for 20 min in a furnace. Then, the Si substrate was etched in a TMAH (5%) solution to make rectangular through-holes underneath the microlens array for high optical transmission. The profile of the fabricated microlens was measured with a confocal microscope, and its optical characteristics (lens size, beam radius and focal length) were evaluated with a 633 nm laser diode beam. The experimental beam waist (minimum beam radius) at the focal point of 1000 µm was 8 µm, which was in good agreement with a calculated value. The results show that the microlens array can be used in a broad wavelength range from UV to the IR region.

A microplasma was generated in a sealed microfluidic glass chip for the application of the miniaturized chemical detection system, especially for water contaminants. The behavior of a microbubble as well as a microplasma was observed using a 1% NaCl solution with no metal contact in a sealed glass microchannel. A microplasma formed by water contents excluding air or inert gas showed clear emission spectrum in UV, visible, and near IR range. The detection of lead was demonstrated by measuring the intensity of the Pb emission line (at 406nm) with respect to the concentration.

The damage induced by CHF3+C2F6 plasma etching on GaAs(100) was studied. We exposed GaAs(100) surfaces to various etching conditions and monitored sheet resistance, carrier concentration, and Hall mobility. Significant losses of Hall mobility and carrier concentration, and an increase in sheet resistance were observed only when CHF3 was introduced into the plasma. After annealing at 400 °C for 55 min, sheet resistance was restored nearly to the value obtained before the plasma exposure. We believe that the damage was produced by hydrogen atoms or ions dissociated from CHF3 in the plasma. In contrast to the general belief that plasma etching induces the least damage among dry etching techniques [such as reactive ion etching (RIE) and reactive ion beam etching (RIBE)], our plasma etching damage was comparable to previously reported RIE or RIBE damage.