Micro and Nanosystems - Volume 6, Issue 2, 2014

Recent outbreak of Ebola virus that causes hemorrhagic fever shows that the quick detection of this virus in a resource-poor environment is extremely important for controlling the epidemic. Existing methods based on enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR) or isolation of the virus require expensive equipment, skilled personnel and the highest biosafety level. We highlight here a recent demonstration of low-cost low-maintenance synthetic biology for detection of Ebola virus based on paper as a device substrate.

This manuscript presents a portable and low cost electronic system for specific point-of-use dielectrophoresis applications. The system is composed of two main modules: a) a multiphase generator based on a Class E amplifier, which provides 4 sinusoidal signals (0°, 90°, 180°, 270°) at 1 MHz with variable output voltage up to 10 Vpp (Vm) and an output driving current of 1 A; and b) a dielectrophoresis-based microfluidic chip containing two interdigitated electrodes. The system has been validated by concentrating Escherichia coli (E. coli) at 1 MHz while applying a continuous flow of 5 µL/min. The device functionalities were verified under different conditions, achieving an 83% trapping efficiency when counter-phased signals are used.

Electric Fields are increasingly used to manipulate bacteria. However, there is no systematic and definitive study on how the different electric parameters change bacteria viability. Here we present a study on the effects of electric field intensity and temperature to bacterial cultures. Escherichia coli colonies have been exposed to different electric field intensities at 1MHz during 5 minutes by means of a microfluidic device specially designed for the experiment. From the analysis of the results it is possible to see that Escherichia coli survival rate diminishes when applying field intensities as low as 220V during 5 minutes. Death rates also increase when stronger fields are applied. However, viability of survived bacteria is maintained. Additionally, temperature shows a synergistic effect with voltage. When temperature was increased, results showed a stronger sensitivity of cells to the electric field. Moreover, the expression patterns of Outer Membrane Protein A and Ribosomal Proteins differ in control and treated samples, suggesting changes in bacterial metabolism and structure.

A prototype membrane aerated polydimethylsiloxane (PDMS) microbioreactor integrated with a photodiode detector was developed for monitoring intracellular green fluorescent protein ultraviolet (GFPUV) expression in Escherichia coli. The developed system is compact, simple and inexpensive and ideal for economical on chip detection of fluorophores in aqueous solution and intracellular GFPUV expression. The detection limit for cell free GFPUV was found to be 4.8 x 10-8 M. Intracellular GFPUV expression in E. coli cells was monitored for 12 h and the lowest detectable signal was recorded from a cell concentration of 2.7 x 107cells/mL with signal to noise ratio (SNR) value of 3. The performance of the photodiode detector was benchmarked with a CCD spectrophotometer and results showed favorable comparison. A miniaturized microbioreactor for monitoring intracellular dynamics in real time is demonstrated.

Collagen due to its filamentous shape and unique properties is a very promising molecule for the development of nanostructures, scaffolds, cell culture platforms and nanobiomaterials. Furthermore, collagen thin films are of great interest as they can cover non-biological surfaces in medical devices and sensors so as to offer them biocompatibility. Since surface nanotopography and mechanical properties can influence cell-biomaterial interactions it is of crucial importance to nano-characterize collagen surface and heterogeneity. Nano-characterization can be performed with Atomic Force Microscopy (AFM), which operates in a variety of modes/techniques and can offer a wide range of information, from topography to mechanical properties. In this paper it was sought to gain insights of structural and mechanical heterogeneity of collagen fibers in thin films by combining AFM multimode-imaging, including phase imaging, with quantitative measurements through nanoindentation. The results demonstrated that the overlap-gap regions on collagen fibers (D-periodicity) yield a significant phase contrast, due to different mechanical properties. In addition, phase contrast was also demonstrated in collagen ‘kinks’, which provides evidence that collagen fiber shell and core possess different properties. The mechanical heterogeneity of the collagen fibers in the kink areas was confirmed by AFM-nanoindentation and the obtained quantitative measurements. In addition, AFM multimode imaging performance was demonstrated on fibroblasts cultured on collagen thin films. The correlation between the heterogeneous structure and the mechanical properties of collagen fibers in thin films will enable the design and development of biomaterials and tissue scaffolds with improved properties.

The C-doped ZnO nanoparticles were synthesized by sol-gel method using different amount of propylene glycol as a complexing agent. The propylene glycol led to the doping of C into the nanoparticles, and the C content in the nanoparticles increased as increasing the amount of propylene glycol. The nanoparticles showed excellent photocatalytic activity in photodegradation of malachite green dye in water. The C-doping expanded the light absorption of the nanoparticles to long wavelength and so speeded up the photodegradation of thye dye. Significantly, the nanoparticles also can completely decolorize the malachite green within a short period in the present of hydrogen peroxide, showing remarkable Fenton-like photocatalytic activity. An optimal H2O2 dosage was observed. The Fenton-like reaction was more faster as increasing the C content and decreasing the average particle size of the ZnO nanoparticles. The quasi-kinetic rate constants of the photocatalysis systems are in the range of ~0.0462–0.0700 min-1 and increase to ~0.112–1.498 min-1 by synthetically using H2O2.

The aim and objective of the present work was to prepare and develop hydrochlorothiazide (HCTZ) nanoparticles for quick and complete release by nanonization technique to overcome the poor water solubility and bioavailability problems. The poor solubility of many drugs along with a slow dissolution rate is a major research and industrial problems for pharmaceutical scientists and industries who are included in pill disclosure and medication improvement. It has been accounted for that something like 40% of the mixes are defectively water dissolvable or basically insoluble in water. HCTZ nanoparticles were prepared by solvent evaporation method under ultra-sonication process. Prepared nanoparticles were evaluated for the yield, drug loading and entrapment efficiency studies. HCTZ nanoparticles were also characterized for drug and polymer interaction by using FT-IR and DSC. Morphological characteristics of the formulation were studied by particle size analysis and surface charge, XRD, and FE-SEM. Additionally, in vitro drug dissolution study and ex vivo drug diffusion study were performed. All the characterization studies together revealed that the ideal properties of HCTZ nanoparticles. From the study, we can conclude that the solvent evaporation method under ultra-sonication is a promising method to produce small, uniform and stable HCTZ nanoparticles.

For lab-on-a-chip applications the defined transport of fluids is mandatory. On-chip metering and aliquoting are challenging and usually achieved with complicated systems so far. This paper describes an integrated electrochemical pump (ECP) and dosing system benefitting from phaseguide techniques for pumping defined batches of biological liquids. This innovative concept combines electrochemical actuation principles with concepts for passive valving and metering, for liquid handling methods and for contamination free transport of various media between microfluidic chambers. We achieve high flexibility, reproducibility, reliability and accuracy without using membranes. The electrolysis actuation and metering principle are implemented in a microfluidic system in a simple and robust way resulting in constant flow rates tested between 7 µl/min and 60 µl/min. Two AA batteries are sufficient to supply the constant low power consumption between 2.7 mW to 11.2 mW of the pump. Microfluidic problems during the filling and emptying of micro-chambers and controlled metering are solved by adaptation of the phaseguide technology for liquid control. Euglena gracilis is pumped in growth medium as proof of concept for pumping cell cultures. In order to simulate viscous biological solutions, pumped liquids also involved glycerine solutions. Furthermore, it is demonstrated that DNA solutions can be pumped without observable loss in concentration and without heating.

Pure and doped Fe2S3 films with n- and p-type electrical conductions were successfully deposited using chemical bath deposition at room temperature by controlling S/Fe molar ratio in the bath solution and doping Cu+ and Sn4+ cation, respectively. The films were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectrophotometry, and electrical resistance measurement. The pure and Cu+-doped Fe2S3 films with the S/Fe3/2 were deposited. Meantime, the pure and Sn4+-doped Fe2S3 films with the S/Fe3/2 were also deposited. The films had the average transmittances of ~20.1– 30.1 % in the wavelength range of 270–800 nm, the direct band gaps ~1.85– 2.42 eV, and the indirect band gaps of ~0.5–1.2 eV. The film with the S/Fe3/2 showed lower average transmittances, wider band gaps, and p-type conductivity, while the films with S/Fe3/2 showed higher average transmittances, narrower band gaps, and n-type conductivity. The Cu+ and Sn4+ dopings obviously increased the bandgap and transmittance of the films and decreased the resistances of the p-type and n-type films, respectively. The refractive index, extinction coefficient, optical conductivity, dielectric constant of the films were calculated with the transmittance and reflectance spectra. Excellent optical and electric properties indicate that the Fe2S3 films is new type of solar energy materials.

Platinum group metals represent a class of anthropogenic pollutants generated as a byproduct of their use in automobile catalytic converters. We prepared palladium nanoparticles (Pd-NPs, about 6 nm) similar to those emitted in auto exhaust, and examined their behavior in different liquids using dynamic light scattering and transmission electron microscopy (TEM). We found that serum-containing DMEM medium or conditioned DMEM provides good dispersion and stability for Pd-NPs at pH 7.2–7.4. We then incubated primary mouse macrophages and epithelial MDCK cells with Pd-NPs for 10 and 30 min, 3, 5 and 24 h, and sampled for TEM. Pd-NPs penetrated into MDCK cells by crossing the plasma membrane and were located in the cytoplasm, organelles and preferentially in the nucleus. The macrophages actively phagocytosed clusters of Pd-NPs, which were observed inside the membrane-bound structures but were not found in the cytoplasm and nucleus. Macrophage phagocytosis could be efficient in the lungs of living organisms, where they move across the surface of the respiratory epithelium and collect inhaled pollutants. Our study showed harmful effect of Pd-NPs on epithelial cells and the possibility of this effect being ameliorated by macrophages, which are resistant to penetration by Pd-NPs and sequestered them in phagolysosomes.