Chitosan-silica Complex Membranes from Sulfonic Acid Functionalized Silica Nanoparticles for Pervaporation Dehydration of Ethanol-water Solutions

Biomacromolecules. Jan-Feb, 2005  |  Pubmed ID: 15638541

Nanosized silica particles with sulfonic acid groups (ST-GPE-S) were utilized as a cross-linker for chitosan to form a chitosan-silica complex membranes, which were applied to pervaporation dehydration of ethanol-water solutions. ST-GPE-S was obtained from reacting nanoscale silica particles with glycidyl phenyl ether, and subsequent sulfonation onto the attached phenyl groups. The chemical structure of the functionalized silica was characterized with FTIR, (1)H NMR, and energy-dispersive X-ray. Homogeneous dispersion of the silica particles in chitosan was observed with electronic microscopies, and the membranes obtained were considered as nanocomposites. The silica nanoparticles in the membranes served as spacers for polymer chains to provide extra space for water permeation, so as to bring high permeation rates to the complex membranes. With addition of 5 parts per hundred of functionalized silica into chitosan, the resulting membrane exhibited a separation factor of 919 and permeation flux of 410 g/(m(2) h) in pervaporation dehydration of 90 wt % ethanol aqueous solution at 70 degrees C.

Simulation and Experimentation of a Microfluidic Device Based on Electrowetting on Dielectric

Biomedical Microdevices. Dec, 2007  |  Pubmed ID: 17520369

Electrowetting on dielectric (EWOD) moving fluid by surface tension effects offers some advantages, including simplicity of fabrication, control of minute volumes, rapid mixing, low cost and others. This work presents a numerical model using a commercial software, CFD-ACE+, and an EWOD system including a microfluidic device, a microprocessor, electric circuits, a LCD module, a keypad, a power supply and a power amplifier. The EWOD model based on a reduced form of the mass conservation and momentum equations is adopted to simulate the fluid dynamics of the droplets. The EWOD device consists of the 2 x 2 mm bottom electrodes (Au/Cr), a dielectric layer of 3,000 A nitride, 500 A Teflon and a piece of indium tin oxide (ITO)-coated glass as the top electrode. The complete EWOD phenomenon is elucidated by comparing simulation with the experimental data on droplet transportation, cutting and creation. In transportation testing, the speed of the droplet is 6 mm/s at 40 V(dc). In addition, the droplet division process takes 0.12 s at 60 V(dc) in the current case. Finally, a 347 nl droplet is successfully created from an on-chip reservoir at 60 V(dc).

Direct White Light Photoluminescent Nanoparticles with One Fluorophore

Nanotechnology. Jun, 2009  |  Pubmed ID: 19451678

Aggregation of Rhodamine B (RhB) fluorophore in confined nanoscale domains changes the photoluminescence behavior of RhB in core-shell silica/PGMA-RhB nanoparticles. Under an excitation at 365 nm, silica/PGMA-RhB nanoparticles exhibit a two-band emission of yellow and blue in a tetrahydrofuran (THF) solution, compared to the yellow emission of RhB in a THF solution. The yellow and blue emissions of silica/PGMA-RhB nanoparticles are of approximately equal intensity, and mix together to show white light emission from the core-shell nanoparticles. Removal of the silica core from the core-shell nanoparticles does not alter its photoluminescence behavior. Therefore, the white light emission of RhB in the nanoparticles originates from the aggregation of RhB molecules in a nanoscale domain. This finding provides a new and convenient approach to the preparation of white light photoluminescent materials.

Effect of Electrode Geometry on Performance of EWOD Device Driven by Battery-based System

Biomedical Microdevices. May, 2009  |  Pubmed ID: 19479379

This study develops a driving system for an electrowetting-on-dielectric (EWOD) device comprising a 9 V battery, an ATmega8535 microprocessor, a DC/DC converter, two regulator ICs and a switch circuit. The driving system greatly improves the portability of the EWOD device and is capable of generating a square wave with voltages ranging from 50~100 V(pp) and frequencies in the range 1~5 kHz. A series of experimental and numerical investigations are performed to investigate the effect of the conducting electrode geometry on the droplet velocity in the EWOD device. Three different electrode configurations are considered, namely a linear array of square electrodes, a series of interdigitated electrodes having either two or three fingers, and a series of interdigitated electrodes having five or six fingers. The experimental results show that the corresponding droplet velocities are 7.25 mm/s, 8.17 mm/s and 7.82 mm/s, respectively. The simulation results indicate that the pressure difference induced within the droplets actuated by the square, interdigitated (2323) and interdigitated (5656) electrodes has a value of 15.5 N/m(2), 262 N/m(2) and 141.1 N/m(2), respectively. The corresponding droplet velocities are 33.8 mm/s, 72.7 mm/s and 64.5 mm/s, respectively. Overall, the experimental and numerical results indicate that the interdigitated (2323) electrode optimizes the transportation of the droplets in the EWOD device. The improved droplet velocity obtained using this particular electrode configuration is attributed to an increased length of the contact line between the droplet and the actuating electrode, which in turn increases the driving force.

Rhodamine B-anchored Silica Nanoparticles Displaying White-light Photoluminescence and Their Uses in Preparations of Photoluminescent Polymeric Films and Nanofibers

Journal of Colloid and Interface Science. Oct, 2010  |  Pubmed ID: 20599206

This work reports white-light photoluminescent (PL) silica nanoparticles and their applications of preparation of PL polymer films and nanofibers. Rhodamine B (RhB) physically adsorbs or chemically bonds to silica nanoparticle (SNP) surfaces, resulting in PL SNPs. The RhB-modified SNPs exhibit white-light PL emissions under an excitation at 365nm, which is different from the inherent yellow light emission of RhB. The SNPs with physically-adsorbed RhB show stimuli-responsive properties. In solutions, the RhB molecules which physically adsorb to SNPs release from SNPs, consequently turning the PL emission from white-light to yellow. On the other hand, the SNPs having covalently-bonded-RhB molecules are effective additives for preparation of white-light PL polymer composites. Both PL poly(methylmethacrylate) (PMMA) films (from casting process) and nanofibers (from electrospinning process) showing white-light PL emission have been prepared.

UV-induced Rhodamine B Aggregation into Nanoparticles Exhibiting Reversible Changes of Yellow- and White-light Photoluminescent Emissions

Chemistry (Weinheim an Der Bergstrasse, Germany). May, 2011  |  Pubmed ID: 21469232

Mesenchymal Stem Cells Promote Formation of Colorectal Tumors in Mice

Gastroenterology. Sep, 2011  |  Pubmed ID: 21699785

Tumor-initiating cells are a subset of tumor cells with the ability to form new tumors; however, they account for less than 0.001% of the cells in colorectal or other types of tumors. Mesenchymal stem cells (MSCs) integrate into the colorectal tumor stroma; we investigated their involvement in tumor initiation.

Robust Design of Biological Circuits: Evolutionary Systems Biology Approach

Journal of Biomedicine & Biotechnology. 2011  |  Pubmed ID: 22187523

Artificial gene circuits have been proposed to be embedded into microbial cells that function as switches, timers, oscillators, and the Boolean logic gates. Building more complex systems from these basic gene circuit components is one key advance for biologic circuit design and synthetic biology. However, the behavior of bioengineered gene circuits remains unstable and uncertain. In this study, a nonlinear stochastic system is proposed to model the biological systems with intrinsic parameter fluctuations and environmental molecular noise from the cellular context in the host cell. Based on evolutionary systems biology algorithm, the design parameters of target gene circuits can evolve to specific values in order to robustly track a desired biologic function in spite of intrinsic and environmental noise. The fitness function is selected to be inversely proportional to the tracking error so that the evolutionary biological circuit can achieve the optimal tracking mimicking the evolutionary process of a gene circuit. Finally, several design examples are given in silico with the Monte Carlo simulation to illustrate the design procedure and to confirm the robust performance of the proposed design method. The result shows that the designed gene circuits can robustly track desired behaviors with minimal errors even with nontrivial intrinsic and external noise.