Biomedical subjects

Po Ki Yuen

Publications and source records attributed to Po Ki Yuen.

6 recordsLinked to original sources

PubMed2005

Characteristics of dynamic mass redistribution of epidermal growth factor receptor signaling in living cells measured with label-free optical biosensors.

This paper reported the identification of a novel optical signature for epidermal growth factor (EGF) receptor signaling in human epidermoid carcinoma A431 cells mediated by EGF. The optical signature was based on dynamic mass redistribution (DMR) in living cells triggered by EGFR activation, as monitored in real time with resonant waveguide grating biosensors. Analysis of the modulation of the EGF-induced DMR signals by a variety of known modulators provided links of various targets to distinct steps in the cellular responses. Results showed that the dynamic mass redistribution in quiescent A431 cells mediated by EGF required EGFR tyrosine kinase activity, actin polymerization, and dynamin and mainly proceeded through MEK. The DMR signals obtained serve as integrated signatures for interaction networks in the EGFR signaling.

Animals↗

PubMed2005

Self-referencing a single waveguide grating sensor in a micron-sized deep flow chamber for label-free biomolecular binding assays.

In order to allow the design of increasingly sensitive label-free biosensors, compensation of environmental fluctuations is emerging as the dominant hurdle. The system and technique presented here utilize a unique combination of microfluidics, optical instrumentation, and image processing to provide a reference signal for each label-free biomolecular binding assay. Moreover, this reference signal is generated from the same sensor used to detect the biomolecular binding events. In this manner, the reference signal and the binding signal share nearly all common-mode noise sources (temperature, pressure, vibration, etc.) and their subtraction leaves the purest binding signal possible. Computational fluid dynamic simulations have been used to validate the flow behavior and thermal characteristics of the fluids inside the sensing region. This system has been demonstrated in simple bulk refractive index tests, as well as small molecule (biotin/streptavidin) binding experiments. The ability to perform not only simple binding but also control experiments has been discussed, indicating the wide applicability of the technique.

Biotin↗

PubMed2003

Microbarcode sorting device.

A novel and simple microfluidic device was developed for sorting 20 microm thick glass microbarcodes for imaging or scanning at the completion of a bead-based assay. Specifically, the microbarcodes are dried and kept from stacking on top of one another such that a monolayer of microbarcodes is created and the microbarcodes lay flat on a surface. The microbarcode sorting device consists of a reservoir, a sorting region, and a network of microchannels. With minimal microbarcodes loss, a monolayer of microbarcodes is created and trapped inside the sorting region for conveniently imaging or scanning. The device can also be used for any geometrical shaped beads with a range of thicknesses and can be adapted to a 96-well plate format for high throughput analysis.

Animals↗

PubMed2003

Rare earth-doped glass microbarcodes.

The development of ultraminiaturized identification tags has applications in fields ranging from advanced biotechnology to security. This paper describes micrometer-sized glass barcodes containing a pattern of different fluorescent materials that are easily identified by using a UV lamp and an optical microscope. A model DNA hybridization assay using these "microbarcodes" is described. Rare earth-doped glasses were chosen because of their narrow emission bands, high quantum efficiencies, noninterference with common fluorescent labels, and inertness to most organic and aqueous solvents. These properties and the large number (>1 million) of possible combinations of these microbarcodes make them attractive for use in multiplexed bioassays and general encoding.

Biotechnology↗

PubMed2002

Microfluidic devices for fluidic circulation and mixing improve hybridization signal intensity on DNA arrays.

Reactions of biomolecules with surface mounted materials on microscope slides are often limited by slow diffusion kinetics, especially in low volumes where diffusion is the only means of mixing. This is a particular problem for reactions where only small amounts of analyte are available and the required reaction volume limits the analyte concentration. A low volume microfluidic device consisting of two interconnected 9 mm x 37.5 mm reaction chambers was developed to allow mixing and closed loop fluidic circulation over most of the surface of a microscope slide. Fluid samples are moved from one reaction chamber to the other by the rotation of a magnetic stirring bar that is driven by a standard magnetic stirrer. We demonstrate that circulation and mixing of different reagents can be efficiently accomplished by this closed loop device with solutions varying in viscosity from 1 to 16.2 centipoise. We also show by example of a microarray hybridization that the reaction efficiency can be enhanced 2-5 fold through fluid mixing under conditions where diffusion is rate limiting. For comparison, similar results were achieved with a disposable commercial device that covers only half of the reaction area of the closed loop device.

DNA↗

PubMed1998

Controlling chaotic convection using neural nets-theory and experiments.

An exploratory study is conducted to assess the feasibility of using neural networks to control flow patterns and to evaluate the performance of these controllers. Neural networks were used to control (suppress) chaotic convection both in experiments and in a theoretical model of a thermal convection loop. It is demonstrated that the neural network controller can successfully cause the flow to behave in a desired way. The performance of the neural network controllers was compared with that of previously used conventional linear proportional controllers.

Journal Article↗