Biomedical subjects

Shean-Jen Chen

Publications and source records attributed to Shean-Jen Chen.

8 recordsLinked to original sources

PubMed2006

Precise determination of the dielectric constant and thickness of a nanolayer by use of surface plasmon resonance sensing and multiexperiment linear data analysis.

Surface plasmon resonance (SPR) sensing and an enhanced data analysis technique are used to obtain precise predictions of the dielectric constant and thickness of a nanolayer. In the proposed approach, a modified analytical method is used to obtain initial estimates of the dielectric constants and thicknesses of the metal film and a nanolayer on the sensing surface of a SPR sensor. A multiexperiment data analysis approach based on a two-solvent SPR method is then employed to improve the initial estimates by suppressing the noise in the measurement data. The proposed two-stage approach is employed to determine the dielectric constant and thickness of a molecular imprinting polymer nanolayer. It is found that the results are in good agreement with those obtained with an ellipsometer and a high-resolution scanning electron microscope.

Journal Article↗

PubMed2006

Adaptive-optics system with liquid-crystal phase-shift interferometer.

We develop an adaptive-optics system based on a Mach-Zehnder radial shearing interferometer with liquid-crystal-device (LCD) phase-shift interferometry (PSI). Using accurate phase calibration and transient nematic driving of the LCD, the developed three-step PSI procedure can be achieved in a time of 5 ms. The proposed Mach-Zehnder radial shearing PSI method reconstructs the phase information using a digital signal processor (DSP). The DSP then computes appropriate control signals to drive a deformable mirror in such a way as to eliminate the wavefront distortion. The current adaptive-optics system is capable of suppressing low-frequency thermal disturbances with a signal-to-noise ratio improvement of more than 20 dB and a steady-state phase error of less than 0.02pi root mean square when the control loop is operated at a frequency of 30 Hz.

Journal Article↗

PubMed2006

Optical waveguide biosensors constructed with subwavelength gratings.

The reflection resonance spectrum of a subwavelength diffraction-grating-coupled waveguide is used to analyze biomolecular interactions in real time. By detecting this resonance wavelength shift, the optical waveguide biosensor provides the ability to identify the kinetics of the biomolecular interaction on an on-line basis without the need for extrinsic labeling of the biomolecules. A theoretical analysis of the subwavelength optical waveguide biosensor is performed. A biosensor with a narrow reflection resonance spectrum, and hence an enhanced detection resolution, is then designed and fabricated. Currently, the detection limit of the optical waveguide sensor is approximately 10(-5) refractive-index units. The biosensor is successfully applied to study of the dynamic response of an antibody interaction with protein G adsorbed on the sensing surface.

Biosensing Techniques↗

PubMed2006

Kinetic analysis of beta-amyloid peptide aggregation induced by metal ions based on surface plasmon resonance biosensing.

Recent studies suggest that beta-amyloid (Abeta) aggregation and toxicity are facilitated by metal ions. This study aims to evaluate the kinetics of Abeta aggregation/dissociation in the presence of metal ions and to investigate the efficacy of a metal chelator to disrupt the metal ion-induced Abeta aggregates. Soluble Abeta(1-40) peptide was immobilized on a surface plasmon resonance biosensing surface and aggregation induced by contact with soluble Abeta with or without metal ions. Our study revealed that all the tested metal ions promoted Abeta aggregation but with different kinetics. Among them, Cu(II) ions had the highest association constant, and reached the maximum binding in 10 min. However, the Cu(II)-induced Abeta aggregates were unstable. Other ions attained the maximum Abeta binding at much longer times: 45 min for Ca(II), 60 min for Fe(II), Fe(III), and Zn(II) ions. The Abeta aggregates induced by Fe(III) ions had the greatest stability. The metal ion-induced Abeta(1-40) aggregates could be disrupted by the metal chelator, EDTA, suggesting a metal chelator may serve as a pharmacological agent to interfere with Abeta aggregation. Finally, this study demonstrates that the SPR biosensor can be an effective and efficient setup to investigate the mechanism of Abeta aggregation.

Algorithms↗

PubMed2005

Angular-interrogation attenuated total reflection metrology system for plasmonic sensors.

We develop an angular-interrogation attenuated total reflection (ATR) metrology system for three different plasmonic sensors, namely, a conventional surface plasmon resonance (SPR) device, a coupled-waveguide SPR device, and a nanoparticle-enhanced SPR device. The proposed metrology system is capable of measuring the reflectivity spectra of the transverse magnetic mode and the transverse electric mode simultaneously. Through the optimal control of the fabrication process and use of sophisticated system instrumentation, the experimental results confirm that the developed ATR system is capable of measuring the resonant angle with an angular accuracy of 10(-4) deg.

Journal Article↗

PubMed2005

Enhanced readout signal of superresolution near-field structure disks by control of the size and distribution of metal nanoclusters.

We present a study in which we enhance the carrier-to-noise ratio of a superresolution near-field structure (super-RENS) disk to read below 100-nm marks by implementing a mask layer comprising a Au nanocluster-embedded dielectric film. Various Au nanocluster-embedded mask layers are fabricated by a radio-frequency cosputtering process, and the size and distribution of Au nanoclusters are controlled. To verify the enhancement of the various films for super-RENS disk applications, the sensitivity enhancement of plasmonic gas sensing is demonstrated.

Journal Article↗

PubMed2004

Two-dimensional phase unwrapping with a multichannel least-mean-square algorithm.

This paper presents a computationally efficient two-dimensional phase-unwrapping method based on a multichannel least-mean-square algorithm. The performance of the proposed method is evaluated by applying phase unwrapping to several simulated very noisy images and to a genuine noisy interferometrical image taken from a five-step phase-shift interferogram obtained from a surface plasmon resonance imaging biosensing experiment. The results confirm that the proposed method is more widely applicable, more computationally efficient, and more robust in the presence of noise than the representative methods presented in this paper.

Journal Article↗

PubMedDate not supplied

Surface plasmon resonance phase-shift interferometry: real-time DNA microarray hybridization analysis.

Surface plasmon resonance (SPR) phase-shift interferometry (PSI) is a novel technique which combines SPR and modified Mach-Zehnder PSI to measure the spatial phase variation caused by biomolecular interactions upon a sensing chip. The SPR-PSI imaging system offers high resolution and high-throughout screening capabilities for microarray DNA hybridization without the need for additional labeling, and provides valuable quantitative information. The SPR-PSI imaging system has an enhanced detection limit of 2.5 x 10(-7) refraction index change, a long-term phase stability of pi/100 in 30 min, and a spatial phase resolution of pi/300 with 100 x 100 microm2 detection area. This study successfully demonstrates the label-free observation of 15-mer DNA microarray.

DNA↗