Biomedical subjects

Kiang Wei Kho

Publications and source records attributed to Kiang Wei Kho.

3 recordsLinked to original sources

PubMed2005

Deposition method for preparing SERS-active gold nanoparticle substrates.

Surface-enhanced Raman scattering or SERS, discovered some 20 years ago, has recently become a promising tool for routine biofluid assays in a clinical setting. Many attempts have been made to produce cheap and reproducible SERS-active substrates. In this study, we report on the fabrication of SERS-active substrates through the convective assembly of gold (Au) particles on electrostatically charged glass slides. We show that, by a proper control of the initial particle concentration in an evaporating Au suspension droplet, it is possible to obtain a closely packed colloidal film capable of generating SERS activity. Finally, AFM and SERS measurements of the resulting films reveal comparability in performance with previous silane-immobilized Au colloidal films. The minimum electromagnetic enhancement factor of our films is estimated to be about 2 x 10(4).

Colloids↗

PubMed2005

Reduction of polarization-induced artifacts in grating-based spectrometers.

An optical device that converts unpolarized light into a single polarization state is described. The device is based on a polarizing beam splitter that separates the two polarization directions. The beam splitter is combined with two pairs of equilateral prisms that are used to collimate the two beams in terms of both propagation and polarization directions. When it is used in combination with a blazed diffraction grating, this device is shown to effectively remove the polarization dependence of the first-order diffracted power. The device has an insertion loss of approximately 14% for purely s-polarized light. However, for unpolarized light incident upon the two gratings studied here, the increased throughput of the p-polarized component leads to an average relative gain in overall efficiency of 13%-19%, depending on the grating. In collimating the two polarization directions, the device may cause a reduction in spectral resolution for a rectangular entrance slit. As a result, the device is more likely to find use in spectrometers that have a circular aperture, such as that provided by an optical fiber.

Journal Article↗

PubMed2004

Confocal endomicroscopic imaging of normal and neoplastic human tongue tissue using ALA-induced-PPIX fluorescence: a preliminary study.

Confocal endomicroscopy is a novel and non-invasive microscopic technique that enables surface and subsurface imaging of living tissues or cells in vivo. The purpose of this study was to assess the possibility of utilizing a rigid confocal endomicroscope (RCE) system developed for detecting morphological changes in living normal and neoplastic human tongue tissue in combination with 5-aminolevulinic acid (ALA)-induced endogenous protoporphyrin IX (PPIX) fluorescence. Three patients with squamous cell carcinoma (SCC) of the tongue were examined using the novel RCE system with the excitation wavelength at 488 nm from an argon-ion laser and the detection wavelengths of the tissue fluorescence above 515 nm. Patients were topically applied with 0.4% of 5-ALA rinsing solution to the oral mucosa for approximately 15 min, and then the confocal endomicroscopic imaging of tissue PPIX fluorescence was performed on the lesion sites of the tongue after an optimal incubation period of 90-120 min. For comparison purposes, ALA-PPIX fluorescence confocal endomicroscopic imaging was also carried out on the normal sites of the tongue in vivo from two healthy volunteers. Image distortions due to tissue motion can be minimized using a specially designed tissue stabilizer attached to the RCE probe. Good quality ALA-mediated confocal fluorescence images of the tongue can be acquired in real-time, providing well-defined micro-morphological structures (e.g., filiform papillae, keratinized epithelium and fungiform papillae) of the tongue in vivo. Changes of tissue structures in oral tissue associated with cancer transformation can also be clearly identified using the RCE imaging. Preliminary results obtained in this study suggest that ALA-mediated rigid confocal endomicroscopy may have a significant potential for the rapid, non-invasive diagnosis and evaluation of early oral cancers in vivo.

Aminolevulinic Acid↗