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Biomedical subjects

D Y Sasaki

Publications and source records attributed to D Y Sasaki.

4 recordsLinked to original sources
PubMed2002

Biocompatible semiconductor optoelectronics.

We investigate optoelectronic properties of integrated structures comprising semiconductor light-emitting materials for optical probes of microscopic biological systems. Compound semiconductors are nearly ideal light emitters for probing cells and other microorganisms because of their spectral match to the transparency wavelengths of biomolecules. Unfortunately, the chemical composition of these materials is incompatible with the biochemistry of cells and related biofluids. To overcome these limitations, we investigate functionalized semiconductor surfaces and structures to simultaneously enhance light emission and the flow of biological fluids in semiconductor microcavities. We have identified several important materials problems associated with the semiconductor/biosystem interface. One is the biofluid degradation of electroluminescence by ionic diffusion into compound semiconductors. Ions that diffuse into the active region of a semiconductor light emitter can create point defects that degrade the quantum efficiency of the radiative recombination process. In this paper we discuss ways of mitigating these problems using materials design and surface chemistry, and suggest future applications for these materials.

Animals↗
PubMed2001

Self-assembly of mesoscopically ordered chromatic polydiacetylene/silica nanocomposites.

Nature abounds with intricate composite architectures composed of hard and soft materials synergistically intertwined to provide both useful functionality and mechanical integrity. Recent synthetic efforts to mimic such natural designs have focused on nanocomposites, prepared mainly by slow procedures like monomer or polymer infiltration of inorganic nanostructures or sequential deposition. Here we report the self-assembly of conjugated polymer/silica nanocomposite films with hexagonal, cubic or lamellar mesoscopic order using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. Polymerization results in polydiacetylene/silica nanocomposites that are optically transparent and mechanically robust. Compared to ordered diacetylene-containing films prepared as Langmuir monolayers or by Langmuir-Blodgett deposition, the nanostructured inorganic host alters the diacetylene polymerization behaviour, and the resulting nanocomposite exhibits unusual chromatic changes in response to thermal, mechanical and chemical stimuli. The inorganic framework serves to protect, stabilize, and orient the polymer, and to mediate its function. The nanocomposite architecture also provides sufficient mechanical integrity to enable integration into devices and microsystems.

Acetylene↗
PubMed2001

Lipid membrane reorganization induced by chemical recognition.

Nanoscale structural reorganization of a lipid bilayer membrane induced by a chemical recognition event has been imaged using in situ atomic force microscopy (AFM). Supported lipid bilayers, composed of distearylphosphatidylcholine (DSPC) and a synthetic lipid functionalized with a Cu(2+) receptor, phase-separate into nanoscale domains that are distinguishable by the 9 A height difference between the two molecules. Upon binding of Cu(2+) the electrostatic nature of the receptor changes, causing a dispersion of the receptor molecules and subsequent shrinking of the structural features defined by the receptors in the membrane. Complete reversibility of the process was demonstrated through the removal of metal ions with EDTA.

Binding Sites↗