Thanh Thuy Thi Tran

Structures of the Alzheimer's Wild-Type Aβ1-40 Dimer from Atomistic Simulations.

We have studied the dimer of amyloid beta peptide Aβ of 40 residues by means of all-atom replica exchange molecular dynamics. The Aβ-dimers have been found to be the smallest toxic species in Alzheimers disease, but their inherent flexibilities have precluded structural characterization by experimental methods. Though the 24-μs-scale simulation reveals a mean secondary structure of 18% β-strand and 10% α helix, we find transient configurations with an unstructured N-terminus and multiple β-hairpins spanning residues 17-21 and 30-36, but the antiparallel and perpendicular peptide orientations are preferred over the parallel organization. Short-lived conformational states also consist of all α topologies, and one compact peptide with β-sheet structure stabilized by a rather extended peptide with α-helical content. Overall, this first all-atom study provides insights into the equilibrium structure of the Aβ1-40 dimer in aqueous solution, opening a new avenue for a comprehensive understanding of the impact of pathogenic and protective mutations in early-stage Alzheimers disease on a molecular level.

Dye-doped silica-based nanoparticles for bioapplications

This paper presents our recent research results on synthesis and bioapplications of dye-doped silica-based nanoparticles. The dye-doped water soluble organically modified silicate (ORMOSIL) nanoparticles (NPs) with the size of 15?100?nm were synthesized by modified St?ber method from methyltriethoxysilane CH3Si(OCH3)3 precursor (MTEOS). Because thousands of fluorescent dye molecules are encapsulated in the silica-based matrix, the dye-doped nanoparticles are extremely bright and photostable. Their surfaces were modified with bovine serum albumin (BSA) and biocompatible chemical reagents. The highly intensive luminescent nanoparticles were combined with specific bacterial and breast cancer antigen antibodies. The antibody-conjugated nanoparticles can identify a variety of bacterium, such as Escherichia coli O157:H7, through antibody?antigen interaction and recognition. A highly sensitive breast cancer cell detection has been achieved with the anti-HER2 monoclonal antibody?nanoparticles complex. These results demonstrate the potential to apply these fluorescent nanoparticles in various biodetection systems.

A new green approach for the reduction of graphene oxide nanosheets using caffeine

A simple and green chemistry approach for the preparation of reduced graphene oxide nanosheets was successfully demonstrated through the reduction of graphene oxide (GO) using caffeine as the reductant. Without using toxic and harmful chemicals, this method is environmentally friendly and suitable for the large-scale production of graphene. The samples of GO, before and after reduction with caffeine have been characterized by X-ray diffraction, Raman, Fourier transform infrared, X-ray photoelectron spectroscopy, thermogravimetric analysis and transmission electron microscopy.

Synthesis, photophysical properties and application of dye doped water soluble silica-based nanoparticles to label bacteria E. coli O157:H7

Organically modified silicate (ORMOSIL) nanoparticles (NPs) doped with rhodamine 6G and rhodamine B (RB) dyes were synthesized by St?ber method from methyltriethoxysilane CH3Si(OCH3)3 precursor (MTEOS). The NPs are surface functionalized by cationic amino groups. The optical characterization of dye-doped ORMOSIL NPs was studied in comparison with that of free dye in solution. The synthesized NPs were used for labeling bacteria E. coli O157:H7. The number of bacteria have been counted using the fluorescent spectra and microscope images of labeled bacteria. The results show the ability of NPs to work as biomarkers.

Optical nanoparticles: synthesis and biomedical application

This paper presents a summary of our results on studies of synthesis and biomedical application of optical nanoparticles. Gold, dye-doped silica based and core–shell multifunctional multilayer (SiO2/Au, Fe3O4/SiO2 ,F e3O4/SiO2/Au) water-monodispersed nanoparticles were synthesized by chemical route and surface modified with proteins and biocompatible chemical reagents. The particles were conjugated with antibody or aptamer for specific detecting and imaging bacteria and cancer cells. The photothermal effects of gold nanoshells (SiO2/Au and Fe3O4/SiO2/Au) on cells and tissues were investigated. The nano silver substrates were developed for surface enhanced Raman scattering (SERS) spectroscopy to detect melamine.

Raman photoluminescence spectra of silicon nanowires synthesized by a vapor phase transport method

Silicon nanowires were successfully synthesized by a thermal evaporation method. We have observed a strong and broad emission band centered at 670?nm, which is attributed to the quantum confinement effect related to Si nanostructures embedded in the complex SiOx matrix. By fitting an experimental Raman spectrum, we confirm that the as-received wires possess crystalline silicon cores whose sizes were around 5?nm. Furthermore, the abnormal dependence of integral photoluminescence intensity on measured temperature was investigated.