Hong Nhung Tran

Synthesis, capping and binding of colloidal gold nanoparticles to proteins

Bovine serum albumin (BSA) was used as a stabilizing agent and biofunctionalized layer for water-dispersed gold nanoparticles (NPs) synthesized from metal precursor HAuCl4. The BSA binding to gold NPs was characterized qualitatively and quantitatively by transmission electron microscopy, UV-VIS and FTIR spectrophotometers. HER2 (human epidermal growth factor receptor 2) specific phage antibodies were attached to BSA stabilized gold NPs to form a gold‐antibody complex. An ELISA (enzyme-linked immunosorbent assay) test was done to confirm the bioactivity of antibodies attached to gold NPs.

Synthesis and optical properties of water soluble CdSe/CdS quantum dots for biological applications

Water soluble CdSe/CdS quantum dots (QDs) have been synthesized directly in aqueous solution with sodium citrate as surfactant agent. The QDs are mono-dispersed in water and have strong luminescent emission intensity under excitation of ultraviolet light. The emission maxima of the QDs can be tuned in a wider range from 555 to 615 nm in water by changing synthesis conditions. The result of the synthesis of water-soluble CdSe and CdSe/CdS QDs shows the high quality of the QDs with the quite narrow luminescence emission band and photostability. The results show the strongest intensity of photoluminescence emission in media with pH value at about from 8–8.5, which are pH physiological environments. The luminescence intensity increases when the QDs are coated with a polyethylene glycol (PEG) or bovine serum albumin (BSA) protein layer, the lifetime also increases.

Capping and in vivo toxicity studies of gold nanoparticles

Water-dispersed colloidal gold nanoparticles (AuNPs) with high concentration were synthesized from metal precursor HAuCl4. The bovine serum albumin (BSA) and heterobiofunctionalized thiol polyethylene glycol acid (HS‐PEG‐COOH) were used as biofunctionalized layers for the synthesized AuNPs. The BSA and HS‐PEG‐COOH bound to the AuNPs were characterized qualitatively and quantitatively by transmission electron microscope and UV-VS spectrophotometer. The fabricated BSA and HS‐PEG‐COOH-capped AuNPs were introduced in mouse to study its toxicity and its availability in the liver.

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.

Rich variety of substrates for surface enhanced Raman spectroscopy

The efficiency of the application of surface enhanced Raman spectroscopy (SERS) technique to each specified purpose significantly depends on the choice of the SERS substrate with an appropriate structure as well as on its performance. Until the present time a rich variety of SERS substrates was fabricated. They can be classified according to their structures. The present work is a review of main types of SERS substrates for using in the trace analysis application. They can be classified into 4 groups: (1) Substrates using gold nanoparticles (AuNPs) with spherical shape such as colloidal AuNPs, AuNPs fabricated by pulsed laser deposition, by sputtering or by capillary force assembly (CFA), substrates fabricated by electrospinning technique, substrates using metallic nanoparticle arrays fabricated by electron beam lithography combined with CFA method, substrates using silver nanoparticle (AgNP) arrays grain by chemical seeded method, substrates with tunable surface plasmon resonance, substrates based on precies subnanometer plasmonic junctions within AuNP assemblies, substrates fabricated by simultaneously immobilizing both AuNPs and AgNPs on the same glass sides etc. (2) Substrates using nanostructures with non-spherical shapes such as gold nanowire (NW), or highly anisotropic nickel NW together with large area, free-standing carpets, substrates with obviously angular, quasi-vertically aligned cuboid-shaped TiO2 NW arrays decorated with AgNPs, substrates using gold nanoprism monolayer films, substrates using silver nanocube dimmers or monodisperse close-packed gold nanotriangle monolayers. (3) Substrates using multiparticle complex nanostructure such as nanoparticle cluster arrays, gold nanoflowers and nanodendrites. (4) Flexible substrate such as paper-based swab with gold nanorods, adhesive polymer tapes fabricated by inkjet printing method and flexible and adhesive SERS tapes fabricated by decorating AuNPs via the conventional drop-dry method.

Photoluminescence enhancement of dye-doped nanoparticles by surface plasmon resonance effects of gold colloidal nanoparticles

Due to the energy transfer from surface plasmons, the fluorescence of fluorophores near metallic nanostructures can be enhanced. This effect has been intensively studied recently for biosensor applications. This work reports on the luminescence enhancement of 100nm Cy3 dye-doped polystyrene nanoparticles by energy transfer from surface plasmons of gold colloidal nanoparticles with sizes of 20 and 100nm. Optimal luminescence enhancement of the fluorophores has been observed in the mixture with 20nm gold nanoparticles. This can be attributed to the resonance energy transfer from gold nanoparticles to the fluorophore beads. The interaction between the fluorophores and gold particles is attributed to far-field interaction.

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.

Enhanced absorption and fluorescence of gold nanoclusters using initial alkali concentrations

Understanding carrier dynamics and electromagnetic interactions between emerging quantum-confined nanostructures and plasmonic structures is crucial for future biological applications. In this research, we fabricate gold monolayer-protected clusters (AuMPC). We demonstrate enhanced light absorption and fluorescence of AuMPCs by varying the initial alkali concentration. We measure absorption bands enhanced up to nine times with extended and distinct features centered at 3.33 eV, and fluorescence enhanced up to 3.9 times. An increased alkali concentration changes the charge transfer capability of the surface thiolate ligands through sulfur-gold bonds, which in turn enhance/reduce the fluorescence intensity.

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.

Gold nanocrescents for remotely measuring and controlling local temperature.

We present a novel technique to remotely measure and control the local temperature within a medium. This technique is based on the observation of the rotational Brownian motion of gold nanocrescent particles, which possess a strong anisotropic light interaction due to their plasmonic properties. Rotational scattering correlation spectroscopy performed on a single nanoparticle is able to determine the local temperature with high accuracy. These nano-thermometers can simultaneously play the role of nano-heaters when absorbing the light of a focused laser beam.