Y. Hwu

Enhancement of cell radiation sensitivity by pegylated gold nanoparticles

Biocompatible Au nanoparticles with surfaces modified by PEG (polyethylene glycol) were developed in view of possible applications for the enhancement of radiotherapy. Such nanoparticles exhibit preferential deposition at tumor sites due to the enhanced permeation and retention (EPR) effect. Here, we systematically studied their effects on EMT-6 and CT26 cell survival rates during irradiation for a dose up to 10 Gy with a commercial biological irradiator (E(average) = 73 keV), a Cu-Kalpha(1) x-ray source (8.048 keV), a monochromatized synchrotron source (6.5 keV), a radio-oncology linear accelerator (6 MeV) and a proton source (3 MeV). The percentage of surviving cells after irradiation was found to decrease by approximately 2-45% in the presence of PEG-Au nanoparticles ([Au] = 400, 500 or 1000 microM). The cell survival rates decreased as a function of the dose for all sources and nanoparticle concentrations. These results could open the way to more effective cancer irradiation therapies by using nanoparticles with optimized surface treatment. Difficulties in applying MTT assays were also brought to light, showing that this approach is not suitable for radiobiology.

Biocompatibility of Fe(3)O(4) nanoparticles evaluated by in vitro cytotoxicity assays using normal, glia and breast cancer cells.

In order to reveal the biocompatibility of Fe(3)O(4) nanoparticles and bipolar surfactant tetramethylammonium 11-aminoundecanoate cytotoxicity tests were performed as a function of concentration from low (0.1 microg ml(-1)) to higher concentration (100 microg ml(-1)) using various human glia, human breast cancer and normal cell lines. Cytotoxicity tests for human glia (D54MG, G9T, SF126, U87, U251, U373), human breast cancer (MB157, SKBR3, T47D) and normal (H184B5F5/M10, WI-38, SVGp12) cell lines exhibited almost nontoxicity and reveal biocompatibility of Fe(3)O(4) nanoparticles in the concentration range of 0.1-10 microg ml(-1), while accountable cytotoxicity can be seen at 100 microg ml(-1). The results of our studies suggest that Fe(3)O(4) nanoparticles coated with bipolar surfactant tetramethylammonium 11-aminoundecanoate are biocompatible and promising for bio-applications such as drug delivery, magnetic resonance imaging and magnetic hyperthermia.

Half-metallic ferromagnetism with high magnetic moment and high Curie temperature in Co2FeSi

Co2FeSi crystallizes in the ordered L21 structure as proven by x-ray diffraction and Moβbauer spectroscopy. The magnetic moment of Co2FeSi was measured to be about 6μB at 5 K. Magnetic circular dichroism spectra excited by soft x-rays were taken to determine the element-specific magnetic moments of Co and Fe. The Curie temperature was measured with different methods to be (1100±20)K. Co2FeSi was found to be the Heusler compound as well as the half-metallic ferromagnet with the highest magnetic moment and Curie temperature.

Electrochemistry: building on bubbles in metal electrodeposition.

In the electrodeposition of metals, a widely used industrial technique, bubbles of gas generated near the cathode can adversely affect the quality of the metal coating. Here we use phase-contrast radiology with synchrotron radiation to witness directly and in real time the accumulation of zinc on hydrogen bubbles. This process explains the origin of the bubble-shaped defects that are common in electrodeposited coatings.

Nondestructive Nanoscale 3D Elemental Mapping and Analysis of a Solid Oxide Fuel Cell Anode

Present solid oxide fuel cells (SOFCs) use complex materials to provide (i) sufficient stability and support, (ii) electronic, ionic, and mass transport, and (iii) electrocatalytic activity. However, there is a limited quantitative understanding of the effect of the SOFCs three dimensional (3D) nano/microstructure on electronic, ionic, and mass-transfer-related losses. Here, a nondestructive tomographic imaging technique at 38.5 nm spatial resolution is used along with numerical models to examine the phase and pore networks within an SOFC anode and to provide insight into the heterogeneous microstructures contributions to the origins of transport-related losses. The microstructure produces substantial localized structure-induced losses, with approximately 50% of those losses arising from phase cross-sectional diameters of 0.2 μm or less.

Coherence-enhanced synchrotron radiology: Refraction versus diffraction mechanisms

Tests performed in different regimes reveal the interplay of two edge-enhancement mechanisms in radiological images taken with coherent synchrotron light. The relative weight of the two mechanisms, related to refraction and to Fresnel edge diffraction, can be changed in a controlled way. This makes it possible to obtain different images of the same object with complementary information.

In situ real-time investigation of cancer cell photothermolysis mediated by excited gold nanorod surface plasmons

The photothermolysis of living EMT-6 breast tumor cells triggered by gold nanorods (AuNRs) with two-photon irradiation was conducted in situ and under real-time observation. The morphology and plasma membrane permeability of the cells were key indicators to the phenomena. AuNRs with an aspect ratio of 3.92, and a longitudinal absorption peak at 800 nm were synthesized with a seed-mediated method. The nanorods surfaces were further modified with polystyrenesulfonate (PSS) for biocompatibility. The prepared nanorods displayed excellent two-photon photoluminescence imaging. In situ real-time results revealed cavities internal to the cells were created from thermal explosions triggered by AuNRs localized photothermal effect. The cavitation dynamic is energy dependent and responsible for the perforation or sudden rupture of the plasma membrane. The energy threshold for cell therapy depended significantly on the number of nanorods taken up per cell. For an ingested AuNR cluster quantity N approximately 10-30 per cell, it is found that energy fluences E larger-than 93 mJ/cm(2) led to effective cell destruction in the crumbled form within a very short period. As for a lower energy level E = 18 mJ/cm(2) with N approximately 60-100, a non-instant, but progressive cell deterioration, is observed.

Coherence-enhanced synchrotron radiology: simple theory and practical applications

The advanced characteristics of synchrotron x-ray sources make it possible to implement radiology with powerful and innovative approaches. We review in simple terms the conceptual background of such approaches, then we present a number of selected examples. The practical tests concern life-sciences specimens as well as materials-science systems.

X-ray absorption of nanocrystal TiO2

Soft-X-ray absorption spectroscopy was used to identify the electronic and crystal structure of titanium dioxide in nanocrystalline form prepared by gas condensation. High energy resolution spectra of the Ti 2p absorption edge revealed detailed spectral features identical to those from titanium in anatase. Based on the Ti 2p and O 1s absorption spectra, we estimated that the Ti is in +4 valence state and the crystal field splitting of nanocrystal TiO2 is approximately 2.1 eV, slightly smaller than that of bulk TiO2.

Optimizing the size and surface properties of polyethylene glycol (PEG)-gold nanoparticles by intense x-ray irradiation

The polyethylene glycol (PEG) modified gold nanoparticle complex was synthesized by a one-solution synchrotron x-ray irradiation method. The impact on the structure and morphology of the gold nanoparticles of process parameters such as the PEG molecular weight, the PEG/gold molar ratio and the x-ray dosage were investigated. The size of PEG modified gold particles was found to decrease with increasing PEG addition and x-ray dosage. With the capability to monitor the absorption spectra in situ during the fast synthesis process, this opens the way to accurate control of the size and distribution. PEG chains with an intermediate length (MW6000) were found optimal for size control and colloidal stability in biologically relevant media. Our x-ray synthesized PEG-gold nanoparticles could find interesting applications in nanoparticle-enhanced x-ray tumour imaging and therapy.