Ivan M. Kempson

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.

Magnetically Engineered Semiconductor Quantum Dots as Multimodal Imaging Probes

Light-emitting semiconductor quantum dots (QDs) combined with magnetic resonance imaging contrast agents within a single nanoparticle platform are considered to perform as multimodal imaging probes in biomedical research and related clinical applications. The principles of their rational design are outlined and contemporary synthetic strategies are reviewed (heterocrystalline growth; co-encapsulation or assembly of preformed QDs and magnetic nanoparticles; conjugation of magnetic chelates onto QDs; and doping of QDs with transition metal ions), identifying the strengths and weaknesses of different approaches. Some of the opportunities and benefits that arise through in vivo imaging using these dual-mode probes are highlighted where tumor location and delineation is demonstrated in both MRI and fluorescence modality. Work on the toxicological assessments of QD/magnetic nanoparticles is also reviewed, along with progress in reducing their toxicological side effects for eventual clinical use. The review concludes with an outlook for future biomedical imaging and the identification of key challenges in reaching clinical applications.

In vivo-in vitro and XANES spectroscopy assessments of lead bioavailability in contaminated periurban soils.

Lead (Pb) bioaccessibility was assessed using 2 in vitro methods in 12 Pb-contaminated soils and compared to relative Pb bioavailability using an in vivo mouse model. In vitro Pb bioaccessibility, determined using the intestinal phase of the Solubility Bioaccessibility Research Consortium (SBRC) assay, strongly correlated with in vivo relative Pb bioavailability (R(2) = 0.88) following adjustment of Pb dissolution in the intestinal phase with the solubility of Pb acetate at pH 6.5 (i.e., relative Pb bioaccessibility). A strong correlation (R(2) = 0.78) was also observed for the relative bioaccessibility leaching procedure (RBALP), although the method overpredicted in vivo relative Pb bioavailability for soils where values were <40%. Statistical analysis of fit results from X-ray absorption near-edge structure (XANES) data for selected soils (n = 3) showed that Pb was strongly associated with Fe oxyhydroxide minerals or the soil organic fraction prior to in vitro analysis. XANES analysis of Pb speciation during the in vitro procedure demonstrated that Pb associated with Fe minerals and the organic fraction was predominantly solubilized in the gastric phase. However, during the intestinal phase of the in vitro procedure, Pb was strongly associated with formation of ferrihydrite which precipitated due to the pH (6.5) of the SBRC intestinal phase. Soils where Fe dissolution was limited had markedly higher concentrations of Pb in solution and hence exhibited greater relative bioavailability in the mouse model. This data suggests that coexistence of Fe in the intestinal phase plays an important role in reducing Pb bioaccessibility and relative bioavailability.

Full-field microimaging with 8 keV X-rays achieves a spatial resolutions better than 20 nm

Fresnel zone plates (450 nm thick Au, 25 nm outermost zone width) used as objective lenses in a full field transmission reached a spatial resolution better than 20 nm and 1.5% efficiency with 8 keV photons. Zernike phase contrast was also realized without compromising the resolution. These are very significant achievements in the rapid progress of high-aspect-ratio zone plate fabrication by combined electron beam lithography and electrodeposition.

Dressing in Layers: Layering Surface Functionalities in Nanoporous Aluminum Oxide Membranes

Enhanced control over the surface properties of porous materials is of great interest owing to applications as diverse as the detection of chemical and biological species, molecular separation, drug delivery, and catalysis. Recent research has made inroads into this issue, devising experimental strategies towards surface manipulation in porous materials. However, the increasingly stringent device requirements for advanced applications, such as energy storage, controlled release, biochemical gates, nanoreactors, sorption, and high-performance molecular transport and separation, demand the development of multiphasic, responsive, and multifunctional materials. Self-organized nanoporous anodic aluminum oxide (AAO) membranes prepared by electrochemical anodization have become popular materials, attractive for their high surface area (up to 250 mg ), high porosity (10 porescm ), highly ordered and monodisperse pores, tunable thickness and pore dimensions, excellent chemical, thermal, and mechanical stability, biocompatibility, and inexpensive fabrication. A considerable number of studies have been devoted to the development of AAO membranes with complex pore geometries in order to improve the membrane properties for applications in molecular separation and to enable the template synthesis of sophisticated nanostructures with novel architectures and unique optical, magnetic, energy-storage, and electrical properties. Membranes with branched, multilayered, and modulated pore structures have been generated by precise and temporal control over the anodization conditions. In contrast, control at a similar level of complexity over the surface inside the pores of AAOmembrane is currently lacking, despite the fact that the functionality on the pore surface is a key determinant for device performance. In particular, the selectivity and efficiency of molecular transport and separation through AAO membranes are not only effectively modulated by changing the size, but also by the charge and polarity of the porous layer and the engineered affinity towards the species of interest. Several surface-modification techniques have been applied to AAO membranes including silanization, formation of self-assembled monolayers, grafting of polymer brushes, plasma processing, sol–gel modification, metal deposition (chemical vapor deposition, electroless and pulse electrochemical plating), and quantumdot adsorption. However, multifunctional and multilayered surface modification has not been demonstrated until our recent work in which we fabricated AAO membranes with distinctly different internal and external surface functionalities. This study provided a glimpse of the opportunities for controlling the surface properties in porous materials but stopped short of demonstrating truly multilayered surface modifications, tunability, and functional properties. Here, we describe AAO membranes having pores with spatially controlled multilayered surface functionalities, selected self-assembly of gold nanoparticles on amino-functionalized layers, and selective membrane transport. Membranes with layered surface functionalities inside the pore channel were prepared by a series of anodization and silanization cycles with pentafluorophenyldimethylpropylchlorosilane (PFPTES), 3-aminopropyltriethoxysilane (APTES), and N-triethoxysilylpropyl-O-polyethyleneoxide urethane (PEGS), respectively, achieving a range of functionalities and wettabilities. The fabrication approach is shown schematically in Scheme 1. Typically, at least three anodization steps were used. The first anodization was carried out on electropolished aluminum foil for 3 h using a constant voltage of 40 V at a temperature of 1 8C in 0.3m aqueous oxalic acid (C2H2O4). Afterwards, the sacrificial layer was removed by treatment with phosphoric acid/chromium trioxide solution to generate a textured concave pattern on the Al surface, which acted as a template for the subsequent pore formation during the second anodization. Upon completion of this step, the generated porous layer was treated with the first silane. The following third anodization was then performed to generate a virgin porous layer below the first silanized porous layer. We found that silanized surfaces were chemically inert and mechanically stable under anodization conditions. The newly generated pore surfaces were then [*] A. M. M. Jani, Prof. Dr. N. H. Voelcker School of Chemical and Physical Sciences Flinders University Bedford Park 5042 SA (Australia) Fax: (+61)8-8201-2905 E-mail: nico.voelcker@flinders.edu.au Homepage: http://www.voelckerlab.com

Quantitative analysis of nanoparticle internalization in mammalian cells by high resolution X-ray microscopy

BackgroundQuantitative analysis of nanoparticle uptake at the cellular level is critical to nanomedicine procedures. In particular, it is required for a realistic evaluation of their effects. Unfortunately, quantitative measurements of nanoparticle uptake still pose a formidable technical challenge. We present here a method to tackle this problem and analyze the number of metal nanoparticles present in different types of cells. The method relies on high-lateral-resolution (better than 30 nm) transmission x-ray microimages with both absorption contrast and phase contrast -- including two-dimensional (2D) projection images and three-dimensional (3D) tomographic reconstructions that directly show the nanoparticles.ResultsPractical tests were successfully conducted on bare and polyethylene glycol (PEG) coated gold nanoparticles obtained by x-ray irradiation. Using two different cell lines, EMT and HeLa, we obtained the number of nanoparticle clusters uptaken by each cell and the cluster size. Furthermore, the analysis revealed interesting differences between 2D and 3D cultured cells as well as between 2D and 3D data for the same 3D specimen.ConclusionsWe demonstrated the feasibility and effectiveness of our method, proving that it is accurate enough to measure the nanoparticle uptake differences between cells as well as the sizes of the formed nanoparticle clusters. The differences between 2D and 3D cultures and 2D and 3D images stress the importance of the 3D analysis which is made possible by our approach.

Localization and speciation of arsenic and trace elements in rice tissues.

The consumption of arsenic (As) contaminated rice is an important exposure route for humans in countries where rice cultivation employs As contaminated irrigation water. Arsenic toxicity and mobility are a function of its chemical-speciation. The distribution and identification of As in the rice plant are hence necessary to determine the uptake, transformation and potential risk posed by As contaminated rice. In this study we report on the distribution and chemical-speciation of As in rice (Oryza sativa Quest) by X-ray fluorescence (XRF) and X-ray absorption near edge structure (XANES) measurements of rice plants grown in As contaminated paddy water. Investigations of muXRF images from rice tissues found that As was present in all rice tissues, and its presence correlated with the presence of iron at the root surface and copper in the rice leaf. X-ray absorption near edge structure analysis of rice tissues identified that inorganic As was the predominant form of As in all rice tissues studied, and that arsenite became increasingly dominant in the aerial portion of the rice plant.

The Occurrence and Incorporation of Copper and Zinc in Hair and their Potential Role as Bioindicators: A Review

This article reviews evidence that suggests Cu and Zn concentrations are not altered significantly by exogenous processes and may be useful in applications of hair analysis. The review attempts to identify what Cu and Zn concentrations may actually indicate biogenically and investigates the mechanisms by which they are incorporated into hair. Associations with specific hair components are proposed and avenues for development as a bioindicator are identified. Areas of research that offer promise in application or confirming the use of Cu and Zn are also indicated. Correlations and relationships with other health disorders are reviewed. Endogenous blood concentrations may also explain alterations in hair structure relating to breast cancer.

Highly specific in vivo gene delivery for p53-mediated apoptosis and genetic photodynamic therapies of tumour

Anticancer therapies are often compromised by nonspecific effects and challenged by tumour environments’ inherent physicochemical and biological characteristics. Often, therapeutic effect can be increased by addressing multiple parameters simultaneously. Here we report on exploiting extravasation due to inherent vascular leakiness for the delivery of a pH-sensitive polymer carrier. Tumours’ acidic microenvironment instigates a charge reversal that promotes cellular internalization where endosomes destabilize and gene delivery is achieved. We assess our carrier with an aggressive non-small cell lung carcinoma (NSCLC) in vivo model and achieve >30% transfection efficiency via systemic delivery. Rejuvenation of the p53 apoptotic pathway as well as expression of KillerRed protein for sensitization in photodynamic therapy (PDT) is accomplished. A single administration greatly suppresses tumour growth and extends median animal survival from 28 days in control subjects to 68 days. The carrier has capacity for multiple payloads for greater therapeutic response where inter-individual variability can compromise efficacy.

Hard x-ray Zernike microscopy reaches 30 nm resolution

Since its invention in 1930, Zernike phase contrast has been a pillar in optical microscopy and more recently in x-ray microscopy, in particular for low-absorption-contrast biological specimens. We experimentally demonstrate that hard-x-ray Zernike microscopy now reaches a lateral resolution below 30 nm while strongly enhancing the contrast, thus opening many new research opportunities in biomedicine and materials science.