Tilo Reinert

Is there penetration of titania nanoparticles in sunscreens through skin? A comparative electron and ion microscopy study

We report on a comparative study by Transmission Electron Microscopy (HRTEM) and Scanning Transmission Ion Microscopy (STIM) combined with Rutherford Backscattering Spectrometry (RBS) and Particle Induced X-Ray Emission (PIXE) on ultra-thin and thin cross-sections, respectively, of various skin samples (porcine skin, healthy human skin, human skin grafted on a severe combined immuno-deficient mouse model) to which we applied topically various formulations containing titanium dioxide (TiO2) nanoparticles with primary particle sizes in the range from 20–100 nm. Whereas the HRTEM and STIM/PIXE images reveal clear differences – mainly related to the different thickness of the cross-sections – they unambiguously show that penetration of TiO2 nanoparticles is restricted to the topmost 3–5 corneocyte layers of the stratum corneum (SC).

The Leipzig high-energy ion nanoprobe: A report on first results

Abstract The high-energy ion nanoprobe LIPSION at the University of Leipzig has been operational since October 1998. Its magnetic quadrupole lens system, arranged as a separated Russian quadruplet, has been developed by the Microanalytical Research Centre (MARC), Melbourne. The ultrastable single-ended 3.5 MV SINGLETRON™ accelerator (High Voltage Engineering Europa) supplies H+ and He+ ion beams with a beam brightness in the range of 10–20 A rad −2 m −2 eV −1 [D.J.W. Mous, R.G. Haitsma, T. Butz, R.-H. Flagmeyer, D. Lehmann, J. Vogt, Nucl. Instr. and Meth. B 130 (1997) 31]. Due to this high brightness, the excellent optical properties of the focusing system of the nanoprobe and the suppression of mechanical vibrations, lateral resolutions of 100 nm for the low current mode (STIM) and 340 nm at a current of 10 pA (PIXE, RBS, SEI modes) were achieved. Further improvements are expected.

Quantitative microanalysis of perineuronal nets in brain tissue

Abstract The relevance of the perineuronal nets (specialised extracellular matrix surrounding a part of the neurons in brain tissue) as a possible protection of neurons against oxidative stress induced by metal ions (e.g. Al, Fe, Cu and Zn) is an actually discussed hypothesis. It is assumed that the perineuronal nets are able to bind metal ions and thus reduce the oxidative stress to neurons. Therefore, we used nuclear microscopy (μPIXE) in order to investigate the concentration and distribution of iron in rat brain loaded with colloidal iron with special emphasis to the perineuronal nets in the extracellular matrix. The elemental microanalysis was performed on 6 μm thin resin embedded sections. The perineuronal nets accumulated more Fe than other extracelullar matrix components leading to well defined, neuron-related structures in the Fe maps. In order to quantify the affinity, the iron accumulations in the perineuronal nets were analysed for different Fe loadings. We present first results that support the hypothesis that perineuronal nets act as chemical protection mechanism against oxidative stress due to their ability to bind metal ions.

Ion exchanger in the brain: Quantitative analysis of perineuronally fixed anionic binding sites suggests diffusion barriers with ion sorting properties.

Perineuronal nets (PNs) are a specialized form of brain extracellular matrix, consisting of negatively charged glycosaminoglycans, glycoproteins and proteoglycans in the direct microenvironment of neurons. Still, locally immobilized charges in the tissue have not been accessible so far to direct observations and quantifications. Here, we present a new approach to visualize and quantify fixed charge-densities on brain slices using a focused proton-beam microprobe in combination with ionic metallic probes. For the first time, we can provide quantitative data on the distribution and net amount of pericellularly fixed charge-densities, which, determined at 0.4–0.5 M, is much higher than previously assumed. PNs, thus, represent an immobilized ion exchanger with ion sorting properties high enough to partition mobile ions in accord with Donnan-equilibrium. We propose that fixed charge-densities in the brain are involved in regulating ion mobility, the volume fraction of extracellular space and the viscosity of matrix components.

Active compensation of stray magnetic fields at LIPSION

Abstract As reported previously, slowly varying stray magnetic fields and, recently, additional 50 Hz fields deteriorate the lateral resolution in the low current mode of the high-energy ion nanoprobe LIPSION. Therefore, the active stray magnetic field compensation system AMK_5 has been installed in the LIPSION laboratory. This system utilizes six coils in a Helmholtz-arrangement and advanced technology for magnetic field sensing and signal processing for its operation and allows to reduce the stray field fluctuations to excellent ±10 nT in all three directions for frequencies from true DC up to the kHz range. A compensation factor >100 was obtained for the vertical direction. The compensation system was also used to determine the sensitivity of LIPSION to stray magnetic fields. It was found that the sensitivity is largest for stray fields along the beam direction leading to a beam spot movement of 1.1 m/T in both horizontal and vertical direction. Thus, the residual stray field fluctuations of ±10 nT result in beam spot movements of ±13 nm assuming a homogeneous stray field and no contribution from stray fields outside the shielded volume. It is demonstrated that the lateral resolution of LIPSION is significantly improved by the active compensation system. However, there are still beam spot fluctuations in both vertical and horizontal direction dominated by 50 Hz components which limit the resolution in the low current mode to approximately 130 nm. The source of these fluctuations is still unclear.

Identification of air pollution sources by single aerosol particle fingerprints - micro-PIXE spectra

Abstract A new method for direct assessment of air pollution is developed by using nuclear microprobe techniques to analyse single aerosol particles (SAP). Every particle is characterized by its PIXE spectrum which can be considered to be its fingerprint. The strategy for fingerprint classification and identification is used to trace a measured aerosol particle to its original source. Most of the particles have a size of up to 3 μm . The particles are separately attached to a clean thin foil. The Leipzig Nanoprobe, LIPSION, is used for this study. There are two steps in the new method. First, collect samples from different sources, measure them and compile their characteristic spectra into a library. Then, assess the environmental samples by comparing their spectra with those in the library. An artificial neural network (ANN) package is used for spectrum comparison.

The architecture of cartilage: Elemental maps and scanning transmission ion microscopy/tomography

Articular cartilage is not just a jelly-like cover of the bone within the joints but a highly sophisticated architecture of hydrated macromolecules, collagen fibrils and cartilage cells. Influences on the physiological balance due to age-related or pathological changes can lead to malfunction and subsequently to degradation of the cartilage. Many activities in cartilage research are dealing with the architecture of joint cartilage but have limited access to elemental distributions. Nuclear microscopy is able to yield spatially resolved elemental concentrations, provides density information and can visualise the arrangement of the collagen fibres. The distribution of the cartilage matrix can be deduced from the elemental and density maps. The findings showed a varying content of collagen and proteoglycan between zones of different cell maturation. Zones of higher collagen content are characterised by aligned collagen fibres that can form tubular structures. Recently we focused on STIM tomography to investigate the three dimensional arrangement of the collagen structures.

Visualisation of collagen fibrils in joint cartilage using STIM

Abstract The scanning transmission ion microscopy (STIM) method was used to investigate the collagen network structure of the articular cartilage from a pigs knee in comparison with high resolution nuclear magnetic resonance imaging (microscopic NMR-tomography) and polarised light microscopy (PLM). Single collagen fibrils down to 200 nm in diameter were visualised. It was proved that the cartilage collagen network consists partly of zones of oriented fibrils as suggested by NMR measurements. Radially oriented fibrils were found in the zone near the calcified zone (hypertrophic zone) of both tibia and femur, and in the tibial radial zone. Tangentially oriented fibrils were found in the femoral and tibial superficial zone and in a second zone of the femoral cartilage. Polarisation light microscopy reveals broader zones of orientation than it was found with STIM.

Study of metal bioaccumulation by nuclear microprobe analysis of algae fossils and living algae cells

Abstract Microscopic ion-beam analysis of palaeo-algae fossils and living green algae cells have been performed to study the metal bioaccumulation processes. The algae fossils, both single cellular and multicellular, are from the late Neoproterozonic (570 million years ago) ocean and perfectly preserved within a phosphorite formation. The biosorption of the rare earth element ions Nd3+ by the green algae species euglena gracilis was investigated with a comparison between the normal cells and immobilized ones. The new Leipzig Nanoprobe, LIPSION, was used to produce a proton beam with 2 μm size and 0.5 nA beam current for this study. PIXE and RBS techniques were used for analysis and imaging. The observation of small metal rich spores ( μm ) surrounding both of the fossils and the living cells proved the existence of some specific receptor sites which bind metal carrier ligands at the microbic surface. The bioaccumulation efficiency of neodymium by the algae cells was 10 times higher for immobilized algae cells. It confirms the fact that the algae immobilization is an useful technique to improve its metal bioaccumulation.

An overview of the facilities, activities, and developments at the University of North Texas Ion Beam Modification and Analysis Laboratory (IBMAL)

The Ion Beam Modification and Analysis Laboratory (IBMAL) at the University of North Texas includes several accelerator facilities with capabilities of producing a variety of ion beams from tens of keV to several MeV in energy. The four accelerators are used for research, graduate and undergraduate education, and industrial applications. The NEC 3MV Pelletron tandem accelerator has three ion sources for negative ions: He Alphatross and two different SNICS-type sputter ion sources. Presently, the tandem accelerator has four high-energy beam transport lines and one low-energy beam transport line directly taken from the negative ion sources for different research experiments. For the low-energy beam line, the ion energy can be varied from ∼20 to 80 keV for ion implantation/modification of materials. The four post-acceleration beam lines include a heavy-ion nuclear microprobe; multi-purpose PIXE, RBS, ERD, NRA, and broad-beam single-event upset; high-energy ion implantation line; and trace-element accelerator...