Investigations on adverse biological effects of nanoparticles (NPs) in the lung by in vitro studies are usually performed under submerged conditions where NPs are suspended in cell culture media. ...However, the behaviour of nanoparticles such as agglomeration and sedimentation in such complex suspensions is difficult to control and hence the deposited cellular dose often remains unknown. Moreover, the cellular responses to NPs under submerged culture conditions might differ from those observed at physiological settings at the air-liquid interface.
In order to avoid problems because of an altered behaviour of the nanoparticles in cell culture medium and to mimic a more realistic situation relevant for inhalation, human A549 lung epithelial cells were exposed to aerosols at the air-liquid interphase (ALI) by using the ALI deposition apparatus (ALIDA). The application of an electrostatic field allowed for particle deposition efficiencies that were higher by a factor of more than 20 compared to the unmodified VITROCELL deposition system. We studied two different amorphous silica nanoparticles (particles produced by flame synthesis and particles produced in suspension by the Stöber method). Aerosols with well-defined particle sizes and concentrations were generated by using a commercial electrospray generator or an atomizer. Only the electrospray method allowed for the generation of an aerosol containing monodisperse NPs. However, the deposited mass and surface dose of the particles was too low to induce cellular responses. Therefore, we generated the aerosol with an atomizer which supplied agglomerates and thus allowed a particle deposition with a three orders of magnitude higher mass and of surface doses on lung cells that induced significant biological effects. The deposited dose was estimated and independently validated by measurements using either transmission electron microscopy or, in case of labelled NPs, by fluorescence analyses. Surprisingly, cells exposed at the ALI were less sensitive to silica NPs as evidenced by reduced cytotoxicity and inflammatory responses.
Amorphous silica NPs induced qualitatively similar cellular responses under submerged conditions and at the ALI. However, submerged exposure to NPs triggers stronger effects at much lower cellular doses. Hence, more studies are warranted to decipher whether cells at the ALI are in general less vulnerable to NPs or specific NPs show different activities dependent on the exposure method.
We developed a fluid dynamic model to predict the size and material dependent particle deposition efficiencies for a commercial available exposure chamber. Validated by measurements with SiO2 and ...polystyrene particle standards between 29nm and 2μm we obtained a parameterization of the particle deposition efficiency for a specific set of practically relevant flow, pressure and temperature conditions that can be used for accurate dose calculations at these conditions. Furthermore, the model predicts that a significant impact on the deposition efficiency due to the fractal-like structure of nanoparticle agglomerates is expected for cluster sizes beyond 200nm mobility equivalent diameter. For the commercially available gravitation–diffusion based exposure chamber investigated here at one specific flow rate, the results indicate that deposition rates of particles smaller than 100nm are too low in order to deposit mass doses that are equivalent to typical cytotoxic LOAELs determined in submerged experiments within reasonable times.
•We model and measure deposition efficiencies in a commercial exposure chamber.•We estimate the difference between spherical and fractal-like structured particles.•The deposition efficiency is given as a function of size and density.•Above 200nm the deposition efficiency decreases compared to spheres•The presented model allows easy and accurate dose estimations.
We developed a fluid dynamic model to predict the size and material dependent particle deposition efficiencies for a commercial available exposure chamber. Validated by measurements with SiO2 and ...polystyrene particle standards between 29 nm and 2 mu m we obtained a parameterization of the particle deposition efficiency for a specific set of practically relevant flow, pressure and temperature conditions that can be used for accurate dose calculations at these conditions. Furthermore, the model predicts that a significant impact on the deposition efficiency due to the fractal-like structure of nanoparticle agglomerates is expected for cluster sizes beyond 200 nm mobility equivalent diameter. For the commercially available gravitationadiffusion based exposure chamber investigated here at one specific flow rate, the results indicate that deposition rates of particles smaller than 100 nm are too low in order to deposit mass doses that are equivalent to typical cytotoxic LOAELs determined in submerged experiments within reasonable times.
Pyrolysis of wood-based polymer compounds Haensel, Thomas; Comouth, Andreas; Zydziak, Nicolas ...
Journal of analytical and applied pyrolysis,
2010, 2010-01-00, Letnik:
87, Številka:
1
Journal Article
Recenzirano
Due to increasing costs of synthetic polymers or plastics, which are directly correlated with the oil and gas prices, natural polymers with similar properties are becoming more and more interesting. ...One such product is a commercially available wood-based compound Arboform
® composed largely of lignin and cellulose. From these two materials, lignin is largely a byproduct of the paper industry, and normally used as a fuel. This material has the property of being able to be injection moulded into complex structures. Additions of carbon fibres to this mixture increase the form stability and the electrical conductivity. The pyrolysis of this material can form conducting materials. Thus, this material can also be used as a low-cost alternative to complex, conducting and non-oxidising components. A chemical and structural analysis with surface sensitive methods (XPS, EELS, and SEM) was performed to understand the pre- and post-pyrolysed material. Results show that pyrolysis increases the graphitic content and conductivity of the wood-based polymer compound. Furthermore, an anisotropic conductivity dependent on carbon fibre alignment in the compound was also observed.
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