Evaluation of sampling methods for toxicological testing of indoor air particulate matter

<p>There is a need for toxicity tests capable of recognizing indoor environments with compromised air quality, especially in the context of moisture damage. One of the key issues is sampling, which should both provide meaningful material for analyses and fulfill requirements imposed by practitioners using toxicity tests for health risk assessment. We aimed to evaluate different existing methods of sampling indoor particulate matter (PM) to develop a suitable sampling strategy for a toxicological assay. During three sampling campaigns in moisture-damaged and non-damaged school buildings, we evaluated one passive and three active sampling methods: the Settled Dust Box (SDB), the Button Aerosol Sampler, the Harvard Impactor and the National Institute for Occupational Safety and Health (NIOSH) Bioaerosol Cyclone Sampler. Mouse RAW264.7 macrophages were exposed to particle suspensions and cell metabolic activity (CMA), production of nitric oxide (NO) and tumor necrosis factor (TNFα) were determined after 24 h of exposure. The repeatability of the toxicological analyses was very good for all tested sampler types. Variability within the schools was found to be high especially between different classrooms in the moisture-damaged school. Passively collected settled dust and PM collected actively with the NIOSH Sampler (Stage 1) caused a clear response in exposed cells. The results suggested the higher relative immunotoxicological activity of dust from the moisture-damaged school. The NIOSH Sampler is a promising candidate for the collection of size-fractionated PM to be used in toxicity testing. The applicability of such sampling strategy in grading moisture damage severity in buildings needs to be developed further in a larger cohort of buildings.</p

Toxicological characterization of particulate emissions from straw, <i>Miscanthus</i>, and poplar pellet combustion in residential boilers

<p>Wood pellets have been used in domestic heating appliances for three decades. However, because the share of renewable energy for heating will likely rise over the next several years, alternative biomass fuels, such as short-rotation coppice or energy crops, will be utilized. We tested particulate emissions from the combustion of standard softwood pellets and three alternative pellets (poplar, <i>Miscanthus</i> sp., and wheat straw) for their ability to induce inflammatory, cytotoxic, and genotoxic responses in a mouse macrophage cell line. Our results showed clear differences in the chemical composition of the emissions, which was reflected in the toxicological effects. Standard softwood and straw pellet combustion resulted in the lowest PM₁ mass emissions. <i>Miscanthus</i> sp. and poplar combustion emissions were approximately three times higher. Emissions from the herbaceous biomass pellets contained higher amounts of chloride and organic carbon than the emissions from standard softwood pellet combustion. Additionally, the emissions of the poplar pellet combustion contained the highest concentration of metals. The emissions from the biomass alternatives caused significantly higher genotoxicity than the emissions from the standard softwood pellets. Moreover, straw pellet emissions caused higher inflammation than the other samples. Regarding cytotoxicity, the differences between the samples were smaller. Relative toxicity was generally highest for the poplar and <i>Miscanthus</i> sp. samples, as their emission factors were much higher. Thus, in addition to possible technical problems, alternative pellet materials may cause higher emissions and toxicity. The long-term use of alternative fuels in residential-scale appliances will require technological developments in both burners and filtration.</p> <p>Copyright © 2016 American Association for Aerosol Research</p

Scalable Synthesis of Biodegradable Black Mesoporous Silicon Nanoparticles for Highly Efficient Photothermal Therapy

Porous silicon (PSi) has attracted wide interest as a potential material for various fields of nanomedicine. However, until now, the application of PSi in photothermal therapy has not been successful due to its low photothermal conversion efficiency. In the present study, biodegradable black PSi (BPSi) nanoparticles were designed and prepared via a high-yield and simple reaction. The PSi nanoparticles possessed a low band gap of 1.34 eV, a high extinction coefficient of 13.2 L/g/cm at 808 nm, a high photothermal conversion efficiency of 33.6%, good photostability, and a large surface area. The nanoparticles had not only excellent photothermal properties surpassing most of the present inorganic photothermal conversion agents (PCAs) but they also displayed good biodegradability, a common problem encountered with the inorganic PCAs. The functionality of the BPSi nanoparticles in photothermal therapy was verified in tumor-bearing mice in vivo. These results showed clearly that the photothermal treatment was highly efficient to inhibit tumor growth. The designed PCA material of BPSi is robust, easy to prepare, biocompatible, and therapeutically extremely efficient and it can be integrated with several other functionalities on the basis of simple silicon chemistry

CMA.

<p>Cellular Metabolic Activity assessed with the MTT-test after a 24 h exposure of three different cell culture setups (A549 and THP-1 monocultures and A549/THP-1 co-culture) to four doses (25, 75, 150 and 200 μg/ml) of particulate samples from the combustion of three different wood logs and wood pellets. Each bar represents the average of eight experiments. Whiskers indicate the standard error of the mean (SEM), asterisks indicate significance from unexposed control cells. <b>a</b> indicates significance from the birch log PM₁ sample, b indicates significance from the beech log PM₁ sample, <b>c</b> indicates significance from the spruce log PM₁ sample, <b>d</b> indicates significance from the pellet combustion PM₁ sample. <b>§</b> indicates significance from the A549 monoculture, <b>#</b> indicates significance from the THP-1 monoculture, <b>$</b> indicates significance from the A549/THP-1 co-culture.</p

Genotoxicity.

<p>DNA fragmentation in THP-1 cells after a 24 h exposure to four doses (25, 75, 150 and 200 μg/ml) of PM₁ samples from the combustion of three different wood logs and wood pellets expressed as percentage of DNA in the tail. Each bar represents the average of four independent experiments with 100 analyzed cells/assay + SEM of the experimental averages. Asterisks indicate statistical significance from blank control, <b>a</b> indicates significance from the birch log PM₁ sample, <b>b</b> indicates significance from the beech log PM₁ sample, <b>c</b> indicates significance from the spruce log PM₁ sample, <b>d</b> indicates significance from the pellet combustion PM₁ sample.</p

Spearman correlation of the chemical constituents with the toxicity endpoints.

<p>Spearman correlation of the chemical constituents with the toxicity endpoints.</p

Oxidative stress.

<p>Oxidative stress assessed with the DCF-assay after a 24 h exposure of three different cell culture setups (A549 and THP-1 monocultures and A549/THP-1 co-culture) to four doses (25, 75, 150 and 200 μg/ml) of particulate samples from the combustion of three different wood logs and wood pellets. Each bar represents the average of eight experiments. Whiskers indicate the standard error of the mean (SEM), asterisks indicate significance from blank control. <b>a</b> indicates significance from the birch log PM₁ sample, <b>b</b> indicates significance from the beech log PM₁ sample, <b>c</b> indicates significance from the spruce log PM₁ sample, <b>d</b> indicates significance from the pellet combustion PM₁ sample. <b>§</b> indicates significance from the A549 monoculture, <b>#</b> indicates significance from the THP-1 monoculture, <b>$</b> indicates significance from the A549/THP-1 co-culture.</p

Cell membrane integrity.

<p>Cell membrane integrity assessed with the PI exclusion assay after a 24 h exposure of three different cell culture setups (A549 and THP-1 monocultures and A549/THP-1 co-culture) to four doses (25, 75, 150 and 200 μg/ml) of particulate samples from the combustion of three different wood logs and wood pellets. Each bar represents the average of eight experiments. Whiskers indicate the standard error of the mean (SEM), asterisks indicate significance from unexposed control cells. <b>a</b> indicates significance from the birch log PM₁ sample, <b>b</b> indicates significance from the beech log PM₁ sample, <b>c</b> indicates significance from the spruce log PM₁ sample, <b>d</b> indicates significance from the pellet combustion PM₁ sample. <b>§</b> indicates significance from the A549 monoculture, <b>#</b> indicates significance from the THP-1 monoculture, <b>$</b> indicates significance from the A549/THP-1 co-culture.</p

Experimental set-up and global omics analyses.

<p>(A) An 80 KW common-rail-ship diesel engine was operated with heavy fuel oil (HFO) or refined diesel fuel (DF). The exhaust aerosols were diluted and cooled with clean air. On-line real-time mass spectrometry, particle-sizing, sensor IR-spectrometry and other techniques were used to characterise the chemical composition and physical properties of the particles and gas phase. Filter sampling of the particulate matter (PM) was performed to further characterise the PM composition. Lung cells were synchronously exposed at the air-liquid-interface (ALI) to aerosol or particle-filtered aerosol as a reference. The cellular responses were characterised in triplicate at the transcriptome (BEAS-2B), proteome and metabolome (A549) levels with stable isotope labelling (SILAC and ¹³C₆-glucose). (B) Heatmap showing the global regulation of the transcriptome, proteome and metabolome.</p

Chemical and physical aerosol characterisation.

<p>(A) The ship diesel engine was operated for 4 h in accordance with the IMO-test cycle. (B) Approximately 28 ng/cm² and 56 ng/cm² were delivered to the cells from DF and HFO, respectively, with different size distributions. The HFO predominantly contained particles <50 nm, and the DF predominantly contained particles >200 nm, both in mass and number. (C) Number of chemical species in the EA particles. (D) Transmission electron microscope (TEM) images and energy-dispersive X-ray (EDX) spectra of DF-EA and HFO-EA; heavy elements (black speckles, arrow); and contributions of the elements V, P, Fe and Ni in the HFO particles using EDX (* = grid-material). (E) Exemplary EA concentrations (right) and concentration ratios (left) for particulate matter-bound species. For all experiments, n = 3.</p