Project 7 (IST)
Project 7: Influence of low-volatile organic pollutants on the intrinsic ROS-production capacity
Fellow: Jiayuan Zhao (ESR7), 36 months
Tutor: Dr. Michael Riediker (IST)
IST has extensive experience in trace analytical chemistry, and in gas and particle exposure measurements and simulations. Low-volatile organic compounds (LVOCs) have by definition a high affinity to surfaces. Usually, airborne concentrations of LVOCs are relatively low. However, airborne NP create an additional large surface, which will lead to much higher concentrations of LVOC than expected when calculating with simple volatiliy constants. These LVOC have not only the potential to interfere with test systems but also to directly modify the cellular and non-cellular potential to generate ROS: They can either block reactive sites on the particle surface (expected for aliphatics), they can be quinons which can contribute to redox-cycling, or they can stimulate cellular pathways involved in cellular defense mechanisms (cellular generation of ROS).
The goal of this project is to first set up a system to generate such LVOC-loaded particles, to then test the effect of different types of solvents (aliphatics and aromatics) on the intrinsic ROS-production capacity; and to evaluate the shipping stability of samples collected in liquid dispersion or onto filters. If possible, samples will then be shipped to partner labs to demonstrate the feasibility of cellular testings. IST has already established a system to aerosolize NP powders and to bring the aerosol into a closed mixing chamber. Chamber sizes vary from 1 liter to about 10 m³. In these chambers, aerosol remains airborne with a stable size distribution for at least 30 minutes. LVOC will be added to this mixing chamber, from where aerosols will be drawn for further testing and characterisation. The exiting air stream will be lead past denuders that remove excess (gaseous) LVOC from the air stream. The system will be set up to be at the break-through concentration so that no detectable amounts of LVOC exit through the sample lines during particle-free control experiments. Testing of the collected particles will include analysis of LVOCs and measurement of airborne (measured by SMPS) and dispersed (measured by NTA) diffusion parameters. The collected particles will be tested for their potential for ROS-generation as described (http://dx.doi.org/10.1080/17435390802245716), as well as new methods developed during the project. Main skills acquired are methods to generate aerosols, to characterize these aerosols with cell-free systems and to prepare them for subsequent cellular testing. Secondments to partners 1 (ROS assays), 11 (on-site assays and collection), 12 (validation of methods to characterize NP).
In WP1 (task 1.5), WP2 (task 2.1), WP3 (tasks 3.2 and 3.3) and WP4 (task 4.5).