Exposure to atmospheric particulate matter (PM) has adverse health impacts including oxidative stress and inflammatory responses linked to cardiovascular and other systemic pathologies in humans, particularly in the elderly. Nanoparticulate matter (nPM) with high surface area and metal contaminants potentially has a greater effect compared to larger particles, although underlying response mechanisms are poorly understood. The heterogeneity of natural airborne PM complicates their use for mechanism-based biological studies and thus, a reproducible model nPM with chemical and physical characteristics that produce similar biological responses as ambient nPM is needed. Design, synthesis and characterization of carbon nanoparticles which are structurally and chemically similar to atmospheric carbon nanoparticles was done based on oxidative treatment (using hydrogen peroxide) followed by iron deposition. Commercially available carbon nanoparticles (M120, Cabot Inc.) were oxidized using hydrogen peroxide, which helped to disperse particles in water at neutral pH. Upon oxidation, the surface area of M120 particles was increased from 16 m2/g to 30 m2/g, confirmed using BET isotherm (N2 sorption). The oxidized particles showed size distribution ranging from ~25 nm to ~200 nm measured using dynamic light scattering (DLS) experiments, whereas the unoxidized particles were not dispersible for DLS measurements. Transmission electron microscopy (TEM) images showed aggregated particles of 80-200 nm in size where individual units were~20 nm particles. amounts of iron were deposited on particle surfaces with total iron measured by ICP-MS and surface iron was confirmed using electron energy loss spectroscopy (EELS) in TEM. Our studies showed that the presence of iron on the surface of the particles (at ppb levels) stimulated inflammatory responses in macrophages at sub-lethal nanoparticle dose (20 µg/mL), whereas the metal-free particles had no response. Since nPM at different locations or seasons may contain different concentrations or types of metal contamination, our study proposes a tool to predict the toxic effects of nPM a priori using these ‘tailor-made’ nanoparticles.

Synthetic nanoparticle analogues for studying biological response to airborne particulate matter

253rd National Meeting (2017)

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