Using two of the most commonly synthesized noble metal nanoparticle preparations, citrate-reduced Au and Ag, the impacts of short-term accidental nanoparticle exposure are examined in primary culture murine adrenal medullary chromaffin cells. Transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and Alamar Blue viability studies revealed that nanoparticles are taken up by cells but do not decrease cell viability within 48 hours of exposure. Carbon-fiber microelectrode amperometry (CFMA) examination of exocytosis in nanoparticle-exposed cells revealed that nanoparticle exposure does lead to decreased secretion of chemical messenger molecules, of up to 32.5% at 48 hours of Au exposure. The kinetics of intravesicular species liberation also slows after nanoparticle exposure, between 30 and 50% for Au and Ag, respectively. Repeated stimulation of exocytosis demonstrated that these effects persisted during subsequent stimulations, meaning that nanoparticles do not interfere directly with the vesicle recycling machinery but also that cellular function is unable to recover following vesicle content expulsion. By comparing these trends with parallel studies done using mast cells, it is clear that similar exocytosis perturbations occur across cell types following noble metal nanoparticle exposure, supporting a generalizable effect of nanoparticle-vesicle interactions.
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Acknowledgements We would like to acknowledge Russell Anderson of the Research Analytical Laboratory in the department of Soil, Water and Climate at the University of Minnesota for conducting ICP-AES measurements. We would also like to acknowledge Diana Freeman of Research Animal Resource at the University of Minnesota for her assistance with the University of Minnesota tissue sharing program. All electron microscopy work was performed in the Institute of Technology Characterization Facility, University of Minnesota, a member of the NSF-funded Materials Research Facilities Network (www.mrfn.org). Financial support of this work was generously provided by a 3M Non-Tenured Faculty Grant for C. L. H. and the National Science Foundation (No. CHE-0645041).