Saber Hussain (Advisor)
Master of Science (MS)
The present study was conducted to assess the toxicity of nanosized silver particles (Ag-15nm, 30nm and 55nm) in rat alveolar macrophages. For toxicity evaluations, cellular morphology, mitochondrial function (MTT assay), membrane leakage (LDH assay) and reactive oxygen species generation (ROS) were assessed after a 24h under control and exposed conditions. The morphological appearance of control and exposed cells were observed by an inverted, phase contrast microscope and the uptake of nanoparticles was observed using the CytoViva Ultra Resolution Imaging (URI) system. Morphological images captured at 100x magnification demonstrated that nanoparticle-exposed cells at higher doses became abnormal in size, and most of the cells were detached from the bottom of the cultured plates. It was also noted that agglomerates of nanoparticles were surrounded by macrophages; while some attached to the cell membrane. Further analysis of CytoViva URI system images exhibit the uptake of agglomerates into macrophages. The results of the biochemical studies revealed that cells exposed to Ag-15nm and 30nm for 24h showed a dose-dependent decrease in mitochondrial function. Calculated EC50 values from MTT data indicate that Ag-15nm and Ag-30nm are more toxic at lower concentrations when compared to Ag-55nm. In correlation with decreased mitochondrial function and subsequent lack of ATP production, cell viability assays also demonstrated a sizeable decrease in the number of viable cells exposed to Ag-15nm and 30nm, including at the lowest dose (5µg/ml). ROS date further supported a size and dose dependent relationship, with a 15.16 ±5.77 fold increase in ROS generation at 50 µg/ml of Ag-15nm. Preliminary apoptosis results reveal a size-dependent increase in caspase 3&7 enzyme activity; an indicator of apoptosis. In conclusion, data reveal that the size of the nanoparticle is a potential contributing factor in exhibiting toxicity, as Ag-15nm is found to be the most toxic when compared to larger nanoparticles (30nm and 55nm). The study also suggests that the mechanism of toxicity is likely due to the generation of reactive oxygen species, inducing oxidative stress and resulting in apoptosis.
Department or Program
Department of Pharmacology and Toxicology
Year Degree Awarded
Copyright 2006, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.