Lancon, Trevor (2014-08). The Role of Neutron Activation Analysis in the Pathological Evaluation of Silver-Eluting Biomedical Devices in Biological Matrices. Master's Thesis.
Thesis
The purpose of this research was to determine the viability of using instrumental neutron activation analysis (INAA) to quantify silver nanoparticle (AgNP) content in biological matrices in the context of pathology evaluations of silver-eluting devices for United States Food and Drug Administration (FDA) approval. This work was comprised of feasibility, experimental, and simulation stages. The extent of how AgNPs presented through transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy-dispersive X-ray microanalysis (EDX), and INAA methodologies within porcine skin was explored in the feasibility trial. Sections of skin containing control and test articles were investigated using these modalities. The control article was skin that contained a driveline coated in material known to elute AgNPs into tissue. TEM findings supported the conclusion that the host reacted to the presence of larger AgNP aggregates surrounding the control article at an ultrastructural level. The test article was skin that contained a driveline coated in material hypothesized to not elute AgNPs into surrounding tissue. AgNPs were not observed to aggregate throughout the tissue adjacent to the test article, and a marked host reaction to their presence was not observed. INAA results correlated with these findings; silver was not detected adjacent to the test article, but a concentration of 74 ppm +- 29% of silver was observed in tissue adjacent to the control article. A complex system of ordinary differential equations (ODEs) was constructed to determine the inventory of the activation and subsequent decay progeny produced in a sample containing silver exposed to a neutron field. These ODEs were constructed into a Simulink(R) model and benchmarked using experimental data. This system was simplified after showing that production of induced ^(109)Ag during irradiation of silver did not significantly affect elemental silver estimation by measurement of ^(110m)Ag. Results from this model suggested that samples should be irradiated for up to 120 s and allowed to decay for 7 d before gamma ray spectroscopy is performed when investigating silver content in similar sodium-rich biological matrices via INAA in the future.
