Gold Nanoparticle Quantification With Total Reflection X-ray Fluoresence

Abstract

<p>The quantification of gold nanoparticle (AuNP) uptake is of importance to a variety of therapeutic, diagnostic and theranostic applications. In particular, the accurate assessment of AuNP delivery remains challenging as current approaches employ cumbersome sample preparation methods. In this work, an easy-to-use and accurate Total reflection X-Ray Fluorescence (TXRF) protocol capable of measuring AuNP uptake in cell suspensions, slices of tissues and blood was developed. Specifically, a TXRF method was optimized and compared with the established technique of inductively coupled plasma atomic emission spectroscopy (ICP-AES) using 10 nm reference material AuNPs. TXRF recovery was nearly 100% while ICP-AES underestimated the Au concentration by nearly 80%. This finding has important implications for the accurate assessment of AuNP uptake using the current ICP-AES wet digestion protocols, and it reveals the effectiveness of TXRF protocols developed here. To extend the potential of TXRF for directly quantifying AuNP uptake in tissues, a theoretical model was first developed, and the impact of sample heterogeneity was investigated. This Monte Carlo based simulation toolkit enabled modelling of all the components of benchtop TXRF spectrometer as well the construction of various thin samples. The modeled TXRF spectra yielded nearly 100% recovery of Au regardless of the spatial distribution of the samples. The direct quantification capabilities of TXRF were also demonstrated experimentally using Au solution and AuNPs that were deposited either above or below thin slices of tissue. A 100% quantification accuracy was observed for all sample permutations tested. These findings strongly suggest that direct quantifications of AuNP uptake can be performed on slices of tissue, complementing histological examinations. The capabilities of TXRF for quantifying the concentration of AuNPs in blood was also investigated. Reference Au solutions and AuNPs in whole blood, plasma, and red blood cell suspensions were analyzed with different dilutants and dilution factors. Near 100% recovery was obtained, provided appropriate sample pre-treatment is employed. This offers a fast and easy to use method for quantifying AuNP-blood interactions. This dissertation provides the foundations for TXRF to become a rapid and accurate tool that can contribute to AuNP quantification in tumor cells, tissues and blood, a topic of interest to nanoparticle research.</p>