Quantification of gold nanoparticles using total reflection X-ray fluorescence by Monte Carlo simulation (MCNP code) applied to cancer cell research

Abstract

Detection and quantification of gold nanoparticles (AuNPs) using total reflection X-rays fluorescence (TXRF) technique is carried out by Monte Carlo simulation (MCNP code, version 6.2). Aiming at applications to cancer cell research, parameters of 50 nm and 100 nm AuNPs from certified solutions were used in the simulations. Two different procedures of sample preparation were considered, one using acid digestion and other without any pre-treatment of AuNPs. For acid digested AuNPs, spectra of five samples with different Au masses (from ng to sub-ng), were simulated so as to obtain a calibration curve. The average detection and quantification limits using these digested samples were (31.0 ± 0.5)pg and (92.9 ± 1.4)pg, respectively. Fluorescence emitted by undigested samples containing spherical 50 nm and 100 nm were also simulated and nanoparticle aggregation was modelled. It is shown that for complete clustering, the intensity of the fluorescence emitted by 50 nm and 100 nm AuNPs drop to 45.82% and 32.29%, respectively, compared to the undigested cases with the same Au mass. For stable colloidal samples of AuNPs, the signal depends on the Au mass only, being statistically the same as the acid digested cases. Our results extend recent studies in TXRF spectroscopy as a tool to quantify the uptake of AuNPs by cancer cells. A potential novel application of TXRF to circulating tumor cell (CTC) detection is proposed.