Gold Nanoparticles Exert Endocrine-Disrupting Effects on Ovarian Steroidogenesis Ex Vivo: Estimation of Target-Tissue Dose Using the In Vitro Sedimentation Diffusion Dosimetry Model.

Gold nanoparticles (GNPs) have gained considerable attention for application in medicine and industry due to their unique and advantageous physicochemical properties; however, their effects on female fertility remain unclear. We have previously demonstrated that GNPs (mean primary diameter [MPD] = 6.81 ± 1.25 nm; [Mean ± SD]) stimulated steroidogenesis differentially, depending upon concentration (1.43x10³, 1.43x10⁶, 1.43x10⁹ GNPs/mL) and independent of oxidative stress, in our rat-ovary-culture model. The In vitro Sedimentation Diffusion Dosimetry (ISDD) Model was used to estimate target-tissue dose because the gold content of the ovarian tissue was below limits of detection. The objectives of the present study were (1) to determine the MPD of GNPs ex vivo using transmission electron microscopy (TEM) and (2) to input the calculated MPD into the ISDD model to theoretically estimate target-tissue doses. We hypothesized that GNPs aggregate in culture, which in turn decreases the delivered target-tissue dose. GNPs at concentrations of 2.85x10⁷ and 2.85x10¹⁰ GNPs/mL were incubated in culture for 12, 24, or 48 hours—in the absence of tissue. These model concentrations were chosen due to pragmatic TEM considerations. Conditions and incubation periods were identical to those of our aforementioned ex-vivo studies. Each GNP solution was prepared for TEM and particle diameter was evaluated using Image J software. Descriptive statistics revealed that the MPD of our GNPs in culture was ~10 nm (mean = 9.6 ± 5.5 nm; range = 2.7-43.5 nm) regardless of concentration or time. This estimated MPD of our GNPs in culture was then used with the ISDD model to estimate the dose delivered to the ovarian cells in our previous study (see above). The theoretical results from the ISDD model yielded the target-tissue doses for each culture concentration to be as follows after ^a12, ^b24, and ^c48 hours: ^a18, ^b25, and ^c35 GNPs/ovary (at culture concentration 1.43x10³ GNPs/mL); ^a~1.79x10⁴, ^b~2.53x10⁴, and ^c ~3.57x10⁴ GNPs/ovary (at 1.43x10⁶ GNPs/mL); and ^a~1.79x10⁷, ^b~2.50x10⁷, and ^c ~3.57x10⁷ GNPs/ovary (at 1.43x10⁹ GNPs/mL). Based on the parameters and limitations of the ISDD model, these dosimetric results suggest that low concentrations of GNPs, along with the possible concomitant presence of dissolved gold, may be capable of altering rat ovarian steroidogenesis ex vivo as such data link particle dose to a specific steroidogenic response. This research is supported by the Children's Environmental Health Sciences Core Center at the University of Wisconsin-Milwaukee and Children's Research Institute (5P30ES004184-24-PRJ32IR).