Figure 4.

Biodistribution analysis of AuNPs after intravenous injection. (A) AuNPs accumulated to a high extent in both the liver and the spleen, although in the liver the accumulation seemed to scale with the presence of antibodies on the surface of the AuNPs, whereas for the spleen, the accumulation tended to follow the TfR-targeting abilities of the functionalized AuNPs. Large accumulation in the liver (B-C) and spleen (D-E) could be detected using TEM. (B-C) In the liver, AuNPs were seen in Kupffer cells situated in the sinusoidal lumen near the endothelial cell layer and hepatocytes. (D-E) In the spleen, AuNPs were also seen in macrophages with the AuNPs clearly accumulating in vesicular structures. Scale bars depict 200 nm. In other peripheral organs, the general accumulation of the AuNPs was low with no differences between the individual groups. The brain accumulation of AuNPs was improved for the targeted variants compared to the non-targeted variants of AuNPs (statistical significance was found for all TfR-targeted AuNPs compared to both controls, except for anti-TfR^A versus isotype IgG (p > 0.05), but not presented in the figure for the sake of a clear overview). The highest brain accumulation was seen for the monovalent anti-TfR^A/BACE1 group, which outperformed both the high and low-affinity variants (p < 0.001 and p < 0.05, respectively). Data are presented as mean ± SEM (n = 7-8) with * p < 0.05 and *** p < 0.001. ec: endothelial cell; hc: hepatocyte; kc: Kupffer cell; mp: macrophage; sl: sinusoidal lumen; vs: vesicular structure; %ID/g: Percentage of injected dose per gram.