The effects of size, shape, and surface functional group of gold nanostructures on their adsorption and internalization by cells

Abstract

In this study, we examined the effects of size, shape, and surface chemistry of gold nanostructures on their uptake (including both adsorption and internalization) by SK-BR-3 breast cancer cells. We used both spherical and cubic Au nanostructures (nanospheres and nanocages, respectively) of two different sizes, and their surface was modified with poly(ethylene glycol) (PEG), antibody anti-HER2, or poly(allyamine hydrochloride) (PAA). Our results showed that the size of the Au nanostructures influenced their uptake by the cells in a similar way regardless of the surface chemistry, while the shape dependency could vary depending on the surface functional group. In addition, the cells preferred to take up the Au nanostructures covered by different surface groups in the following order: PAA>> anti-HER2> PEG. The fraction of Au nanostructures attached to the cell surface was also dependent on the aforementioned parameters.

Figure 1

TEM images of (A) 15-nm Au nanospheres, (B) 45-nm Au nanospheres, (C) 33-nm Au nanocages, and (D) 55-nm Au nanocages.

Figure 2

(A) Schematic showing Au nanostructures whose surface was modified with different functional groups. (B) Summary of zeta-potentials for the Au nanostructures whose surface were modified with different chemical species. Abbreviation: PEG = poly(ethylene glycol); PAA = poly(allyamine hydrochloride); MPA = mercaptopropionic acid.

Figure 3

(A, B) SEM images of SK-BR-3 cells after incubation with the PAA-coated (A) 45-nm Au nanospheres and (B) 33-nm Au nanocages at 37 °C for 24 h, respectively. (C, D) SEM images of SK-BR-3 cells after incubation with the PAA-coated (C) 45-nm Au nanospheres and (D) 33-nm Au nanocages at 37 °C for 24 h, respectively, followed by etching with 0.34 mM I₂ for 5 min. The particle concentration of Au nanostructures in the culture medium was 0.02 nM.

Figure 4

(A) Uptake of surface-modified Au nanospheres by SK-BR-3 cells after incubation at 37 °C for 24 h, followed by etching with 0.34 mM I₂ for 5 min. N represents the number of uptaken Au nanostructures per cell. (B) Uptake of surface-modified Au nanocages by SK-BR-3 cells under the same conditions as for nanospheres. (C) Ratio of the numbers of Au nanostructures after etching (N_after) to that before etching (N_before) for the surface-modified Au nanostructures. The number of samples we tested was 6 for each data point.