Decoupling the shape parameter to assess gold nanorod uptake by mammalian cells

Abstract

The impact of nanoparticles (NPs) upon biological systems can be fundamentally associated with their physicochemical parameters. A further often-stated tenet is the importance of NP shape on rates of endocytosis. However, given the convoluted parameters concerning the NP-cell interaction, it is experimentally challenging to attribute any findings to shape alone. Herein we demonstrate that shape, below a certain limit, which is specific to nanomedicine, is not important for the endocytosis of spherocylinders by either epithelial or macrophage cells in vitro. Through a systematic approach, we reshaped a single batch of gold nanorods into different aspect ratios resulting in near-spheres and studied their cytotoxicity, ( pro-)inflammatory status, and endocytosis/exocytosis. It was found that on a length scale of ∼10-90 nm and at aspect ratios less than 5, NP shape has little impact upon their entry into either macrophages or epithelial cells. Conversely, nanorods with an aspect ratio above 5 were preferentially endocytosed by epithelial cells, whereas there was a lack of shape dependent uptake following exposure to macrophages in vitro. These findings have implications both in the understanding of nanoparticle reshaping mechanisms, as well as in the future rational design of nanomaterials for biomedical applications.

Gold Nanorods for Light-Based Lung Cancer Theranostics

“…Work by Chithrani et al [ 41 ] suggested that as the AR of AuNRs increases, the cellular uptake decreases. However, a more recent study by Kinnear et al [ 67 ] considered the uptake of AuNRs with almost identical properties except AR (AuNR volume, zeta potential, colloidal stability, among others) by an A549 lung cancer cell line. They observed no correlation between AuNR aspect ratio and cellular uptake, below an AR of 7.2 ( nm, SPR nm), suggesting that the AuNRs used in this study may show no size dependence on cellular uptake.…”

Understanding nanoparticle endocytosis to improve targeting strategies in nanomedicine

“…Kinnear et al synthesized different gold rods of varied aspect ratios and studied their interaction with macrophages and epithelial cells. 140 Rods of B10-90 nm in length and with small aspect ratios (o5), revealed similar uptake efficiencies in both cells. In contrast, nanorods with higher aspect ratio (45) were preferentially internalized by epithelial cells, whereas the uptake in macrophages revealed to be shape independent.…”

Polymer-Coated Gold Nanospheres Do Not Impair the Innate Immune Function of Human B Lymphocytes in Vitro

“…Specifically, these were citrate-stabilized gold nanospheres (Citrate-GNS) and polymer-functionalized gold nanospheres coated either with PEG (PEG-GNS) or a combination of PEG and PVA (PEG/PVA-GNS), as well as PEGylated gold nanorods (PEG-GNR). 16,17 Gold core diameters were measured by transmission electron microscopy (TEM) as 13.4 ± 2.3, 15.7 ± 1.9, and 14.6 ± 1.8 nm for citrate-GNS, PEG-GNS, and PEG/ PVA-GNS, respectively. Dimensions of the PEG-GNR were measured at 57 ± 12 nm × 15 ± 3 nm, giving an aspect ratio of 3 ± 0.8 ( Figure 1A and Table 1).…”