Gold nanoparticles are taken up by cells. They have been found to be toxic as well as non-toxic. This difference is dependent on size, surface charge and coating of the particles.

 

In several studies it has been shown that gold particles are toxic when size is less than 5 nm in diameter [1,2] and they are non-toxic when larger than 10 nm [2-4]. The conflicting results regarding the toxicity of gold nanoparticles, thus, reflect mainly the differences in their physico-chemical properties but also the variability in the cell systems and the assays used. Actually, most of these studies are summarized in an overview recently published [1]. Besides the fact that the very small gold particles are most toxic, those with negative surface charge show a toxic effect (<3 nm). The gold nanoparticles can enter the cells via vesicular uptake, but they do not enter other organelles, e.g. the cellular nucleus [1].

 

Stable gold particle suspensions in physiological media can only be achieved if the particles were coated [5]. Therefore the effects of the coatings have been investigated as well. The shape of the gold particles was not crucial for their effects as no direct toxicity was found for nanorods of different aspect ratios [3]. The cytotoxicity shown in this study could be clearly related to the chemical substance cetyltrimethylammonium bromide (CTAB) used to stabilize the gold nanorods. The same study demonstrated that serum proteins from the growth media were found to adsorb on the gold nanoparticles, which slightly increased the net size of the nanoparticles and also converted the surface charge to that of the bovine serum albumin. The results show that each of the gold nanorod preparations, regardless of initial surface charge, adopted the charge of serum proteins and were found to enter the cells. This is a well-known effect for metal oxide nanoparticles [6] as well as carbon-based nanoparticles (e.g. carbon nanotubes) [7], too.

 

A more realistic in vitro model, a triple cell co-culture model at the “air-liquid interface”, revealed no adverse effects, not even in an inflammation stimulating environment [8]. Non-functionalized gold particles with a size of 13–20 nm in diameter do not cause acute adverse effects.

Gold nanoparticles of various sizes have been shown to be taken up by cells via different mechanisms but they end all within vesicular structures [9]. The cells totally recover after removal of the gold particles from the supernatant.

 

Literature arrow down

  1. Alkilany, AM et al. (2010), J Nanopart Res, 12(7): 2313-2333.
  2. Pan, Y et al. (2007), Small, 3(11): 1941-1949.
  3. Alkilany, AM et al. (2009), Small, 5(6): 701-708.
  4. Brandenberger, C et al. (2010), Toxicol Appl Pharm, 242(1): 56-65.
  5. Gosens, I et al. (2010), Part Fibre Toxicol, 7(1): 37.
  6. Limbach, LK et al. (2007), Environ Sci Technol, 41(11): 4158-4163.
  7. Gasser, M et al. (2010), J Nanobiotechnology, 8 31.
  8. Mironava, T et al. (2010), Nanotoxicology, 4(1): 120-137.

 

 

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