Gold nanoparticles delivery in mammalian live cells: a critical review

Abstract

Functional nanomaterials have recently attracted strong interest from the biology community, not only as potential drug delivery vehicles or diagnostic tools, but also as optical nanomaterials. This is illustrated by the explosion of publications in the field with more than 2,000 publications in the last 2 years (4,000 papers since 2000; from ISI Web of Knowledge, 'nanoparticle and cell' hit). Such a publication boom in this novel interdisciplinary field has resulted in papers of unequal standard, partly because it is challenging to assemble the required expertise in chemistry, physics, and biology in a single team. As an extreme example, several papers published in physical chemistry journals claim intracellular delivery of nanoparticles, but show pictures of cells that are, to the expert biologist, evidently dead (and therefore permeable). To attain proper cellular applications using nanomaterials, it is critical not only to achieve efficient delivery in healthy cells, but also to control the intracellular availability and the fate of the nanomaterial. This is still an open challenge that will only be met by innovative delivery methods combined with rigorous and quantitative characterization of the uptake and the fate of the nanoparticles. This review mainly focuses on gold nanoparticles and discusses the various approaches to nanoparticle delivery, including surface chemical modifications and several methods used to facilitate cellular uptake and endosomal escape. We will also review the main detection methods and how their optimum use can inform about intracellular localization, efficiency of delivery, and integrity of the surface capping.

Keywords: bionanotechnology; cell delivery; cell imaging; gold nanoparticles; intracellular fate; nanomaterials; photothermal microscopy.

Fig. 1

Properties and potential applications of gold nanoparticles in biology and medicine.

Fig. 2

Uptake of functionalized polystyrene particles in HUVEC cells correlate with protein adsorption capacity (adapted from Reference 38). The lines indicate standard deviation from three independent experiments. Reproduced from Ehrenberg MS, Friedman AE, Finkelstein JN, Oberdorster G, McGrath JL. The influence of protein adsorption on nanoparticle association with cultured endothelial cells. Biomaterials 2009; 30: 603–10. Copyright 2009 with permission from Elsevier.

Fig. 3

Comparison of nanoparticle uptake as a function of size reported by (a) Chithrani et al. (49) and (b) Lu et al. (50). (c) The results of Chithrani et al. are re-plotted with the particle uptake expressed in pg/cell (as in Reference 50) instead of number of particles per cell. (A and C) Adapted with permission from Chithrani et al. (49). Copyright 2006 American Chemical Society. (B) Lu F, Wu SH, Hung Y, Mou CY. Size effect on cell uptake in well-suspended, uniform mesoporous silica nanoparticles. Small 2009; 5: 1408–13. Copyright Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with permission.

Fig. 4

Transmission electron microscopy image of the uptake of 10 nm gold nanoparticles coated with 10% CALNN-HA2 – 20% CALNN-PEG – 70% CALNN. The particles (6 nM) were incubated in the presence of serum with HeLa cells for 3 h before fixation and TEM imaging. The scale bar is 500 nm.

Fig. 5

TEM images of 10 nm CALNN-capped gold nanoparticles internalized with Fugene-6 (15 µl Fugene-6, 15 µM CALNN-capped gold nanoparticles). TEM images clearly show endosomal localization as well as some large aggregates taken up by the cells by macropinocytosis (right panel).

Fig. 6

SLO enhances intracellular uptake of 10 nm gold nanoparticles. Overlay of a bright field and a photothermal image of 5 nm gold nanoparticles (coated with 10% CCALNN-PEG – 90% CALNN, 600 nM) delivered in HeLa cells with SLO (B) compared to a control without SLO (A).

Fig. 7

Cathepsin-dependent cleavage of the peptide monolayer. Adapted with permission from See et al. (86). Copyright 2009 American Chemical Society. HeLa cells were incubated for 4 h with 6 nM of fluorescently labeled 10 nm peptide-capped gold nanoparticles. (A–D) Confocal images of fluorescence release inside cells after 4 h incubation, (A) nanoparticles only, (B) nanoparticles in the presence of 100 µM chloroquine, (C) nanoparticles in the presence of 20 µM Z-FF-fmk (irreversible cathepsin inhibitor), (D) nanoparticles in the presence of both 100 µM chloroquine and 20 µM Z-FF-fmk. (E) Quantification of five different fields for each condition described in A–D. (F–I) Photothermal images of nanoparticle uptake, (F) nanoparticles only, (G) nanoparticles in the presence of 100 µM chloroquine, (H) nanoparticles in the presence of 20 µM Z-FF-fmk, (I) gold nanoparticles in the presence of both 100 µM chloroquine and 20 µM ZFF-fmk. (K) Quantification of photothermal intensity for each condition described in A–D. Average intensity of at least 40 cells is shown for each condition. Uptake is not affected by chloroquine or Z-FF-fmk, but degradation of the monolayer is reduced by chloroquine and suppressed by Z-FF-fmk.