Gold nanoparticles (GNPs) are widely used in biological and clinical applications due to their favorable chemical and optical properties. GNPs can be used for drug delivery to targeted cells. In addition, GNPs serve as ideal probes for biological and cell imaging applications. Recent studies indicate that the size diversity of GNPs plays an important role in targeting cellular components for biomedical applications. In this study, we conducted a series of studies using different sizes of gold nanoparticles, including 3, 10, 25, and 50？nm, to determine the effect of size variations on their intracellular localizations. Our cytotoxicity studies of GNPs into the HEp-2 cells using MTT assay indicated that 3？nm GNPs possess the highest toxicity. We exposed HEp-2 cells with various sizes of gold nanoparticles for different time intervals (1, 2, 4, 12, and 24？h) followed by imaging using scanning electron microscope (SEM) and atomic force microscope (AFM). Our SEM and AFM results showed that, after 1？hr incubation, 3 and 10？nm gold nanoparticles entered the nucleus, whereas 25 and 50？nm particles accumulated around the nucleus. As the time of exposure increased, GNPs entered the cells and accumulated in the cytosol and nucleus based solely on their sizes. 1. Introduction Metal nanoparticles are currently used for a variety of biomedical applications [1–4]. The nanoscale size makes them comparable to the cellular components and proteins hence, nanoparticles can easily bypass natural barriers [5]. Metal nanoparticles exhibit remarkable optic, electronic, and chemical properties that can be tailored by size variations [6, 7]. Recent studies showed that the size diversity of nanoparticles plays a significant role in their extracellular and intracellular mechanisms [1, 8–10]. GNPs have been actively investigated in a wide variety of biomedical applications for several reasons; they have the advantage of small size, which is highly tunable (1–100？nm), they are capable of evading the immune system, and they are easily characterized by UV-Vis spectrometries and microscopies [11, 12]. The optical properties of GNPs, such as surface plasmon resonance, provide excellent florescence and photostability necessary for imaging applications [13, 14]. The chemical properties of GNPs, such as chemical inertness, low toxicity to human cells [15], and high selectivity [16], allow them to interact easily with biological systems. Recent studies of GNPs and their abilities to enter cellular compartments have opened doors for many other biomedical applications beyond GNPs as labels
References
[1]
P. K. Jain, X. Huang, I. H. El-Sayed, and M. A. El-Sayed, “Noble metals on the nanoscale: optical and photothermal properties and some applications in imaging, sensing, biology, and medicine,” Accounts of Chemical Research, vol. 41, no. 12, pp. 1578–1586, 2008.
[2]
S. Dhar, E. Maheswara Reddy, A. Shiras, V. Pokharkar, and B. L. V. Prasad, “Natural gum reduced/stabilized gold nanoparticles for drug delivery formulations,” Chemistry, vol. 14, no. 33, pp. 10244–10250, 2008.
[3]
H. M. Joshi, D. R. Bhumkar, K. Joshi, V. Pokharkar, and M. Sastry, “Gold nanoparticles as carriers for efficient transmucosal insulin delivery,” Langmuir, vol. 22, no. 1, pp. 300–305, 2006.
[4]
L. Olofsson, T. Rindzevicius, I. Pfeiffer, M. K？ll, and F. H？？k, “Surface-based gold-nanoparticle sensor for specific and quantitative DNA hybridization detection,” Langmuir, vol. 19, no. 24, pp. 10414–10419, 2003.
[5]
Y. Pan, S. Neuss, A. Leifert, et al., “Size-dependent cytotoxicity of gold nanoparticles,” Small, vol. 3, no. 11, pp. 1941–1949, 2007.
[6]
L. Zang, Y. Che, and J. S. Moore, “One-dimensional self-assembly of planar pi-conjugated molecules: adaptable building blocks for organic nanodevices,” Accounts of Chemical Research, vol. 41, no. 12, pp. 1596–1608, 2008.
[7]
H. Ringsdorf, B. Schlarb, and J. Venzmer, “Molecular architecture and function of polymeric oriented systems: models for the study of organization, surface recognition, and dynamics of biomembrnaes,” Angewandte Chemie, vol. 27, no. 1, pp. 113–158, 1988.
[8]
W. S. Cho, M. Cho, J. Jeong, et al., “Acute toxicity and pharmacokinetics of 13？nm-sized PEG-coated gold nanoparticles,” Toxicology and Applied Pharmacology, vol. 236, no. 1, pp. 16–24, 2009.
[9]
B. D. Chithrani, A. A. Ghazani, and W. C. W. Chan, “Determining the size and shape dependence of gold nanoparticle uptake into mammalian cells,” Nano Letters, vol. 6, no. 4, pp. 662–668, 2006.
[10]
F. Osaki, T. Kanamori, S. Sando, T. Sera, and Y. Aoyama, “A quantum dot conjugated sugar ball and its cellular uptake. On the size effects of endocytosis in the subviral region,” Journal of the American Chemical Society, vol. 126, no. 21, pp. 6520–6521, 2004.
[11]
J. D. Gibson, B. P. Khanal, and E. R. Zubarev, “Paclitaxel-functionalized gold nanoparticles,” Journal of the American Chemical Society, vol. 129, no. 37, pp. 11653–11661, 2007.
[12]
S. J. Yoon, S. Mallidi, J. M. Tam, et al., “Utility of biodegradable plasmonic nanoclusters in photoacoustic imaging,” Optics Letters, vol. 35, no. 22, pp. 3751–3753, 2010.
[13]
W. Huang, W. Qian, P. K. Jain, and M. A. El-Sayed, “The effect of plasmon field on the coherent lattice phonon oscillation in electron-beam fabricated gold nanoparticle pairs,” Nano Letters, vol. 7, no. 10, pp. 3227–3234, 2007.
[14]
G. Saikia, A. Murugadoss, P. J. Sarmah, A. Chattopadhyay, and P. K. Iyer, “Tuning the optical characteristics of poly(p-phenylenevinylene) by in situ Au nanoparticle generation,” Journal of Physical Chemistry B, vol. 114, no. 46, pp. 14821–14826, 2010.
[15]
E. E. Connor, J. Mwamuka, A. Gole, C. J. Murphy, and M. D. Wyatt, “Gold nanoparticles are taken up by human cells but do not cause acute cytotoxicity,” Small, vol. 1, no. 3, pp. 325–327, 2005.
[16]
D. P. O'Neal, L. R. Hirsch, N. J. Halas, J. D. Payne, and J. L. West, “Photo-thermal tumor ablation in mice using near infrared-absorbing nanoparticles,” Cancer Letters, vol. 209, no. 2, pp. 171–176, 2004.
[17]
W. H. de Jong, W. I. Hagens, P. Krystek, M. C. Burger, A. J. A. M. Sips, and R. E. Geertsma, “Particle size-dependent organ distribution of gold nanoparticles after intravenous administration,” Biomaterials, vol. 29, no. 12, pp. 1912–1919, 2008.
[18]
A. Kumar, H. Ma, X. Zhang, et al., “Gold nanoparticles functionalized with therapeutic and targeted peptides for cancer treatment,” Biomaterials, vol. 33, no. 4, pp. 1180–1189, 2012.
[19]
R. Wilson, “The use of gold nanoparticles in diagnostics and detection,” Chemical Society Reviews, vol. 37, no. 9, pp. 2028–2045, 2008.
[20]
S. Song, L. Wang, J. Li, C. Fan, and J. Zhao, “Aptamer-based biosensors,” TrAC Trends in Analytical Chemistry, vol. 27, no. 2, pp. 108–117, 2008.
[21]
M. Tsoli, H. Kuhn, W. Brandau, H. Esche, and G. Schmid, “Cellular uptake and toxicity of Au55 clusters,” Small, vol. 1, no. 8-9, pp. 841–844, 2005.
[22]
C. Uboldi, D. Bonacchi, G. Lorenzi et al., “Gold nanoparticles induce cytotoxicity in the alveolar type-II cell lines A549 and NCIH441,” Particle and Fibre Toxicology, vol. 6, article 18, 2009.
[23]
C. C. Berry, J. M. de la Fuente, M. Mullin, S. W. L. Chu, and A. S. G. Curtis, “Nuclear localization of HIV-1 tat functionalized gold nanoparticles,” IEEE Transactions on Nanobioscience, vol. 6, no. 4, pp. 262–269, 2007.
[24]
E. Oh, J. B. Delehanty, K. E. Sapsford et al., “Cellular uptake and fate of PEGylated gold nanoparticles is dependent on both cell-penetration peptides and particle size,” ACS Nano, vol. 5, no. 8, pp. 6434–6448, 2011.
[25]
P. S. Ghosh, C.-K. Kim, G. Han, N. S. Forbes, and V. M. Rotello, “Efficient gene delivery vectors by tuning the surface charge density of amino acid-functionalized gold nanoparticles,” ACS Nano, vol. 2, no. 11, pp. 2213–2218, 2008.
[26]
N. L. Rosi, D. A. Giljohann, C. S. Thaxton, A. K. R. Lytton-Jean, M. S. Han, and C. A. Mirkin, “Oligonucleotide-modified gold nanoparticles for infracellular gene regulation,” Science, vol. 312, no. 5776, pp. 1027–1030, 2006.
[27]
M. P. Rout, J. D. Aitchison, A. Suprapto, K. Hjertaas, Y. Zhao, and B. T. Chait, “The yeast nuclear pore complex: composition, architecture, transport mechanism,” Journal of Cell Biology, vol. 148, no. 4, pp. 635–651, 2000.
[28]
J. Chen, F. Saeki, B. J. Wiley, et al., “Gold nanocages: bioconjugation and their potential use as optical imaging contrast agents,” Nano Letters, vol. 5, no. 3, pp. 473–477, 2005.
[29]
S. Klein, S. Petersen, U. Taylor, D. Rath, and S. Barcikowski, “Quantitative visualization of colloidal and intracellular gold nanoparticles by confocal microscopy,” Journal of Biomedical Optics, vol. 15, no. 3, article 036015, 2010.
[30]
C. Brandenberger, C. Mühlfeld, Z. Ali et al., “Quantitative evaluation of cellular uptake and trafficking of plain and polyethylene glycol-coated gold nanoparticles,” Small, vol. 6, no. 15, pp. 1669–1678, 2010.
[31]
B. Kang, M. A. Mackey, and M. A. El-Sayed, “Nuclear targeting of gold nanoparticles in cancer cells induces DNA damage, causing cytokinesis arrest and apoptosis,” Journal of the American Chemical Society, vol. 132, no. 5, pp. 1517–1519, 2010.
[32]
A. Arnida, A. Malugin, and H. Ghandehari, “Cellular uptake and toxicity of gold nanoparticles in prostate cancer cells: a comparative study of rods and spheres,” Journal of Applied Toxicology, vol. 30, no. 3, pp. 212–217, 2010.
[33]
S. H. Wang, C. W. Lee, A. Chiou, and P. K. Wei, “Size-dependent endocytosis of gold nanoparticles studied by three-dimensional mapping of plasmonic scattering images,” Journal of Nanobiotechnology, vol. 8, article 33, 2010.
[34]
H. Gao, W. Shi, and L. B. Freund, “Mechanics of receptor-mediated endocytosis,” Proceedings of the National Academy of Sciences of the United States of America, vol. 102, no. 27, pp. 9469–9474, 2005.
[35]
M. Raoof, Y. Mackeyev, M. A. Cheney, L. J. Wilson, and S. A. Curley, “Internalization of C60 fullerenes into cancer cells with accumulation in the nucleus via the nuclear pore complex,” Biomaterials, vol. 33, no. 10, pp. 2952–2960, 2012.
[36]
P. di Gianvincenzo, M. Marradi, O. M. Martínez-Avila, L. M. Bedoya, J. Alcamí, and S. Penadés, “Gold nanoparticles capped with sulfate-ended ligands as anti-HIV agents,” Bioorganic & Medicinal Chemistry Letters, vol. 20, no. 9, pp. 2718–2721, 2010.
[37]
I. Papp, C. Sieben, A. L. Sisson et al., “Inhibition of influenza virus activity by multivalent glycoarchitectures with matched sizes,” ChemBioChem, vol. 12, no. 6, pp. 887–895, 2011.
[38]
T. Mustafa, F. Watanabe, W. Monroe, et al., “Impact of gold nanoparticle concentration on their cellular uptake by MC3T3-E1 mouse osteoblastic cells as analyzed by transmission electron microscopy,” Journal of Nanomedicine & Nanotechnology, vol. 2, pp. 2–7, 2011.
[39]
K. Unfried, C. Albrecht, L.-O. Klotz, A. von Mikecz, S. Grether-Beck, and R. P. F. Schins, “Cellular responses to nanoparticles: target structures and mechanisms,” Nanotoxicology, vol. 1, no. 1, pp. 52–71, 2007.
