Gold Nanoparticles in Biology: Beyond Toxicity to Cellular Imaging

Abstract

Gold, enigmatically represented by the target-like design of its ancient alchemical symbol, has been considered a mystical material of great value for centuries. Nanoscale particles of gold now command a great deal of attention for biomedical applications. Depending on their size, shape, degree of aggregation, and local environment, gold nanoparticles can appear red, blue, or other colors. These visible colors reflect the underlying coherent oscillations of conduction-band electrons ("plasmons") upon irradiation with light of appropriate wavelengths. These plasmons underlie the intense absorption and elastic scattering of light, which in turn forms the basis for many biological sensing and imaging applications of gold nanoparticles. The brilliant elastic light-scattering properties of gold nanoparticles are sufficient to detect individual nanoparticles in a visible light microscope with approximately 10(2) nm spatial resolution. Despite the great excitement about the potential uses of gold nanoparticles for medical diagnostics, as tracers, and for other biological applications, researchers are increasingly aware that potential nanoparticle toxicity must be investigated before any in vivo applications of gold nanoparticles can move forward. In this Account, we illustrate the importance of surface chemistry and cell type for interpretation of nanoparticle cytotoxicity studies. We also describe a relatively unusual live cell application with gold nanorods. The light-scattering properties of gold nanoparticles, as imaged in dark-field optical microscopy, can be used to infer their positions in a living cell construct. Using this positional information, we can quantitatively measure the deformational mechanical fields associated with living cells as they push and pull on their local environment. The local mechanical environment experienced by cells is part of a complex feedback loop that influences cell metabolism, gene expression, and migration.

Cellular Uptake, Intracellular Trafficking and Biological Responses of Gold Nanoparticles

“…These surface modifications have a vital influence on toxicity, endocytosis, and other biological effects of GNPs. It was reported that GNPs coated by CTAB molecules when synthesized by seed-growth method were found to be cytotoxic 35,[50][51] . However, after further coated with negatively charged PSS (sodium polystyrene sulfonate), their cytotoxicity decreases greatly.…”

Synthesis of gold nanoparticles using renewable Punica granatum juice and study of its catalytic activity

“…During the past two decades an enormous effort has been invested in the investigations of AuNPs because of its applications in catalysis (Zhang et al 2012), biotechnology (Murphy et al 2008), drug delivery, biodiagnostics (Dykman and Khlebtsov 2012;Beeram and Zamborini 2010;Saha et al 2012), etc. AuNPs exhibit different colors depending upon their size, shape and degree of aggregation.…”

Gold nanostructures: a class of multifunctional materials for biomedical applications

“…17 Nevertheless, it is important that we continue to study the biocompatibility of these materials, as This journal is c The Royal Society of Chemistry 2011 their suitability for different applications will depend heavily on a number of factors, including the size and shape of the particles, the surface coatings, and the method of administration. 11,15 Though non-reactive in most situations, the surface of gold is well-known for forming strong, stable gold-thiolate bonds (Au-S, B50 kcal/mol) to molecules with thiol (-SH) or disulfide groups (S-S). 19 This binding has been extensively studied with self-assembled monolayers (SAMs), where molecules (typically long-chain alkanethiols) generate highly ordered monolayers when they adsorb onto a gold surface.…”

“…The generated heat can be used to initiate release in drug delivery systems, enhance contrast in optical imaging techniques like photoacoustic imaging, and provide photothermal treatment. [8][9][10][11]21,39,45,47,48 A selection of these techniques will be described in greater detail below. This journal is c The Royal Society of Chemistry 2011…”