Gold Nanoparticles for Photothermal and Photodynamic Therapy.

Cancer cells exposed to 13 nm gold nanoparticles and irradiated with cw laser light at 532 nm are shown to undergo cell death via two competing causes. When cells contain relatively high quantities of gold nanoparticles and/or receive a high dose of light, photothermal effects dominate, which are independent of the cellular location of the gold nanoparticles and affect all cells in the irradiated area due to the rapid diffusion of heat. In contrast, at lower doses of nanoparticles and light, the photogeneration of singlet oxygen triggers cell death only in cells that contain a sufficient number of nanoparticles.

Ion shuttling between emulsion droplets by crown ether modified gold nanoparticles.

Selective unidirectional transport of barium ions between droplets in a water-in-chloroform emulsion is demonstrated. Gold nanoparticles (GNPs) modified with a thiolated crown ether act as barium ion complexing shuttles that carry the ions from one population of droplets () to another (). This process is driven by a steep barium ion concentration gradient between and droplets.

Electrodeposition of Gold Nanostructures at the Interface of a Pickering Emulsion.

The controlled electrodeposition of nanoparticles at the surface of an emulsion droplet offers enticing possibilities in regards to the formation of intricate structures or fine control over the locus or duration of nanoparticle growth. In this work we develop electrochemical control over the spontaneous reduction of aqueous phase Au(III) by heterogeneous electron transfer from decamethylferrocene present in an emulsion droplet - resulting in the growth of nanoparticles. As gold is a highly effective conduit for the passage of electrical current, even on the nanoscale, the deposition significantly enhances the current response for the single electron transfer of decamethylferrocene when acting as a redox indicator.

Multimodal cell tracking from systemic administration to tumour growth by combining gold nanorods and reporter genes.

Understanding the fate of exogenous cells after implantation is important for clinical applications. Preclinical studies allow imaging of cell location and survival. Labelling with nanoparticles enables high sensitivity detection, but cell division and cell death cause signal dilution and false positives.

Entropy-Driven Reversible Agglomeration of Crown Ether Capped Gold Nanoparticles.

It is shown that plasmonic gold nanoparticles functionalised with a thiolated 18-crown-6 ligand shell agglomerate spontaneously from aqueous dispersion at elevated temperatures. This process takes place over a narrow temperature range, is accompanied by a colour change from red to purple-blue and is fully reversible. Moreover, the temperature at which it occurs can be adjusted by the degree of complexation of the crown ether moiety with appropriate cations.

Ion Transport across Biological Membranes by Carborane-Capped Gold Nanoparticles.

Carborane-capped gold nanoparticles (Au/carborane NPs, 2-3 nm) can act as artificial ion transporters across biological membranes. The particles themselves are large hydrophobic anions that have the ability to disperse in aqueous media and to partition over both sides of a phospholipid bilayer membrane. Their presence therefore causes a membrane potential that is determined by the relative concentrations of particles on each side of the membrane according to the Nernst equation.

Sensitive Analysis of Protein Adsorption to Colloidal Gold by Differential Centrifugal Sedimentation.

It is demonstrated that the adsorption of bovine serum albumin (BSA) to aqueous gold colloids can be quantified with molecular resolution by differential centrifugal sedimentation (DCS). This method separates colloidal particles of comparable density by mass. When proteins adsorb to the nanoparticles, both their mass and their effective density change, which strongly affects the sedimentation time.

Conserved effects and altered trafficking of Cetuximab antibodies conjugated to gold nanoparticles with precise control of their number and orientation.

Gold nanoparticles (17 nm) have been functionalized with the antiangiogenic monoclonal antibody drug Cetuximab at a well-defined orientation and coverage density of antibodies. Functionalization has been carried out through site-directed chemistry via the selective oxidation of the carbohydrate moiety of antibodies linked to a thiolated hydrazide. A431 tumor cells have been exposed to these conjugates for in vitro evaluation of their effects.

Design of artificial membrane transporters from gold nanoparticles with controllable hydrophobicity.

Gold nanoparticles with variable hydrophobicity have been prepared in three different size regimes following established methods. The control of hydrophobicity was achieved by complexation of the 18-crown-6-CH-thiolate ligand shell with potassium ions. Potassium dependent phase transfer of these particles from dispersion in water to chloroform was demonstrated, and the equilibrium partitioning of the particles in water-chloroform liquid/liquid systems was quantified by optical spectroscopy.

Preventing Plasmon Coupling between Gold Nanorods Improves the Sensitivity of Photoacoustic Detection of Labeled Stem Cells in Vivo.

Gold nanorods are excellent contrast agents for imaging technologies which rely on near-infrared absorption such as photoacoustic imaging. For cell tracking applications, the cells of interest are labeled with the contrast agent prior to injection. However, after uptake into cells by endocytosis, the confinement and high concentration in endosomes leads to plasmon band broadening and reduced absorbance.

Monitoring pattern formation in drying and wetting dispersions of gold nanoparticles by ESEM.

We report an investigation of the self-assembly of patterns from functionalized gold nanoparticles (GNPs) by monitoring the process in situ by environmental scanning electron microscopy (ESEM) during both evaporation and condensation of the dispersant. As this method limits the choice of dispersants to water, GNPs functionalized with hydrophilic thiol ligands, containing poly(ethylene)glycol (PEG) groups, were used on a variety of substrates including pre-patterned ones. Particular emphasis was given to early stage deposition of GNPs, as well as redispersion and lift-off upon condensation of water droplets.

Interactions of gold nanoparticles with a phospholipid monolayer membrane on mercury.

It is demonstrated that a compact monolayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine adsorbed to a hanging mercury drop electrode can serve as a simple electrochemical model system to study biomembrane penetration by gold nanoparticles. The hydrogen redox-chemistry characteristic of ligand-stabilized gold nanoparticles in molecularly close contact with a mercury electrode is used as an indicator of membrane penetration. Results for water-dispersible gold nanoparticles of two different sizes are reported, and comparisons are made with the cellular uptake of the same preparations of nanoparticles by a common human fibroblast cell line.

Preparation and characterization of Au nanoparticles capped with mercaptocarboranyl clusters.

The preparation of 3-4 nm and 10 nm gold nanoparticles capped with neutral carborane-based mercaptocarboranes, via two different preparative routes, is reported. The resulting boron-enriched nanomaterials exhibit complete dispersibility in water, opening the way for the use of these monolayer protected clusters (MPCs) in medical applications, such as boron neutron capture therapy (BNCT). These newly prepared MPCs have been characterized by FTIR, (1)H and (11)B NMR spectroscopy, UV-visible, centrifugal particle sizing (CPS), and, in some cases, inductively coupled plasma atomic emission spectrometry (ICP-AES).

High-resolution sizing of monolayer-protected gold clusters by differential centrifugal sedimentation.

Differential centrifugal sedimentation (DCS) has been applied to accurately size ligand-protected gold hydrosols in the 10 to 50 nm range. A simple protocol is presented to correct for particle density variations due to the presence of the ligand shell, which is formed here by either polyethylene glycol-substituted alkane thiols (PEG-alkane thiols) of different chain length or oligopeptides. The method gives reliable data for all particle sizes investigated and lends itself to rapid routine sizing of nanoparticles.

Electrocatalytic hydrogen redox chemistry on gold nanoparticles.

Electrocatalytic proton reduction leading to the formation of adsorbed molecular hydrogen on gold nanoparticles of 1-3 and 14-16 nm diameter stabilized by 1-mercapto-undecane-11-tetra(ethyleneglycol) has been demonstrated by cyclic voltammetry using a hanging mercury drop electrode. The nanoparticles were adsorbed to the electrode from aqueous dispersion and formed robust surface layers transferrable to fresh base electrolyte solutions. Unique electrocatalytic proton redox chemistry was observed that has no comparable counterpart in the electrochemistry of bulk gold electrodes.

Mercaptocarborane-capped gold nanoparticles: electron pools and ion traps with switchable hydrophilicity.

A simple single-phase method for the preparation of ca. 2 nm gold nanoparticles capped with mercaptocarborane ligands is introduced. The resultant monolayer protected clusters (MPCs) exhibit redox-dependent solubility and readily phase transfer between water and nonpolar solvents depending on the electronic and ionic charge stored in the metal core and in the ligand shell, respectively.

Intracellular mapping with SERS-encoded gold nanostars.

Here we report on the design, synthesis and application of small, highly bright, star-shaped SERS encoded single nanoparticles with the ability of providing an optical signal upon excitation with near infrared light. These particles are colloidally stable, fully biocompatible and can be internalized into living cells for intracellular imaging.