Adsorption of nanoparticles on minerals affects the fate and transport of nanoparticles directly and is of great significance to many fields, including research into ore deposits, geochemistry, the environment and mineral materials. Whereas many previous studies have been conducted under the equilibrium pH and low solid (mineral) to liquid (nanoparticle suspension) ratio conditions, adsorption processes under initial pH and high solid/liquid ratio conditions may represent many important yet underexamined complex scenarios. To fill in this research gap, the adsorption of gold nanoparticles on illite was investigated experimentally at a relatively high solid/liquid ratio of 5 g L–1 and the effects of initial pH, ionic strength, citrate concentration, temperature and illite particle size were evaluated. The adsorbed amount of gold nanoparticles (from <5% to nearly 100%) increased with increasing ionic strength, temperature and citrate concentration and decreased with increasing pH and illite particle size. The presence of illite resulted in the dynamic evolution of the pH of the suspension, which, along with solution chemistry parameters, controlled the electrostatic interaction of illite and gold nanoparticles. The adsorption results, scanning electron microscopy observations and surface properties of illite suggest that the negatively charged gold nanoparticles were adsorbed predominantly on the positive illite edges through electrostatic interaction. The electrostatic attraction between illite and gold nanoparticles appeared to be strong, supported by the minor amount of desorption. These research findings are expected to provide a valuable reference regarding many critical issues in the geosciences as well as for industrial applications.

Golden perch (Macquaria ambigua) is a freshwater game-fish native to central and southeast Australia. Larvae of this fish species were used in two different types of experiments to evaluate the effects of short-term exposures (up to 6 days) to aqueous gold, 5 nm gold nanoparticles (AuNPs), or 50 nm AuNPs. Relative to the control, increased gold concentrations corresponded with yolk-sac edema (swelling). Larvae exposed to 50 μM of 5 nm AuNPs had yolk-sacs that were ~1.5 times larger resulting in the appearance of bent notochords. After two days of exposure, 100% mortality was observed. Total mortalities were <25% in the other larvae–gold systems, suggesting that these larvae can quickly adapt to the presence of gold. In terms of an oxidative stress response, the larvae from all systems did not express high enzymatic activity. The state of the gold determined how much could be taken up (or immobilised) by a larva. Aqueous gold and 5 nm AuNPs easily pass through cells; therefore, larvae exposed to these forms of gold contained the highest concentrations. Scanning electron microscopy confirmed that cells comprising the epithelium and fins contained AuNPs. Aqueous gold was reduced to nanometre-scale particles within cells. Comparatively, 5 nm AuNPs appeared to be aggregated within cells forming clusters hundreds of nanometres in size. On the contrary, 50 nm AuNPs were not observed within cells but were detected within larvae by (single particle) inductively coupled plasma mass spectroscopy, suggesting that these AuNPs were probably taken up through the mouth or gills. The results of the present study demonstrate that exposure to AuNPs had adverse effects on developing golden perch larvae. Additionally, these effects were dependent on the size of the AuNPs.

A de novo drug delivery nanosystem based on gold nanoparticles (GNPs), decorated poly(ethylene glycol) (PEG), and folate (FA)-conjugated graphene oxide (GO) was designed and developed successfully. Initially, the graphite (G) powder was oxidized to the GO, and then functionalized with chloroacetic acid to afford a carboxylated graphene oxide (GO–COOH). The obtained GO–COOH was functionalized with an amine end-caped PEG, FA, as well as 3-amino-1-propanethiol to produce a GO–PEG–FA–SH. In another experimental section, GNPs were synthesized through a citrate-mediated reduction approach, and subsequently decorated onto/into GO–PEG–FA–SH through the formation of Au–S bond to afford a GO–PEG–FA/GNP nanosystem. The resultant nanosystem was loaded with doxorubicin hydrochloride (DOX) as a model anticancer drug, and its drug-loading capacity as well as pH-dependent drug release behavior were investigated. The anticancer activity of the developed theranostic nanomedicine was extensively evaluated using MTT assay against human breast cancer cells (MCF7). The developed GO–PEG–FA/GNPs–DOX theranostic nanomedicine exhibited an excellent cancer chemotherapy feature. In addition, this nanomedicine can be used in chemo-photothermal therapy of solid tumors because of the presence of GO and GNPs in its structure.

We present liquid-cell transmission electron microscopy (liquid-cell TEM) imaging of fixed and non-fixed prostate cancer cells (PC3 and LNCaP) with high resolution in a custom developed silicon nitride liquid cell. Fixed PC3 cells were imaged for 90–120 min without any discernable damage. High contrast on the cellular structures was obtained even at low electron doses (~2.5 e−/nm2 per image). The images show distinct structures of cell compartments (nuclei and nucleoli) and cell boundaries without any further sample embedding, dehydration, or staining. Furthermore, we observed dynamics of vesicles trafficking from the cell membrane in consecutive still frames in a non-fixed cell. Our findings show that liquid-cell TEM, operated at low electron dose, is an excellent tool to investigate dynamic events in non-fixed cells with enough spatial resolution (few nm) and natural amplitude contrast to follow key intracellular processes.

Whole cells can be studied in their native liquid environment using electron microscopy, and unique information about the locations and stoichiometry of individual membrane proteins can be obtained from many cells thus taking cell heterogeneity into account. Of key importance for the further development of this microscopy technology is knowledge about the effect of electron beam radiation on the samples under investigation. We used environmental scanning electron microscopy (ESEM) with scanning transmission electron microscopy (STEM) detection to examine the effect of radiation for whole fixed COS7 fibroblasts in liquid. The main observation was the localization of nanoparticle labels attached to epidermal growth factor receptors (EGFRs). It was found that the relative distances between the labels remained mostly unchanged (<1.5%) for electron doses ranging from the undamaged native state at 10 e−/Å2 toward 103 e−/Å2. This dose range was sufficient to determine the EGFR locations with nanometer resolution and to distinguish between monomers and dimers. Various different forms of radiation damage became visible at higher doses, including severe dislocation, and the dissolution of labels.

Safety issues for the use of products containing nanoparticles need to be considered, since these nanoparticles may break through human skin to damage cells. In this paper, applied mathematical techniques are used to model the penetration of a spherical gold nanoparticle into an assumed circular hole in a lipid bilayer. The 6–12 Lennard-Jones potential is employed, and the total molecular interaction energy is obtained using the continuous approximation. Nanoparticles of three different radii, namely, 10, 15 and 20 Å, are studied, which are initiated at rest, confined to the axis of the hole. A similar behaviour for these three cases is observed. The critical hole radii at which these nanoparticles enter the bilayer are 12.65, 17.62 and 22.60 Å, respectively. Further, once the hole radii become larger than 20.79, 23.14 and 27.02 Å, respectively, the gold nanoparticles tend to remain at the mid-plane of the bilayer, and do not pass through the bilayer.

Understanding the morphological structure of membranes is essential to improve performance of membrane-based applications. In this paper, macroporous membranes were investigated and two methods introduced as an alternative for characterization of stereo-structure of the membranes. We combined the use of synchrotron X-ray nanotomography and small-angle X-ray scattering to examine the internal structure of cellulose acetate membranes with studies of the capture of surface-modified gold nanoparticles within these membranes. Finally, the morphological structures of macroporous membranes were visualized and their relationships with penetration tendency of surface-modified gold nanoparticles were explained.

The size of gold nanoparticles (AuNPs) can influence various aspects of their cellular uptake. Light microscopy is not capable of resolving most AuNPs, while electron microscopy (EM) is not practically capable of acquiring the necessary statistical data from many cells and the results may suffer from various artifacts. Here, we demonstrate the use of a fast EM method for obtaining high-resolution data from a much larger population of cells than is usually feasible with conventional EM. A549 (human lung carcinoma) cells were subjected to uptake protocols with 10, 15, or 30 nm diameter AuNPs with adsorbed serum proteins. After 20 min, 24 h, or 45 h, the cells were fixed and imaged in whole in a thin layer of liquid water with environmental scanning electron microscopy equipped with a scanning transmission electron microscopy detector. The fast preparation and imaging of 145 whole cells in liquid allowed collection of nanoscale data within an exceptionally small amount of time of ~80 h. Analysis of 1,041 AuNP-filled vesicles showed that the long-term AuNP storing lysosomes increased their average size by 80 nm when AuNPs with 30 nm diameter were uptaken, compared to lysosomes of cells incubated with AuNPs of 10 and 15 nm diameter.

Transmission electron microscopy (TEM) in combination with electron tomography is widely used to obtain nanometer scale three-dimensional (3D) structural information about biological samples. However, studies of whole eukaryotic cells are limited in resolution and/or contrast on account of the effect of chromatic aberration of the TEM objective lens on electrons that have been scattered inelastically in the specimen. As a result, 3D information is usually obtained from sections and not from whole cells. Here, we use chromatic aberration-corrected TEM to record bright-field TEM images of nanoparticles in a whole mount macrophage cell. Tilt series of images are used to generate electron tomograms, which are analyzed to assess the spatial resolution that can be achieved for different vertical positions in the specimen. The uptake of gold nanoparticles coated with low-density lipoprotein (LDL) is studied. The LDL is found to assemble in clusters. The clusters contain nanoparticles taken up on different days, which are joined without mixing their nanoparticle cargo.

The interaction of light with free electrons in a gold or silver nanostructure can give rise to collective excitations commonly known as surface plasmons. Plasmons provide a powerful means of confining light to metal/dielectric interfaces, which in turn can generate intense local electromagnetic fields and significantly amplify the signal derived from analytical techniques that rely on light, such as Raman scattering. With plasmons, photonic signals can be manipulated on the nanoscale, enabling integration with electronics (which is now moving into the nano regime). However, to benefit from their interesting plasmonic properties, metal structures of controlled shape (and size) must be fabricated on the nanoscale. This issue of MRS Bulletin examines how gold and silver nanostructures can be prepared with controllable shapes to tailor their surface plasmon resonances and highlights some of the unique applications that result, including enhancement of electromagnetic fields, optical imaging, light transmission, colorimetric sensing, and nanoscale waveguiding.

Nanoscale materials are beginning to have an impact in the field of molecular diagnostics. In particular, gold nanoparticles surface-functionalized with DNA have garnered much recent interest. Due to the unusual optical and catalytic properties of gold nanoparticle labels, several distinct advantages for assay readout have been realized. This review focuses on the progress made in our group over the past seven years in the development of particle surface chemistry and ultrasensitive protein and nucleic acid assays based upon DNA-functionalized gold nanoparticles. For DNA targets, experiments demonstrate that assays based upon gold nanoparticle labels have enhanced target specificity and in certain cases the sensitivity of polymerase chain reaction (PCR), without the need for target amplification. For protein targets, similar experiments demonstrate that assays based upon gold nanoparticles are up to one million times more sensitive than conventional protein detection methods. Recent data using human samples demonstrate the utility of such assays.