Gold nanoparticles are widely used in biomedical imaging and diagnostic tests. Based on their established use in the laboratory and the chemical stability of Au(0), gold nanoparticles were expected to be safe. The recent literature, however, contains conflicting data regarding the cytotoxicity of gold nanoparticles. Against this background a systematic study of water-soluble gold nanoparticles stabilized by triphenylphosphine derivatives ranging in size from 0.8 to 15 nm is made. The cytotoxicity of these particles in four cell lines representing major functional cell types with barrier and phagocyte function are tested. Connective tissue fibroblasts, epithelial cells, macrophages, and melanoma cells prove most sensitive to gold particles 1.4 nm in size, which results in IC(50) values ranging from 30 to 56 microM depending on the particular 1.4-nm Au compound-cell line combination. In contrast, gold particles 15 nm in size and Tauredon (gold thiomalate) are nontoxic at up to 60-fold and 100-fold higher concentrations, respectively. The cellular response is size dependent, in that 1.4-nm particles cause predominantly rapid cell death by necrosis within 12 h while closely related particles 1.2 nm in diameter effect predominantly programmed cell death by apoptosis.

Size-Dependent Cytotoxicity of Gold Nanoparticles

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Toward Greener Nanosynthesis

A literature review of modern transition-metal nanoclusters, with an emphasis on those nanoclusters which are catalytically active, is presented in two parts. Part One presents background information on transition-metal nanoclusters, including an overview of common synthetic routes, a description of how nanoclusters are stabilized, and a brief summary of the multiple characterization techniques used (and the type of information that they can provide). In Part Two, five specific nanocluster case studies are presented, case studies which compare and contrast the syntheses, characterization approaches, and catalytic applications of transition-metal nanoclusters.

A review of modern transition-metal nanoclusters: their synthesis, characterization, and applications in catalysis

Mono- and bimetallic colloidal particles have gained increasing attention in science and application throughout the last several years. In this contribution, we present a synopsis of the wet chemical syntheses of these materials and survey potential applications in catalysis and materials science. Methods for the characterization of these particles and their surfaces are not reviewed here.

Nanoscopic Metal Particles − Synthetic Methods and Potential Applications

Ligand stabilized transition metal clusters and colloids in the size range of 1–15 nm show size dependent quantization phenomena. Quantum size effects become the more evident the smaller the particle is. Whereas particles >2 nm behave like quantum dots only at low temperatures, the 1.4 nm Au55 cluster follows quantum mechanical rules even at room temperature. First steps to organize clusters and colloids three- (3D), two- (2D) and one- (1D) dimensionally have been performed. 3D arrays are reached by using spacer molecules to link the clusters and to enlarge the distances between them. 2D assemblies are realized in cluster and colloid monolayers on chemically modified surfaces. One-dimensional cluster wires become available by using nanoporous aluminum oxide membranes as templates.

Ludger Korste

Papers

Large transition metal clusters—VI. Ligand exchange reactions on Au55(PPh3)12Cl6—the formation of a water soluble Au55 cluster