Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Nanomaterials are engineered structures with at least one dimension of 100 nanometers or less. These materials are increasingly being used for commercial purposes such as fillers, opacifiers, catalysts, semiconductors, cosmetics, microelectronics, and drug carriers. Materials in this size range may approach the length scale at which some specific physical or chemical interactions with their environment can occur. As a result, their properties differ substantially from those bulk materials of the same composition, allowing them to perform exceptional feats of conductivity, reactivity, and optical sensitivity. Possible undesirable results of these capabilities are harmful interactions with biological systems and the environment, with the potential to generate toxicity. The establishment of principles and test procedures to ensure safe manufacture and use of nanomaterials in the marketplace is urgently required and achievable.

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Toxic Potential of Materials at the Nanolevel

Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications

Rapid growth in nanotechnology is increasing the likelihood of engineered nanomaterials coming into contact with humans and the environment. Nanoparticles interacting with proteins, membranes, cells, DNA and organelles establish a series of nanoparticle/biological interfaces that depend on colloidal forces as well as dynamic biophysicochemical interactions. These interactions lead to the formation of protein coronas, particle wrapping, intracellular uptake and biocatalytic processes that could have biocompatible or bioadverse outcomes. For their part, the biomolecules may induce phase transformations, free energy releases, restructuring and dissolution at the nanomaterial surface. Probing these various interfaces allows the development of predictive relationships between structure and activity that are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and surface coatings. This knowledge is important from the perspective of safe use of nanomaterials.

Understanding biophysicochemical interactions at the nano–bio interface

http://sistemas.eel.usp.br/docentes/arquivos/2166002/1234Nb/Geetha-review2009.pdf

Ti based biomaterials, the ultimate choice for orthopaedic implants – A review

The crystal growth and morphology in 150-nm-thick PET nanocomposite thin films with alumina (Al{sub 2}O{sub 3}) nanoparticle fillers (38 nm size) were investigated for nanoparticle loadings from 0 to 5 wt%. Transmission electron microscopy of the films showed that at 1 wt% Al{sub 2}O{sub 3}, the nanoparticles were well dispersed in the film and the average size was close to the reported 38 nm. Above 2 wt% Al{sub 2}O{sub 3}, the nanoparticles started to agglomerate. The crystal growth and morphological evolution in the PET nanocomposite films kept at an isothermal temperature of 217 C were monitored as a function of the holding time using in situ atomic force microscopy. It was found that the crystal nucleation and growth of PET was strongly dependent on the dispersed particles in the films. At 1 wt% Al{sub 2}O{sub 3}, the overall crystal growth rate of PET lamellae was slower than that of the PET homopolymer films. Above 2 wt% Al{sub 2}O{sub 3}, the crystal growth rate increased with nanoparticle loading because of heterogeneous nucleation. In addition, in these PET nanocomposite thin films, the Al{sub 2}O{sub 3} nanoparticles induced preferentially oriented edge-on lamellae with respect to the surface, which was not the case inmore » unfilled PET as determined by grazing-incidence X-ray diffraction.« less

Crystal growth in alumina/poly(ethylene terephthalate) nanocomposite films

The Glass Transition at Silica/PMMA Nanocomposite Interfaces

Processing and Mechanical Properties of C‐Nanotube Reinforced Alumina Composites

Synthesis of tartrate-resistant acid phosphatase (TRAP) and formation of resorption pits by osteoclast-like cells, the bone-resorbing cells, on nanophase (that is, material formulations with grain sizes less than 100nm) alumina and hydroxyapatite (HA) were investigated in the present in vitro study. Compared to conventional (that is, grain sizes larger than 100 nm) ceramics, synthesis of TRAP was significantly greater in osteoclast-like cells cultured on nanophase alumina and on nanophase HA after 10 and 13 days, respectively. In addition, compared to conventional ceramics, formation of resorption pits was significantly greater by osteoclast-like cells cultured on nanophase alumina and on nanophase HA after 7, 10, and 13 days, respectively. The present study, therefore, demonstrated, for the first time, enhanced osteoclast-like cell function on ceramic surfaces with nanometer-size surface topography.

Enhanced osteoclast like-cell functions on nanophase ceramics

Polymethylmethacrylate (PMMA) nanocomposites were synthesized by free radical polymerization in the presence of various weight percentages of alumina (Al2O3) nanoparticles. The resulting nanocomposites show an average increase of 600% in strain-to-failure and the appearance of a well-defined yield point. Concurrently, the glass transition temperature (Tg) of the composites decreased 20°C, while the ultimate strength and the Young’s modulus decreased by 20% and 15%, respectively.

Richard W. Siegel

Papers

Crystal growth in alumina/poly(ethylene terephthalate) nanocomposite films

The Glass Transition at Silica/PMMA Nanocomposite Interfaces

Processing and Mechanical Properties of C‐Nanotube Reinforced Alumina Composites

Enhanced osteoclast like-cell functions on nanophase ceramics

Investigation into the Thermal and Mechanical Behavior of PMMA/Alumina Nanocomposites