Research on fluorescent semiconductor nanocrystals (also known as quantum dots or qdots) has evolved over the past two decades from electronic materials science to biological applications. We review current approaches to the synthesis, solubilization, and functionalization of qdots and their applications to cell and animal biology. Recent examples of their experimental use include the observation of diffusion of individual glycine receptors in living neurons and the identification of lymph nodes in live animals by near-infrared emission during surgery. The new generations of qdots have farreaching potential for the study of intracellular processes at the single-molecule level, high-resolution cellular imaging, long-term in vivo observation of cell trafficking, tumor targeting, and diagnostics.

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Quantum Dots for Live Cells, in Vivo Imaging, and Diagnostics

▪ Abstract Among the heavy metal-binding ligands in plant cells the phytochelatins (PCs) and metallothioneins (MTs) are the best characterized. PCs and MTs are different classes of cysteine-rich, heavy metal-binding protein molecules. PCs are enzymatically synthesized peptides, whereas MTs are gene-encoded polypeptides. Recently, genes encoding the enzyme PC synthase have been identified in plants and other species while the completion of the Arabidopsis genome sequence has allowed the identification of the entire suite of MT genes in a higher plant. Recent advances in understanding the regulation of PC biosynthesis and MT gene expression and the possible roles of PCs and MTs in heavy metal detoxification and homeostasis are reviewed.

PHYTOCHELATINS AND METALLOTHIONEINS: Roles in Heavy Metal Detoxification and Homeostasis

Based on fundamental chemistry, biotechnology and materials science have developed over the past three decades into today's powerful disciplines which allow the engineering of advanced technical devices and the industrial production of active substances for pharmaceutical and biomedical applications. This review is focused on current approaches emerging at the intersection of materials research, nanosciences, and molecular biotechnology. This novel and highly interdisciplinary field of chemistry is closely associated with both the physical and chemical properties of organic and inorganic nanoparticles, as well as to the various aspects of molecular cloning, recombinant DNA and protein technology, and immunology. Evolutionary optimized biomolecules such as nucleic acids, proteins, and supramolecular complexes of these components, are utilized in the production of nanostructured and mesoscopic architectures from organic and inorganic materials. The highly developed instruments and techniques of today's materials research are used for basic and applied studies of fundamental biological processes.

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Nanoparticles, Proteins, and Nucleic Acids: Biotechnology Meets Materials Science

Nanomaterials (NMs) have gained prominence in technological advancements due to their tunable physical, chemical and biological properties with enhanced performance over their bulk counterparts. NMs are categorized depending on their size, composition, shape, and origin. The ability to predict the unique properties of NMs increases the value of each classification. Due to increased growth of production of NMs and their industrial applications, issues relating to toxicity are inevitable. The aim of this review is to compare synthetic (engineered) and naturally occurring nanoparticles (NPs) and nanostructured materials (NSMs) to identify their nanoscale properties and to define the specific knowledge gaps related to the risk assessment of NPs and NSMs in the environment. The review presents an overview of the history and classifications of NMs and gives an overview of the various sources of NPs and NSMs, from natural to synthetic, and their toxic effects towards mammalian cells and tissue. Additionally, the types of toxic reactions associated with NPs and NSMs and the regulations implemented by different countries to reduce the associated risks are also discussed.

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Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations.

Biological synthesis of metallic nanoparticles.

NANOMETRE-SCALE semiconductor quantum crystallites exhibit size-dependent and discrete excited electronic states which occur at energies higher than the band gap of the corresponding bulk solid1–4. These crystallites are too small to have continuous energy bands, even though a bulk crystal structure is present. The onset of such quantum properties sets a fundamental limit to device miniaturization in microelectronics5. Structures with either one, two or all three dimensions on the nanometer scale are of particular interest in solid state physics6. We report here our discovery of the biosynthesis of quantum crystallites in yeasts Candida glabrata and Schizosaccharomyces pombe, cultured in the presence of cad-mium salts. Short chelating peptides of general structure (γ-Glu-Cys)n-Gly control the nucleation and growth of CdS crystallites to peptide-capped intracellular particles of diameter 20 A. These quantum CdS crystallites are more monodisperse than CdS par-ticles synthesized chemically. X-ray data indicate that, at this small size, the CdS structure differs from that of bulk CdS and tends towards a six-coordinate rock-salt structure.

C. T. Dameron

Papers

Biosynthesis of cadmium sulphide quantum semiconductor crystallites