Current Nanoscience - Volume 1, Issue 2, 2005

Nanostructures are inorganic, organic or composite materials synthesized in various forms with sizes down to the nanometer. A special interest in these nanomaterials emerged during the last decades because it was progressively recognized that the components of which they were made acquired or improved specific and interesting physical properties, as a result from their organizational packaging within such nanostructures. Among the physical properties of interest are the enhanced opto-electronic signals produced by such materials upon stimulation by external stimuli. Biology and biochemistry are disciplines devoted to the understanding of life at the cellular and molecular levels, respectively. The technological tools used until recently in these fields of research to detect interactions or visualize structures within cells, were usually of limited capacity because they required specific instrumentation and were rather cumbersome. Such shortcomings were upheld with the advent of biosensors, which are instruments transducing directly events occurring at the molecular or cellular levels into electrical or optical signals. The combination of nanoscience with the biological sciences has recently given birth to bionanotechnology, a new discipline devoted to the development of nanostructures as biosensors capable of transducing signals down to a single molecule or a single cell. This article reviews the current developments in the synthesis of nanomaterials, our current understanding of their physical properties, and the new possibilities offered by their application to the biological sciences. The discussion will also focus on the cutting edge developments in bionanotechnology foreseeable in a very near future.

Nanotechnology can be defined as the science and engineering involved in the design, synthesis, characterization, and application of materials and devices whose smallest functional organization in at least one dimension is on the nanometer scale or one billionth of a meter. One of the great promises of nanotechnology is the application to biology and medicine. In medicine, the cardiovascular field is one of the most technically advanced disciplines. Engineering achievements have helped us develop novel diagnostic and therapeutic technologies that provide safe and efficient solutions for cardiovascular patients. In spite of such progress, cardiovascular disease remains a major cause of death, morbidity, and disability in Occidental and Oriental societies. To address this formidable public health issue, substantial advances will be needed, and in particular, some important technological hurdles need to be overcome. The burgeoning new field of nanotechnology might open up a brand new approach in addressing some of these technical challenges. In fact, recent rapid advances in nanotechnology and nanoscience offer a wealth of new opportunities for diagnosis, prevention, and therapy of cardiovascular diseases, especially atherosclerosis. The aim of this article is to provide a brief survey at promising, important targets for nanotechnology in atherosclerosis. We review some of the main advances in the field of nanotechnology over the past few years, explore the prospects of clinical application in atherosclerosis, and discuss the concepts, issues, approaches, and challenges, with the goal of triggering the interest of biomedical scientists in the field of extremely tiny world.

New drug delivery technologies have an important niche in treatments as they enable drugs to be more effective. Remarkably, drug delivery is still considered a poor relation to drug discovery with greater than 95% of all new potential therapeutics having poor pharmacokinetics. The greatest obstruction for cytosolic release of therapeutic molecules is the membrane barrier of target cells. The use of protein transduction domains (PTD), capable of transporting effector molecules, such as compounds, proteins and DNA, into cells has become increasingly attractive in the design of drugs as they promote the cellular uptake of cargo molecules. The PTDs are also often referred to as Trojan peptides, membrane translocating sequences or cell permeable proteins. They are generally 10-16 amino acids in length. The mechanism of internalisation remains unclear, however, recent evidence supports an energy dependant process involving endocytosis. PTDs may be grouped according to their composition, for example peptides rich in arginine and/or lysine (Tat protein from HIV-1), or secondary structure, for example α-helix (HA2 from influenza virus hemagglutinin) and β- sheet (protegrins derived from antimicrobial peptides).

The cuticle is the largest active organ in the insect. It consists of many parallel lamellae with vertical interlamellar support between them and of interlamellar tubular membranes. The upper part of the cuticle in the abdominal region, the epicuticle, reveals several structures: 1) at intervals of 100μm or more apart, there are depressions housing a peripheral electromagnetic photoreceptor (PER), and 2) between every two of these, there are horizontal flats resembling an irregular polygon which are mostly elongated and about 104μm2 in area. 3) Upon each such terrace-like flat there are tile-shaped protuberances up to several micrometers in length and mostly running parallel to one another, covering the entire surface. In addition, most of the cuticle also displays numerous setae (small hairs). We suppose that the described structures and configurations contribute to enlargement of the cuticular surface and act as an optical grid enhancing the absorption of light. The cuticle of hornets is composed of mostly brown stripes and of some yellow stripes. In the brown cuticle the colour stems from incrustation of the pigment melanin, while in the yellow stripes the yellow pigment is concentrated in granular pockets between the lower layers of the endocuticle and the yellow colour shows through the transparent cuticle. Both brown and yellow cuticles are composed of more than 30 layers. The upper layers are about 1- 5μm thick and as we proceed inwards, they become thinner so that the deepest ones are thinner than the uppermost layer by about two orders of magnitude. Hornets are flying outside their nest, only in daytime, mostly at noon hours, when the UVB sun irradiation is at maximum. Vespan cuticle is photovoltaic, so that upon exposure to light one can record levels of spontaneous voltage of 30-180mV. The cuticular response to light is a two-phased affair, to wit: 1) immediately upon exposure to light there is a rise of the current from zero to nearly 5μA within the first minute, and in the next minute a further rise to about 6μA. During this phase of the response, the cuticle behaves as a positive photoelectric material. Later on current generation decreases along with a morphological reorganization of the cuticle to protect it from the damage of exposure to UV light.

Recent colloid chemistry research has shown that it is possible to engineer surface architectures using combinations of proteins and surfactants. The architectures were investigated by a range of chemical and physical methods across a number of international research groups. These spontaneous soft-matter assemblies were examined as they form on the surface of bubbles, thin liquid films (TLF's) and macroscopic interfaces. Isolated suspended thin liquid films and macroscopic planar interfaces, both act as models of the bubble surface. Studies clearly show domain formation in the interfacial adsorbed layer of meta-stable TLF's. Consequently, it is likely that such condensed soft-matter architectures could find applications in an array of new and scientifically significant nanotechnology areas. Examples of areas which might benefit from these recent highly relevant developments are the fabrication of new drug delivery systems, incorporation of specific surface templates into biosensors, optimised biomedical coatings and nanofluidic miniature analytical devices.

In this review, we summarize the current progress in the gas adsorptions of carbon nanotubes. Experimentally, the electronic and transport properties of carbon nanotubes are found to be sensitive to the adsorption of gaseous molecules. From first principle calculations, most molecules (e.g. NH3, N2, CO2, CH4, H2O, Ar, C6H6 and C6H12, etc.) adsorb weakly on nanotubes and act as charge donors to the nanotubes. With adsorption of some acceptor molecules such as NO2, O2 and C8N2O2Cl2 (DDQ), the hybridization between nanotube and molecules substantially affects the electronic and transport properties of SWNTs. Hence, gas adsorption on nanotube has significant effect on the field emission properties and might lead to new opportunities in chemical sensors.