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Biologically inspired nanotechnology

Nanoscience is the design and fabrication of materials from the nanometer-length scale up to create novel and significantly improved devices and materials. In contrast, traditional materials science builds from large-scale objects down. The semiconductor industry, for example, has relied on developing smaller and smaller features in large silicon wafers to fabricate computer chips. In contrast, using a nanoscience approach, one can self-assemble chains of molecules to replace wires on conventional computer chips, and it allows the semiconductor industry to produce revolutionary computer chips that are not only smaller, but also faster and more powerful than anything that exists today.

To put a nanometer-length scale into perspective, one nanometer—one billionth of a meter—is 100,000 times smaller than the width of a human hair. The building blocks in the biological world are nanometer-sized molecules such as proteins and sugars that, when assembled into intermediate length-scaled objects, deter- mine and control biological function.

In addition to developing nanoelectronics, many other features of the biosynthetic process lend themselves to devising nanotechnological materials. To do its work, nature uses highly sophisticated processes, for example, selection; self-organization; and self- assembly to provide an enormous range of "bio"-materials that ultimately form cells, tissues and organs. These materials exhibit remarkable powers of memory, replication, self-healing and self-repair.

In the case of bone, for example, nature has developed a composite ceramic material with overlap- ping levels of structural hierarchy and functional complexity. Self-assembled bio-organic materials, such as lipids and proteins, form nanoscale templates for inorganic components, guiding the final structure and shape of bone. It is the mixture of two very different materials—inorganic silicates and organic proteins— that gives bone its exceptional strength.

Biological membranes, which encapsulate all cellular machinery, represent another such example. Here, nanoscale organization and complex interactions of its constituents such as lipids and cholesterol, allow them to filter undesirable molecules from entering the cell. Recent advances in materials synthesis and biotechnology have enabled scientists to use these lessons from biology to produce highly ordered nanostructured materials with unique properties.

At Los Alamos National Laboratory, researchers recently have developed nanofilters by mimicking the biosynthesis of bone. These nanofilters are made up of ordinary glass, which has pores and channels that can be adjusted in size from four to 20 nanometers. By controlling the size and chemical properties of the pores, the constituents of complex mixtures can be separated. These nanofilters could be employed, for example, as masks to prevent exposure to biological pathogens such as viruses that can be as small as 30 nanometers in diameter. This work is supported by the Department of Energy's Office of Basic Energy Sciences in a joint project with Sandia National Laboratories and the University of New Mexico.

Los Alamos researchers also have developed miniaturized biosensors that can detect bioagents and markers for disease by mimicking cellular membranes and depositing these membranes onto optical chips. The surface of these membrane-based sensors look like the natural target of a biological agent, receptor molecules that decorate the surface of a cell membrane. By copying nature's functions using nanoscaled materials, the useful properties of sensors can be optimized permitting entirely new approaches to, for example, the early detection of disease. This cross-disciplinary effort spans fundamental science in Los Alamos' Strategic and Supporting Research Directorate and systems engineering in the Threat Reduction Directorate and is supported by the departments of Energy and Defense and by Laboratory-Directed Research and Development funds (see "Early Detection for Protection" for more on LDRD projects)).

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