Another opportunity in this area is the challenge of inserting polymer genes into plants and then using biomass conversion to make protein-and polyester-based polymers. This would be an entirely new method of polymer production that might be more environmentally benign than present techniques.

Materials with highly specialized functions are likely candidates for the first applications of polymer biosynthesis. The major advantage of polymers is their easy and versatile processing into useful shapes such as fibers and films. Single-step processing in which the overall shaping of a part is achieved simultaneously with its detailed structural arrangements (possibly on several length scales) will be an important factor in acceptance into the marketplace. Likely early candidates for thin film applications are those in which surface, optical, electrical, or transport characteristics are critical. Because of the small quantities of materials required, the first specialty applications of biosynthesized materials will probably be biocompatible coatings.

Sensors

Perhaps the earliest example of a biosensor is the use of canaries to detect lethal fumes in mines. Even today animals are the method of choice to search for the highly prized truffle, and dogs are used to track missing persons and to search for earthquake victims.

One of the goals of biomolecular materials research is to couple the sensitivity and selectivity of biosensing with the robustness and mass-production attributes of silicon and the reliability of electronics.40 To this end, optical-fiber-based and microelectronics-based biosensors have been fabricated to detect a large number of chemicals, including glucose, nerve gas, and ethanol.41 Many of these devices take advantage of highly selective antigen-antibody recognition events, others employ receptors as the sensing element, and yet others use catalytic selectivity of enzymes such as horseradish peroxidase to produce a detectable byproduct.

One of the major as yet underexplored opportunities in sensor research is the coupling of biological sensing units, whether they be receptors, antibodies, or enzymes, with microelectromechanical machines (MEMs). MEM devices have been fabricated with free-standing components that can be made to oscillate at a frequency that changes with the binding of a very small number of molecules.

Biomolecular-based sensors will have a wide range of applications, including the detection of low levels of toxic or harmful chemicals, the detection of biological warfare agents, and diagnostic applications in health care, agriculture, and food quality and safety. For example, one can envision nanoscale reactors and sensors that are safe and reliable parts of artificial organs, depending on the seamless integration of biomaterials with other high-performance materials.

Molecular Machines

Active transport by biomotors (discussed in Section 2, “Status”) suggests the possibility of molecular-level bioengineering and construction on a unit-by-unit basis. This capability would require the use of in situ biorecognition sensors. In other words, integrated systems might be fabricated that would use biomotors to build up supermolecular assemblies much as children construct tinker toy models.

Other examples of molecular machines are discussed elsewhere in this report, such as bacteriorhodopsin in the subsection titled “Membrane-associated Proteins” and RNA polymerases in the subsection titled “Polymers—Synthesis and Processing.” The idea of combining such machines presents a number of interesting opportunities. For example, one might couple a biomotor with an energy

40  

“Nanofabrication and Biosystems—The Frontiers and Challenges,” in Nanofabrication and Biosystems: Integrating Materials Science, Engineering, and Biology, H.C. Hoch, L.W. Jelinski, and H.G. Craighead, eds. (Cambridge University Press, New York, 1996).

41  

J.S. Schultz, “Biosensors,” Scientific American 265(August):64–69 (1991).



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement