Inspired by Biology From Molecules to Materials to Machines (2008) / Chapter Skim
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3 Advanced Functional Materials
3 Advanced Functional Materials
Pages 31-75
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From page 31... ...
In this chapter, key advances, opportunities, and challenges are reviewed in creating biomolecular materials with these specific functional attributes. To organize this chapter, important socioeconomic areas are described where applied biomolecular functional materials are having a strong impact: alternative and renewable energy, health and medicine, and national security.
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From page 32... ...
These include the chemical conversion of high-energy-containing materials such as poly saccharides (one of which is cellulose) into fuels, the production of electrical energy with enzymes for fuel cell or battery applications, the conversion of light energy into chemical energy in photosynthesis, and the conversion of chemical to mechanical energy by biological motor proteins.
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From page 33... ...
Microbial fuel cells are electrochemical cells that convert chemical energy into electrical energy by using bacteria as a catalyst to convert substrate materials into
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From page 34... ...
The principle of operation of a microbial fuel cell is illustrated in Figure 3.2. Organic substrates (e.g., glucose)
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From page 35... ...
Verstraete, and K Rabaey, "Microbial fuel cells: Methodology and technology," Environmental Science and Technology 40:5181-5192 (2006)
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From page 36... ...
Biomimetic Photosynthesis Photosynthesis, the conversion of solar energy into stored chemical energy, is a key biological process that sustains life on Earth. The energy-rich molecules produced by photosynthesis are primarily reduced carbon compounds such as cellulose, hemicellulose, and lignin, which are difficult to convert into chemical fuels.
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From page 37... ...
Biomolecular energy transducers are a rich area for basic research, with poten tially important applications in the field of renewable fuels and chemicals pro duction. The key challenge, following the example of natural photosynthesis, is the conversion of solar energy into stored chemical energy using electromagnetic energy contained in the visible portion of solar emission spectrum.
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From page 38... ...
Drawing further inspiration from natural photosynthesis, light-induced charge separations of photosynthetic reaction centers occur across a membrane that separates oxidizing and reducing equivalents. Bioinspired pho tosynthesis will build on this example by constructing artificial photosynthetic membranes that can photoproduce oxygen and fuel molecules on opposite sides of the membrane.
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From page 39... ...
The biomolecular principles for converting light energy into chemical energy are now understood to follow a conceptually simple plan that provides guidance for bioinspired research. Design principles drawn from naturally occurring biological systems can be used to form the basis of near-term (5 years)
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From page 40... ...
Reprinted with permission. BR has taken on a life of its own in fields removed from the biological origin and energy-transducing function of the protein, including protein-based field-effect transistors, artificial retinas, spatial light modulators, three-dimensional volumet ric memories, and optical holographic processors.
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From page 41... ...
. Biomolecular Motors All active cellular movements, such as separation of the chromosomes and the two daughter cells during cell division, determination and modulation of cell shape, locomotion, and targeted transport of intracellular cargos, such as mem brane bound vesicles containing neurotransmitters or waste products, involve the
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From page 42... ...
The mechanoenzymes that carry out these essential roles are termed molecular motors, and they sort into several families with related structural and mechanistic features. Understanding and controlling these functional properties in detail could facilitate harnessing them or their operating mechanisms for actuators in nanoscale devices, such as molecular sorters, filters, concentrators, switches, and power sources.
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From page 43... ...
Whether this produces force between two cellular components or causes them to move relative to each other is dependent on their mechanical properties and how they are tethered to other structures. Typical forces produced by individual molecular motors are 2-10 pN, and the distances they move per ATPase cycle are 10-40 nm.
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From page 44... ...
44 Inspired by Biology FIGURE 3.7 Typical scheme molecular motors use to generate force or move a cargo.
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From page 45... ...
. This is a rotary motor-generator that is cranked around by another motor, F0, which in turn derives its energy from a proton gradient across the outer mitochon drial membrane.
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From page 46... ...
The efficiency of energy transduction, either synthesizing or splitting ATP, can approach 100 percent! From the perspective of new materials and new nanotechnologies, these and other biological motors exemplify nanomachines that (1)
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From page 47... ...
It is likely to take 20 years before researchers can construct stable and robust molecular-scale devices that utilize biomotors or their propulsion principles. Many exciting scientific and technical challenges remain in understanding these mechano-chemical energy transducers, which offer the promise of power and propulsion systems for nanotechnology.
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From page 48... ...
Advanced Functional Materials in Health and Medicine One obvious area for the application of advanced functional materials that incorporate or mimic biomolecular components is health and medicine. In this section, three specific examples of the application of such materials in health and medicine are explored: medical diagnostics, drug delivery, and prosthetics.
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From page 49... ...
One area in which the unique molecular recognition and binding properties of biomolecules have been exploited to advantage is medical diagnostics. This $6 billion industry currently has a tremendous impact on health and medicine.
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From page 50... ...
demonstrat ing that it is similarly possible to engineer binding-induced folding into small proteins and (2) by developing optical reporter groups that couple folding-induced changes in biopolymer dynamics into easily measurable optical outputs.
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From page 51... ...
A number of challenges also remain in implementing detection elements in diagnostic devices. One of these is controlling functionality at an interface, because most of these applications immobilize functional biomolecular components.
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From page 52... ...
Transdermal delivery is also widespread, and it is recognized that delivery through the skin can be an effective way to use biomolecular materials in this application. New advances have been made that take advantage of nanoparticles for tag ging, labeling, and targeted drug delivery.
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From page 53... ...
Antibodies are being developed and identified in increasing numbers that can be used to help target either drugs or nanoparticle carriers of drugs to specific locations. In addi tion, as genetic information about disease becomes increasingly sophisticated, additional biomarkers are being identified that can also be used to target drug delivery.
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From page 54... ...
Even ultrasonic imaging is increasingly benefiting from the development of contrast agents to enhance its sensitivity. Neural Prosthetics Medical prosthetics are a good example of integrating a number of fundamen tal challenges in the design, fabrication, and integration of functional biomaterials and will require interdisciplinary advances in the physical, chemical, biological, and engineering sciences.
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From page 55... ...
. The development of these new devices presents a host of challenges in research on and application of advanced functional materials.
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From page 56... ...
growth factor) and the incorporation of biomolecular components that can reduce inflammation and stimulate growth into the surrounding tissue.
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From page 57... ...
A few examples of the focus areas of this research are artificial sight, weak electric field nanosystems for the study and control of cells and neurons, virtual-reality-based rehabilitation, rehabilitation robotics, deep brain stimulation, and next-generation neural interfaces, including molecular prosthetics. Advanced Functional Materials and National Security The unique functional properties of biological molecules offer new opportuni ties to create useful devices and systems for national security.
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From page 58... ...
The lifetime of biomolecular components (and thus the shelf life of biosensors) is also a limiting feature of these systems.
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From page 59... ...
Biological materials are also often multifunc tional, a characteristic highly desirable in artificial materials and processes. The various "super" properties of biological materials come from a sophisti cated structural design exerted by self-assembled biomolecules, but the details of how this is achieved are still largely unknown, so that now more than ever is the time to study the underlying biological control mechanisms using advances in the physical sciences and applying this knowledge to bioinspired engineering.
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From page 60... ...
60 Inspired by Biology wings, and brittle stars, described below, are just several inspirational examples that have escalated interest in smart biological materials on the part of physical scientists and engineers. These attributes lie beyond conventional engineering.
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From page 61... ...
Artificial bioinspired composites and elastic polymers are significantly inferior to their natural analogues. While this challenge is not new, it remains critical to study the structural complexity of unique biological materials and the underlying biomolecular mecha nisms of their synthesis and organization.
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Scale bars from top down: 5 mm, 100 μm, 25 µm, 5 µm, 500 nm. Glass fibers forming a crown at the base of the sponge house possess wave-guiding properties similar to those of commercial fibers.
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From page 63... ...
The threads show unusual mechanical properties: a stiff tether at one end and a shock absorber with 160 percent exten sibility at the other end (compared with a typical ~10 percent extensibility of other collagenous materials)
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From page 64... ...
Biooptics Manipulation of light is a basic feature of many living organisms. Well-known examples of biological optical structures and processes are the eyes of higher organisms and the photosynthesis mechanism in plants.
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From page 65... ...
Structural color appears to be a common strategy in nature: "Living opals" are reported to be present in peacocks, beetles, and marine organisms. FIGURE 3.15 Optical microscope photograph of scales on a Morpho wing.
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From page 66... ...
The ability to take inorganic building blocks and organize them into nanoscale, microscopic, or bulk materials is of importance in electronics, catalysis, magnetism, optics, sensors, and mechanical design. Again, the best guidance in the search for new inorganic materials and fabrica tion strategies should come from the study of biological processes.
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From page 67... ...
"Currently we are only at the beginning of a biomimetic approach to inorganic materials, and there is a long way to go, but it is feasible that one day, the dusty, dirty world of minerals could be transformed by biological insights. A quiet revolution is underway." Materials That Mimic Proteins and Membranes There are considerable efforts to mimic many of the functional properties of biomolecules and their assemblies.
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From page 68... ...
An exciting research area that has emerged in the past decade involves the mimicry of these functions in new man-made polymeric materials that are informational and designed to have a wide range of sequence-structure-function relationships. For example, microbes are transfected with artificial genes with de novo designed monomer sequences, allowing these biological cells to be harnessed for the production of nonnatural proteins.
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From page 69... ...
Integration of Functional Biomolecular Materials Exciting progress is now being made, but a great deal of work remains, toward seamlessly integrating functional, nonbiological materials and devices with living, mobile biological systems, including cells and tissues. Such nonbiological materials must be stable for a tunable period of time and remain uninfected and ideally non encapsulated when implanted in vivo.
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From page 70... ...
Today's approach to integrating elastomeric or inorganic materials with living cells or tissue is to functionalize the surfaces with biocompatible and/or bioac tive materials. Such tailored interfaces are now starting to make their way into clinical trials but still represent technology that is primarily academic and not yet commercialized.
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From page 71... ...
Particu lar functional properties of biological systems were also reviewed, and superior functional properties that have not yet been fully appreciated or exploited were described. Finally, issues in mimicry, synthesis, and integration of functional bio molecular materials were discussed as important underpinnings to the science and technology of functional biomolecular materials.
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From page 72... ...
• Challenges to scientific understanding: New functional biomolecular mate rials for diagnostic array detection with desired sensitivity and specificity -- Opportunity: Sample preparative and other methods to enhance signal detection and reduce background noise in a diagnostic platform -- Opportunity: Computational analysis of multiplexed, large diagnostic and profiling datasets for prognostic medicine • Challenges to scientific understanding: Improved delivery of drugs using functionalized and controlled-size biomolecular materials
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From page 73... ...
Decontamination materials that can detect and protect, degrade, and perhaps regenerate are under investigation by a number of agencies and provide good application platforms to integrate advanced functional materials. • Challenges to scientific understanding: Biosensors that reliably detect threats in time to prevent exposure and consequences of environmental threats (detect to warn)
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From page 74... ...
Peppas, "Advances in biomaterials, drug delivery, and bionanotechnology," American Institute of Chemical Engineers Journal 49(12)
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From page 75... ...
Drevon, and R.R. Koepsel, "Biomaterials for mediation of chemical and biological warfare agents," Annual Review of Biomedical Engineering 5:1-27 (2003)
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