Chemical Education Today
Research Advances: Nanotechnology Research Attacks Cancer, Offers Big Development in Light Harvesting, and Addresses the 3Rs: Recover, Recycle, and Reuse by Angela G. King Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109
[email protected] Science of the Ultrasmall Promises Big Benefits for Cancer Patients A $145-million federal government effort to harness the power of nanotechnology to improve the diagnosis, treatment, and prevention of cancer is producing innovations that will radically improve care for those with the disease. That is the conclusion of an update on the status of the program, called the National Cancer Institute Alliance for Nanotechnology in Cancer (1). Piotr Grodzinski and colleagues note in an article that the alliance, launched in 2004, funds and coordinates research specifically intended to move knowledge about nanomedicine out of laboratories and into hospitals and doctor's offices in a effective way. The alliance builds on more than 50 years of advances in cancer care that, although substantial, still confront the reality of cancer as the leading cause of death in the United States and globally. The article describes a range of advances, including some showing significant promise in clinical trials that are poised to make a significant impact on cancer. They promise earlier disease diagnosis, highly targeted treatments that kill cancer cells while leaving normal cells alone, fewer side effects, and improved survival, the article reports. Avenues of exploration include in vitro diagnostics, targeted anticancer and contrast enhancement agent delivery, and therapeutic monitoring (Figure 1). The Institute's Web site (2) includes an excellent explanation of what nanotechnology is and how it is being applied in cancer research. Additionally, Research Advances published in this Journal have previously reported on cutting-edge work that uses nanotechnology to detect and treat cancer (3-7). Criswell's article (8) also offers excellent examples of and incentives for introducing nanotechnology into secondary school chemistry classes. Details on two other recent advances in nanotechnology research are described below. Golden Nanoscale System Turns Light into Electrical Current Material scientists in the Nano/Bio Interface Center at the University of Pennsylvania have demonstrated the transduction of optical radiation to electrical current in a molecular circuit (9). The system, an array of nanosized molecules of gold, responds to electromagnetic waves by creating surface plasmons that induce and project electrical current across molecules, similar to the process involved in photovoltaic solar cells.
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The results of the scientists' research may provide a technological approach for higher-efficiency energy harvesting with a nanosized circuit that can power itself, potentially through sunlight. Recently, surface plasmons have been engineered into a variety of light-activated devices such as biosensors. It is also possible that the system could be used for computer data storage. While the traditional computer processor represents data in binary form (either on or off), a computer that used such photovoltaic circuits could store data corresponding to wavelengths of light. Because molecular compounds exhibit a wide range of optical and electrical properties, the strategies for fabrication, testing, and analysis elucidated in this study can form the basis of a new set of devices in which plasmon-controlled electrical properties of single molecules could be designed with wide implications for plasmonic circuits and optoelectronic and energy-harvesting devices. Dawn Bonnell, a professor of materials science and the director of the Nano/Bio Interface Center, and colleagues fabricated an array of light-sensitive gold nanoparticles (AuNPs), linking them on a glass substrate. Optimizing the space between the nanoparticles, researchers used optical radiation to excite conductive electrons, called plasmons, to ride the surface of the gold nanoparticles and focus light to the junction where the molecules were connected. The plasmon effect increases the efficiency of current production in the molecule by a factor of 400-2000%, which can then be transported through the network to the outside world. In the case where the optical radiation excites a surface plasmon and the nanoparticles are optimally coupled, a large electromagnetic field is established between the particles and captured by gold nanoparticles. The particles then couple to one another, forming a percolative path across opposing electrodes. The size, shape, and separation can be tailored to engineer the region of focused light. When the size, shape, and separation of the particles are optimized to produce “resonant” optical antennae, enhancement factors of thousands might result. Bonnell's team used dithiol meso-to-meso ethyne-bridged (porphinato)zinc(III) oligomers synthesized by Therien's group to tether the AuNPs because they display a large absorptive oscillator strength in the g520 nm wavelength region where isolated and coupled plasmon resonances occur. Furthermore, the team demonstrated that the magnitude of the photoconductivity of the plasmon-coupled nanoparticles can
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r 2010 American Chemical Society and Division of Chemical Education, Inc. pubs.acs.org/jchemeduc Vol. 87 No. 9 September 2010 10.1021/ed100639j Published on Web 07/16/2010
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Figure 1. Gold nanoparticles, the bright structures attached to the cultured human cell in this electron microscope image, are among the ultrasmall technologies that may help improve the diagnosis and treatment of cancer in the future. Image courtesy of Catherine C. Berry, National Science Foundation.
be tuned independently of the optical characteristics of the molecule, a result that has significant implications for future nanoscale optoelectronic devices. “If the efficiency of the system could be scaled up without any additional, unforeseen limitations, we could conceivably manufacture a one-amp, one-volt sample the diameter of a human hair and an inch long”, Bonnell reports. More information on the Nano/Bio Interface Center at the University of Pennsylvania is available online (10). Recovering Pricey Nanoparticles Scientists are reporting the first use of a new method that may make it easier for manufacturers to recover, recycle, and reuse nanoparticles, some of which can be more precious than gold, ounce for ounce (11). The method, which offers a solution to a nagging problem, could speed application of nanotechnology in new generations of solar cells, flexible electronic displays, and other products, the scientists suggest. Julian Eastoe and colleagues point out that scientists are seeking better ways to recover and reuse nanoparticles. Without such technology, manufacturing processes that take advantage of nanoparticles' unusual properties might be prohibitively expensive. Recovering and recycling nanoparticles is especially difficult because they tend to form complex, hard-to-separate mixtures with other substances. Eastoe and colleagues describe the development of a special type of microemulsion that may solve this problem. In laboratory tests using cadmium and zinc nanoparticles (Cd-NPs and ZnNPs), they showed how the oil and water in the microemulsion separated into two layers when heated (Figure 2). One layer contained nanoparticles that could be recovered; the other contained none. The separation process is reversible, and the recovered particles retain their shape and chemical properties, which is crucial for their reuse, the scientists note. Additional information on Eastoe's research can be found online (12). Related to this research from Bristol, U.K. is a range of fully developed nanotech-relevant demonstrations and experiments appropriate for science educators (13-15). Educators interested in discussing this work may integrate it with a published activity using simple electrostatic ideas to introduce lower-level undergraduates to size-dependent phenomena or a laboratory experiment synthesizing Cd-NP (16, 17).
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Figure 2. Recent advances in nanotechnology have made recovering pricey nanoparticles easier. Scientists have employed a novel, reversible control over colloid stability to separate and recover NPs without significant change to the NPs' properties or functionality. Images provided by J. Eastoe and used with permission.
Literature Cited 1. Farrell, D.; Alper, J.; Ptak, K.; Panaro, N.; Grodzinski, P.; Barker, A. Recent Advances from the National Cancer Institute Alliance for Nanotechnology in Cancer. ACS Nano 2010, 4, 589–594. 2. NCI Alliance for Nanotechnology in Cancer Home Page. http:// nano.cancer.gov/ (accessed Jul 2010). 3. King, A. Research Advances. J. Chem. Educ. 2005, 82, 1274–1278. 4. King, A. Research Advances. J. Chem. Educ. 2009, 86, 670–673. 5. King, A. Research Advances. J. Chem. Educ. 2010, 87, 464–466. 6. King, A. Research Advances. J. Chem. Educ. 2010, 87, 3–4. 7. King, A. Research Advances. J. Chem. Educ. 2007, 84, 1082–1085. 8. Criswell, B. Connecting Acids and Bases with Encapsulation...and Chemistry with Nanotechnology. J. Chem. Educ. 2007, 84, 1136– 1139. 9. Banerjee, P.; Conklin, D.; Nanayakkara, S.; Park, T.-H.; Therien, M.; Bonnell, D. Plasmon-Induced Electrical Conduction in Molecular Devices. ACS Nano 2010, 4, 1019–25. 10. Nano/Bio Interface Center Home Page. http://www.nanotech. upenn.edu/ (accessed Jul 2010). 11. Myakonkaya, O.; Guibert, C.; Eastoe, J.; Grillo, I. Recovery of Nanoparticles Made Easy. Langmuir 2010, 26, 3794–3797. 12. Julian Eastoe Research Group Advanced Surfactants and Interfaces Home Page. http://www.chm.bris.ac.uk/eastoe/jeres.htm (accessed Jul 2010). 13. Bristol ChemLabS Home Page. http://www.chemlabs.bris.ac.uk/ (accessed Jul 2010). 14. Bristol ChemLabS Outreach. http://www.chemlabs.bris.ac.uk/ outreach/ (accessed Jul 2010). 15. Bristol ChemLabS Outreach Resources for Schools. http://www. chemlabs.bris.ac.uk/outreach/resources/ (accessed Jul 2010). 16. Baker, M.; Baker, D. Teaching Nanochemistry: Madelung Constants of Nanocrystals. J. Chem. Educ. 2010, 87, 280–284. 17. Winkelmann, K.; Noviello, T.; Brooks, S. Preparation of CdS Nanoparticles by First-Year Undergraduates. J. Chem. Educ. 2007, 84, 709–710.
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r 2010 American Chemical Society and Division of Chemical Education, Inc.
