Rochester Institute of Technology’s Golisano Institute for Sustainability (GIS) and Thomas H. Gosnell School of Life Sciences are the recipients of a new research grant from the National Science Foundation (NSF) to study the lifecycle environmental impacts of fullerene-based materials—a form of engineered nanomaterials used in solar cells, drug delivery systems and cosmetics.
Callie Babbitt, assistant professor at GIS, is serving as principal investigator for the $300,854 research grant. Gabrielle Gaustad, also a GIS assistant professor, and Christy Tyler, associate professor at the Gosnell School, will assist Babbitt in the research along with Gosnell Assistant Professor Sandi Connelly.
Researchers (left to right) Callie Babbitt, Christy Tyler, Gabrielle Gaustad and Sandi Connelly set up an experiment to test the ecological impact of fullerene exposure on samples of sediment from a Finger Lakes ecosystem.
While nanomaterials enable new technologies that benefit society, including applications in medicine, water treatment and renewable energy, “their potential for release into the natural environment and ultimate impact on ecosystem health is poorly understood,” according to Babbitt.
“Through this research, we hope to quantify the risks of these emerging materials—both when they are released into an ecosystem as well as when they are produced, which often has its own toxicity risks due to high electricity and chemical consumption,” Babbitt said.
The research project, which began earlier this month and is scheduled to be completed by the summer of 2017, will analyze the potential toxicity of fullerenes on aquatic organisms and then model the broader impact of nanomaterials exposure on a freshwater ecosystem. In addition, RIT researchers plan to analyze variability in the ecological impact between alternate fullerene production methods; uses in both solar cells and products such as face creams/cosmetics; and disposal pathways such as landfills or recycling.
According to Babbitt, research findings will also be integrated into educational modules developed for classroom and summer enrichment programs aimed at engaging K-12 students—primarily from underrepresented groups—in sustainability research and inspiring them to pursue careers in sustainability as well as other science, technology, engineering and mathematics fields.
NSF is an independent federal agency that supports fundamental research and education across all fields of science and engineering. The foundation’s funding reaches all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives about 50,000 competitive requests for funding, and makes about 11,500 new funding awards. NSF also awards about $593 million in professional and service contracts yearly.
An outline of Marilyn Monroe’s iconic face appeared on the clear, plastic film when a researcher fogs it with her breath. Terry Shyu, a doctoral student in chemical engineering at the University of Michigan, was demonstrating a new high-tech label for fighting drug counterfeiting. While the researchers don’t envision movie stars on medicine bottles, but they used Monroe’s image to prove their concept.
Counterfeit drugs, which at best contain wrong doses and at worst are toxic, are thought to kill more than 700,000 people per year. While less than 1 percent of the U.S. pharmaceuticals market is believed to be counterfeit, it is a huge problem in the developing world where as much as a third of the available medicine is fake.
To fight back against these and other forms of counterfeiting, researchers at U-M and in South Korea have developed a way to make labels that change when you breathe on them, revealing a hidden image. This work is reported in Advanced Materials (“Shear-Resistant Scalable Nanopillar Arrays with LBL-Patterned Overt and Covert Images”). “One challenge in fighting counterfeiting is the need to stay ahead of the counterfeiters,” said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Chemical Engineering who led the Michigan effort.
The method requires access to sophisticated equipment that can create very tiny features, roughly 500 times smaller than the width of a human hair. But once the template is made, labels can be printed in large rolls at a cost of roughly one dollar per square inch. That’s cheap enough for companies to use in protecting the reputation of their products—and potentially the safety of their consumers.
Terry Shyu, MSE PhD Student, demonstrates use of nanopillars that reveal hidden images via condensation of fluid on the structures.
“We use a molding process,” Shyu said, noting that this inexpensive manufacturing technique is also used to make plastic cups.
The labels work because an array of tiny pillars on the top of a surface effectively hides images written on the material beneath. Shyu compares the texture of the pillars to a submicroscopic toothbrush. The hidden images appear when the pillars trap moisture.
“You can verify that you have the real product with just a breath of air,” Kotov said.
The simple phenomenon could make it easy for buyers to avoid being fooled by fake packaging.
Previously, it was impossible to make nanopillars through cheap molding processes because the pillars were made from materials that preferred adhering to the mold rather than whatever surface they were supposed to cover. To overcome this challenge, the team developed a special blend of polyurethane and an adhesive.
The liquid polymer filled the mold, but as it cured, the material shrunk slightly. This allowed the pillars to release easily. They are also strong enough to withstand rubbing, ensuring that the label would survive some wear, such as would occur during shipping. The usual material for making nanopillars is too brittle to survive handling well.
The team demonstrated the nanopillars could stick to plastics, fabric, paper and metal, and they anticipate that the arrays will also transfer easily to glass and leather.
Following seed funding from the National Science Foundation’s Innovation Corps program and DARPA’s Small Business Technology Transfer program, the university is pursuing patent protection for the intellectual property and is seeking commercialization partners to help bring the technology to market.
Consistent with the adaptive management process described in this strategy, the NEHI Working Group has made significant progress through the use of various evaluation tools to understand the current status of nanotechnology-related EHS (nanoEHS) research and the Federal nanoEHS research investment.
Most notably, the participating agencies reported to the NEHI Working Group examples of ongoing, completed, and anticipated EHS research (from FY 2009 through FY 2012) relevant to implementation of the 2011 NNI EHS Research Strategy.
These examples, described in this document, demonstrate the breadth of activities in all six core research areas of the 2011 NNI EHS Research Strategy: Nanomaterial Measurement Infrastructure, Human Exposure Assessment, Human Health, Environment, Risk Assessment and Risk Management Methods, and Informatics and Modeling. Overall, coordination and implementation of the 2011 NNI EHS Strategy across the NEHI agencies has enabled:
Development of comprehensive measurement tools that consider the full life cycles of engineered nanomaterials (ENMs) in various media.
Collection of exposure assessment data and resources to inform workplace exposure control strategies for key classes of ENMs.
Enhanced understanding of the modes of interaction between ENMs and physiological systems relevant to human biology.
Improved assessment of transport and transformations of ENMs in various environmental media, biological systems, and over full life cycles.
Development of principles for establishing robust risk assessment and risk management practices for ENMs and nanotechnology-enabled products that incorporate ENMs, as well as approaches for identifying, characterizing, and communicating risks to all stakeholders.
Coordination of efforts to enhance data quality, modeling, and simulation capabilities for nanotechnology, towards building a collaborative nanoinformatics infrastructure.
Extensive collaboration and coordination among the NEHI agencies as well as with international organizations is evident by the numerous research examples and by other activities such as co-sponsored workshops and interagency agreements described in this review document. These examples and activities are a small subset of the extensive research efforts at the NEHI agencies. This document addresses the NEHI Working Group’s broader efforts in coordination, implementation, and social outreach in nanoEHS, as identified in the 2011 NNI EHS Research Strategy. As the NNI agencies sustain a robust budget for EHS research, Federal agencies will continue to invest in tools and share information essential to assess and manage potential risks of current and anticipated ENMs and nanotechnology-enabled products throughout their life cycles. The agencies will also continue to engage with the stakeholder community to establish a broad EHS knowledge base in support of regulatory decision making and responsible development of nanotechnology.
(Nanowerk News) If the promise of nanotechnology is to be fulfilled, then research programs must leapfrog to new nanomanufacturing processes. That’s the conclusion of a review of the current state of nanoscience and nanotechnology to be published in the International Journal of Nanomanufacturing (“Nanomanufacturing: path to implementing nanotechnology”).
Khershed Cooper of the Materials Science and Technology Division, at the Naval Research Laboratory, in Washington, DC and Ralph Wachter of the Division of Computer and Network Systems, at the National Science Foundation, in Arlington, Virginia, USA, explain how research in nanoscience and the emerging applications in nanotechnology have led to new understanding of the properties of matter as well producing many novel materials, structures and devices.
Indeed, the list of possible applications of nanotechnology continues to grow: water filtration and purification, engineered composite materials with modified mechanical properties controlled electrical behaviour and corrosion resistance. There are nano-based materials being used as sealants, anti-fogging and abrasion resistant coatings for glass and other materials, conductive resins, paints and electromagnetic shielding as well as sensors, self-healing materials, super-hydrophobic surfaces, solar cells and ultracapacitors for energy storage as well as materials for armour and protection against bullets and bombs.
The team’s own research has focused on developing tools and techniques to make scalable processes for nanomanufacturing. They are investigating massively parallel techniques, masks and maskless processes for making 3D structures with nanoscopic features. However, they also suggest that several obstacles must be surmounted for nanotechnology to thrive as a future industrial endeavour. In particular, the team believes that research and development should be directed in the following areas:
– Multi-scale design, modelling and simulation of nanosystems.
– Component integration within large-scale systems.
– Integration across physical scales.
– Qualification, certification, verification and validation.
– Cyber-enabled manufacturing systems.
“Looking ahead, nanotechnology is slated to move into complex, multi-functional, multi-component nanosystems, e.g., nano-machines and nano-robots,” the team concludes. “These nanosystems will be adaptive, responsive to external stimuli, biomimetic, intelligent, smart and autonomous. Nanomanufacturing R&D will be needed to develop the knowledge base for the reliable production of these complex nanosystems.”
MIT chemical engineers have designed tiny particles that can “steer” themselves along preprogrammed trajectories and align themselves to flow through the center of a microchannel, making it possible to control the particles’ flow through microfluidic devices without applying any external forces.
A slightly asymmetrical particle flows along the center of a microfluidic channel
Such particles could make it more feasible to design lab-on-a-chip devices, which hold potential as portable diagnostic devices for cancer and other diseases. These devices consist of microfluidic channels engraved on tiny chips, but current versions usually require a great deal of extra instrumentation attached to the chip, limiting their portability.
Much of that extra instrumentation is needed to keep the particles flowing single file through the center of the channel, where they can be analyzed. This can be done by applying a magnetic or electric field, or by flowing two streams of liquid along the outer edges of the channel, forcing the particles to stay in the center.
The new MIT approach, described in Nature Communications, requires no external forces and takes advantage of hydrodynamic principles that can be exploited simply by altering the shapes of the particles.
Lead authors of the paper are Burak Eral, an MIT postdoc, and William Uspal, who recently received a PhD in physics from MIT. Patrick Doyle, the Singapore Research Professor of Chemical Engineering at MIT, is the senior author of the paper.
Exploiting asymmetry
The work builds on previous research showing that when a particle is confined in a narrow channel, it has strong hydrodynamic interactions with both the confining walls and any neighboring particles. These interactions, which originate from how particles perturb the surrounding fluid, are powerful enough that they can be used to control the particles’ trajectory as they flow through the channel.
The MIT researchers realized that they could manipulate these interactions by altering the particles’ symmetry. Each of their particles is shaped like a dumbbell, but with a different-size disc at each end.
When these asymmetrical particles flow through a narrow channel, the larger disc encounters more resistance, or drag, forcing the particle to rotate until the larger disc is lagging behind. The asymmetrical particles stay in this slanted orientation as they flow.
Because of this slanted orientation, the particles not only move forward, in the direction of the flow, they also drift toward one side of the channel. As a particle approaches the wall, the perturbation it creates in the fluid is reflected back by the wall, just as waves in a pool reflect from its wall. This reflection forces the particle to flip its orientation and move toward the center of the channel.
Slightly asymmetrical particles will overshoot the center and move toward the other wall, then come back toward the center again until they gradually achieve a straight path. Very asymmetrical particles will approach the center without crossing it, but very slowly. But with just the right amount of asymmetry, a particle will move directly to the centerline in the shortest possible time.
“Now that we understand how the asymmetry plays a role, we can tune it to what we want. If you want to focus particles in a given position, you can achieve that by a fundamental understanding of these hydrodynamic interactions,” Eral says.
“The paper convincingly shown that shape matters, and swarms can be redirected provided that shapes are well designed,” says Patrick Tabeling, a professor at the École Supérieure de Physique et de Chimie Industrielles in Paris, who was not part of the research team. “The new and quite sophisticated mechanism … may open new routes for manipulating particles and cells in an elegant manner.”
Diagnosis by particles
In 2006, Doyle’s lab developed a way to create huge batches of identical particles made of hydrogel, a spongy polymer. To create these particles, each thinner than a human hair, the researchers shine ultraviolet light through a mask onto a stream of flowing building blocks, or oligomers. Wherever the light strikes, solid polymeric particles are formed in the shape of the mask, in a process called photopolymerization.
During this process, the researchers can also load a fluorescent probe such as an antibody at one end of the dumbbell. The other end is stamped with a barcode — a pattern of dots that reveals the particle’s target molecule.
This type of particle can be useful for diagnosing cancer and other diseases, following customization to detect proteins or DNA sequences in blood samples that can be signs of disease. Using a cytometer, scientists can read the fluorescent signal as the particles flow by in single file.
“Self-steering particles could lead to simplified flow scanners for point-of-care devices, and also provide a new toolkit from which one can develop other novel bioassays,” Doyle says.
The research was funded by the National Science Foundation, Novartis, and the Institute for Collaborative Biotechnologies through the U.S. Army Research Office.
From solar cells to optoelectronic sensors to lasers and imaging devices, many of today’s semiconductor technologies hinge upon the absorption of light. Absorption is especially critical for nano-sized structures at the interface between two energy barriers called quantum wells, in which the movement of charge carriers is confined to two-dimensions. Now, for the first time, a simple law of light absorption for 2D semiconductors has been demonstrated.
Working with ultrathin membranes of the semiconductor indium arsenide, a team of researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has discovered a quantum unit of photon absorption, which they have dubbed “AQ,” that should be general to all 2D semiconductors, including compound semiconductors of the III-V family that are favored for solar films and optoelectronic devices. This discovery not only provides new insight into the optical properties of 2D semiconductors and quantum wells, it should also open doors to exotic new optoelectronic and photonic technologies.
“We used free-standing indium arsenide membranes down to three nanometers in thickness as a model material system to accurately probe the absorption properties of 2D semiconductors as a function of membrane thickness and electron band structure,” says Ali Javey, a faculty scientist in Berkeley Lab’s Materials Sciences Division and a professor of electrical engineering and computer science at the University of California (UC) Berkeley. “We discovered that the magnitude of step-wise absorptance in these materials is independent of thickness and band structure details.”
Javey is one of two corresponding authors of a paper describing this research in the Proceedings of the National Academy of Sciences (PNAS). The paper is titled “Quantum of optical absorption in two-dimensional semiconductors.” Eli Yablonovitch, an electrical engineer who also holds joint appointments with Berkeley Lab and UC Berkeley, is the other corresponding author. Co-authors are Hui Fang, Hans Bechtel, Elena Plis, Michael Martin and Sanjay Krishna.
Previous work has shown that graphene, a two-dimensional sheet of carbon, has a universal value of light absorption. Javey, Yablonovitch and their colleagues have now found that a similar generalized law applies to all 2D semiconductors. This discovery was made possible by a unique process that Javey and his research group developed in which thin films of indium arsenide are transferred onto an optically transparent substrate, in this case calcium fluoride.
“This provided us with ultrathin membranes of indium arsenide, only a few unit cells in thickness, that absorb light on a substrate that absorbed no light,” Javey says. “We were then able to investigate the optical absorption properties of membranes that ranged in thickness from three to 19 nanometers as a function of band structure and thickness.”
Using the Fourier transform infrared spectroscopy (FTIR) capabilities of Beamline 1.4.3 at Berkeley Lab’s Advanced Light Source, a DOE national user facility, Javey, Yablonovitch and their co-authors measured the magnitude of light absorptance in the transition from one electronic band to the next at room temperature. They observed a discrete stepwise increase at each transition from indium arsenide membranes with an AQ value of approximately 1.7-percent per step.
“This absorption law appears to be universal for all 2D semiconductor systems,” says Yablonovitch. “Our results add to the basic understanding of electron–photon interactions under strong quantum confinement and provide a unique insight toward the use of 2D semiconductors for novel photonic and optoelectronic applications.”
Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more information, visit http://www.lbl.gov.
The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov.
The Advanced Light Source is a third-generation synchrotron light source producing light in the x-ray region of the spectrum that is a billion times brighter than the sun. A DOE national user facility, the ALS attracts scientists from around the world and supports its users in doing outstanding science in a safe environment. The Advanced Light Source is a third-generation synchrotron light source producing light in the x-ray region of the spectrum that is a billion times brighter than the sun. A DOE national user facility, the ALS attracts scientists from around the world and supports its users in doing outstanding science in a safe environment. For more information, visit http://www.als.lbl.gov/.
Making large quantities of reliable, inexpensive nanoparticles for batteries, solar cells, catalysts and other energy applications has proven challenging due to manufacturing limits. A Cornell research team is working to improve such processes with a $1.5 million National Science Foundation (NSF) grant to support scalable nanomanufacturing and device integration.
Richard Robinson, assistant professor of materials science and engineering, and Tobias Hanrath, associate professor of chemical and biomolecular engineering, have been awarded a four-year Nanoscale Interdisciplinary Research Team grant through the NSF’s Scalable Nanomanufacturing Program.
Their goal is to improve large-scale, solution-phase synthesis of high-quality nanoparticles – in particular metal sulfides – and demonstrate their integration into devices including battery electrodes and solar photovoltaics.
As Robinson explains, “the properties of colloidal quantum dots can be tuned by changing their size and composition, and the field has really come a long way over the years to learn how to tailor those properties to be ideal for energy applications. We’re really on the forefront of this technology. The problem is that there hasn’t been a way to make a massive amount of particles that are all exactly the same size and composition. Scalable methods to manufacture nanoparticles could really change the landscape.”
The key to their project will be the use of a reactive precursor that had previously only been limited to aqueous-phase synthesis of nanomaterials. Their method could potentially benefit the application of semiconductors and semi-metalcolloidal nanocrystals by providing a nontoxic alternative to metal chalcogenide systems, including the widely used semiconductor cadmium selenide.
Hanrath, co-principal investigator, analogized the research goals with the development of polymers and plastics 50 years ago. Transforming polymers from a bench-scale scientific discovery to a multibillion dollar industry involved “several interesting chemical engineering challenges,” Hanrath noted.
“We’re excited about the prospect of applying similar concepts to develop methods for the scalable production of high-quality nanoparticles to enable the deployment and commercialization of emerging nanotechnologies,” Hanrath said.
The grant, which runs through 2017, also covers outreach and education activities, including an NSF-sponsored K-12 education program to work with high school teachers for enhancing nanoscience curricula.
One of the most promising types of solar cells has a few drawbacks. A scientist at Michigan Technological University may have overcome one of them.
Dye-sensitized solar cells are thin, flexible, easy to make and very good at turning sunshine into electricity. However, a key ingredient is one of the most expensive metals on the planet: platinum. While only small amounts are needed, at $1,500 an ounce, the cost of the silvery metal is still significant.
Yun Hang Hu, the Charles and Caroll McArthur Professor of Materials Science and Engineering, has developed a new, inexpensive material that could replace the platinum in solar cells without degrading their efficiency: 3D graphene.
Regular graphene is a famously two-dimensional form of carbon just a molecule or so thick. Hu and his team invented a novel approach to synthesize a unique 3D version with a honeycomb-like structure. To do so, they combined lithium oxide with carbon monoxide in a chemical reaction that forms lithium carbonate (Li2CO3) and the honeycomb graphene.
The Li2CO3 helps shape the graphene sheets and isolates them from each other, preventing the formation of garden-variety graphite. Furthermore, the Li2CO3 particles can be easily removed from 3D honeycomb-structured graphene by an acid.
The researchers determined that the 3D honeycomb graphene had excellent conductivity and high catalytic activity, raising the possibility that it could be used for energy storage and conversion.
So they replaced the platinum counter electrode in a dye-sensitized solar cell with one made of the 3D honeycomb graphene. Then they put the solar cell in the sunshine and measured its output.
The cell with the 3D graphene counter electrode converted 7.8 percent of the sun’s energy into electricity, nearly as much as the conventional solar cell using costly platinum (8 percent).
Synthesizing the 3D honeycomb graphene is neither expensive nor difficult, said Hu, and making it into a counter electrode posed no special challenges.
The research has been funded by the American Chemical Society Petroleum Research Fund (PRF-51799-ND10) and the National Science Foundation (NSF-CBET-0931587).
Michigan Technological University (www.mtu.edu) is a leading public research university developing new technologies and preparing students to create the future for a prosperous and sustainable world. Michigan Tech offers more than 130 undergraduate and graduate degree programs in engineering; forest resources; computing; technology; business; economics; natural, physical and environmental sciences; arts; humanities; and social sciences.
Next generation solar panels could yield substantially lower costs per kilowatt-hour with this technological development.
Two crucial tasks exist for realizing high-efficiency polymer solar cells: increasing the range of the spectral absorption of light and efficiently harvesting photo-generated excitons. In this work, Förster resonance energy transfer (FRET)-based heterojunction polymer solar cells that incorporate squaraine dye (SQ) were fabricated and investigated.
The high absorbance of squaraine in the near-infrared region broadens the spectral absorption of the solar cells and assists in developing an ordered nano-morphology for enhanced charge transport. Femtosecond spectroscopic studies revealed highly efficient (up to 96%) excitation energy transfer from poly(3-hexylthiophene), also known as P3HT, to squaraine occurring on a picosecond timescale.
A 38% increase in power conversion efficiency was realized to reach 4.5%; this finding suggests that this system has improved exciton migration over long distances. This architecture transcends traditional multiblend systems, allowing multiple donor materials with separate spectral responses to work synergistically, thereby enabling an improvement in light absorption and conversion. This discovery opens up a new avenue for the development of high-efficiency polymer solar cells.
Why Does This Matter?
A new energy transfer mechanism has been exploited for the first time, allowing significantly more efficient energy harvesting in P3HT/dye solar cells compared to P3HT-alone solar cells. Also, broadening the light absorption spectrum into the near-infrared region and developing nanoscale parts to the solar cell has improved the device.
Allowing different light-absorbing materials to work synergistically has led to well-ordered polymer networks without post-processing.
Energy level diagram of the components of the ternary blend solar cell highlighting pathways for charge generation.
What Are the Specifics?
CFN Capability: CFN’s Advanced Optical Spectroscopy & Microscopy Facility was used to understand the energy conversion mechanism and rate of electronic transfer between the dye and polymer in the solar cells.
The use of squaraine dye and FRET of charge carriers improved the efficiency of polymer solar cells. Femtosecond spectroscopic studies revealed highly efficient excitation energy transfer from P3HT to SQ occurring on a picosecond timescale. This suggested that this system has improved exciton migration over long distances.
For the first time, FRET was exploited to enhance exciton harvesting in polymer bulk heterojunction solar cells.
Reference
Jing-Shun Huang1, Tenghooi Goh1, Xiaokai Li1, Matthew Y. Sfeir2, Elizabeth A. Bielinski3, Stephanie Tomasulo4, Minjoo L. Lee4, Nilay Hazari3, and André D. Taylor1, Polymer bulk heterojunction solar cells employing Förster resonance energy transfer, Nature Photonics 7, 479-485 (2013).
Department of Chemistry, Yale University, New Haven, Connecticut 06511, USA
Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA
Acknowledgment of Support
This work was supported primarily by the SOLAR program of the National Science Foundation (NSF; DMR-0934520) and the Yale Climate and Energy Institute. A.D.T. acknowledges support from a NSF-CAREER award (CBET-0954985) and NASA (CT Space Grant Consortium). Research was carried out in part at the Centre for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the US Department of Energy, Office of Basic Energy Sciences (contract no. DE-AC02-98CH10886). The authors thank C. Schmuttenmaer, E. Yan and S. Wang for informative discussions.
CAMBRIDGE, Mass.MIT News Office: Chemical engineers find that arrays of carbon nanotubes can detect flaws in drugs and help improve production. — MIT chemical engineers have discovered that arrays of billions of nanoscale sensors have unique properties that could help pharmaceutical companies produce drugs — especially those based on antibodies — more safely and efficiently.
Using these sensors, the researchers were able to characterize variations in the binding strength of antibody drugs, which hold promise for treating cancer and other diseases. They also used the sensors to monitor the structure of antibody molecules, including whether they contain a chain of sugars that interferes with proper function. “This could help pharmaceutical companies figure out why certain drug formulations work better than others, and may help improve their effectiveness,” says Michael Strano, an MIT professor of chemical engineering and senior author of a recent paper describing the sensors in the journal ACS Nano.
The team also demonstrated how nanosensor arrays could be used to determine which cells in a population of genetically engineered, drug-producing cells are the most productive or desirable, Strano says. Lead author of the paper is Nigel Reuel, a graduate student in Strano’s lab. The labs of MIT faculty members Krystyn Van Vliet, Christopher Love and Dane Wittrup also contributed, along with scientists from Novartis. Testing drug strength
Strano and other scientists have previously shown that tiny, nanometer-sized sensors, such as carbon nanotubes, offer a powerful way to detect minute quantities of a substance. Carbon nanotubes are 50,000 times thinner than a human hair, and they can bind to proteins that recognize a specific target molecule. When the target is present, it alters the fluorescent signal produced by the nanotube in a way that scientists can detect.
Some researchers are trying to exploit large arrays of nanosensors, such as carbon nanotubes or semiconducting nanowires, each customized for a different target molecule, to detect many different targets at once. In the new study, Strano and his colleagues wanted to explore unique properties that emerge from large arrays of sensors that all detect the same thing.
The first feature they discovered, through mathematical modeling and experimentation, is that uniform arrays can measure the distribution in binding strength of complex proteins such as antibodies. Antibodies are naturally occurring molecules that play a key role in the body’s ability to recognize and defend against foreign invaders. In recent years, scientists have been developing antibodies to treat disease, particularly cancer. When those antibodies bind to proteins found on cancer cells, they stimulate the body’s own immune system to attack the tumor.
For antibody drugs to be effective, they must strongly bind their target. However, the manufacturing process, which relies on nonhuman, engineered cells, does not always generate consistent, uniformly binding batches of antibodies.
Currently, drug companies use time-consuming and expensiveanalytical processes to test each batch and make sure it meets the regulatory standards for effectiveness. However, the new MIT sensor could make this process much faster, allowing researchers to not only better monitor and control production, but also to fine-tune the manufacturing process to generate a more consistent product.
“You could use the technology to reject batches, but ideally you’d want to use it in your upstream process development to better define culture conditions, so then you wouldn’t produce spurious lots,” Reuel says. Measuring weak interactions
Another useful trait of such sensors is their ability to measure very weak binding interactions, which could also help with antibody drug manufacturing.
Antibodies are usually coated with long sugar chains through a process called glycosylation. These sugar chains are necessary for the drugs to be effective, but they are extremely hard to detect because they interact so weakly with other molecules. Drug-manufacturing organisms that synthesize antibodies are also programmed to add sugar chains, but the process is difficult to control and is strongly influenced by the cells’ environmental conditions, including temperature and acidity.
Without the appropriate glycosylation, antibodies delivered to a patient may elicit an unwanted immune response or be destroyed by the body’s cells, making them useless.
“This has been a problem for pharmaceutical companies and researchers alike, trying to measure glycosylated proteins by recognizing the carbohydrate chain,” Strano says. “What a nanosensor array can do is greatly expand the number of opportunities to detect rare binding events. You can measure what you would otherwise not be able to quantify with a single, larger sensor with the same sensitivity.” This tool could help researchers determine the optimal conditions for the correct degree of glycosylation to occur, making it easier to consistently produce effective drugs. Mapping production
The third property the researchers discovered is the ability to map the production of a molecule of interest. “One of the things you would like to do is find strains of particular organisms that produce the therapeutic that you want,” Strano says. “There are lots of ways of doing this, but none of them are easy.”
The MIT team found that by growing the cells on a surface coated with an array of nanometer-sized sensors, they could detect the location of the most productive cells. In this study, they looked for an antibody produced by engineered human embryonic kidney cells, but the system could also be tailored to other proteins and organisms.
Once the most productive cells are identified, scientists look for genes that distinguish those cells from the less productive ones and engineer a new strain that is highly productive, Strano says.
The researchers have built a briefcase-sized prototype of their sensor that they plan to test with Novartis, which funded the research along with the National Science Foundation.
“Carbon nanotubes coupled to protein-binding entities are interesting for several areas of bio-manufacturing as they offer great potential for online monitoring of product levels and quality. Our collaboration has shown that carbon nanotube-based fluorescent sensors are applicable for such purposes, and I am eager to follow the maturation of this technology,” says Ramon Wahl, an author of the paper and a principal scientist at Novartis.
Rochester Institute of Technology’s Golisano Institute for Sustainability (GIS) and Thomas H. Gosnell School of Life Sciences are the recipients of a new research grant from the National Science Foundation (NSF) to study the lifecycle environmental impacts of fullerene-based materials—a form of engineered nanomaterials used in solar cells, drug delivery systems and cosmetics.
Next generation solar panels could yield substantially lower costs per kilowatt-hour with this technological development.
Genesis Nanotechnology 
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