News Article | November 24, 2016
(MEDFORD/SOMERVILLE, Mass., Nov. 24, 2016)--Learning by taking practice tests, a strategy known as retrieval practice, can protect memory against the negative effects of stress, report scientists from Tufts University in a new study published in Science on Nov. 25. In experiments involving 120 student participants, individuals who learned a series of words and images by retrieval practice showed no impairment in memory after experiencing acute stress. Participants who used study practice, the conventional method of re-reading material to memorize it, remembered fewer items overall, particularly after stress. "Typically, people under stress are less effective at retrieving information from memory. We now show for the first time that the right learning strategy, in this case retrieval practice or taking practice tests, results in such strong memory representations that even under high levels of stress, subjects are still able to access their memories," said senior study author Ayanna Thomas, Ph.D., associate professor and director of the graduate program in psychology at Tufts. "Our results suggest that it is not necessarily a matter of how much or how long someone studies, but how they study," said Amy Smith, graduate student in psychology at Tufts and corresponding author on the study. The research team asked participants to learn a set of 30 words and 30 images. These were introduced through a computer program, which displayed one item at a time for a few seconds each. To simulate note taking, participants were given 10 seconds to type a sentence using the item immediately after seeing it. One group of participants then studied using retrieval practice, and took timed practice tests in which they freely recalled as many items as they could remember. The other group used study practice. For these participants, items were re-displayed on the computer screen, one at a time, for a few seconds each. Participants were given multiple timed periods to study. After a 24-hour break, half of each group was placed into a stress-inducing scenario. These participants were required to give an unexpected, impromptu speech and solve math problems in front of two judges, three peers and a video camera. Participants took two memory tests, in which they recalled the words or images they studied the previous day. These tests were taken during the stress scenario and twenty minutes after, to examine memory under immediate and delayed stress responses. The remaining study participants took their memory tests during and after a time-matched, non-stressful task. Stressed individuals who learned through retrieval practice remembered an average of around 11 items out of each set of 30 words and images, compared to 10 items for their non-stressed counterparts. Participants who learned through study practice remembered fewer words overall, with an average of 7 items for stressed individuals and an average of a little under 9 items for those who were not stressed. "Even though previous research has shown that retrieval practice is one of the best learning strategies available, we were still surprised at how effective it was for individuals under stress. It was as if stress had no effect on their memory," Smith said. "Learning by taking tests and being forced to retrieve information over and over has a strong effect on long-term memory retention, and appears to continue to have great benefits in high-stakes, stressful situations." While a robust body of evidence has previously shown that stress impairs memory, few studies have examined whether this relationship can be affected by different learning strategies. The current results now suggest that learning information in an effective manner, such as through retrieval practice, can protect memory against the adverse effects of stress. Although the research team used an experimentally verified stress-inducing scenario (Trier Social Stress Test) and measured participant stress responses through heart-rate monitors and standardized self-reported questionnaires, they note that stress effects are variable between individuals and additional work is needed to expand on their results. The team is now engaged in studies to replicate and extend their findings, including whether retrieval practice can benefit complex situations such as learning a foreign language or stressful scenarios outside of a testing environment. "Our one study is certainly not the final say on how retrieval practice influences memory under stress, but I can see this being applicable to any individual who has to retrieve complex information under high stakes," Thomas said. "Especially for educators, where big exams can put a great deal of pressure on students, I really encourage employing more frequent more low-stakes testing in context of their instruction." An additional author on the study is Victoria Floerke, graduate student in psychology at Tufts University. This research was funded by the U.S. Army Natick Soldier Research, Development and Engineering Center. Tufts University, located on campuses in Boston, Medford/Somerville, and Grafton, Massachusetts, and in Talloires, France, is recognized among the premier research universities in the United States. Tufts enjoys a global reputation for academic excellence and for the preparation of students as leaders in a wide range of professions. A growing number of innovative teaching and research initiatives span all campuses, and collaboration among the faculty and students in the undergraduate, graduate and professional programs across the university is widely encouraged.
News Article | October 23, 2015
In one project, Brad Olsen’s lab seeks to engineer soaps that can be sprayed onto a toxic chemical release and not only wash off the chemical, but detoxify it. In another, he is joining with numerous collaborators to lay the foundations for “sustainable biorefineries” that can turn solid waste or algae into a renewable feedstock for a wealth of new materials. A third effort aims to develop new kinds of injectable hydrogels that can stabilize a deep wound, or carry treatments into diseased tissues. These are just a few of the Olsen lab’s investigations, driven by new materials that are derived from, or inspired by, biology. “We focus on engineering new materials out of proteins, protein-polymer hybrids, and different types of polymers, with a particular focus on materials that can be processed in water,” says Olsen, an assistant professor of chemical engineering at MIT. “We apply these materials to a variety of applications, from biomaterials to new sustainable polymers to technologies that address concerns in national defense and in energy.” The new materials “can act as interesting models for testing fundamental scientific questions,” Olsen adds. “For example, we can build polymers with new shapes, or new sequences of monomers that endow them with specific properties. We try to understand how construction of these molecules leads to changes in the mechanics of the material, or the way in which material self-assembles, or aspects of how the material might undergo certain dynamic processes. And then by understanding these fundamental scientific questions, we can move the capabilities of the materials forward to address many different applications.” In several programs for MIT’s Institute for Soldier Nanotechnologies, Olsen and colleagues are addressing chemical and biological threats with innovative biological materials, which potentially offer “a selectivity for compounds within diverse environments that is hard to get with other types of technologies,” he says. One initiative, in which his lab collaborates with the Army’s Natick Soldier Research, Development and Engineering Center (NSRDEC), is developing soaps that can decontaminate large areas in an environmentally friendly manner. “Many toxic chemicals are hydrophobic, so they don’t easily dissolve in water,” Olsen explains. “One needs to use some kind of soap to get the chemical off the surface and into water. One would also like to be able to degrade this chemical, rather than having to recover the water, which can be very difficult if you’re trying to wash large areas or complex structures, and treat it as a toxic waste.” Olsen’s lab and NSRDEC are pursuing a solution in which soap forms a “nanoreactor” whose outside is coated with enzymes that can actively degrade the toxic chemical. “In an ideal situation, the chemical becomes a harmless solution that won’t have to be recovered for wastewater treatment,” he says. “The great thing is that if you use both soaps and enzymes that are environmentally friendly, potentially you won’t have a toxic soap formulation either.” With working prototypes in the lab, the researchers are now tuning the nanoreactor chemistry to be faster and more stable, and testing how well the approach functions against a broader set of toxins. Two other security projects look at producing new protective barrier membranes that respond only to dangerous threats in the environment. One effort “is to make smart membranes that will protect you when you are in the presence of a toxic chemical, but be breathable and easy to wear in the absence of a toxic chemical,” he says. This effort is a partnership with researchers at MIT, NSRDEC, and the University of California at Santa Barbara. A second study, with Katharina Ribbeck, the Eugene Bell Career Development Assistant Professor of Tissue Engineering in the MIT Department of Biological Engineering, aims to understand the biology of certain biological barriers, and to find ways to copy them to keep people free of pathogens. Another major theme in Olsen’s research is tapping biological feedstocks to supplement petroleum feedstocks for the next generation of chemical processes. “As these new processes and products start to be identified, the chemical industry will see important near-term impact,” he predicts. Olsen has joined in a major collaboration with Professor George Stephanopoulos, Associate Professor Kristala Prather, and Assistant Professor Yuriy Román of MIT's chemical engineering department, along with researchers at the Masdar Institute in Abu Dhabi. The project will examine the use of biomass from Abu Dhabi municipal and agricultural waste and algae to explore chemical and biochemical pathways and processes that can help in producing biofuels and other advanced biomaterials. “We’re hearing from many companies about the strong interest in exploring this wider variety of feedstocks in chemical processing,” Olsen says. “What really excites my group is looking at how these biological feedstocks can help us develop the next generation of materials, with more favorable lifecycle analysis, or less use of toxic monomers, or better combinations of properties than those of existing materials.” On the medical front, one leading project is to engineer different kinds of hydrogels with mechanical properties that haven’t previously been achievable in a biomaterial system, Olsen says. “Hydrogels are traditionally quite brittle and quite fragile,” he points out. “If you want a hydrogel to be more like human tissue, there’s a long way to go between Jell-O and human tissue. So we work on targeting some of those technology gaps.” In an Institute for Solider Nanotechnologies collaboration with Ali Khademhosseini of the Harvard-MIT Division of Health Sciences and Technology and Professor Gareth McKinley from MIT’s Department of Mechanical Engineering, Olsen’s team focuses on injectable hydrogels that are designed to stop bleeding in battlefield wounds. Their goal is to create a nanostructured protein hydrogel for an implant that can not only stop the flow of blood but aid in subsequent healing, and then be absorbed by the body. Existing “shear-thinning” hydrogels have the ability to switch from solidlike to liquidlike states when under mechanical stress, Olsen notes. When injected in the body, they can switch from liquidlike form in the syringe into solidlike form for the implant. However, the hydrogels then must durably maintain that form despite any mechanical stresses they encounter. Olsen and his colleagues are developing a hydrogel that reinforces a network of proteins with polymers that are soluble in water at lower temperatures but are insoluble when heated to body temperature, so that they form a grid that makes the hydrogel much stiffer and slower to degrade. Additionally, the proteins in the hydrogel are chosen partly for their role in promoting wound healing. Other work in the Olsen lab, funded by the Department of Energy, the Air Force Office of Scientific Research, and the National Science Foundation, focuses on advances in sustainability, with an emphasis on biocatalysis. “We’re looking at ways to control the structure and self-assembly of proteins that allow you to put them together to make a biocatalyst that looks a lot like a traditional heterogeneous catalyst used in the chemical-processing industry,” Olsen says. “But instead of using transition metals, we want to use proteins, and enable the very effective enzymatic properties of proteins to be leveraged in chemical conversions.” “Biocatalysis is already a very active area in the pharmaceutical industry,” he notes. “People also have been investigating this for applications such as biofuel synthesis and biofuel cells. Additionally, there are many potential applications in biosensing — in medicine, industrial practice, and detection of harmful compounds in the environment that are relevant to national security.” “Our group has many different efforts at the interface of natural and synthetic materials, trying to understand the fundamental science of bioinspired and biohybrid polymer systems and to bring these capabilities to bear on a wide variety of industrially and societally important challenges,” Olsen says. “We hope that these new materials will lead to a more secure, healthier, and more sustainable world.”
News Article | April 1, 2016
An independent nonprofit founded by MIT has been selected to run a new, $317 million public-private partnership announced today by Secretary of Defense Ashton Carter. The partnership, named the Advanced Functional Fibers of America (AFFOA) Institute, has won a national competition for federal funding to create the latest Manufacturing Innovation Institute. It is designed to accelerate innovation in high-tech, U.S.-based manufacturing involving fibers and textiles. The proposal for the institute was led by Professor Yoel Fink, director of MIT’s Research Laboratory of Electronics (RLE). The partnership includes 32 universities, 16 industry members, 72 manufacturing entities, and 26 startup incubators, spread across 27 states and Puerto Rico. This is the eighth Manufacturing Innovation Institute established to date, and the first to be headquartered in New England. The headquarters will be established in Cambridge, Massachusetts, in proximity to the MIT campus and its U.S. Army-funded Institute for Soldier Nanotechnology, as well as the Natick Soldier Research Development and Engineering Center. This unique partnership, Fink says, has the potential to create a whole new industry, based on breakthroughs in fiber materials and manufacturing. These new fibers and the fabrics made from them will have the ability to see, hear, and sense their surroundings; communicate; store and convert energy; monitor health; control temperature; and change their color. The new initiative will receive $75 million in federal funding out of a total of $317 million through cost sharing among the Department of Defense, industrial partners, venture capitalists, universities, nonprofits, and states including the Commonwealth of Massachusetts. The initial funding will cover a five-year period and will be administered through the new, independent, nonprofit organization set up for the purpose. The partnership, which will focus on both developing new technologies and training the workforce needed to operate and maintain these production systems, also includes a network of community colleges and experts in career and technical education for manufacturing. “Massachusetts’s innovation ecosystem is reshaping the way that people interact with the world around them,” says Massachusetts Gov. Charlie Baker. “This manufacturing innovation institute will be the national leader in developing and commercializing textiles with extraordinary properties. It will extend to an exciting new field our ongoing efforts to nurture emerging industries, and grow them to scale in Massachusetts. And it will serve as a vital piece of innovation infrastructure, to support the development of the next generation of manufacturing technology, and the development of a highly skilled workforce.” “Through this manufacturing innovation institute, Massachusetts researchers and Massachusetts employers will collaborate to unlock new advances in military technology, medical care, wearable technology, and fashion,” adds Massachusetts Lt. Gov. Karyn Polito. “This, in turn, will help drive business expansion, support the competitiveness of local manufacturers, and create new employment opportunities for residents across the Commonwealth.” Announcing the new institute at an event at MIT, Carter stressed the importance of technology and innovation to the mission of the Department of Defense and to national security broadly: “The intersection of the two is truly an opportunity-rich environment. These issues matter. They have to do with our protection and our security, and creating a world where our fellow citizens can go to school and live their lives, and dream their dreams, and one day give their children a better future. Helping defend your country and making a better world is one of the noblest things that a business leader, a technologist, an entrepreneur, or a young person can do, and we’re all grateful to all of you for doing that with us.” For thousands of years, humans have used fabrics in much the same way, to provide basic warmth and aesthetics. Clothing represents “one of the most ancient forms of human expression,” Fink says, but one that is now, for the first time, poised to undergo a profound transformation — the dawn of a “fabric revolution.” “What makes this point in time different? The answer is research,” Fink says: Objects that serve many complex functions are always made of multiple materials, whereas single-material objects, such as a drinking glass, usually have just a single, simple function. But now, new technology — some of it developed in Fink’s own laboratory — is changing all that, making it possible to integrate many materials and complex functional structures into a fabric’s very fibers, and to create fiber-based devices and functional fabric systems. The semiconductor industry has shown how to combine millions of transistors into an integrated circuit that functions as a system; as described by “Moore’s law,” the number of devices and functions has doubled in computer chips every couple of years. Fink says the team envisions that the number of functions in a fiber will grow with similar speed, paving the way for highly functional fabrics. The challenge now is to execute this vision, Fink says. While many textile and apparel companies and universities have figured out pieces of this puzzle, no single one has figured it all out. “It turns out there is no company or university in the world that knows how to do all of this,” Fink says. “Instead of creating a single brick-and-mortar center, we set out to assemble and organize companies and universities that have manufacturing and ‘making’ capabilities into a network — a ‘distributed foundry’ capable of addressing the manufacturing challenges. To date, 72 manufacturing entities have signed up to be part of our network.” “With a capable manufacturing network in place,” Fink adds, “the question becomes: How do we encourage and foster product innovation in this new area?” The answer, he says, lies at the core of AFFOA’s activities: Innovators across the country will be invited to execute “advanced fabric” products on prototyping and pilot scales. Moreover, the center will link these innovators with funding from large companies and venture capital investors, to execute their ideas through the manufacturing stage. The center will thus lower the barrier to innovation and unleash product creativity in this new domain, he says. The federal selection process for the new institute was administered by the U.S. Department of Defense’s Manufacturing Technology Program and the U.S. Army’s Natick Soldier Research, Development and Engineering Center and Contracting Command in New Jersey. Retired Gen. Paul J. Kern will serve as chairman of the AFFOA Institute. As explained in the original call for proposals to create this institute, the aim is to ensure “that America leads in the manufacturing of new products from leading edge innovations in fiber science, commercializing fibers and textiles with extraordinary properties. Known as technical textiles, these modern day fabrics and fibers boast novel properties ranging from being incredibly lightweight and flame resistant, to having exceptional strength. Technical textiles have wide-ranging applications, from advancing capabilities of protective gear allowing fire fighters to battle the hottest flames, to ensuring that a wounded soldier is effectively treated with an antimicrobial compression bandage and returned safely.” In addition to Fink, the new partnership will include Tom Kochan, the George Maverick Bunker Professor of Management at MIT’s Sloan School of Management, who will serve as chief workforce officer coordinating the nationwide education and workforce development (EWD) plan. Pappalardo Professor of Mechanical Engineering Alexander Slocum will be the EWD deputy for education innovation. Other key MIT participants will include professors Krystyn Van Vliet from the Materials Science and Engineering and Biological Engineering departments; Peko Hosoi and Kripa Varanasi from the Department of Mechanical Engineering; and Gregory Rutledge from the Department of Chemical Engineering. Among the industry partners who will be members of the partnership are companies such as Warwick Mills, DuPont, Steelcase, Nike, and Corning. Among the academic partners are Drexel University, the University of Massachusetts at Amherst, the University of Georgia, the University of Tennessee, and the University of Texas at Austin. In a presentation last fall about the proposed partnership, MIT President L. Rafael Reif said, “We believe that partnerships — with industry and government and across academia — are critical to our capacity to create positive change.” He added, “Our nation has no shortage of smart, ambitious people with brilliant new ideas. But if we want a thriving economy, producing more and better jobs, we need more of those ideas to get to market faster.” Accelerating such implementation is at the heart of the new partnership’s goals. This partnership, Reif said, will be “a system that connects universities and colleges with motivated companies and with far-sighted government agencies, so we can learn from each other and work with each other. A system that connects workers with skills, and skilled workers with jobs. And a system that connects advanced technology ideas to the marketplace or to those who can get them to market.” Part of the power of this new collaboration, Fink says, is combining the particular skills and resources of the different partners so that they “add up to something that’s more than the sum of the parts.” Existing large companies can contribute both funding and expertise, smaller startup companies can provide their creative new ideas, and the academic institutions can push the research boundaries to open up new technological possibilities. “MIT recognizes that advancing manufacturing is vital to our innovation process, as we explored in our Production in the Innovation Economy (PIE) study,” says MIT Provost Martin Schmidt. “AFFOA will connect our campus even more closely with industries (large and small), with educational organizations that will develop the skilled workers, and with government at the state and federal level — all of whom are necessary to advance this new technology. AFFOA is an exciting example of the public-private partnerships that were envisioned in the recommendation of the Advanced Manufacturing Partnership.” “Since MIT’s start, there has always been an emphasis on ‘mens et manus,’ using our minds and hands to make inventions useful at scales that impact the nation and the world,” adds Van Vliet, the director of manufacturing innovation for MIT’s Innovation Initiative, who has served as the faculty lead in coordinating MIT’s response to manufacturing initiatives that result from the Advanced Manufacturing Partnership. “What makes this new partnership very exciting is, this is for the first time a manufacturing institute headquartered in our region that connects our students and our faculty with local and national industrial partners, to really scale up production of many new fiber and textile technologies.” “Participating in this group of visionaries from government, academia, and industry — who are all motivated by the goal of advancing a new model of American textile manufacturing and helping to develop new products for the public and defense sectors — has been an exciting process,” says Aleister Saunders, Drexel University’s senior vice provost for research and a leader of its functional fabrics center. “Seeing the success we’ve already had in recruiting partners at the local level leads me to believe that on a national level, these centers of innovation will be able to leverage intellectual capital and regional manufacturing expertise to drive forward new ideas and new applications that will revolutionize textile manufacturing across the nation.” “Revolutionary fabrics and fibers are modernizing everything from battlefield communication to medical care,” says U.S. Congressmen Joe Kennedy III (D-Mass.). “That the Commonwealth would be chosen to lead the way is no surprise. From Lowell to Fall River, our ability to merge cutting-edge technology with age-old ingenuity has sparked a new day for the textile industry. With its unparalleled commitment to innovation, MIT is the perfect epicenter for scaling these efforts. I applaud President Reif, Professor Fink, and all of the partners involved for this tremendous success.” The innovations that led to the “internet of things” and the widespread incorporation of digital technology into manufacturing have brought about a revolution whose potential is unlimited and will generate “brilliant ideas that people will be able to bring to this task of making sure that America stays number one in each and every one of these fields,” said Senator Ed Markey (D-Mass.) at the MIT event. “The new institute we are announcing today will help ensure that both Massachusetts and the United States can expand our technological edge in a new generation of fiber science.” A wide range of industries are expected to benefit from these revolutionary fibers and textiles, including apparel, consumer products, automotive, medical devices, and consumer electronics. “Fibers and fabrics are ubiquitous,” Fink says. “Our institute will go everywhere a fiber and fabric goes.”
News Article | August 22, 2016
Superlens in the skies: liquid-crystal-polymer technology for telescopes Fresnel lenses are made of stacked concentric rings, a design that allows the construction of large-aperture lenses with relatively small weight and thickness. However, their structural discontinuity means they cannot be refined enough to act as primary optics for large telescopes. Overcoming limitations on efficiency and spectral bandwidth, and the technological complexities of fabricating a multilevel Fresnel lens of relatively large size, have so far proven a challenge, even for organizations at the forefront of optical developments. The fourth-generation (4G) optics technology revives the prospect of building large, thin, and nearly weightless lenses for both deep-space optical communications and imaging telescopes. The 4G optical components are essentially waveplates: thin polymer films with optical anisotropy due, in particular, to the presence of liquid crystalline molecules in their structure. We obtain the specific performance of these components by modulating the orientation of the anisotropy axis in the plane of the waveplate.1 This is in contrast with previous-generation optics, which were characterized by the modulation of lens shape or thickness (1G), the refractive index (as in Bragg gratings and gradient-index lenses, 2G), or the magnitude of the optical anisotropy (as in liquid crystal displays, 3G). A linear variation of the orientation of the anisotropy axis in the plane of the waveplate results in a prism-like action. These components are often referred to as cycloidal diffractive waveplates due to the pattern characterizing the spatial distribution of the anisotropy axis. The variation of the orientation angle around an axis perpendicular to the plane of the waveplate yields the equivalent of a spiral waveplate, often referred to as a vector vortex waveplate. By varying the angle proportional to the square of the distance from the axis (parabolic variation), we obtain a lens: see Figure 1.2 The efficiency of 4G optics reaches 100% for each of the circularly polarized components of radiation for wavelengths fulfilling the half-wave phase retardation condition. This is the state wherein the phase shift introduced by the waveplate between the two orthogonal polarization states of light is equal to half wave. Given their nature, we can make the 4G optical components broadband, particularly using techniques similar to those used in the fabrication of conventional broadband waveplates. Half-wave plates are commonly used for rotating the plane of a linearly polarized light by an angle 2α with respect to the polarization of an input beam, where α is the angle between the input polarization direction and the waveplate axis. For a circular polarized beam, this change in angle translates into a phase shift and reversal of the polarization handedness. Thus, we can generate a ±2α phase shift in a circularly polarized beam with the sign of the phase shift depending on the polarization handedness. This phase, known as geometrical or Pancharatnam–Berry phase, plays in full force for a waveplate with spatially modulated anisotropy axis α=α(x; y), where x and y are the coordinates in the plane of the waveplate. Recent advances in liquid-crystal-polymer materials and alignment technology allowed us to produce the desired modulation patterns at high spatial frequencies and with high optical quality: see Figure 2. Therefore, to make a lens or any other optical component, we can simply spin or spray a droplet of a polymerizable liquid crystal on a flat substrate pretreated for inducing boundary conditions for the corresponding alignment pattern. The latter requires exposure of the substrate coated with a photoanisotropic material to, typically, a UV light beam of correspondingly modulated polarization pattern. The whole fabrication process takes only a few minutes, the cost is small compared to other high-quality optics, and we find no discontinuities in the structure of the optical element. We can produce diffractive waveplate films on any desired substrate or transfer to it. In addition, the liquid-crystal-polymer coatings can impart imaging capability to flat mirrors. Our analysis has shown that, in combination with specially designed receiver mirrors coated with diffractive waveplates, we can significantly enhance the bandwidth for diffraction-limited functionality for optical communication and imaging applications of large telescopes. A system of waveplate lenses can also exhibit polarization-independent imaging functionality. In the future, we will investigate the novel opportunities provided by 4G optics for applications such as large-aperture space-based telescopes and space communications. This work was supported by the NASA Innovative Advanced Concepts (NIAC) Program and the US Army Natick Soldier Research, Development and Engineering Center.
Suthiwangcharoen N.,Natick Soldier Research |
Nagarajan R.,Natick Soldier Research
Biomacromolecules | Year: 2014
Enhancing the stability of enzymes under different working environments is essential if the potential of enzyme-based applications is to be realized for nanomedicine, sensing and molecular diagnostics, and chemical and biological decontamination. In this study, we focus on the enzyme, organophosphorus hydrolase (OPH), which has shown great promise for the nontoxic and noncorrosive decontamination of organophosphate agents (OPs) as well as for therapeutics as a catalytic bioscavanger against nerve gas poisoning. We describe a facile approach to stabilize OPH using covalent conjugation with the amphiphilic block copolymer, Pluronic F127, leading to the formation of F127-OPH conjugate micelles, with the OPH on the micelle corona. SDS-PAGE and MALDI-TOF confirmed the successful conjugation, and transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed ∼100 nm size micelles. The conjugates showed significantly enhanced stability and higher activity compared to the unconjugated OPH when tested (i) in aqueous solutions at room temperature, (ii) in aqueous solutions at higher temperatures, (iii) after multiple freeze/thaw treatments, (iv) after lyophilization, and (v) in the presence of organic solvents. The F127-OPH conjugates also decontaminated paraoxon (introduced as a chemical agent simulant) on a polystyrene film surface and on a CARC (Chemical Agent Resistant Coating) test panel more rapidly and to a larger extent compared to free OPH. We speculate that, in the F127-OPH conjugates (both in the micellar form as well as in the unaggregated conjugate), the polypropylene oxide block of the copolymer interacts with the surface of the OPH and this confinement of the OPH reduces the potential for enzyme denaturation and provides robustness to OPH at different working environments. The use of such polymer-enzyme conjugate micelles with improved enzyme stability opens up new opportunities for numerous civilian and Warfighter applications. © 2014 American Chemical Society.
Wang K.F.,Worcester Polytechnic Institute |
Nagarajan R.,Natick Soldier Research |
Mello C.M.,Natick Soldier Research |
Camesano T.A.,Worcester Polytechnic Institute
Journal of Physical Chemistry B | Year: 2011
Antimicrobial peptides (AMPs) are naturally occurring polymers that can kill bacteria by destabilizing their membranes. A quartz crystal microbalance with dissipation monitoring (QCM-D) was used to better understand the action of the AMP chrysophsin-3 on supported lipid bilayers (SLB) of phosphatidylcholine. Interaction of the SLB with chrysophsin-3 at 0.05 μM demonstrated changes in frequency (Δf) and energy dissipation (ΔD) that were near zero, indicating little change in the membrane. At higher concentrations of chyrsophsin-3 (0.25-4 μM), decreases in Δf of up to 7 Hz were measured. These negative frequency changes suggest that mass was being added to the SLB, possibly due to peptide insertion into the membrane. At a chrysophsin-3 concentration of 10 μM, there was a net mass loss, which was attributed to pore formation in the membrane. QCM-D can be used to describe a mechanistic relationship between AMP concentration and interaction with a model cell membrane. © 2011 American Chemical Society.
Nagarajan R.,Natick Soldier Research
Journal of Colloid and Interface Science | Year: 2014
Micelles generated in water from most amphiphilic block copolymers are widely recognized to be non-equilibrium structures. Typically, the micelles are prepared by a kinetic process, first allowing molecular scale dissolution of the block copolymer in a common solvent that likes both the blocks and then gradually replacing the common solvent by water to promote the hydrophobic blocks to aggregate and create the micelles. The non-equilibrium nature of the micelle originates from the fact that dynamic exchange between the block copolymer molecules in the micelle and the singly dispersed block copolymer molecules in water is suppressed, because of the glassy nature of the core forming polymer block and/or its very large hydrophobicity. Although most amphiphilic block copolymers generate such non-equilibrium micelles, no theoretical approach to a priori predict the micelle characteristics currently exists. In this work, we propose a predictive approach for non-equilibrium micelles with glassy cores by applying the equilibrium theory of micelles in two steps. In the first, we calculate the properties of micelles formed in the mixed solvent while true equilibrium prevails, until the micelle core becomes glassy. In the second step, we freeze the micelle aggregation number at this glassy state and calculate the corona dimension from the equilibrium theory of micelles. The condition when the micelle core becomes glassy is independently determined from a statistical thermodynamic treatment of diluent effect on polymer glass transition temperature. The predictions based on this "non-equilibrium" model compare reasonably well with experimental data for polystyrene-polyethylene oxide diblock copolymer, which is the most extensively studied system in the literature. In contrast, the application of the equilibrium model to describe such a system significantly overpredicts the micelle core and corona dimensions and the aggregation number. The non-equilibrium model suggests ways to obtain different micelle sizes for the same block copolymer, by the choices we can make of the common solvent and the mode of solvent substitution. © 2015.
Wang K.F.,Worcester Polytechnic Institute |
Nagarajan R.,Natick Soldier Research |
Camesano T.A.,Worcester Polytechnic Institute
Colloids and Surfaces B: Biointerfaces | Year: 2014
Alamethicin is a 20-amino-acid, α-helical antimicrobial peptide that is believed to kill bacteria through pore formation in the inner membranes. We used quartz crystal microbalance with dissipation monitoring (QCM-D) to explore the interactions of alamethicin with a supported lipid bilayer. Changes in frequency (. δf) and dissipation (. δD) measured at different overtones as a function of peptide concentration were used to infer peptide-induced changes in the mass and rigidity of the membrane as well as the orientation of the peptide in the bilayer. The measured δf were positive, corresponding to a net mass loss from the bilayer, with substantial mass losses at 5. μM and 10. μM alamethicin. The measured δf at various overtones were equal, indicating that the mass change in the membrane was homogeneous at all depths consistent with a vertical peptide insertion. Such an orientation coupled to the net mass loss was in agreement with cylindrical pore formation and the negligibly small δD suggested that the peptide walls of the pores stabilized the surrounding lipid organization. Dynamics of the interactions examined through δf vs. δD plots suggested that the peptides initially inserted into the membrane and caused disordering of the lipids. Subsequently, lipids were removed from the bilayer to create pores and alamethicin caused the remaining lipids to reorder and stabilize within the membrane. Based on model calculations, we concluded that the QCM-D data cannot confirm or rule out whether peptide clusters coexist with pores in the bilayer. We have also proposed a way to calculate the peptide-to-lipid ratio (. P/. L) in the bilayer from QCM-D data and found the calculated P/. L as a function of the peptide concentration to be similar to the literature data for vesicle membranes. © 2014.
Suthiwangcharoen N.,Natick Soldier Research |
Nagarajan R.,Natick Soldier Research
RSC Advances | Year: 2014
Controlled design of nanoparticles (NPs) displaying multiple functionalities is of great interest to many applications such as targeted drug or gene delivery, diagnostic imaging, cancer theranostics, delivery of protein therapeutics, sensing chemical and biomolecular analytes in complex environments, and design of future soldier protective clothing resembling a second skin. Current methods of synthesizing multifunctional nanoparticles (MNPs) typically involve sequential chemical processing of NPs; for example, drug-encapsulated NPs are first formed, followed by surface modifications involving the sequential conjugation of ligands to provide other functionalities such as targeting, responsiveness to stimuli, etc. We describe an alternate flexible approach to constructing MNPs employing the machinery of molecular self-assembly, starting with individually functionalized amphiphilic block copolymers. The commercially available polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is used as the building block for illustrative purposes and functionalities are provided by other chemical moieties conjugated to it via degradable linkers. For demonstrative purposes, we have chosen folic acid (a targeting ligand), bovine serum albumin (resembling a therapeutic protein), and gadolinium (a MRI contrast agent) as the functionalities, but the choice of functionalities is not limited. The self-assembly of the conjugated block copolymers is induced by solvent polarity control, resulting in the production of MNPs. Quantitative determination of the amount of each conjugated functionality is done using spectrophotometry, which shows that the composition of the MNP is controlled by the composition of the precursor functionalized block copolymers and that self-assembly preserves the compositional control. The size of the MNP can be controlled by adding a second block copolymer. The combination of the ability to introduce multiple functionalities, vary the relative proportion of functionalities, and control the nanoparticle size, all independent of one another, renders the self-assembly approach uniquely efficient for producing interesting multifunctional nanoparticles for numerous applications. © 2014 The Royal Society of Chemistry.
News Article | October 31, 2016
NATICK, MA--(Marketwired - October 31, 2016) - The Natick Soldier Research, Development, and Engineering Center (NSRDEC) - Warfighter Directorate, in Natick, Massachusetts is looking for a contractor to provide it with velocity detection equipment for ballistic material evaluation to use with its projectile acceleration equipment. The NSRDEC intends to use this equipment to detect striking and residual velocity of various projectiles, and in tandem with the detection equipment to provide an output signal that is used as a trigger at the time striking velocity is captured. The U.S. Department of the Army released this sources sought notice on Monday, October 31, 2016, to identify businesses -- especially those that qualify for a set-aside contract (e.g., small business concerns and/or certified 8(a), HUBZone, Service-Disabled Veteran-Owned Small Businesses (SDVOSB) and Women-Owned Small Businesses (WOSSB) -- that can provide the requirements. The North American Industry Classification System (NAICS) code for this effort is 334516 - Analytical Laboratory Instruments Manufacturing, and the Small Business Administration (SBA) size standard is 1,000 employees. The following are specifications for the velocity detection equipment Contractors who can provide velocity detection equipment must submit the following information by no later than November 10, 2016 at 4 p.m. EST to Contract Specialists Tony Kayhart (firstname.lastname@example.org) and Andrea Albanese (email@example.com).: The response can be no longer than six pages and must be submitted as a PDF. To receive the contract, contractors must be registered with the System for Award Management (SAM) database, and have as part of the Registration all current Representations and Certifications. Contractors also must be registered with FEMA. US Federal Contractor Registration, the world's largest third-party government registration firm, completes the required Registrations on behalf of its clients. It also makes available information about opportunities like this, as well as training on how to locate, research, and respond to opportunities. For more information, to get started with a SAM registration, or to learn more about how US Federal Contractor Registration can help your business succeed, call 877-252-2700, ext. 1.