For this project, Hammond and her graduate student, Stephen Morton, devised dozens of candidate particles. The most effective were a type of particle called liposomes spherical droplets surrounded by a fatty outer shell.
The MIT team designed their liposomes to carry doxorubicin inside the particle core, with erlotinib embedded in the outer layer.
The particles are coated with a polymer called PEG, which protects them from being broken down in the body
or filtered out by the liver and kidneys. Another tag folate, helps direct the particles to tumor cells,
which express high quantities of folate receptors. Once the particles reach a tumor and are taken up by cells, the particles start to break down.
Erlotinib, carried in the outer shell, is released first, but doxorubicin release is delayed and takes more time to seep into cells,
giving erlotinib time to weaken the cellsdefenses. here a lag of somewhere between four and 24 hours between
The researchers tested the particles in mice implanted with two types of human tumors: triple-negative breast tumors and non-small-cell lung tumors.
even when those drugs were given in a time-staggered order. his particle delivery system not only provides a platform for time-staggered treatment strategies in cancer,
As a next step before possible clinical trials in human patients, the researchers are now testing the particles in mice that are programmed genetically to develop tumors on their own,
however, extra energy produces extra electrons behavior that could significantly increase solar-cell efficiency. An MIT team has identified now the mechanism by
In most photovoltaic (PV) materials, a photon (a packet of sunlight) delivers energy that excites a molecule,
causing it to release one electron. But when high-energy photons provide more than enough energy,
the molecule still releases just one electron plus waste heat. A few organic molecules don follow that rule.
Instead, they generate more than one electron per high-energy photon. That phenomenon known as singlet exciton fission was identified first in the 1960s.
However, achieving it in a functioning solar cell has proved difficult and the exact mechanism involved has become the subject of intense controversy in the field.
For the past four years, Van Voorhis and Baldo have been pooling their theoretical and experimental expertise to investigate this problem.
In 2013, they reported making the first solar cell that gives off extra electrons from high-energy visible light,
which makes up almost half the sun electromagnetic radiation at the Earth surface. According to their estimates, applying their technology as an inexpensive coating on silicon solar cells could increase efficiency by as much as 25 percent.
Exciton fission has now been observed in a variety of materials all discovered like the original ones by chance. e can rationally design materials
and devices that take advantage of exciton fission until we understand the fundamental mechanism at work until we know what the electrons are actually doing,
To support his theoretical study of electron behavior within PVS, Van Voorhis used experimental data gathered in samples specially synthesized by Baldo and Timothy Swager, MIT John D. Macarthur Professor of Chemistry.
The samples were made of four types of exciton fission molecules decorated with various sorts of pinachbulky side groups of atoms that change the molecular spacing without altering the physics or chemistry.
To detect fission rates which are measured in femtoseconds (10-15 seconds) the MIT team turned to experts including Moungi Bawendi, the Lester Wolfe Professor of Chemistry,
Van Voorhisnew first-principles formula successfully predicts the fission rate in materials with vastly different structures.
an electron in an excited molecule swaps places with an electron in an unexcited molecule nearby.
The excited electron brings some energy along and leaves some behind, so that both molecules give off electrons.
The result: one photon in, two electrons out. he simple theory proposed decades ago turns out to explain the behavior,
Van Voorhis says. he controversial, or xotic, mechanisms proposed more recently aren required to explain what being observed here.
They show that molecular packing is important in defining the rate of fission but only to a point.
When the molecules are very close together, the electrons move so quickly that the molecules giving
and receiving them don have time to adjust. Indeed, a far more important factor is choosing a material that has the right inherent energy levels.
Each molecule has about 50 atoms, and each atom has six to 10 electrons. hese are complicated systems to calculate,
Van Voorhis says. hat the reason that 50 years ago they couldn compute these things
considers the new findings very important contribution to the singlet fission literature. Via a synergistic combination of modeling, crystal engineering,
and experiment, the authors have provided the first systematic study of parameters influencing fission rates, he says.
Their findings hould strongly influence design criteria of fission materials away from goals involving molecular packing
including environmental pollutants, ultraviolet light, and radiation. Fortunately, cells have several major DNA repair systems that can fix this damage,
or to determine how much radiation treatment a patient can tolerate. The researchers also believe this test could be exploited to screen for new drugs that inhibit
such as radiation. Another important application for this test could be studying fundamental biological processes such as how cells recruit backup repair systems to fill in
Using this kind of sensor doctors may be able to better determine radiation doses and to monitor whether treatments are having the desired effect according to the researchers who describe the device in the Proceedings of the National Academy of Sciences the week of April 21.
Long-term MRIMRI uses magnetic fields and radio waves that interact with protons in the body to produce detailed images of the body s interior.
and predict how it might respond to radiation treatment according to the researchers. Radiation kills tumors by initiating DNA damage
but oxygen is required to help finish the job. An accurate reading of how much oxygen is present would help doctors calculate how much radiation might be necessary.
Measuring oxygen levels could also reveal the metastatic potential of a tumor: Those with lower oxygen levels tend to spread more aggressively.
they also created smaller particles (tens of microns long) that can be injected through a needle.
After injection these particles clump together to form a solid sensor. DDMPS absorbs molecular oxygen
which alters the proton spins inside the silicone a phenomenon that can be detected with MRI.
The knee now used by thousands of patients worldwide utilizes iron particles suspended in oil between steel plates
#Excitons observed in action for the first time A quasiparticle called an exciton responsible for the transfer of energy within devices such as solar cells LEDS
The particles determine how energy moves at the nanoscale. The efficiency of devices such as photovoltaics and LEDS depends on how well excitons move within the material he adds.
An exciton which travels through matter as though it were a particle pairs an electron
which carries a negative charge with a place where an electron has been removed known as a hole. Overall it has a neutral charge
For example in a solar cell an incoming photon may strike an electron kicking it to a higher energy level.
That higher energy is propagated through the material as an exciton: The particles themselves don t move but the boosted energy gets passed along from one to another.
While it was previously possible to determine how fast on average excitons could move between two points we really didn t have any information about how they got there Akselrod says.
Plants absorb energy from photons and this energy is transferred by excitons to areas where it can be stored in chemical form for later use in supporting the plant s metabolism.
Some molecules, known as photoswitches, can assume either of two different shapes, as if they had a hinge in the middle.
or volume of material it is necessary to pack the molecules very close together, which proved to be more difficult than anticipated.
Grossman team tried attaching the molecules to carbon nanotubes (CNTS), but t incredibly hard to get these molecules packed onto a CNT in that kind of close packing,
Kucharski says. But then they found a big surprise: Even though the best they could achieve was a packing density less than half of
Seeing a heat flow much greater than expected for the lower energy density prompted further investigation,
After additional analysis, they realized that the photoswitching molecules, called azobenzene, protrude from the sides of the CNTS like the teeth of a comb.
they were interleaved with azobenzene molecules attached to adjacent CNTS. The net result: The molecules were actually much closer to each other than expected.
The interactions between azobenzene molecules on neighboring CNTS make the material work, Kucharski says. While previous modeling showed that the packing of azobenzenes on the same CNT would provide only a 30 percent increase in energy storage,
the experiments observed a 200 percent increase. New simulations confirmed that the effects of the packing between neighboring CNTS,
Instead of searching for specific photoswitching molecules the researchers can now explore various combinations of molecules
and substrates. ow wee looking at whole new classes of solar thermal materials where you can enhance this interactivity,
#Tiny particles could help verify goods Some 2 to 5 percent of all international trade involves counterfeit goods, according to a 2013 United nations report.
smartphone-readable particle that they believe could be deployed to help authenticate currency, electronic parts, and luxury goods, among other products.
The particles, which are invisible to the naked eye, contain colored stripes of nanocrystals that glow brightly
These particles can easily be manufactured and integrated into a variety of materials, and can withstand extreme temperatures, sun exposure,
the senior author of a paper describing the particles in the April 13 issue of Nature Materials.
'A massive encoding capacity'The new particles are about 200 microns long and include several stripes of different colored nanocrystals,
To manufacture the particles, the researchers used stop-flow lithography, a technique developed previously by Doyle.
a reaction is set off that forms a solid polymeric particle. In this case, each polymer stream contains nanocrystals that emit different colors,
allowing the researchers to form striped particles. So far, the researchers have created nanocrystals in nine different colors,
With particles that contain six stripes, there are 1 million different possible color combinations; this capacity can be enhanced exponentially by tagging products with more than one particle.
For example, if the researchers created a set of 1, 000 unique particles and then tagged products with any 10 of those particles,
there would be 1030 possible combinations far more than enough to tag every grain of sand On earth. t really a massive encoding capacity,
while on the technical staff at Lincoln Lab. ou can apply different combinations of 10 particles to products from now until long past our time
Versatile particles The microparticles could be dispersed within electronic parts or drug packaging during the manufacturing process,
The researchers demonstrated the versatility of their approach by using two polymers with radically different material properties one hydrophobic and one hydrophilic o make their particles.
suggesting that the process could easily be adapted to many types of products that companies might want to tag with these particles,
Another advantage to these particles is that they can be read without an expensive decoder like those required by most other anti-counterfeiting technologies.
anyone could image the particles after shining near-infrared light on them with a laser pointer. The researchers are also working on a smartphone app that would further process the images
and reveal the exact composition of the particles. The research was funded by the U s. Air force, the Office of the Assistant Secretary of defense for Research and Engineering, the Singapore-MIT Alliance, the National Science Foundation, the U s army Research Office,
and express an adhesion molecule called JAM-B that helps them connect with the other cells they need to communicate with.
which respond to their environment produce complex biological molecules and span multiple length scales with the benefits of nonliving materials
but only under certain conditions specifically when a molecule called AHL is present. This puts control of curli fiber production in the hands of the researchers who can adjust the amount of AHL in the cells environment.
but only when a molecule called atc is present. The two types of engineered cells can be grown together in a colony allowing researchers to control the material composition of the biofilm by varying the amounts of AHL and atc in the environment.
Based on Lu graduate school research at MIT, the assay uses biological particles called bacteriophages, or phages,
and for other means across other industries. hages are the most abundant biological particle On earth.
which excites electrons that flow through the thylakoid membranes of the chloroplast. The plant captures this electrical energy
These particles are very strong antioxidants that scavenge oxygen radicals and other highly reactive molecules produced by light
and oxygen, protecting the chloroplasts from damage. The researchers delivered nanoceria into the chloroplasts using a new technique they developed called lipid exchange envelope penetration, or LEEP.
Wrapping the particles in polyacrylic acid a highly charged molecule, allows the particles to penetrate the fatty, hydrophobic membranes that surrounds chloroplasts.
In these chloroplasts, levels of damaging molecules dropped dramatically. Using the same delivery technique, the researchers also embedded semiconducting carbon nanotubes,
coated in negatively charged DNA, into the chloroplasts. Plants typically make use of only about 10 percent of the sunlight available to them,
photosynthetic activity measured by the rate of electron flow through the thylakoid membranes was 49 percent greater than that in isolated chloroplasts without embedded nanotubes.
and boosted photosynthetic electron flow by about 30 percent. Yet to be discovered is how that extra electron flow influences the plantssugar production. his is a question that we are still trying to answer in the lab:
What is the impact of nanoparticles on the production of chemical fuels like glucose? Giraldo says.
When the target molecule binds to a polymer wrapped around the nanotube, it alters the tube fluorescence. e could someday use these carbon nanotubes to make sensors that detect in real time, at the single-particle level,
free radicals or signaling molecules that are at very low-concentration and difficult to detect, Giraldo says. his is a marvelous demonstration of how nanotechnology can be coupled with synthetic biology to modify
and enhance the function of living organisms in this case, plants, says James Collins, a professor of biomedical engineering at Boston University who was involved not in the research. he authors nicely show that self-assembling nanoparticles can be used to enhance the photosynthetic capacity of plants,
a professor of radiation oncology at Harvard Medical school and Massachusetts General Hospital. ur knowledge about the abundance of extracellular matrix proteins in tumors has been limited.
The system s powertrain includes an electric traction motor a lithium-ion battery advanced power converters
XL Hybrids installs small 1. 8-kwh lithium-ion batteries that provide a 20 percent fuel savings Hynes says.
and Institute for Medical Engineering and Science is the senior author of a paper describing the particles in the Proceedings of the National Academy of Sciences the week of Feb 24.
These particles congregate at tumor sites where MMPS cleave hundreds of peptides which accumulate in the kidneys
However these instruments are not readily available in the developing world so the researchers adapted the particles
Nonliving particles of similar size and shape show no such effect the team found nor do nonmotile bacteria that are swept along passively by the water.
Previous studies have revealed that when foreign particles such as the dye bind to albumin immune cells in the lymph nodes efficiently capture the albumin. e realized that might be an approach that you could try to copy in a vaccine design a vaccine molecule that binds to albumin
and hitchhikes to the lymph node, Irvine says. To get protein fragments, known as peptides, to bind to albumin,
the researchers took advantage of albumin function as a transporter of molecules called fatty acids. Albumin has binding pockets that can capture fatty, hydrophobic molecules,
so the researchers added a fatty tail called a lipid to their vaccine peptides. They created a few different vaccines
Controlled inflammation The researchers also tested this delivery strategy with an adjuvant a molecule that enhances the immune responses of vaccines.
Think of a cordless drill that spins to pull a rope instead of driving a drill bit. As the spindle rotates,
#3-D images with only one photon per pixel Lidar rangefinders which are common tools in surveying
and measuring the time it takes for reflected photons to arrive back and be detected. In this week s issue of the journal Science researchers from MIT s Research Laboratory of Electronics (RLE) describe a new lidar-like system that can gauge depth
when only a single photon is detected from each location. Since a conventional lidar system would require about 100 times as many photons to make depth estimates of similar accuracy under comparable conditions the new system could yield substantial savings in energy and time
which are at a premium in autonomous vehicles trying to avoid collisions. The system can also use the same reflected photons to produce images of a quality that a conventional imaging system would require 900 times as much light to match
and it works much more reliably than lidar in bright sunlight when ambient light can yield misleading readings.
and Computer science and lead author on the new paper explains the very idea of forming an image with only a single photon detected at each pixel location is counterintuitive.
The way a camera senses images is through different numbers of detected photons at different pixels Kirmani says.
Darker regions would have fewer photons and therefore accumulate less charge in the detector while brighter regions would reflect more light
and lead to more detected photons and more charge accumulation. In a conventional lidar system the laser fires pulses of light toward a sequence of discrete positions
and reflected photons are detected that it can rule out the misleading signals produced by stray photons.
The MIT researchers system by contrast fires repeated bursts of light from each position in the grid only until it detects a single reflected photon;
A highly reflective surface one that would show up as light rather than dark in a conventional image should yield a detected photon after fewer bursts than a less-reflective surface would.
So the MIT researchers system produces an initial provisional map of the scene based simply on the number of times the laser has to fire to get a photon back.
Filtering out noisethe photon registered by the detector could however be a stray photodetection generated by background light.
They ve used a very clever set of information-theoretic techniques to extract a lot of information out of just a few photons
Another thing that s really fascinating is that they re also getting intensity information out of a single photon
the new ano-cameraprobes the scene with a continuous-wave signal that oscillates at nanosecond periods.
This allows the team to use inexpensive hardware off-the-shelf light-emitting diodes (LEDS) can strobe at nanosecond periods,
#Creating synthetic antibodies MIT chemical engineers have developed a novel way to generate nanoparticles that can recognize specific molecules, opening up a new approach to building durable sensors for many different compounds
In the past, researchers have exploited this phenomenon to create sensors by coating the nanotubes with molecules, such as natural antibodies, that bind to a particular target.
or diabetes in living systems. his new technique gives us an unprecedented ability to recognize any target molecule by screening nanotube-polymer complexes to create synthetic analogs to antibody function,
Another family of commonly used recognition molecules are DNA aptamers, which are short pieces of DNA that interact with specific targets,
there are not aptamers specific to many of molecules that one might want to detect, Strano says. In the new paper, the researchers describe molecular recognition sites that enable the creation of sensors specific to riboflavin, estradiol (a form of estrogen),
but they are now working on sites for many other types of molecules, including neurotransmitters, carbohydrates, and proteins.
which target molecule will be able to wedge into the loops and alter the carbon nanotube fluorescence.
is that the molecular recognition could not be predicted by looking at the structure of the target molecule
because the polymer itself can selectively recognize these molecules. It has to adsorb onto the nanotube and then,
Laurent Cognet, a senior scientist at the Institute of Optics at the University of Bordeaux, says this approach should prove useful for many applications requiring reliable detection of specific molecules. his new concept,
or equivalent molecules to achieve specific molecule recognitions and thus provides a promising alternative route for n demandmolecular sensing,
so this is a step forward in getting more data to address the problem of how to design a target for a specific molecule,
and then coat it with particles about 100 times smaller. Using that approach, they produced textured surfaces that could be heated to temperatures at least 100 degrees Celsius higher than smooth ones before droplets bounced.
To decouple those two effects, the researchers coated the surface featuring spaced-out microscale posts with nanoscale particles.
This icro-nanosurface texture provides both the extensive surface area of the tiny particles and the wide spacing of the posts to let the vapor flow.
#Self-steering particles go with the flow MIT chemical engineers have designed tiny particles that can teerthemselves along preprogrammed trajectories
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.
Much of that extra instrumentation is needed to keep the particles flowing single file through the center of the channel,
or by flowing two streams of liquid along the outer edges of the channel, forcing the particles to stay in the center.
and takes advantage of hydrodynamic principles that can be exploited simply by altering the shapes of the particles.
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 particlestrajectory as they flow through the channel.
The MIT researchers realized that they could manipulate these interactions by altering the particlessymmetry. 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. ow 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. he paper convincingly shown that shape matters,
and swarms can be redirected provided that shapes are designed well, 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. he new and quite sophisticated mechanism may open new routes for manipulating particles and cells in an elegant manner.
In 2006, Doyle 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 target molecule.
This type of particle can be useful for diagnosing cancer and other diseases, following customization to detect proteins
scientists can read the fluorescent signal as the particles flow by in single file. elf-steering particles could lead to simplified flow scanners for point-of-care devices,
The new targeted molecule is designed an elegantly platinum complex says Paul Dyson a professor of chemistry at the École Polytechnique Fédérale de Lausanne who was not part of the research team.
By targeting specific cellular organelles with the same therapeutic molecules we can learn a lot about how the cells respond to a given compound
Overtext Web Module V3.0 Alpha
Copyright Semantic-Knowledge, 1994-2011