Nanomedicine Archive

Thursday, November 19, 2009

Nanopillars Capture Circulating Tumor Cells

Well, we're back with more circulating tumor cell (CTC) news. This one comes from a new study published by UCLA scientists that describes a new technology to capture CTCs for analysis. The device is a silicon chip covered in nano-pillars coated with a special antibody to cause circulating tumor cells to stick. The chip can then be used with existing lab technology to analyze the collected tumor cells. The new device is faster and will hopefully be cheaper than similar existing technology.

Metastatic disease is usually identified by performing biopsies of solid metastatic tumors. This is often late in the disease, however, and it's better to identify metastatic disease earlier (such as by detecting CTCs) so that treatment can possibly be more effective.

More info from the press release:

In a study published this month in the journal Angewandte Chemie, the UCLA team developed a 1-by-2-centimeter silicon chip that is covered with densely packed nanopillars and looks like a shag carpet. To test cell-capture performance, researchers incubated the nanopillar chip in a culture medium with breast cancer cells. As a control, they performed a parallel experiment with a cell-capture method that uses a chip with a flat surface. Both structures were coated with anti-EpCAM, an antibody protein that can help recognize and capture tumor cells.
The researchers found that the cell-capture yields for the UCLA nanopillar chip were significantly higher; the device captured 45 to 65 percent of the cancer cells in the medium, compared with only 4 to 14 percent for the flat device.

Read the press release here...

Read the abstract here...

CTC flashbacks: Microchips for Tumor Detection, CellTraffix Aims to Cleanse Blood of CA, Collect Stem Cells, Watching Circulating Tumor Cell Count Helps Predict Breast Cancer Development

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Wednesday, November 18, 2009

Quantum Dots Light Up Internal Cellular Activities

If we could continuously monitor conditions inside individual cells, we would open a host of new research tools and diagnostic modalities. And that is what investigators from the National Institute of Standards and Technology (NIST) and the National Institute of Allergy and Infectious Diseases (NIAID) are trying to accomplish. The biophysics researchers analyzed how bioconjugated nanocrystals, or quantum dots, fluoresce in various environments over an extended period of time. And since these particles can be attached to just about any protein, they might offer a bright future for intracellular monitoring.

For their recent study, the team focused primarily on characterizing quantum dot properties, contrasting them with other imaging techniques. In one example, they employed quantum dots designed to target a specific type of human red blood cell protein that forms part of a network structure in the cell’s inner membrane. When these proteins cluster together in a healthy cell, the network provides mechanical flexibility to the cell so it can squeeze through narrow capillaries and other tight spaces. But when the cell gets infected with the malaria parasite, the structure of the network protein changes.
“Because the clustering mechanism is not well understood, we decided to examine it with the dots,” says NIAID biophysist Fuyuki Tokumasu. “We thought if we could develop a technique to visualize the clustering, we could learn something about the progress of a malaria infection, which has several distinct developmental stages.”

The team’s efforts revealed that as the membrane proteins bunch up, the quantum dots attached to them are induced to cluster themselves and glow more brightly, permitting scientists to watch as the clustering of proteins progresses. More broadly, the team found that when quantum dots attach themselves to other nanomaterials, the dots’ optical properties change in unique ways in each case. They also found evidence that quantum dot optical properties are altered as the nanoscale environment changes, offering greater possibility of using quantum dots to sense the local biochemical environment inside cells.

Image: Human red blood cells, in which membrane proteins are targeted and labeled with quantum dots, reveal the clustering behavior of the proteins. The number of purple features, which indicate the nuclei of malaria parasites, increases as malaria development progresses. The NIST logo at bottom was made by a photo lithography technique on a thin film of quantum dots, taking advantage of the property that clustered dots exhibit increased photoluminescence. (White bars: 1 μm; red: 10 μm.)

Press release: Small Nanoparticles Bring Big Improvement to Medical Imaging ...

Abstract in WIREs Nanomedicine and Nanobiotechnology: Probing dynamic fluorescence properties of single and clustered quantum dots toward quantitative biomedical imaging of cells

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Nanotech Exterminators: Scientists Capture, Destroy Cancer Cells in Bloodstream

A research team led by folks from the University of Arkansas for Medical Sciences used a combination of preprogrammed nanoparticles and external magnets to capture and collect circulating tumor cells (CTCs) within blood vessels. Additionally, they were able to use laser light to kill CTCs that were accumulated under the skin by magnets placed near the surface.

Vladimir Zharov, director of the Phillips Classic Laser and Nanomedicine Laboratory at UAMS, said his team of researchers can inject a cocktail of magnetic and gold nanoparticles with a special biological coating into the bloodstream to target circulating tumor cells. A magnet attached to the skin above peripheral blood vessels can then capture the cells.

Once the tumor cells are targeted and captured by the magnet, they can either be microsurgically removed from vessels for further genetic analysis or can be noninvasively eradicated directly in blood vessels by laser irradiation through the skin that is still safe for normal blood cells.

A second related discovery by Zharov’s team was published in Cancer Research in October. It demonstrated that periodic laser irradiation of blood vessels decreases the level of circulating metastatic tumor cells more than 10 times and eventually led to an interruption of metastasis development in distant organs.

Press release: Nanotechnology Team Captures Tumor Cells in Bloodstream ...

Abstract in Nature Nanotechnology: In vivo magnetic enrichment and multiplex photoacoustic detection of circulating tumour cells

Abstract in Cancer Research: In vivo, Noninvasive, Label-Free Detection and Eradication of Circulating Metastatic Melanoma Cells Using Two-Color Photoacoustic Flow Cytometry with a Diode Laser

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Tuesday, November 10, 2009

Nanoparticles Able to Damage DNA Without Entering Cell

A team of British researchers has shown that cobalt-chromium nanoparticles can damage the intracellular DNA without ever having to enter the cell itself. These findings may throw a new wrench into the use of nanoparticles in medicine.

From the abstract in Nature Nanotechnology:

Here, we show that cobalt-chromium nanoparticles (29.5 plusminus 6.3 nm in diameter) can damage human fibroblast cells across an intact cellular barrier without having to cross the barrier. The damage is mediated by a novel mechanism involving transmission of purine nucleotides (such as ATP) and intercellular signalling within the barrier through connexin gap junctions or hemichannels and pannexin channels. The outcome, which includes DNA damage without significant cell death, is different from that observed in cells subjected to direct exposure to nanoparticles. Our results suggest the importance of indirect effects when evaluating the safety of nanoparticles. The potential damage to tissues located behind cellular barriers needs to be considered when using nanoparticles for targeting diseased states.

Abstract in Nature Nanotechnology...

(hat tip: POPSCI)

Image: Optical image of cobalt nanoparticles onto HOPG substrate by victorpuntes on Flickr...

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Monday, November 9, 2009

Review of Magnetic Nanoparticles In The Life Sciences

The Journal of Physics D: Applied Physics this month is featuring a set of articles that looks at "how far magnetic nanoparticles for application in biomedicine have come and what exciting promise they hold for the future."

To learn more about the journal's review articles check out this statement by Institute of Physics, or head to the following open access papers:

Progress in applications of magnetic nanoparticles in biomedicine by Kevin O'Grady

Progress in applications of magnetic nanoparticles in biomedicine by Q A Pankhurst, N K T Thanh, S K Jones and J Dobson

Progress in the preparation of magnetic nanoparticles for applications in biomedicine by A G Roca, R Costo, A F Rebolledo, S Veintemillas-Verdaguer, P Tartaj, T González-Carreño, M P Morales and C J Serna

Progress in functionalization of magnetic nanoparticles for applications in biomedicine by Catherine C Berry

Image: Map showing magnetic flux lines for nickel nanoparticles. ... (Brookhaven NL)

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Monday, November 2, 2009

Harvard Scientists Bend Nanowires 2-D, 3-D

Harvard Gazette is reporting that the university's nanotechnologists developed a new methodology to produce 2-D and 3-D shaped nanowires by introducing bends through a series of stereocenters:

“We are very excited about the prospects this research opens up for nanotechnology,” said Lieber, Mark Hyman Jr. Professor of Chemistry in Harvard’s Faculty of Arts and Sciences. “For example, our nanostructures make possible integration of active devices in nanoelectronic and photonic circuits, as well as totally new approaches for extra- and intracellular biological sensors. This latter area is one where we already have exciting new results, and one we believe can change the way much electrical recording in biology and medicine is carried out.”
Lieber and Tian’s approach involves the controlled introduction of triangular “stereocenters” – essentially, fixed 120-degree joints – into nanowires, structures that have previously been rigidly linear. These stereocenters, analogous to the chemical hubs found in many complex organic molecules, introduce kinks into 1-D nanostructures, transforming them into more complex forms.

The researchers were able to introduce stereocenters as nanowires, which are self-assembled. The researchers halted growth of the 1-D nanostructures for 15 seconds by removing key gaseous reactants from the chemical brew in which the process was taking place, replacing these reactants after joints had been introduced into the nanostructures. This approach resulted in a 40 percent yield of bent nanowires, which can then be purified to achieve higher yields.

“The stereocenters appear as kinks, and the distance between kinks is completely controlled,” said Tian, a research assistant in Harvard’s Department of Chemistry and Chemical Biology. “Moreover, we demonstrated the generality of our approach through synthesis of 2-D silicon, germanium, and cadmium sulfide nanowire structures.”

The research by Lieber and Tian is the latest in the years-long efforts by scientists to control the composition and structure of nanowires during synthesis. Despite advances in these areas, the ability to control the design and growth of self-assembling nanostructures has been limited. Lieber and Tian’s work takes the formation of 2-D nanostructures a step further by enabling the introduction of electronic devices at the stereocenters.

“An important concept that emerged from these studies is that of introducing functionality at defined nanoscale points for the first time – in other words, nanodevices that can ‘self-label,’ ” Lieber said. “We illustrated this novel capability by the insertion of p–n diodes and field-effect transistors precisely at the stereocenters.”

Such self-labeled structures could open up the possibility of introducing nanoelectronics, photodetectors, or biological sensors into complex nanoscale structures.

Full story: Nanowires go 2-D, 3-D...

Abstract in Nature Nanotechnology: Single-crystalline kinked semiconductor nanowire superstructures

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Tuesday, October 27, 2009

Nanoplosmonic Detection Within Catalytic Reactions

Scientists from Chalmers University of Technology in Gothenburg, Sweden have developed a method that uses optical resonance within nanoparticles to study catalytic reactions. The technology should make possible the development of ultrasensitive detection methods for a wide range of uses in the life sciences.

From the article abstract in Science:

Optical probes of heterogeneous catalytic reactions can be valuable tools for optimization and process control in that they can operate under realistic conditions, but often these probes lack sensitivity. We have developed a plasmonic sensing method for such reactions based on arrays of nanofabricated gold disks, covered by a thin (~10 nm) coating (catalyst support) on which the catalyst is deposited. The sensing particles monitor changes in surface coverage of reactants (below 0.1 monolayers) during catalytic reaction through peak shifts in the optical extinction spectrum. Sensitivities to below 10^-3 monolayers are estimated. The capacity of the method is demonstrated for three catalytic reactions, CO and H₂ oxidation on Pt and NO_x conversion to N₂ on Pt/BaO.

More details from Chalmers University of Technology press release: New nanomethod paves the way for new measuring technology and hypersensitive sensors....

Abstract in Science: Nanoplasmonic Probes of Catalytic Reactions...

CleanSense...

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Wednesday, October 21, 2009

Scientists Enslave Bacteria to Power Tiny Microsized Motor

Italian scientists from the University of Rome managed to harness free floating E. coli bacteria to turn a tiny crankshaft. Although potential uses for such a tiny and unusual motor drive are not yet clear, no doubt interesting applications in medicine and life sciences should present themselves over time.

The Physics arXiv Blog explains:

Angelani and co say there is in important difference between Brownian and bacterial motion: the former is in equilibrium but the latter is an open system with a net income of energy provided by nutrients. This breaks the time symmetry allowing energy to be extracted in the form of directed motion.
Now Angelani and co have built one these asymmetric and persuaded a bath full of E. Coli to push it round at a of 1rpm. Interestingly, Angelani and co report that most of the work is done by just a few bacteria, saying that only 2 out of 10 bacteria attached to a single tooth seem to be contributing to the torque.

In theory, they could speed up the rotation rate by persuading the others to put their backs into it. The linear motion of the gears is currently about 2 micrometres per second while the maximum speed of the bacteria is about 20 micrometers per second.

More at The Physics arXiv Blog...

Full article in arXiv: A bacterial ratchet motor

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Thursday, October 8, 2009

Titanium Dioxide Nanoparticles Help Target Brain Cancer

Nanowerk is spotlighting research by Argonne National Laboratory scientists to develop bioconjugated nanoparticles that seek out brain tumor cells while avoiding attack on healthy tissue. Although various nanoparticles tend to passively gather in larger numbers in tumor cells due to the so-called "permeability and retention effect", the differentiation is not specific enough when dealing with particularly fragile brain tissue.

Nanowerk explains:

The delivery platform developed by Rozhkova [Elena Rozhkova from Argonne's NanoBio Interfaces group] and her colleagues uses 5 nm titanium dioxide nanoparticles that are covalently conjugated with an antibody that specifically targets certain tumors, including GBM. A naturally occurring metabolite of dopamin, DOPAC, is used as a linker molecule to tether the antibody to the nanoparticles. The whole thing works like this: the titanium dioxide/antibody nanobiocomposite binds exclusively to GBM cells. The hybrid semiconductor particles absorb energy from light, which is then transferred to molecular oxygen, producing cytotoxic reactive oxygen species (ROS). ROS damages the cell membrane and induces programmed death of the cancer cell.

More from Nanowerk: Nanotechnology therapy for brain cancer...

Abstract in Nano Letters: A High-Performance Nanobio Photocatalyst for Targeted Brain Cancer Therapy...

Flashback: Quantum Dots May Prove Effective Against Cancer Cells...

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Monday, October 5, 2009

Quantum Dots May Prove Effective Against Cancer Cells

Researchers from McGill University and Argonne National Laboratory have published a paper in Nanoscale discussing the potential use of quantum nanodots, or nano sized particles of semiconductor material, to produce reactive oxygen species for killing cancer cells using photodynamic therapy.

According to Nadeau [Jay Louise Nadeau, an Assistant Professor of Microbiology and Immunology at McGill --ed.] 'some nanoparticles don't make singlet oxygen but they do when they are connected to small molecules like [the neurotransmitter] dopamine. That opens up a whole other avenue for investigation,' she says. Her team also found that the dopamine-conjugated quantum dots can be used to kill mammalian cells but only on irradiation with UV-to-blue light. This means the quantum dots are unlikely to be toxic in the body, where the light cannot penetrate, but could have an effect on skin, the researchers claim. They suggest that similar conjugated nanoparticles could potentially be used in photodynamic therapy for skin cancer treatment.
Juan Mareque-Rivas, an expert in fluorescent nanoparticles, from the University of Edinburgh, UK, says 'this is a long overdue investigation. It is nice to see a study in which generation of different reactive oxygen species is demonstrated, quantified and rationalised, and linked to interactions with dopamine - it warns that biomolecules can enhance the phototoxicity of quantum dots.'

More from Chemistry World: Topical treatment for quantum dots?

Full article in Nanoscale...

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Thursday, October 1, 2009

Nanobees Sting Tumors to Death

We have known for many years that melittin, an ingredient in bee venom, is a poison to tumor cells. Development of therapeutic uses of the substance has been stymied by the fact that melittin does damage to healthy cells as well. Now researchers from Washington University in St. Louis have developed nanoparticles called "nanobees" that can ferry the melittin directly to tumor cells with great specificity.

The Wall Street Journal reports:

Among Dr. Soman's first experiments was to see how melittin interacted with the nanoparticles. He found that not only did it attach quickly to the outer, lipid layer of the nanoparticles, but that the attachment was stable, suggesting that the nanoparticle-melittin combination, or nanobee, might be able to circulate in the body and not attack healthy cells.
The next issue was to figure out how to get the melittin, once it came upon a tumor, to detach from the nanoparticle and transfer to the cancer cells, taking its cell-killing properties with it. The researchers accomplished this by attaching a third component to the mix—a ligand, which is a chemical that binds two distinct compounds. The ligand they used in this case—which Dr. Schlesinger likens to a "molecular ZIP Code"—has an affinity for attaching to a receptor plentiful in newly formed blood vessels. That's useful in cancer treatment because tumors tend to form new blood vessels to feed themselves and grow.

The scientists began testing the resulting mix, which resembles a milky substance, in mice in 2007. They tried it on a few dozen lab mice with three kinds of tumors: a mouse form of skin cancer; a form of human breast cancer transplanted into the mice; and precancerous lesions caused by human papillomavirus, which can cause cervical cancer in humans.

After about two weeks of treatment, the nanobees slowed the growth of the breast-cancer tumors, shrank the melanoma tumors and reduced the precancerous lesions, compared with control groups that received saline injections and nanoparticles lacking melittin.

Full paper in J. Clin. Invest.: Molecularly targeted nanocarriers deliver the cytolytic peptide melittin specifically to tumor cells in mice, reducing tumor growth

Link to WSJ: The Buzz: Targeting Cancer With Bee Venom ...

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Tuesday, September 29, 2009

Graphene May Serve as Building Block for Microscopic Biosensors

Sheets of carbon latice one atom thick, known as graphene, are likely to become useful tools in a variety of biomedical applications. Researchers at Pacific Northwest National Laboratory and Yale University have developed a method to mesh DNA and graphene into nanoscale structures coupled with accompanying fluorescent molecules that help visualize the interaction.

Tests showed that the fluorescence dimmed significantly when single-stranded DNA rested on graphene, but that double-stranded DNA only darkened slightly - an indication that single-stranded DNA had a stronger interaction with graphene than its double-stranded cousin. The researchers then examined whether they could take advantage of the difference in fluorescence and binding. When they added complementary DNA to single-stranded DNA-graphene structures, they found the fluorescence glowed anew. This suggested the two DNAs intertwined and left the graphene surface as a new molecule.
DNA's ability to turns its fluorescent light switch on and off when near graphene could be used to create a biosensor, the researchers propose. Possible applications for a DNA-graphene biosensor include diagnosing diseases like cancer, detecting toxins in tainted food and detecting pathogens from biological weapons. Other tests also revealed that single-stranded DNA attached to graphene was less prone to being broken down by enzymes, which makes graphene-DNA structures especially stable.

Image: An illustration of how fluorescent-tagged DNA interacts with functionalized graphene. Both single-stranded DNA (A) and double-stranded DNA (B) are adsorbed onto a graphene surface, but the interaction is stronger with ssDNA, causing the fluorescence on the ssDNA to darken more. C) A complimentary DNA nears the ssDNA and causes the adsorbed ssDNA to detach from the graphene surface. D) DNA adsorbed onto graphene is protected from being broken down

Press release: Graphene bolsters battery work, biosensors...

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Friday, September 25, 2009

A Quantum Sparkle: Diamonds for Computers and MRIs

Researchers from MIT, Harvard, Texas A&M University, and the National Institute of Standards and Technology (NIST) have identified a diamond "impurity" as a potential tool to visualize things on the molecular level using MRI technology. By embedding these "quantum dots" within cells and molecules, heretofore unprecedented resolution could be possible to visualize the living world.

The candidate system, formed from a nitrogen atom lodged within a diamond crystal, is promising not only because it can sense atomic-scale variations in magnetism, but also because it functions at room temperature. Most other such devices used either in quantum computation or for magnetic sensing must be cooled to nearly absolute zero to operate, making it difficult to place them near live tissue. However, using the nitrogen as a sensor or switch could sidestep that limitation.
Diamond, which is formed of pure carbon, occasionally has minute imperfections within its crystalline lattice. A common impurity is a “nitrogen vacancy”, in which two carbon atoms are replaced by a single atom of nitrogen, leaving the other carbon atom’s space vacant. Nitrogen vacancies are in part responsible for diamond’s famed luster, for they are actually fluorescent: when green light strikes them, the nitrogen atom’s two excitable unpaired electrons glow a brilliant red.

The team can use slight variations in this fluorescence to determine the magnetic spin of a single electron in the nitrogen. Spin is a quantum property that has a value of either “up” or “down,” and therefore could represent one or zero in binary computation. The team’s recent achievement was to transfer this quantum information repeatedly between the nitrogen electron and the nuclei of adjacent carbon atoms, forming a small circuit capable of logic operations. Reading a quantum bit’s spin information—a fundamental task for a quantum computer—has been a daunting challenge, but the team demonstrated that by transferring the information back and forth between the electron and the nuclei, the information could be amplified, making it much easier to read.

Still, NIST theoretical physicist Jacob Taylor said the findings are “evolutionary, not revolutionary” for the quantum computing field and that the medical world may reap practical benefits from the discovery long before a working quantum computer is built. He envisions diamond-tipped sensors performing magnetic resonance tests on individual cells within the body, or on single molecules drug companies want to investigate—a sort of MRI scanner for the microscopic. “That’s commonly thought not to be possible because in both of these cases the magnetic fields are so small,” Taylor says. “But this technique has very low toxicity and can be done at room temperature. It could potentially look inside a single cell and allow us to visualize what’s happening in different spots.”

Image: A nitrogen vacancy (small circles) within a diamond crystal shows promise as a “bit” for quantum computers in part because of its great sensitivity to magnetic fields—a sensitivity that also could enable MRI-like studies on objects as small as living cells or single molecules. When green light strikes the nitrogen vacancy, it fluoresces red; detecting variations in this fluorescence permit scientists to extract its information.

Press release: Diamonds May Be the Ultimate MRI Probe, Say Quantum Physicists...

Abstract in Science: Repetitive Readout of a Single Electronic Spin via Quantum Logic with Nuclear Spin Ancillae

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Thursday, September 24, 2009

Sugar Coated Nanoparticles Successful at Killing Tumor Cells

An international team of collaborators from a number of academic institutions and a couple pharmaceutical firms has been working with researchers at the National Institute of Standards and Technology (NIST) to study how special sugar coated iron oxide nanoparticles interact with each other to destroy cancer cells under laboratory conditions. The 100 nanometer wide particles, which are attracted by tumor cells, are particularly prone to magnetically induced heating.

Minuscule balls of iron oxide can be coated with sugar molecules making them particularly attractive to resource-hungry cancer cells. Once the particles are injected, cancer cells would then ingest them, and doctors would then be able to apply an alternating magnetic field that causes the iron oxide centers to heat, killing the cancer but leaving surrounding tissue unharmed.

Two biotech companies, Micromod Partikeltechnologie and Aduro BioTech, created particles that showed great potential in treating cancers in mice, and they asked NIST to help understand why it worked so well. “But they sent us particles that were much larger than what the conventional wisdom says they should be,” says NIST materials scientist Cindi Dennis. “Larger particles are more strongly magnetic and tend to clump together, which makes them large enough to attract the body’s defense systems before they can reach a tumor. The companies’ nanoparticles, however, did not have this problem.”

Neutron scattering probes at the NIST Center for Neutron Research revealed that the particles’ larger iron oxide cores attract one another, but that the sugar coating has fibers extending out, making it resemble a dandelion—and these fibers push against one another when two particles get too close together, making them spring apart and maintain an antibody-defying distance rather than clumping. Moreover, when the particles do get close, the iron oxide centers all rotate together under the influence of a magnetic field, both generating more heat and depositing this heat locally. All these factors helped the nanoparticles destroy breast tumors in three out of four mice after one treatment with no regrowth.

Side image: When tumor cells ingest them, the particles still congregate closely enough to share heat when stimulated by a magnetic field, killing the cells. White arrow indicates a red blood cell.

Press release: Therapeutic Nanoparticles Give New Meaning to Sugar-Coating Medicine...

Abstract in Nanotechnology: Nearly complete regression of tumors via collective behavior of magnetic nanoparticles in hyperthermia

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Monday, September 21, 2009

Light Activated Mixing of Chemicals at Target Site

Sometimes bringing separated ingredients of a chemical reaction to a disease is wiser than ferrying the reaction's final product. Pharmacokinetics is a finicky science. Drug molecules are often not very stable, or can get absorbed or cleared on the way to a distant site. Or the problem might be the drug's large molecular weight or ionization, preventing it from crossing physiologic boundaries. To address many of these issues, UC Berkeley researchers have developed tiny nylon microspheres laden with reactive chemicals, that can burst and mix only when a particular light source is applied.

They mix the chemical to be encapsulated with a small amount of carbon nanotubes and the precursors for making nylon, while continuously stirring. The stirring causes the nylon to form spheres that capture the nanotubes and the reactant. By varying the stir rate, the Berkeley chemists can vary the size of the resulting capsules from about 100 to 1,000 micrometers. When they aim a laser at a capsule, the carbon nanotubes absorb the light, heating up the liquid inside and causing it to expand until it explodes, releasing the contents. "The novelty is not the particle itself, but the fact that it can be addressed by a cheap laser," says Fréchet. This is possible because carbon nanotubes -- the blackest known substance -- absorb a broad spectrum of light very efficiently.

Wednesday, September 16, 2009

DNA Strands Used to Create Complicated Branching Structures

Scientists from Brigham Young University have been developing new "DNA origami" techniques to create complicated structures that were previously impossible. Using PCR amplification they were able to create strands of arbitrary length and to make multiple branching points, allowing them to write letters as seen in the picture on right.

From the abstract:

Designs for DNA origami have previously been limited by the size of the available single-stranded genomes for scaffolds. Here we present a straightforward method for the production of scaffold strands having various lengths, using polymerase chain reaction amplification followed by strand separation via streptavidin-coated magnetic beads. We have applied this approach in assembling several distinct DNA nanostructures that have thin (10 nm) features and branching points, making them potentially useful templates for nanowires in complex electronic circuitry.

Press release: Spelling B-Y-U with DNA...

Abstract in Nano Letters: Polymerase Chain Reaction Based Scaffold Preparation for the Production of Thin, Branched DNA Origami Nanostructures of Arbitrary Sizes

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Thursday, September 10, 2009

Lasers and Nanoparticles Team Up to Target Tumor Cells

Scientists at University of California, Santa Barbara have developed a gene silencing technique that uses a combination of gold nanoshells and siRNA (silencing ribonucleic acid) conjugates for delivery. A low energy laser is then used to activate and release the siRNA at the specific site of a tumor where treatment is needed.

The scientists used cancer cells from mice, and grew them in culture. They then introduced gold nanoshells, with a peptide-lipid coating, that encapsulated "silencing ribonucleic acid" (siRNA), which was the drug that was taken up by the cells. Next, they exposed the cells to a non-harmful infrared laser.

"A major technical hurdle is how to combine multiple biochemical components into a compact nanoparticle which may be taken up by cells and exist stably until the release is desired," said Gary Braun, first author and a graduate student in UCSB's Department of Chemistry and Biochemistry. "Laser-controlled release is a convenient and powerful tool, allowing precise dosing of particular cells within a group. The use of biologically friendly tissue penetration with near-infrared light is the ideal for extending this capability into larger biological systems such as tissues and animals."

The authors demonstrated, for the first time, the delivery of a potent siRNA cargo inside mammalian cancer cells, released by exposing the internalized nanoparticles for several seconds to a pulsed near-infrared laser tuned for peak absorption with a specific spatial pattern. The technique can be expanded to deliver numerous drug molecules against diverse biological targets.

Press release: UCSB Researchers Develop Drug Delivery System Using Nanoparticles and Lasers

Abstract in ACS NANO: Laser-Activated Gene Silencing via Gold Nanoshell-siRNA Conjugates

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Tuesday, September 8, 2009

Instantaneous Bacteria Detector Powered by Carbon Nanotubes

Scientists from Rovira i Virgili University (URV) in Tarragona, Spain are reporting the development of a device capable of rapidly detecting the presence of bacteria in a sample, even at very low concentration of organisms. The system uses carbon nanotubes coupled with aptamers--in this case, artificial DNA and RNA strings that stick to bacteria--to be able to discern a single Salmonella cell within a five-milliliter sample.

This new biosensor functions using a method, described this month in the scientific journal Angewandte Chemie International Edition, which involves carbon nanotubes with inbuilt aptamers providing electrochemical readings.
The aptamers are small fragments of artificial DNA or RNA designed to attach themselves specifically to a particular molecule, cell or micro organism, in this case Salmonella. If the bacteria are not present, the aptamers remain on the walls of the carbon nanotubes. However, if they detect bacteria, they become activated and stick to it, and the carbon nanotubes generate an electric signal that is picked up by a simple potentiometer connected to the biosensor.

"The presence of the bacteria sparks a change in the interaction between the aptamers and the nanotubes, which takes place in a few seconds and creates an increase in the voltage of the electrode", says Rius.

Traditional methods for identifying and measuring micro organisms require one or two days' analysis. "This technique means small quantities of micro organisms can be detected simply and practically in real time, just the same as measuring the pH of water", adds the researcher.

This study is part of the international research being carried out to find the most effective and fast ways of detecting all kinds of pathogens. The new biosensor makes it possible to identify a single cell of Salmonella in a five-millilitre sample and can successfully make quantitative measurements of up to 1,000 bacteria per millilitre.

Press release: New biosensor detectect bacteria instantaneously...

Abstract in Angewandte Chemie International Edition: Immediate Detection of Living Bacteria at Ultralow Concentrations Using a Carbon Nanotube Based Potentiometric Aptasensor

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Tuesday, September 1, 2009

Gold Particles for Lung CA Diagnosis from Breath

Scientists at Technion ("Israel Institute of Technology") are reporting in the latest issue of Nature Nanotechnology the development of a device capable of distinguishing the breath of patients with lung cancer from those free of the disease. The volatile organic compounds, some of which might be markers for the lung CA, are notoriously hard to detect because of the low concentration of molecules in the exhalant air. The breakthrough that Technion investigators made was to use gold nanoparticles as detectors, and that has yielded promising results in an early clinical study.

MIT Technology Review reports:

Using breath samples from 40 healthy volunteers and 56 lung-cancer patients, the group used the sensors to identify which biomarkers would collectively act as an accurate sign of lung-cancer signature. After training the sensors to identify the signature and testing it again, Haick and his colleagues found that their device could reliably differentiate between cancerous and healthy breath. They're now testing the device on a larger group of people in various stages of the disease and believe they'll be ready to start clinical trials within two or three years.
Preliminary tests indicate that the gold-nanoparticle sensors can not only differentiate among stages of lung cancer, they can detect distinct signatures for other ailments, such as liver failure. Haick's group has even tested the electronic nose above colonies of cells grown in culture. This study found that while the sensor was able to sniff out compounds already known to be in breath, other lung-cancer-associated VOCs weren't detected.

Read on at the MIT Tech Review...

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