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Posts Tagged ‘nanotech’

Livermore researchers use carbon nanotubes for molecular transport

Molecular transport across cellular membranes is essential to many of life’s processes, for example electrical signaling in nerves, muscles and synapses.

In biological systems, the membranes often contain a slippery inner surface with selective filter regions made up of specialized protein channels of sub-nanometer size. These pores regulate cellular traffic, allowing some of the smallest molecules in the world to traverse the membrane extremely quickly, while at the same time rejecting other small molecules and ions.

Researchers at Lawrence Livermore National Laboratory are mimicking that process with manmade carbon nanotube membranes, which have pores that are 100,000 times smaller than a human hair, and were able to determine the rejection mechanism within the pores.

“Hydrophobic, narrow diameter carbon nanotubes can provide a simplified model of membrane channels by reproducing these critical features in a simpler and more robust platform,” said Olgica Bakajin, who led the LLNL team whose study appeared in the June 6 online edition of the journal Proceedings of the National Academy of Sciences.

In the initial discovery, reported in the May 19, 2006 issue of the journal Science, the LLNL team found that water molecules in a carbon nanotube move fast and do not stick to the nanotube’s super smooth surface, much like water moves through biological channels. The water molecules travel in chains – because they interact with each other strongly via hydrogen bonds.

“You can visualize it as mini-freight trains of chain-bonded water molecules flying at high speed through a narrow nanotube tunnel,” said Hyung Gyu Park, an LLNL postdoctoral researcher and a team member.

One of the most promising applications for carbon nanotube membranes is sea water desalination. These membranes will some day be able to replace conventional membranes and greatly reduce energy use for desalination.

In the recent study, the researchers wanted to find out if the membranes with 1.6 nanometer (nm) pores reject ions that make up common salts. In fact, the pores did reject the ions and the team was able to understand the rejection mechanism.

“Our study showed that pores with a diameter of 1.6nm on the average, the salts get rejected due to the charge at the ends of the carbon nanotubes,” said Francesco Fornasiero, an LLNL postdoctoral researcher, team member and the study’s first author

Fast flow through carbon nanotube pores makes nanotube membranes more permeable than other membranes with the same pore sizes. Yet, just like conventional membranes, nanotube membranes exclude ions and other particles due to a combination of small pore size and pore charge effects.

“While carbon nanotube membranes can achieve similar rejection as membranes with similarly sized pores, they will provide considerably higher permeability, which makes them potentially much more efficient than the current generation of membranes,” said Aleksandr Noy, a senior member of the LLNL team.

Researchers will be able to build better membranes when they can independently change pore diameter, charge and material that fills gaps between carbon nanotubes.

Source: DOE/Lawrence Livermore National Laboratory

Francesco Fornasiero, Hyung Gyu Park, Jason K. Holt, Michael Stadermann, Costas P. Grigoropoulos, Aleksandr Noy, and Olgica Bakajin. Colloquium Paper: Ion exclusion by sub-2-nm carbon nanotube pores. PNAS published June 6, 2008, 10.1073/pnas.0710437105

Josh says:

This does have a lot of implications. They must work very similar to ion channels in membranes, where only certain ions can travel through. I wonder if it would be possible to design custom transmembrane membrane channels to help with drug delivery?

Scientists make chemical cousin of DNA for use as new nanotechnology building block

In the rapid and fast-growing world of nanotechnology, researchers are continually on the lookout for new building blocks to push innovation and discovery to scales much smaller than the tiniest speck of dust.

In the Biodesign Institute at Arizona State University, researchers are using DNA to make intricate nano-sized objects. Working at this scale holds great potential for advancing medical and electronic applications. DNA, often thought of as the molecule of life, is an ideal building block for nanotechnology because they self-assemble, snapping together into shapes based on natural chemical rules of attraction. This is a major advantage for Biodesign researchers like Hao Yan, who rely on the unique chemical and physical properties of DNA to make their complex nanostructures. … Continue Reading »

Nano-sized technology has super-sized effect on tumors

Anyone facing chemotherapy would welcome an advance promising to dramatically reduce their dose of these often harsh drugs. Using nanotechnology, researchers at Washington University School of Medicine in St. Louis have taken a step closer to that goal.

The researchers focused a powerful drug directly on tumors in rabbits using drug-coated nanoparticles. They found that a drug dose 1,000 times lower than used previously for this purpose markedly slowed tumor growth.

“Many chemotherapeutic drugs have unwanted side effects, and we’ve shown that our nanoparticle technology has the potential to increase drug effectiveness and decrease drug dose to alleviate harmful side effects,” says lead author Patrick M. Winter, Ph.D., research assistant professor of medicine and biomedical engineering. … Continue Reading »

Promising new nanotechnology for spinal cord injury

A spinal cord injury often leads to permanent paralysis and loss of sensation below the site of the injury because the damaged nerve fibers can’t regenerate. The nerve fibers or axons have the capacity to grow again, but don’t because they’re blocked by scar tissue that develops around the injury.

Northwestern University researchers have shown that a new nano-engineered gel inhibits the formation of scar tissue at the injury site and enables the severed spinal cord fibers to regenerate and grow. The gel is injected as a liquid into the spinal cord and self -assembles into a scaffold that supports the new nerve fibers as they grow up and down the spinal cord, penetrating the site of the injury.

When the gel was injected into mice with a spinal cord injury, after six weeks the animals had a greatly enhanced ability to use their hind legs and walk. … Continue Reading »

Femtogram-level chemical measurements now possible

Finding a simple and convenient technique that combines nanoscale structural measurements and chemical identification has been an elusive goal. With current analytical instruments, spatial resolution is too low, signal-to-noise ratio too poor, sample preparation too complex or sample size too large to be of good service.Now, researchers at the University of Illinois have demonstrated a method for simultaneous structural and chemical characterization of samples at the femtogram level (a femtogram is one quadrillionth of a gram) and below.

The measurement technique combines the extraordinary resolution of atomic force microscopy and the excellent chemical identification of infrared spectroscopy. … Continue Reading »

Self-assembled materials form mini stem cell lab

Imagine having one polymer and one small molecule that instantly assemble into a flexible but strong sac in which you can grow human stem cells, creating a sort of miniature laboratory. And that sac, if used for cell therapy, could cloak the stem cells from the human body’s immune system and biodegrade upon arriving at its destination, releasing the stem cells to do their work.A research team from Northwestern University’s Institute for BioNanotechnology in Medicine has created such sacs and demonstrated that human stem cells will grow in them. The researchers also report that the sacs can survive for weeks in culture and that their membranes are permeable to proteins. Proteins, even large ones, can travel freely across the membrane. … Continue Reading »