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Magnetic medical nano
RESEARCH NEWS
Modeling is helped by going Green MODELING
Molecular dynamics (MD) of timedependent processes can now be modeled at the nanoscale without separating the process into small sections, thanks to the introduction of a mathematical function called Green’s function [Tewary V., Phys Rev B (2009) 80, 161409]. Until now, two techniques have been available for researchers to study a material’s properties, and each method has its drawbacks. Researchers can either accurately model processes at the nanoscale in increments measured in picoseconds to femtoseconds, or else they can model the bulk material over longer periods of time. Unfortunately, many physical processes such as defect formation and thermal conductance should be atomistically studied and occur on the nanosecond to microsecond scale. Such a study would require a huge number of steps. Vinod Tewary who developed the new method at the National Institute of Standards and Technology (NIST) in the US explains, “MD calculations are usually based on the physics of individual atoms or molecules.
Colorized simulation of what happens to 1,100 carbon atoms in a ‘flat’ sheet of graphene about 20 microseconds after the central atom is moved slightly upwards. Darker violet colors indicate atoms that have dropped below their original position, whereas the lighter green colors show where atoms have risen. Image courtesy of Vinod Tewary, National Institute of Standards and Technology.
This traditional approach is limited not only by time scale, but also by system size. It cannot be extended to processes involving thousands of atoms or more, because today’s computers – even supercomputers – cannot
handle the billions of time steps required”. His technique has already been tested on ripple propagation through graphene, a material composed of a one-dimensional lattice of carbon atoms. The ripple passes through the flat sheet and as a result the material undulates to remain stable. Tewary was able to follow the rippling process for up to 45 microseconds, an increase of around eight orders of magnitude over traditional modeling methods. The total energy of the system was found to be conserved to within 10-4 %, an improvement on current models where energy conservation is difficult. “The new NIST technique can access these longer time scales and scientists can now measure and understand what happens at key points in time that were not previously accessible, and throughout the full spectrum of time scales of interest in MD,” says Tewary. NIST researchers now plan to write a software program encoding the new technique to make it available to other users. Katerina Busuttil
Magnetic medical nano NANOMEDICINE Magnetic nanoparticles that could diagnose, monitor and then treat the wide range of common illnesses and injuries are on the way, according to research reviewed in a special cluster of papers [O’Grady et al., J. Phys. D: Appl. Phys. (2009) 42, 220,301, 224,001, 224,002, 224,003] Researchers are attaching nanoparticles to sensory units that can be dragged to a target site using an external magnetic field, such as that from a permanent magnet. Also magnetic nanoparticles represent a new generation of contrast agents for medical imaging technology using MRI. Similar magnetic nanoparticles could carry a therapeutic agent to the site, whether that is a drug or a gene therapy vector. Indeed, they are arming white blood cells with magnetic nanoparticles to seek out and destroy a tumour or using them to target nerve channels to restore an ailing heart. Indeed, magnetic nanoparticles have been tested in vivo to remedy heart injury in rats and in humans to
6
destroy, through heat generated by the action of an AC magnetic field, to which tumour cells are more sensitive. This technique has been used to treat a particularly severe form of brain cancer in fourteen patients. A similar approach has been used in treating prostate cancer. Magnetic nanoparticles are usually produced from the common iron oxide magnetite and then given a biocompatible coating, which provides stability and protection for the chemical particles and their companions as they are moved through the body. The coating is often comprised of fatty acids. It is a relatively simple matter to attach sensory molecules, dye indicators, or a pharmaceutical to the magnetic nanoparticles using various anchor groups. Catherine Berry from the Center for Cell Engineering in Glasgow, UK is author of one of the cluster of papers entitled “Progress in functionalization
VOLUME 12 – ELECTRON MICROSCOPY SPECIAL ISSUE
of magnetic nanoparticles for applications in biomedicine.” “One of the main forerunners in the development of multifunctional particles is Theranostics [therapeutic diagnostics] is magnetic nanoparticles, “Berry says,” Following recent advances in nanotechnology, the composition, size, morphology and surface chemistry of particles can all be tailored which, in combination with their nanoscale magnetic phenomena, makes them highly desirable. “ Kevin O’Grady of the University of York, UK, affirms in an editorial that there have been significant advances in this area since the last cluster review in J.Phys.D. published in 2003. He points out that, “none of these applications could have been realized without dramatic progress beyond the state of the art in 2003 in the areas of particle synthesis and functionalization.”
David Bradley
Modeling is helped by going Green MODELING
Molecular dynamics (MD) of timedependent processes can now be modeled at the nanoscale without separating the process into small sections, thanks to the introduction of a mathematical function called Green’s function [Tewary V., Phys Rev B (2009) 80, 161409]. Until now, two techniques have been available for researchers to study a material’s properties, and each method has its drawbacks. Researchers can either accurately model processes at the nanoscale in increments measured in picoseconds to femtoseconds, or else they can model the bulk material over longer periods of time. Unfortunately, many physical processes such as defect formation and thermal conductance should be atomistically studied and occur on the nanosecond to microsecond scale. Such a study would require a huge number of steps. Vinod Tewary who developed the new method at the National Institute of Standards and Technology (NIST) in the US explains, “MD calculations are usually based on the physics of individual atoms or molecules.
Colorized simulation of what happens to 1,100 carbon atoms in a ‘flat’ sheet of graphene about 20 microseconds after the central atom is moved slightly upwards. Darker violet colors indicate atoms that have dropped below their original position, whereas the lighter green colors show where atoms have risen. Image courtesy of Vinod Tewary, National Institute of Standards and Technology.
This traditional approach is limited not only by time scale, but also by system size. It cannot be extended to processes involving thousands of atoms or more, because today’s computers – even supercomputers – cannot
handle the billions of time steps required”. His technique has already been tested on ripple propagation through graphene, a material composed of a one-dimensional lattice of carbon atoms. The ripple passes through the flat sheet and as a result the material undulates to remain stable. Tewary was able to follow the rippling process for up to 45 microseconds, an increase of around eight orders of magnitude over traditional modeling methods. The total energy of the system was found to be conserved to within 10-4 %, an improvement on current models where energy conservation is difficult. “The new NIST technique can access these longer time scales and scientists can now measure and understand what happens at key points in time that were not previously accessible, and throughout the full spectrum of time scales of interest in MD,” says Tewary. NIST researchers now plan to write a software program encoding the new technique to make it available to other users. Katerina Busuttil
Magnetic medical nano NANOMEDICINE Magnetic nanoparticles that could diagnose, monitor and then treat the wide range of common illnesses and injuries are on the way, according to research reviewed in a special cluster of papers [O’Grady et al., J. Phys. D: Appl. Phys. (2009) 42, 220,301, 224,001, 224,002, 224,003] Researchers are attaching nanoparticles to sensory units that can be dragged to a target site using an external magnetic field, such as that from a permanent magnet. Also magnetic nanoparticles represent a new generation of contrast agents for medical imaging technology using MRI. Similar magnetic nanoparticles could carry a therapeutic agent to the site, whether that is a drug or a gene therapy vector. Indeed, they are arming white blood cells with magnetic nanoparticles to seek out and destroy a tumour or using them to target nerve channels to restore an ailing heart. Indeed, magnetic nanoparticles have been tested in vivo to remedy heart injury in rats and in humans to
6
destroy, through heat generated by the action of an AC magnetic field, to which tumour cells are more sensitive. This technique has been used to treat a particularly severe form of brain cancer in fourteen patients. A similar approach has been used in treating prostate cancer. Magnetic nanoparticles are usually produced from the common iron oxide magnetite and then given a biocompatible coating, which provides stability and protection for the chemical particles and their companions as they are moved through the body. The coating is often comprised of fatty acids. It is a relatively simple matter to attach sensory molecules, dye indicators, or a pharmaceutical to the magnetic nanoparticles using various anchor groups. Catherine Berry from the Center for Cell Engineering in Glasgow, UK is author of one of the cluster of papers entitled “Progress in functionalization
VOLUME 12 – ELECTRON MICROSCOPY SPECIAL ISSUE
of magnetic nanoparticles for applications in biomedicine.” “One of the main forerunners in the development of multifunctional particles is Theranostics [therapeutic diagnostics] is magnetic nanoparticles, “Berry says,” Following recent advances in nanotechnology, the composition, size, morphology and surface chemistry of particles can all be tailored which, in combination with their nanoscale magnetic phenomena, makes them highly desirable. “ Kevin O’Grady of the University of York, UK, affirms in an editorial that there have been significant advances in this area since the last cluster review in J.Phys.D. published in 2003. He points out that, “none of these applications could have been realized without dramatic progress beyond the state of the art in 2003 in the areas of particle synthesis and functionalization.”
David Bradley