Issue 4 2009 of Chemical Technology is now available online. The complete issue can also be downloaded in pdf format.
Instant insight: Bone repair breakthrough
Thomas Webster and colleagues at Brown University, Providence, US, explain why today's bone implants are so much more than your grandparent's hip replacement thanks to nanotechnology.
Interview: Molecular logic
A Prasanna de Silva tells Nicola Wise about sensors, supramolecular chemistry and how Sri Lankan percussion can play a part in Irish music.
This issue's Application highlights include UV-sensitive indicators that change colour when there is a danger of sunburn.
Chemical Technology is free to view online and news items link directly to the original research articles, which are free to access for a limited period of time.
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Chemical Technology issue 4 2009 PDF (1264k)
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Saturday, April 4, 2009
Lasers blow cells over microwalls
Scientists have used the unusual curving properties of laser beams to hurl microparticles and cells over walls.
Jörg Baumgartl at the University of St Andrews, UK, and colleagues used non-diffracting laser beams to transport particles between microwells. Baumgartl likens the laser beams to micrometre-sized snowblowers. The microparticles and cells are attracted to the bottom of the chip and then 'blown' upwards in an arc by the laser , he says.
Normal laser beams travel in a straight line and their light spreads out over distances. 'For instance, the beam emitted by a laser pointer would have the size of several hundred kilometres were it to reach the Moon,' explains Baumgartl. However, the non-diffracting laser beams he used travel in a curve without spreading out.
Jörg Baumgartl at the University of St Andrews, UK, and colleagues used non-diffracting laser beams to transport particles between microwells. Baumgartl likens the laser beams to micrometre-sized snowblowers. The microparticles and cells are attracted to the bottom of the chip and then 'blown' upwards in an arc by the laser , he says.Normal laser beams travel in a straight line and their light spreads out over distances. 'For instance, the beam emitted by a laser pointer would have the size of several hundred kilometres were it to reach the Moon,' explains Baumgartl. However, the non-diffracting laser beams he used travel in a curve without spreading out.
In most microfluidic studies, scientists move particles between chambers using a liquid flow. 'Our method opens an alternative route to transport, mix or sort microparticles and cells within the same microfluidic chip,' says Baumgartl.
'This is an important step forward in increasing the functionality of microfluidic environments by allowing particles to be transferred between different media,' says Ewan Wright, an expert in optical sciences and physics at the University of Arizona, Tucson, US. 'It is a wonderful example of how, over time, fundamental research, here on novel laser fields, can bring about highly innovative results in applied science.'
Baumgartl anticipates the method will lead to high-throughput, automated chips that will mix and sort microparticles and cells or mediate chemical reactions. It could be used to study cell processes and selectively expose cancer cells to drugs, he adds.
'This is an important step forward in increasing the functionality of microfluidic environments by allowing particles to be transferred between different media,' says Ewan Wright, an expert in optical sciences and physics at the University of Arizona, Tucson, US. 'It is a wonderful example of how, over time, fundamental research, here on novel laser fields, can bring about highly innovative results in applied science.'
Baumgartl anticipates the method will lead to high-throughput, automated chips that will mix and sort microparticles and cells or mediate chemical reactions. It could be used to study cell processes and selectively expose cancer cells to drugs, he adds.
Magnets control drug release
A smart tissue-like biomaterial that can release drugs in response to a magnetic trigger has been created by UK scientists.
Simon Webb and colleagues from the University of Manchester used magnetic nanoparticles to glue together dye-containing vesicles then embedded them in a hydrogel. Webb positioned the vesicles within the hydrogel using magnetism and showed he could release the dye using an alternating magnetic field as a trigger. Webb says this indicates that the tissue-like gel could be used to store drugs and deliver them to the site of disease without affecting the surrounding tissue.
Although the group have previously used vesicles to mimic cells sticking together, Webb says the magnetic particles and hydrogel matrix strengthen the assemblies and make them easier to control. 'Gratifyingly, this combination has provided robust materials that can be patterned and release biochemicals in response to a magnetic trigger,' he says.
'The clever part of all this is the way in which the authors interface their magnetic triggers with vesicles using precisely controlled non-covalent interactions,' says David Smith, who investigates nanoscale gel-phase materials at the University of York, UK. 'Embedding the resulting triggered-release system within a hydrogel then generates the kind of material which could be used for drug delivery.' He adds that an alternating magnetic field is ideal for clinical use as it does not adversely affect healthy tissue.
Webb says they are working to create smaller patterns in the hydrogel matrix, and to magnetically trigger the release of cell messenger molecules such as growth factors, to enable use of this technology for biomedical applications.
Simon Webb and colleagues from the University of Manchester used magnetic nanoparticles to glue together dye-containing vesicles then embedded them in a hydrogel. Webb positioned the vesicles within the hydrogel using magnetism and showed he could release the dye using an alternating magnetic field as a trigger. Webb says this indicates that the tissue-like gel could be used to store drugs and deliver them to the site of disease without affecting the surrounding tissue.Although the group have previously used vesicles to mimic cells sticking together, Webb says the magnetic particles and hydrogel matrix strengthen the assemblies and make them easier to control. 'Gratifyingly, this combination has provided robust materials that can be patterned and release biochemicals in response to a magnetic trigger,' he says.
'The clever part of all this is the way in which the authors interface their magnetic triggers with vesicles using precisely controlled non-covalent interactions,' says David Smith, who investigates nanoscale gel-phase materials at the University of York, UK. 'Embedding the resulting triggered-release system within a hydrogel then generates the kind of material which could be used for drug delivery.' He adds that an alternating magnetic field is ideal for clinical use as it does not adversely affect healthy tissue.
Webb says they are working to create smaller patterns in the hydrogel matrix, and to magnetically trigger the release of cell messenger molecules such as growth factors, to enable use of this technology for biomedical applications.
A new twist on actuator architecture
Scientists have built a novel type of actuator - a device that converts energy into motion - with an artificial opal embedded within it.
To make the actuator, Kwang-Un Jeong at Chonbuk National Unversity, Jeonju, South Korea, and colleagues put colloidal silica in water, where it formed a strip of single crystalline opal one tenth of a millimetre thick. They embedded the strip in a layer of poly(dimethylsiloxane) polymer then added a layer of polyurethane (PU)/2-hydroxyethyl methacrylate polymer on top. Finally, they sealed the bi-layer strip inside a layer of glass.
The team placed the strip in different solvents and found that it responded differently depending on the solvent's hydrophobicity. The strip curled up to form a right handed spiral in hydrophilic solvents, such as acetic acid, and a left handed spiral in hydrophobic solvents, such as hexane. The curling effect is due to the difference in swelling ratios between the two polymer layers, explains Jeong. He showed that the right-handed spirals display different colours depending on the angle they are viewed from but the left-handed ones do not.
'Using a bilayer polymer photonic system to create colour-tunable spiral photonic actuators is a simple and elegant idea,' says Christopher Li, an expert in soft matter and hybrid materials at Drexel University, Philadelphia, US. 'Being able to control the macroscopic handedness of the spiral is fascinating. Slightly changing the sample architecture could lead to profound shapes, such as a helix.'
According to Jeong, the actuators even respond to gaseous solvents. He says that the device may have varied applications: 'These colour-tunable, reversible spiral photonic switches can be useful as mechanical actuators and electrical devices, as well as optical components. Our ultimate goal is to construct complicated 3D objects from programmed 2D structures.'
To make the actuator, Kwang-Un Jeong at Chonbuk National Unversity, Jeonju, South Korea, and colleagues put colloidal silica in water, where it formed a strip of single crystalline opal one tenth of a millimetre thick. They embedded the strip in a layer of poly(dimethylsiloxane) polymer then added a layer of polyurethane (PU)/2-hydroxyethyl methacrylate polymer on top. Finally, they sealed the bi-layer strip inside a layer of glass.The team placed the strip in different solvents and found that it responded differently depending on the solvent's hydrophobicity. The strip curled up to form a right handed spiral in hydrophilic solvents, such as acetic acid, and a left handed spiral in hydrophobic solvents, such as hexane. The curling effect is due to the difference in swelling ratios between the two polymer layers, explains Jeong. He showed that the right-handed spirals display different colours depending on the angle they are viewed from but the left-handed ones do not.
'Using a bilayer polymer photonic system to create colour-tunable spiral photonic actuators is a simple and elegant idea,' says Christopher Li, an expert in soft matter and hybrid materials at Drexel University, Philadelphia, US. 'Being able to control the macroscopic handedness of the spiral is fascinating. Slightly changing the sample architecture could lead to profound shapes, such as a helix.'
According to Jeong, the actuators even respond to gaseous solvents. He says that the device may have varied applications: 'These colour-tunable, reversible spiral photonic switches can be useful as mechanical actuators and electrical devices, as well as optical components. Our ultimate goal is to construct complicated 3D objects from programmed 2D structures.'
Wednesday, April 1, 2009
Process technology
Haldor Topsoe, is providing its process technology for the ammonia production plants. The contract was awarded in May 2008. Haldor Topsoe commented that it saw the contract award as an "important milestone for the coming increased requirement for fertilisers worldwide".Based in Denmark, Haldor Topsoe is a specialist in the development and use of catalysts. The company says that its ammonia synthesis catalysts are installed in more than half of the world's ammonia converters.
Urea process technology is being supplied by Italy's Snamprogetti, while Germany's Uhde Fertiliser Technology is supplying its urea granulation process technology.
Sunday, March 29, 2009
PLASTIC PUMPS FOR ACIDS AND ALKALIS
Acids, alkalis and detergents can be safely handled by plastic pumps made from PP or PVDF. Bürkle offers many plastic pumps with both rigid discharge pipes and also with discharge tubing and shut-off valve for filling distant or higher standing containers. When handling corrosive or aggressive liquids the user should take appropriate precautions. Protective clothing such as gloves, goggles, aprons and face masks is essential.We recognise the health hazard posed by harmful vapours, and the importance of the correct choice of pump. Apart from the type and size of the container, the required pump capacity and the suitability of the pump for the particular medium are important for the choice of the most suitable product. The pump must not only be resistant to the medium to be filled, but in many cases particular occupational safety and environmental protection regulations must also be taken into consideration.
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