Journal of Materials Chemistry Blog

UK researchers have modified plant spore microcapsules to take up to three and a half times their own weight in oil by a simple mixing process, giving them potential as natural oil-spill clean-up materials.

Grahame Mackenzie at the University of Hull and colleagues at Sporomex, a company that deals in micro-encapsulation for the pharmaceutical, food, cosmetics and personal care industries in Hull, extracted the outer layer of Lycopodium clavatum  (clubmoss)  spores, removed the inner contents using a simple, non-toxic process and modified the surface functional groups to make them more lipophilic. They then put the microcapsules into an oil in water emulsion, shook it by hand for 15 seconds, and filtered the microcapsules out to leave an oil-free sample. The microcapsules could be used two or three times without a change in oil recovery efficiency, which the team attributed to the high strength of the sporopollenin polymer in the spore walls.

‘The advantage over conventional methods, for example phase separation paper or simple solvent extraction, is that the emulsion is simply mixed with the shells and then filtered, which is more rapid,’ says Mackenzie. Compared to other oil remediation methods, he says, ‘the spores are a natural material, are very robust and have a consistent size, making them easy to filter’.

Sporopollenin is also known to be very elastic and so the group tested the release of oil from the microcapsules under prolonged friction. They found that the oil could be released slowly over short time periods, indicating that the microcapsules could be used as delivery vehicles in the pharmaceutical and cosmetic industries.

‘A major breakthrough is the ability to evacuate the spores without toxic solvents,’ says Miriam Rafailovich, an expert in nanoscale materials engineering at Stony Brook University, US. However, she says that ‘since these spores can be allergens in their native form, the interactions of these processed capsules with higher organisms will need to be tested’.

Mackenzie considers one drawback to be ‘the high cost and lack of large-scale availability’ of the spores, however he adds that ‘research is ongoing and applications are being explored by various companies’.

Thibaud Coradin of the materials and biology team at the College of France in Paris says that the approach ‘should be highly inspiring for the future identification and processing of biocapsules’.

Sequestration of edible oil from emulsions using new single and double layered microcapsules from plant spores
Alberto Diego-Taboada, Priscille Cousson, Elodie Raynaud, Youkui Huang, Mark Lorch, Bernard P. Binks, Yves Queneau, Andrew N. Boa, Stephen L. Atkin, Stephen T. Beckett and Grahame Mackenzie
DOI: 10.1039/C2JM00103A

Read the original Chemistry World article here

Dye sensitised solar cells (DSSCs) have long been recognised as a possible answer to the energy crisis we are facing. Unfortunately, many current solar cells rely on expensive platinum or inflexible carbon based materials in their manufacture. Now, scientists in China have found a cheaper and more efficient alternative in commercial fountain pen ink.

Until now, none of the materials investigated has managed to achieve the light weight, low-cost and biodegradable properties that are attractive in manufacturing flexible electronics. However, Dechun Zou and co-workers at Peking University have found a material that has all these attributes in fountain pen ink.

The idea to use ink in DSSCs came from the concept of ‘paper electronics’, says Zou. Compared to traditional, rigid electronic devices, paper electronics may be the future in achieving the flexibility needed in many commercial applications. An example for the eco-friendly fashion conscious being the application of DSSCs on backpacks and bags for powering portable electronic devices.

Commercial pen ink consists of well-dispersed carbon nanoparticles. Here, the researchers took advantage of the good catalytic activity, high stability and well-established industrial production of the material and directly introduced the ink as a counter electrode material for DSSCs. The ink film was prepared via a spin-coating technique and the layer was shown to be only 3m thick.

Andrew Hamnett, an expert in solar energy and  president of the Scottish Marine Institute, UK, comments how the authors have ‘cleverly exploited’ the effort that has gone into optimising carbon suspensions in fountain pen inks and congratulates them on ‘a nice bit of lateral thinking’.

The energy efficiency of the cells is currently at 6.2%, which is comparable to a standard Pt electrochemical device that would be around 1000 times more expensive. Future strategies to increase the catalytic activity may include utilising other film preparation processes or further investigation into the catalytic mechanism of the ink nanoparticles, which Zou says may be ‘challenging but also promising’.

Direct application of commercial fountain pen ink to efficient dye-sensitized solar cells
Xin Cai, Zhibin Lv, Hongwei Wu, Shaocong Hou and Dechun Zou
DOI: 10.1039/C2JM16265B

Read the original Chemistry World article here

Scientists from China and Canada have found that a drug-loaded shape memory polymer can be manipulated by ultrasound and that they can control when and how the drugs are released.

Shape memory polymers (SMPs) can be deformed and fixed into a temporary shape and then recover their original permanent shape under external stimuli such as heat, explains lead researcher Hesheng Xia from Sichuan University, Chengdu. ‘When a piece of polymer is placed in the body, it is subjected to heating at 37°C everywhere and the whole piece undergoes shape recovery,’ he says. Xia and co-workers directed an ultrasound beam on a selected area of a polymer, causing a local rise in temperature and triggering shape recovery only in that area. Xia adds that ultrasound has the advantage of easily penetrating body tissue.

Using high intensity focused ultrasound (HIFU), the polymer was changed from its permanent M shape to a temporary I shape, then a V then an N and back to the M, releasing drugs with each change

Xia’s group loaded their SMP sample with a drug and folded it into a temporary ‘I’ shape. By directing the ultrasound onto different positions on the polymer, they could control its shape on demand, changing it from ‘I’ to ‘V’ to ‘N’ and back to the original ‘M’, releasing drugs with each shape change. They stopped the drug release by switching off the ultrasound. This caused a quick temperature drop, which allowed the polymer to adopt a stable intermediate shape.

Tao Xie, who works on shape memory polymers at the General Motors Research and Development Center, Michigan, US, was impressed that ultrasound controls the shape in a spatial and temporal manner, allowing selected regions of the polymer to be controlled on demand. He added that this would ‘significantly widen the application potential’.

Xia hopes that the switchable release of drugs from SMPs could be applied to polymer implants for minimally invasive surgery and that ultrasound may reduce infection risks. To minimise side effects, however, he says that the challenge will be to reduce the power and irradiation time of the ultrasound needed for the shape changes.

Spatial and temporal control of shape memory polymers and simultaneous drug release using high intensity focused ultrasound
Guo Li , Guoxia Fei , Hesheng Xia , Jianjun Han and Yue Zhao
DOI: 10.1039/C2JM30848G

Read the original Chemistry World article here

Seth Marder discusses the importance of materials chemistry to society with Liz Davies.

Watch the video interview on YouTube here:

If you’re interested to know more about how new materials could improve people’s lives you can read reports on:

• A Sustainable Global Society: How Can Materials Chemistry Help? 
• Or the RSC Roadmap report: Chemistry for Tomorrow’s World.

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