RSC Advances Blog

Silver is commonly used both in ionic form and in nanoparticulate form as a bactericidal agent. This is generally ascribed to a higher toxicity towards prokaryotic cells than towards mammalian cells.

Scientists in Germany have carried out studies to compare silver ions (such as silver acetate) and polyvinylpyrrolidone (PVP)-stabilised silver nanoparticles (70 nm). They found that silver’s toxic effect occurs in a similar concentration range for Escherichia coli, Staphylococcus aureus, human mesenchymal stem cells and peripheral blood mononuclear cells (0.5 to 5ppm for silver ions and 12.5 to 50ppm for silver nanoparticles).

For a better comparison, the team cultivated bacteria in Lysogeny broth medium and in Roswell Park Memorial Institute medium/10% fetal calf serum medium, as the state of silver ions and silver nanoparticles may be different owing to the presence of salts and biomolecules such as proteins. They found that the effective toxic concentration of silver towards bacteria and human cells is almost the same.

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The toxic effect of silver ions and silver nanoparticles towards bacteria and human cells occurs in the same concentration range

Christina Greulich,  Dieter Braun,  Alexander Peetsch,  Jörg Diendorf,  Bettina Siebers,  Matthias Epple and Manfred Köller
RSC Adv., 2012, 2, 6981-6987

Schematic drawings of (A) different designs of assay probes for cocaine detection: (left) monolithic aptamer (MA), (middle) double-fragment aptamer (DFA), and (right) triple-fragment aptamer (TFA); (B) gold nanoparticle based optical cocaine detection using TFA. The same oligonucletide sequences were drawn in the same colors.

Chinese scientists have developed a  colorimetric sensor consisting of a triple-fragment aptamer (TFA) that is able to assemble in the presence of cocaine. Xinhui Lou and Yueying Liu and co-workers at the Capital Normal University in Beijing, showed that the aptasensor was specific for cocaine and worked equally well in complex urine samples containing 100 μM cocaine or filtered serum containing cocaine.   

This new type of aptamer probe design showed a gradual colour change from red to blue when the concentrations of cocaine was increased from 0 to 200 μM . “TFA broadens the repertoire of probe designs and provides good opportunities for the future development of novel detection approaches and for nanostructure constructions,” says Liu et al. 

Even though the assays need to be conducted at low temperature (4 °C), the authors believe that the detection method can be further improved by increasing the stem length. 

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Highly specific triple-fragment aptamer for optical detection of cocaine
Ruxing Zou ,  Xinhui Lou ,  Huichao Ou ,  Ying Zhang ,  Wenjie Wang ,  Min Yuan ,  Ming Guan ,  Zhaofeng Luo and Yueying Liu 

RSC Adv., 2012,2, 4636-4638
DOI: 10.1039/C2RA20307C

SEM image of an ordered array of MnSO4 bowls obtained after calcination of the MnSO4–PVP composite film at 550 °C for 5 h.

Scientists at the  Jawaharlal Nehru Centre for Advanced Scientific Research, in Bangalore, India, report a simple method for the “spontaneous formation of ordered, mesoscale structures made up of inorganic salt bowls”. These tiny bowls are said to be generating a lot of interest due to their unique application as ‘containers’ to hold ultra-low volumes.

The team led by Eswaramoorthy showed that when manganese sulfate is heated with the water soluble polymer PVP, the mix spontaneously forms arrays of tiny water-soluble bowls of the manganese sulfate salt. The beautiful structures are the result of the salt crystallising around the PVP as it bubbles and evaporates. The salt bowl were coated in gold, before the salt is washed away leaving some of the tiniest gold bowls ever made.

Scheme showing formation process of different MnSO4 morphologies through gas-bubble template method, Scheme A: Bowls, Scheme B: Ball-in-bowl shaped structures, Scheme C: Ring shaped structures (for convenience, all morphologies are shown to be evolved from the same film).

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Shaping up: spontaneous formation of ordered mesoscopic salt bowls

Katla Sai Krishna, Bosukonda V. V. S. Pavan Kumar and Muthusamy Eswaramoorthy
RSC Adv., 2012, Advance Article
DOI: 10.1039/C2RA20596C, Communication

‘Flaxseed gum beads can be used to remove oil from wastewater systems,’ claim Chinese scientists.
Flaxseed gum is a mixture of proteins and polysaccharides such as arabinose, rhamnose, fucose, xylose and others. Yu-Jie Fu and co-workers, at the Ministry of Education, Northeast Forestry University, Harbin, China, explain that the flaxseed gum beads can remove 0.55 g of oil per gram of beads. They showed that flaxseed gum beads have better adsorption capacities than activated carbon.

The flaxseed gum content in the immobilised beads was 30 mg per gram and oil removal was carried out with 2mm diameter beads at room temperature and pH of 7.5. 

When investigating the removal of 1.0 kg of oil from oil–water emulsions by immobilized flaxseed gum beads v/s activated carbon. 1.82kg of flaxseed gum beads was required to remove 1.0kg of oil, costing only 2.67 RMB (chinese currency) compared to 2.17 kg of powdered activated carbon costing 43.40 RMB.  Furthermore, the flaxseed gum beads is resuable allowing lower processing costs than traditional oil removal methods. Flaxseed gum bead technology holds great promise as an alternative environmentally-friendly method for oil removal from wastewater.

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Oil removal from oily water systems using immobilized flaxseed gum gel beads
Jing-jing Long, Yuan-gang Zu, Yu-jie Fu, Meng Luo, Pan-song Mu, Chun-jian Zhao, Chun-ying Li, Wei Wang and Ji Li
RSC Adv., 2012, Advance Article
DOI: 10.1039/C2RA20375H, Paper

Honeybee secretions such as royal jelly or “queen” substance are used to feed queen larvae to make them develop into sexually mature females. It is also known that secretions inhibit ovarian development in worker bees.

Honeybee secretions consists mainly of 10-hydroxy-2E-decenoic acid and 9-oxo-2E-decenoic acid, respectively. Sabrina Castellano and co-workers at the Università di Salerno, Italy report for the first time the multigram scale syntheses of honeybee secretions. The team used a TEMPO catalyzed oxidation of readily available alcohols and subsequent Doebner-Knoevenagel reaction between the resulting aldehydes and malonic acid. The syntheses are cheap and metal-free.

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Straightforward, Metal-free, and Stereoselective Synthesis of 9-Oxo- and 10-Hydroxy-2(E)-decenoic acids, Important Components of Honeybee (Apis mellifera) secretions
Ciro Milite, Monica Viviano, Marisabella Santoriello, Fabio Aricò, Gianluca Sbardella, and Sabrina Castellano
RSC Adv., 2012, Accepted Manuscript, DOI: 10.1039/C2RA20275A, Paper

This article also features in Chemistry World. Read the full story and get more details about potential antitumour activity of honeybee secretions here.

Adrian Fisher and colleagues at the University of Cambridge, UK, have grown purple bacteria Rhodopseudomonas palustris, which fed on cyanobacteria Arthrospira maxima for carbon source. The bacteria duo was used in microbial fuel cell applications. Rhodopseudomonas palustris uses light for energy but does not use carbon dioxide as a carbon source, so the purple bacteria fed on the cyanobacteria for its carbon source.

The authors have compared the cyanobacteria to two other chemical sources of carbon, namely, acetate and glycerol. They showed that the cyanobacteria gave the highest volumetric power of the three.

This work could provide valuable information for the development of future renewable energy systems.

The manuscript has just been accepted. You can read the full paper for free by clicking on the link below. Please note that you may need to register online for free access.

Rhodopseudomonas palustris purple bacteria fed Arthrospira maxima cyanobacteria: demonstration of application in a microbial fuel cell
Alister Edward Inglesby, David Alexander Beatty and Adrian C Fisher 
RSC Adv., 2012, DOI: 10.1039/C2RA20264F, Accepted Manuscript

Are you scared of injections and syringes? Australian and UK scientists have developed a patch to deliver vaccines through the skin.

The patch consists of micropillars attached to silicon wafers for dermal penetration. In this RSC Advances article, the researchers have produced patches with a high projection density (20,000 cm^-2) by using controlled mixed plasma in a deep reactive ion etching process to produce long tapered tips without limiting the overall feature density. With this tailored process, the team fabricated structures of tuneable shape and height with high uniformity across the face of the silicon wafers.  

They also showed that the patch can be used to extract specific biomarker samples from the skin.

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Reference:

High density and high aspect ratio solid micro-nanoprojection arrays for targeted skin vaccine delivery and specific antibody extraction
Derek Jenkins,  Simon Corrie,  Christopher Flaim and Mark Kendall
RSC Adv., 2012, Advance Article, DOI: 10.1039/C2RA20153D

Do you spend your day running HPLC or other lengthy column chromatography to purify your proteins or other biological entities? 

The development of affinity capture devices—a nanoscale purification platform for biological in situ transmission electron microscopy
Katherine Degen ,  Madeline Dukes ,  Justin R. Tanner and Deborah F. Kelly
RSC Adv., 2012, Advance Article, DOI: 10.1039/C2RA01163H