Researchers who want to combine tiny volumes of liquid have few simple options when it comes to mixing for lab-on-a-chip applications or microliter bioassays. Passive diffusion is slow, and violent stirring can break droplets apart instead of mixing them together.Thanks to a team in Singapore, researchers can now reach for the world’s smallest magnetic stir bars. At just 17 μm long and 75 nm to 1.4 μm thick, these super small stir bars can mix as little as 4 pL of liquid (Angew. Chem. Int. Ed. 2013, DOI:10.1002/anie.201303249). A team at Nanyang Technological University led by Hongyu Chen created the stir bars from oleic acid-stabilized Fe3O4 nanoparticles that are 40 nm in diameter. They modified the nanoparticles with citric acid to render them water-soluble and dissolved them.
The team then used a magnet to align the nanoparticles and gave them a silica coating to ensure they stayed straight and rigid. They centrifuged the mixture to purify the stir bars, which they dispersed in solutions of various concentrations for stirring. While stirring, the nanosized stir bars remain suspended in solution indefinitely. And removing them is as simple as placing a stationary magnet beneath the droplet and letting the stir bars settle out of solution over the course of about five minutes.
As recently highlighted at the ACS (American Chemical Society) meeting, nanomaterial and especially magnetic-particle-based sensors might one day help to prevent food-borne illness by quickly detecting bacteria such as Listeria on food and in the water used to wash food.
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MagForce AG (Frankfurt, XETRA: MF6), a leading medical technology company in the field of nanomedicine in oncology, announced today that it has received approval from the German Federal Institute for Drugs and Medical Devices (BfArM) to start the post-marketing clinical study in recurrent glioblastoma. The approval of the ethics committee was previously granted end of December 2012 and the Company will now proceed to install the required NanoActivators™ in the treatment centers and preparing for the clinical study initiation.
The trial is an open-label, randomized, controlled study to determine the efficacy and safety of NanoTherm® monotherapy alone and in combination with radiotherapy versus radiotherapy alone in up to 280 glioblastoma patients. It will be conducted in about 15 centers in Germany and will be initially started in five leading centers, including the University Hospitals Berlin, Duesseldorf, Giessen, Cologne and Muenster. Together with a steering committee of leading experts in neurooncology, MagForce has designed a study protocol to support and supplement the results of a previous study, which led to the approval of the NanoTherm® Therapy and its medical devices in brain cancer. In addition, the application procedure of the NanoTherm® particles into the tumor should be optimized. This study is also designed to comply with the current guidelines for the development of medicinal products.
"We are excited about the BfArM approval that now triggers the start of our post-marketing clinical study, which we have carefully prepared over the last few months in collaboration with leading neurosurgeons, neurooncologists, and radiotherapists. With this trial we intend to provide validation of the available results with our NanoTherm® Therapy involving leading medical experts in the field of neurooncology, the key opinion leaders in the application of this technology", Prof Dr Hoda Tawfik, COO and co- CEO of MagForce, commented.
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Quite interesting research from Tim St. Pierre's lab in Perth, Western Australia was recently published in PLOS Neglected Tropical Diseases. Approximately 200 million people in the world are infected with schistosomes. Diagnosis of schistosomiasis is often difficult and improved diagnostic methods are urgently needed to evaluate the success of elimination programs. Recently, a magnetic fractionation method for isolation of parasite eggs from feces was described, which uses magnetic microspheres to form parasite egg – magnetic microsphere conjugates. In an elegant investigation, Stephan Karl and Lucia Gutierrez followed up on the unexplained mechanism of formation of the conjugates.
The researchers determined the magnetic properties of the eggs, studied the motion of eggs and egg-microsphere conjugates in magnetic fields and determined species specific affinity of parasite eggs to magnetic microspheres. Iron is predominantly localized in pores in the eggshell. Beautiful electron microscopy pictures and investigations suggest that the interaction of magnetic microspheres and parasite eggs is unlikely to be magnetic in origin. Instead, the filamentous surface of the eggshells may be important in facilitating the binding. Modification of microsphere surface properties may therefore be a way to optimize magnetic fractionation of parasite eggs.
Nanoparticles can be the bricks for constructing materials from the ground up, with DNA linkers as the mortar that holds them together. Because of the difficulty of attaching DNA strands to nanoparticles, the approach has so far been limited to a few types of nanoparticles. Chad A. Mirkin and coworkers at Northwestern University have devised a general approach that expands the types of nanoparticles that can be used with DNA-guided assembly (Nat. Mater. 2013, DOI: 10.1038/nmat3647).
Mirkin and coworkers take advantageof the fact that most nanoparticles are capped with hydrophobic ligands. They coat those ligands with an azide-containing amphiphilic polymer. They use DNA that contains a strained octyne ring and attach the DNA to the polymer via azide-alkyne cycloaddition. The nanoparticles are then ready to be used as building blocks in DNA-based colloidal crystallization. They make colloidal lattices with various nanoparticles, including CdSe/ZnS core-shell quantum dots, gold nanoparticles, iron oxide nanoparticles, and platinum nanoparticles. They control the size and crystal packing of the lattices by changing the radius of the nanoparticles and the length of the DNA linkers.
A big obstacle to developing stem cell therapies is being able to visualize the cells inside the body. This will be critical to confirm that the stem cells are targeted to the right place and are providing therapeutic benefit. Current imaging technology are not adequate for tracking stem cells in vivo. Magnetic Particle Imaging, MPI, is a new methodology that has promise to be 200 times more sensitivity than magnetic resonance imaging (MRI). Steven Conolly, whose UC Berkeley lab is pioneering MPI, spoke to the CIRM governing board on May 24, 2012 about his research.
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Riboflavin (Rf) and its metabolic analogs flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) are essential for normal cellular growth and functionfunction. Their intracellular transport is regulated by the riboflavin carrier protein (RCP), which has been shown to be over-expressed by metabolically active cancer cells. Fabian Kiessling, Jabadurai Jayapaul et al. made now magnetic nanoparticles bound to FAD (FAD-USPIO) and and confirmed that they were strongly and specifically taken up by cancer (LnCap) and endothelial (HUVEC) cells. RCP-targeted diagnostic nanoparticles might thus be interesting new materials for the assessment of vascular metabolism in tumors.
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The performance of magnetic nanoparticles is intimately entwined with their structure, mean size and magnetic anisotropy. This was nicely shown in a recent article by Carlos Martinez-Boubeta et al. They reported on an experimental and theoretical analysis of magnetic hyperthermia. Experimentally, they demonstrated that single-domain cubic iron oxide particles resembling bacterial magnetosomes have superior magnetic heating efficiency compared to spherical particles of similar sizes. Monte Carlo simulations at the atomic level corroborate the larger anisotropy of the cubic particles in comparison with the spherical ones, thus evidencing the beneficial role of surface anisotropy in the improved heating power.
The article is available on Scientific Reports 3, 1652 (2013).
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