Iron and Magnetism in Schistosome Eggshells

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.

DNA Driven Assembly with Nanoparticles

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.

Stem Cell Tracking with Magnetic Particle Imaging (MPI)

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.

Check out the youtube video here.

Riboflavin carrier protein-targeted fluorescent USPIO for the assessment of vascular metabolism in tumors

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.

Check it out in detail here.

Learning from Nature to Improve Heat Generation with Magnetic Nanoparticles

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).

Clinically Relevant Magnetic Particle Applications in New Publications

Two new publications are advancing the in vivo use of magnetic particles.

The first is a research paper by Johannes Riegler et al. about the use of magnetically loaded stem cells to improve cell retention in cell therapies for treating vascular injuries. This is a joint research project carried out in both University College London and the National University of Ireland. The article can be downloaded here.

The other is a book chapter included in the last edition of the Specialist Periodical Reports published by the Royal Society of Chemistry (RSC). It is co-authored by Daniel Ortega and Quentin Pankhurst, and it covers the basic physical-chemical-biological aspects of magnetic hyperthermia, including a review of some clinical case studies. If you are interested, you can find it here.

Nobel Laureate Roger Tsien to Speak at MPI Workshop

Prof. Roger Y. Tsien, 2008 Nobel Laureate in Chemistry, will deliver a keynote speech on Magnetic Particle Imaging (MPI) at the upcoming International Workshop on MPI (IWMPI 2013) to take place at University of California, Berkeley on March 23-24, 2013. 

Magnetic Nanoparticles Remove Bacteria from Blood

When bacteria build up in the blood, it's bad news. The condition can lead to a serious infection known as sepsis, which can turn deadly even with aggressive treatment using antibiotics. Researchers at Massachusetts Institute of Technology and Harvard Medical School may have found a way to pluck bacterial invaders from blood by magnetic separation. Daniel S. Kohane and coworkers coated magnetic nanoparticles with zinc coordinated bis(dipicolylamine), a complex known to bind strongly to anionic phospholipids that densely decorate the surfaces of bacteria. The researchers added these modified nanoparticles to blood tainted with Escherichia coli and ran the blood through a magnetic microfluidic device. They were able to pull almost all of the bacteria from the blood, even at blood flow rates of 60 mL per hour. The technology, the researchers say. could be adapted to treat sepsis in people, which in the U.S. has become the seventh-leading cause of infant mortality and the 11th-leading cause of death.

For more info, check out the preprint.