Aug 10, 2010
Tiny magnets revealed under the microscope
Researchers from Lisbon and Porto in Portugal are studying methods of specifically detecting single magnetic nanoparticles, while removing signals from other non-magnetic materials. Magnetic force microscopy (MFM) is a very powerful imaging tool, but is subject to interference from non-magnetic materials, making the technique less useful. In the study, published in the journal Nanotechnology, the team shows that by applying a bias to the MFM probe, non-magnetic particles can be excluded from the MFM image.
Using a standard AFM instrument, the scientists have applied the method to a variety of magnetic nanoparticles, including tiny superparamagnetic materials, and core:shell particles. The aim of the work is to further develop biological applications of magnetic nanoparticles. "We want to be able to locate the nanoparticles, with specificity for their magnetic properties, in or on human cells," explained Dr Peter Eaton, corresponding author.
One long-standing goal of nanomagnetics has been the use of magnetic nanoparticles for therapeutic applications. The idea is that particles specifically target cancer cells and are then used to heat the cells and kill them. In order to develop these applications, researchers need tools that can locate the tiny magnetic particles to see if they are really finding their targets. The group of Dr Eaton, including PhD student Cristina Neves from Requimte, wants to develop these tools.
"One of the problems people have when working with biological samples is contamination. Finding 40 nm particles in a specimen that also contains the various materials needed by the cells is tough. In our work, we show methods that will be useful to distinguish the magnetic particles from signals that relate to all of that other stuff," said Eaton. "Even better, we were astonished to find that we could detect the particles even with the probe hundreds of nanometres away from them. This means that MFM might be capable of detecting the particles inside the cells, and that's where we are going next."
About the author
Peter Eaton, Cristina Neves, Pedro Quaresma and Eulália Pereira, are all researchers from Requimte/ Faculty of Sciences of the University of Porto. Their "NanoBio" group researches the optimization and characterization of the interface between nanostructures and biological molecules and cells. Dr Eaton is an assistant researcher and leads the force microscopy characterisation unit of the NanoBio group. He has recently published a book on force microscopy, "Atomic Force Microscopy" by Eaton and West, OUP, 2010. Cristina Neves is the PhD student of Dr Eaton and is studying the preparation and application of novel nanoparticles. Dr Araújo works in the IFIMUP, Porto, and carries out magnetic characterization of the particles. Dr Carvalho works at IST, Lisbon, and carries out TEM characterization of nanostructures. Dr Baptista and Pedro Quaresma form the Bio component of the NanoBio group and are members of the CIGMH/FCT-UNL, Lisbon. Their current project involves magnetic nanoparticles for interacting with biological targets.