Oct 26, 2010
Mild magnetic field drives nanoparticles towards the brain
Externally applied magnetic fields can be used to target certain superparamagnetic particles to various organs. If the delivered nanoparticles have a high content of magnetic material, a mild magnetic field is enough to target them towards the brain, and hold them there. Previously, we've had particles that delivered drugs at a controlled rate within the circulation, and relied on the predisposition of some drugs to penetrate the blood-brain barrier. Now, we have a formulation of magnetic nanoparticles that can not only entrap drugs/dyes, but can deliver them to the brain. A carefully controlled parallel group animal study revealed a significantly higher brain concentration of the near-infrared imaging agent indocyanine green, when delivered using magnetic nanoparticles under the influence of a weak magnetic field of lower intensity than standard MRI equipment.
The blood-brain barrier, while being a bulwark for the brain, protecting it from danger, can also be a nemesis for some. Delivering foreign compounds across this barrier for imaging or therapy has been formidable for years. Earlier approaches were akin to using a sledgehammer where a screw driver was warranted, usually weakening the barrier using harsh chemical intervention.
Evaluation of magnetic carriers
This method involves the administration of an imaging dye encapsulated inside biodegradable polymeric nanoparticles with an iron oxide core. These particles distribute throughout the circulatory system, and under the influence of a weak magnetic field applied to the head, accumulate near the brain. As a result, researchers observe a much higher brain concentration of the encapsulated dye compared with control experiments.
These nanoparticles are completely biodegradable. The iron oxide cores are absorbed into the hemoglobin cycle and thus pose no danger. The polymeric matrices are also harmlessly metabolized.
Breaking through the roadblock
Delivering drugs to brain tissue is still tough, but scientists are constantly making headway towards that elusive goal. Imaging select regions in the brain has been troublesome, requiring invasive methods. This method significantly reduces the amount of therapeutic/imaging agent to be administered in order to produce a biologically relevant concentration in the brain.
Our future goals would be to further reduce the intensity of the external magnetic field as well as control the exact site of delivery within the brain.
The researchers presented their work in the journal Nanotechnology.
About the author
This study was conducted jointly by the graduate students of Dr Mostafa Sadoqi (Physics and Pharmaceutical Sciences, St. John's University, US) and Dr Emilio Squillante (Pharmaceutical Sciences, St. John's University). Sangram Raut is now a doctoral student at the Center for Commercialization of Fluorescence Technology, University of North Texas, US. Bharat Kirthivasan and Murali Mohan Bommana are doctoral students in Industrial Pharmacy at St. John's University.