Nanoparticles

Bio-Applications of Magnetic Nanoparticles

Small particles have been in use for biomedical research and in vitro diagnostic protocols since the ‘50s.  For example, polymeric micro-particles (e.g. latex microspheres) obtained as highly monosized assemblies have the advantages of biocompatibility and large reactive surface for biological units. These micro-particles have been adopted by food industry for diagnostics and testing in the production line, such as latex agglutination (LA) for identifying staphylococci, streptococci or Escherichia coli (E. coli). Clinical uses of polymeric microspheres include immunology diagnostics for malignant proliferative plasma cell disorders (i.e., multiple myeloma); immunodiagnostic assay systems using antibody-charged particles for quantification of immunoglobulin molecules in serum or cerebrospinal fluid, and fluorescent neuronal markers for studying the visual cortex.

Magnetic nanoparticles (MNPs) are one sub-class of this broad bio-related classification. The first therapeutic applications of magnetic devices to humans can be chased back to the 16^th century, when Austrian physician Franz Anton Mesmer (1734-1815) developed his theories about magnetic fluids. He sustained the influence of invisible ‘universal fluids’ on the human body (after the Newtonian ideas of ‘aether’ associated to gravitational forces and tidal cycles), and proposed his theory of ‘animal magnetism’ gaining notoriety across Europe. Since then Mesmerism (a therapeutics based mainly on hypnotism) has triggered a sustained flood of both research and ‘supernatural’ quackery (e.g. look here, here or here). An excellent discussion of these issues by Stephen Lower can be found here.

MNPs in Oncology

 

For cancer diagnostics and therapy there are currently a number of techniques based on different types of nanoparticles. Nanotechnological advances are at the bottom of the next paradigm shift in cancer research, diagnostics and therapy by improving direct visualization of malignant cells, targeting at molecular level and safely delivering large amounts of chemotherapeutic agents to desired cells. These techniques should be capable of rapid and sensitive detection of malignant cells at early stages.

The common feature of all nanoparticle-based cancer therapies is the need of specific NPs for achieving the desired therapeutic effect. However, each diagnostic/therapeutic technique requires a different chemical or physical property of the particles involved, which depends on the specific function played by the NPs in that therapy (e.g., vector, porous receptacle, heating agent, magnetic moment carrier, etc…). Sometimes the particle function is activated using an external agent (magnetic fields, light, radiation, etc…) that interacts with the NPs. Therefore the requirements for NPs as biomedical agents span a broad range of novel materials, synthesis strategies, and research fields .

 

There are three main strategies for bio-applications of MNPs:

 

· The application of controlled magnetic field gradients (i.e., a magnetic force) around the desired target location for remotely positioning MNPs in organs or tissues (targeting, magnetic implants, magnetic separation applied to the sequencing of DNA, etc… );

 

· The utilization of the magnetic moment of the MNPs as a disturbance of the proton nuclear resonance (e.g., contrast media for Magnetic Resonance Imaging, MRI).

 

· The magnetic losses of nanometric particles in colloids for heating purposes (magnetic hyperthermia)