Nano Today
ReviewMagnetic nanoparticles for drug delivery
Section snippets
The development of magnetic drug delivery
Any overview on drug delivery should start with the deserved recognition of Paul Ehrlich (1854-1915), who proposed that if an agent could selectively target a disease-causing organism, then a toxin for that organism could be delivered along with the agent of selectivity. Hence, a ‘magic bullet’ would be created able to kill the targeted organism exclusively. Ehrlich received the 1908 Nobel Prize in Medicine for his work in the field of immunity, and the magic bullet idea was even used as a
Fate
The distribution of NPs and their loads throughout the body depends on numerous physicochemical factors: size of particles, toxicity, surface charge, capacity for protein adsorption, surface hydrophobicity, drug loading and release kinetics, stability, degeneration of carrier systems, hydration behavior, electrophoretic mobility, porosity, specific surface characteristics, density, crystallinity, contact angle, and molecular weight39. Nevertheless, the fate (and also the possible toxicity) of
Safety: influence of the magnetic field
Although all the components of the body are either dia-, para-, superpara-, ferri-, or ferromagnetic, the magnetic fields required to produce obvious effect in the body are very large. Even red blood cells, which each contain micrograms of the Fe protein hemoglobin, show a relatively low response to large fields or steep field gradients, although this low value is enough to be used in functional MRI (fMRI). The other natural Fe-containing compounds in the body are hemosiderin, ferritin,
Toxicity
When discussing the toxicity of NPs, generalization becomes difficult because their toxicity depends on numerous factors including the dose, chemical composition, method of administration, size, biodegradability, solubility, pharmacokinetics, biodistribution, surface chemistry, shape, and structure, to name but a few. With NPs, as with any new biomedical discovery, the risk-benefit trade-off must be considered to assess whether the risks can be justified. In general, the size, surface area,
Perspectives and future challenges
In therapy, we are witnessing the early use of magnetic NPs as drug delivery vectors and as tools for hyperthermia/thermal ablation. Magnetic drug delivery constitutes a promising technology to treat cancer, and several products are already on the market. The limitations inherent in the use of external magnetic fields can, in some cases, be circumvented by means of internal magnets located in the proximity of the target by minimally invasive surgery40, 43, 44, 98, 118. Magnetic fluid
Acknowledgments
Support from the Spanish Nanoscience Action NAN200409270-C3-1/2 and from the Consolider CSD2006-00012 and Ciber Ingenio 2010 CB06/01/0026 programs, is gratefully acknowledged. MA acknowledges support of a contract from the Juan de la Cierva program (project PPQ2003-04986). The authors also gratefully acknowledge the Serveis Cientificotécnics of the University of Barcelona for the use of the TEM, and Jordi Arbiol i Cobos for the TEM photographs and helpful discussions.
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