Editors' ChoiceBioengineering

Target Acquired: Magnetic Nanoparticles Lock-On and Deliver

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Science Translational Medicine  19 May 2010:
Vol. 2, Issue 32, pp. 32ec81
DOI: 10.1126/scitranslmed.3001278

When cooking oil and grease are poured down your kitchen sink, they inevitably coat your pipes and clog your drain. Similarly, in your body a buildup of fatty deposits combined with inflammation narrows your arteries and impairs blood flow, a condition called atherosclerosis. Though atherosclerosis itself is often asymptomatic, it increases the risks of heart attack and stroke, two of the major causes of death in the developed world. One surgical treatment is angioplasty, in which a balloon is inserted and inflated to open the narrowed vessel and then a stent, a wire-mesh tube, is inserted to prop the artery open. After surgery, however, there is the risk of restenosis, the re-narrowing of the treated artery. This problem has motivated the creation of coated stents that release drugs over time in the treated area to inhibit the in-growth of the arterial wall. Current limitations of coated stents are that once the stent is in place, the drug cannot be replenished, and that most of the drug remains tightly bound to the stent and may not actively prevent restenosis. Also, this device cannot help patients who have already been treated with a bare-metal stent without any drug coating unless a second surgery is performed.

To address these limitations of coated stents, Chorny et al. developed new technology using magnetic, drug-carrying nanoparticles. Surgical, stainless steel stents were implanted into the leg arteries of rats and then temporarily magnetized by an externally applied magnetic field. Magnetic nanoparticles loaded with paclitaxel, an anti-restenosis drug, were then injected into the animals. These nanoparticles were attracted to the magnetized stent, resulting in localized drug delivery and significantly decreasing arterial re-narrowing over time. After discontinuation of the magnetic field, the nanoparticles circulated systemically and eventually were cleared from the animal. This technology has tremendous clinical potential because it allows for repeated, targeted delivery of drugs to implanted stents over time and also can be applied to millions of bare-metal stents already in use.

M. Chorny et al., Targeting stents with local delivery of paclitaxel-loaded magnetic nanoparticles using uniform fields. Proc. Natl. Acad. Sci. U.S.A. 107, 8346–8351 (2010). [Abstract]

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