Recent technical innovation has enabled chemical modifications of small materials and various kinds of nanoparticles have been created. In clinical settings, nanoparticle-mediated drug delivery systems have been used in the field of cancer care to deliver therapeutic agents specifically to cancer tissues and to enhance the efficacy of drugs by gradually releasing their contents. In addition, nanotechnology has enabled the visualization of various molecular processes by targeting proteinases or inflammation. Nanoparticles that consist of poly (lactic-co-glycolic) acid (PLGA) deliver therapeutic agents to monocytes/macrophages and function as anti-inflammatory nanoparticles in combination with statins, angiotensin receptor antagonists, or agonists of peroxisome proliferator-activated receptor-(PPAR ). PLGA nanoparticle-mediated delivery of pitavastatin has been shown to prevent inflammation and ameliorated features associated with plaque ruptures in hyperlipidemic mice. PLGA nanoparticles were also delivered to tissues with increased vascular permeability and nanoparticles incorporating pitavastatin, injected intramuscularly, were retained in ischemic tissues and induced therapeutic arteriogenesis. This resulted in attenuation of hind limb ischemia. Ex vivo treatment of vein grafts with imatinib nanoparticles before graft implantation has been demonstrated to inhibit lesion development. These results suggest that nanoparticle-mediated drug delivery system can be a promising strategy as a next generation therapy for atherosclerotic vascular diseases. nm. In tumor tissues or at the site of inflammation, the integrity of these endothelial layers is impaired and the nanoparticles can extravasate to the extravascular space through the enlarged interspace between endothelial cells. In tumor tissues, immature lymphatic vessels retard elimination of nanoparticles. These effects are known as enhanced permeability and retention effects 22,23) . Surface modification with polyethylene glycol (PEG) prevents entrapment of nano particles by the reticuloendothelial system due to its hydrophilic property. Therefore, these nanoparticles are called stealth nanoparticles 24,25) .
J Atheroscler
Nanoparticles as a Research Tool for AtherosclerosisClinical applications of nanoparticles are advanced in the field of diagnostic medicine. For example, magnetic nanoparticles with iron cores are available in MRI for macrophage imaging 26) . These so-called superparamagnetic iron oxide (SPIO) nanoparticles are used as a negative contrast agent in MRI. The iron core is modified with hydrophilic polymers including dextran, carboxymethylated dextran, polyvinyl alcohol, starches, chitosan, polymethyl methacrylate, PEG, poly (lactic-co-glycolic) acid (PLGA), polyvinylpyrrolidone, and polyacrylic acid 27) . These particles have been tested in patients to evaluate inflammation, plaque vulnerability, and therapeutic effects of lipid lowering drugs, especially in the carotid arteries of patients 26,28,29) . Adhesion molecules are also targets of molecu...