Abstract. The magnetite (Fe3O4) nanoparticles (MNPs) coated with poly(N-vinyl pyrrolidone) (PVP) via covalent bonds were prepared as T2 contrast agent for magnetic resonance imaging (MRI). The surface of MNPs was first coated with 3-(trimethoxysilyl) propyl methacrylate (silan A) by a silanization reaction to introduce reactive vinyl groups onto the surface, then poly(N-vinyl pyrrolidone) was grafted onto the surface of modified-MNPs via surface-initiated radical polymerization. The obtained nanoparticles were characterized by FT-IR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), TEM (transmission electron microscopy), VSM (vibrating sample magnetometer), and TGA (thermogravimetric analysis). The MNPs had an average size of 14 nm and exhibited superparamagnetism and high saturation magnetization at room temperature. T2-weighted MRI images of PVP-grafted MNPs showed that the magnetic resonance signal is enhanced significantly with increasing nanoparticle concentration in water. The r1 and r2 values per millimole Fe, and r2/r1 value of the PVP-grafted MNPs were calculated to be 2.6 , 72.1, and 28.1(mmol/l) -1 ·s -1 , respectively. These results indicate that the PVP-grafted MNPs have great potential for application in MRI as a T2 contrast agent. Vol.4, No.6 (2010) 329-338 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2010.42 region that they are accumulated, and hence cause negative contrast and provide a dark state in the image where the compounds are accumulated [15]. However, the direct use of magnetic nanoparticles as in vivo MRI contrast agent results in biofouling of the particles in blood plasma and formation of aggregates that are quickly sequestered by cells of the reticular endothelial system (RES) such as macrophages [16,17]. Furthermore, aggregated nanoparticles change their superparamagnetic response [7]. Therefore, in order to minimize biofouling and aggregation of particles and escape from the RES for longer circulation times, the nanoparticles are usually coated with a layer of hydrophilic and biocompatible polymer such as dextran [18], dendrimers [19], poly(ethylene glycol) (PEG) [20], and poly(vinyl pyrrolidone) (PVP) [21][22][23]. Of synthetic polymers, PVP is water-soluble, non-charged, non-toxic, and is used in various medical applications [24]. While there is a potential concern about covalent interaction between hydrophilic polymers and magnetic nanoparticles in order to increase their stability in physiological medium [25][26][27][28][29], PVP coating on Fe 3 O 4 nanoparticles in all previous works has been achieved through noncovalent interaction. Now, polymers grafting of magnetic nanoparticles is one of the most attractive methods of surface modification [30,31]. In the present study, we carried out chemical synthesis and characterization of PVP-functionalized magnetite (Fe 3 O 4 ) nanoparticles. Since the PVP was bonded to the surface of magnetite nanoparticles through covalent bonds, the prepared magnetic fluid (ferrofluid) was ve...

In the emerging field of molecular and cellular imaging, flexible strategies to synthesize multimodal contrast agents with targeting ligands are required. Liposomes have the ability to combine with a large variety of nanomaterials, including superparamagnetic iron oxide nanoparticles, to form magnetoliposomes (MLs). MLs can be used as highly efficient MRI contrast agents. Owing to their high flexibility, MLs can be associated with other imaging modality probes to be used as multimodal contrast agents. By using a thermosensitive lipid bilayer in the ML structure, these biocompatible systems offer many possibilities for targeting and delivering therapeutic agents for 'theragnostics', a coincident therapy and diagnosis strategy. This article deals with the fast-growing field of MLs as biomedical diagnostic tools. Different kinds of MLs, their preparation methods, as well as their surface modification with different imaging probes, are discussed. ML applications as multimodal contrast agents and in theragnostics are reviewed. Some important issues for the biomedical uses of magnetic liposomes, such as toxicity, are summarized.

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Magnetic iron oxide nanoparticles and their dispersion in various mediums are of wide interest for their biomedical applications and physicochemical properties. MFe(2)O(4) or MOFe(2)O(3) (where M = Co, Li, Ni or Mn, for example) can be molecularly engineered to provide a wide range of magnetic properties. In this article, we survey the literature, integrating the results of our work to give a rational view on the synthesis, physicochemical properties and applications of MFe(2)O(4), especially for MRI. However, retrieving detailed biological information on a subcellular level is difficult, owing to the limited resolution and low sensitivity of the MRI technique. Thus, this article also concentrates on the development of a magnetic iron oxide nanoparticles/quantum dot hybrids, as a dual-mode magnetic-fluorescent probe. The synthesis and physicochemical properties of the magnetic iron oxide nanoparticles/quantum dot hybrids and, especially, its application as an MRI-fluorescent probe, will also be described.

The number of cores with high grade prostatic intraepithelial neoplasia seems to be associated with the presence of cancer on second biopsy. A 6-month biopsy is recommended in patients with high grade prostatic intraepithelial neoplasia when 4 or more cores with high grade prostatic intraepithelial neoplasia are detected in the initial biopsy sample independent of prostate specific antigen.

Polyglycerol as a water-soluble and biocompatible hyperbranched polymer was covalently grafted on the surface of superparamagnetic iron oxide nanoparticles. With this aim, superparamagnetic magnetite nanoparticles were prepared by coprecipitation in aqueous media, then the surface of nanoparticles was modified to introduce the reactive groups on the surface of nanoparticles. After that, polyglycerol was grafted on the surface of nanoparticles by ring-opening anionic polymerization of glycidol using n-bulyllithium as initiator. The magnetometry, relaxometry and phantom MRI experiments of this highly stable ferrofluid showed its high potential as a negative MRI contrast agent. Calculated r(1) and r(2) relaxivities at different magnetic fields were higher than the values reported for commercially available iron oxide contrast agents. The in vivo MRI studies showed that, after intravenous injection into mice, the particles produced a strong negative contrast in liver and kidneys, which persisted for 80 min (in liver) to 110 min (in kidneys). The negative contrast of the liver and kidneys weakened over the time, suggesting that polyglycerol coating renders the nanoparticles stealth and possibly optimal for renal excretion.

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