New intrinsically radiopaque hydrophilic microspheres for embolization: Synthesis and characterization

Centre for Biomaterials Research, Faculty of Health, Medicine and Life Sciences, University of Maastricht, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
Biomacromolecules (Impact Factor: 5.79). 02/2008; 9(1):84-90. DOI: 10.1021/bm7008334
Source: PubMed

ABSTRACT Polymeric particles currently used for embolization procedures have the disadvantage that they are radiolucent, that is, invisible on X-ray images, and consequently the interventional radiologist has to resort to angiography to (indirectly) monitor the fate of the particles. Here, we introduce intrinsically radiopaque hydrophilic microspheres. Since these microspheres can directly be visualized on X-ray images, using these microspheres for embolization purposes will allow superprecise location of the embolic material, both during and after the procedure. The microspheres, which are prepared by suspension polymerization, are based on the radiopaque monomer 2-[4-iodobenzoyl]-oxo-ethylmethacrylate and hydroxyethylmethacrylate (HEMA) and/or 1-vinyl-2-pyrrolidinone (NVP) as hydrophilic component. It has been shown that for clinically relevant X-ray visibility the spheres should contain at least 20 wt % iodine. At this iodine content, copolymerization with HEMA results in spheres that hardly imbibe water (EQ = 1.08). When HEMA is replaced by NVP, the volume swelling ratio can be significantly increased (to 1.33).

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    ABSTRACT: Recently temperature sensitive polymers have been developed as novel embolization materials. However, their flowability and embolization have been seriously impacted by iodine-based X-ray contrast agents. In order to resolve the drawbacks of these contrast agents, high concentrated complex (HCC) dispersions of gold nanopaticles (GNPs) with p(N-isopropylacrylamide-co-butyl methylacrylate) (PIB) nanogels are developed as dual functional materials of blood-pool imaging and blood-vessel embolizing properties. Although GNPs have better X-ray attenuation than iodinated compounds, their poor dispersion stability limits the blood-pool imaging application. HCC dispersions show excellent X-ray attenuation ability which is 1.8 times higher than Omipaque at 60.9 mg/mL. It can be attributed to the fact that the sol-gel transition of nanogel dispersions improves the colloid stability of GNPs. In two sol-gel transitions temperature (Tg-s and T's-g) of nanogel dispersions, GNPs have no influence on the T's-g, and great influence on the Tg-s. The in vivo experimental data indicate that HCC dispersions show high angiographic ability and good blood-vessel embolization, and can be used to postoperative examination for long periods owing to the entrapment of GNPs into the embolic sites. The HCC dispersions are hopeful to be developed as novel interventional diagnosis and therapy materials of blood-pool imaging and blood-vessel embolizing properties
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