Preparation of Syndiotactic Poly(vinyl alcohol) Microfibrils with Radiopaque Inorganic Particles

Abstract

Poly(vinyl pivalate) (PVPi) was bulk polymerized to make poly(vinyl alcohol) (PVA) microfibrils to apply for polymeric embolization coils replacing metalic coils. Then, syndiotactic PVA (s-PVA) microfibrils having number-average degree of polymerization of 1100 and s-diad content of 60.4% were prepared via saponification of the PVPi with no separate spinning process. To make s-PVA microfibrils with radiopacity, zirconium dioxide (ZrO 2 ) and barium sulfate (BaSO 4 ) were added into s-PVA microfibrils during saponification. The computed tomography (CT) value indicating radiopacity reached up to over 1000 when the amount of ZrO 2 and BaSO 4 were 12 and 6 wt%, respectively.Keywords: s-PVA, microfibrils, radiopacity, bulk polymerization, embolic materials.

X-ray Visible and Uniform Alginate Microspheres Loaded with in Situ Synthesized BaSO4 Nanoparticles for in Vivo Transcatheter Arterial Embolization

“…Some assessment on the toxicity of barium compounds including BaCl 2 , BaSO 4 , and BaCO 3 has been reported in the context of oral or inhalation studies. , These reports showed that the barium toxicity usually originated from soluble salts such as BaCl 2 , while insoluble salts such as BaSO 4 rendered promising biocompatibility via oral applications. However, we are not aware of any report on the toxicity of BaSO 4 via intravascular diagnostic procedures, even though polymeric materials with BaSO 4 encapsulation have been reported as embolic agents. ,,− One possible scenario is that BaSO 4 might migrate to important organs (such as the brain or heart) by ectopic embolism or random migration of BaSO 4 upon degradation of embolic microspheres. However, ectopic embolism was not observed upon injection in our in vivo experiments.…”

“…To synthesize inherent radiopaque embolic materials, a common method involves the copolymerization of acrylate and comonomers containing iodine. − However, the preparation of such copolymers is rather complicated and labor intensive. For example, the copolymeric monomer containing iodine (2-(4′-iodobenzoyl)-oxo-ethyl methacrylate (4IEMA)) needs to be initially prepared from 4-iodobenzoyl chloride and distilled hydroxyethyl methacrylate in an esterification reaction, followed by free-radical polymerizations. − Another method to achieve radiopacity involves encapsulation of heavy metal salts in polymeric microspheres. − For instance, the heavy metal salt BaSO 4 , widely employed as an X-ray contrast agent in the gastrointestinal tract, has been encapsulated in the polymeric matrix and applied to implants, embolization, − and immunoprotection . Although heavy metal salts themselves exhibit good imaging quality and are relatively safe, , these inorganic powders are difficult to disperse homogeneously in the embolic material matrices due to the precipitation and aggregation of heavy metal salts, yielding inaccurate positioning .…”