Fabrication of Radiopaque Poly(vinyl alcohol) Hydrogel Bilayers for Use as Embolization Coils

On purpose to replace the metallic embolization coils with a polymeric material, a series of poly(vinyl alcohol) (PVA) hydrogels was fabricated into the form of bilayers. A hydrogel layer was prepared by mixing aqueous PVA solution with tantalum particles for radiopacity, crosslinking the mixture with glutaraldehyde crosslinking agent, and casting to a film of desired thickness. The properties of the hydrogel films including expansion ratio and modulus were characterized. Two hydrogel films with different crosslinking density were attached to form a bilayer, which formed coils in the water with the diameter dictated by the difference in swelling ratio. The coils and bundles of coils with diameters between 1 to 6 mm were employed in the occlusion tests using glass models approximating brain aneurysms. The number and sequence of coil insertion to give high packing density were investigated. Packing density much higher than that of platinum coils was achieved with the polymer coils fabricated.