The present study deals with the synthesis and characterization of radiopaque
polymers which could, when solubilized in an appropriate water-miscible
solvent, be useful embolic materials for the treatment of
cerebral aneurysms and
arteriovenous malformations. For this purpose
cellulose (both microcrystalline and powdered) and partially substituted
cellulose acetate (two different viscosity grades) were selected as starting materials to prepare
iodine-containing
polymers through various synthetic routes. The materials obtained were characterized by IR and NMR spectroscopy, molecular weight,
iodine content, radiopacity and solubility in selected
injectable organic
solvents. The embolic liquids were evaluated for their precipitation behavior in a
phosphate buffer solution (pH 7.4) mimicking physiological conditions using an in vitro
aneurysm model. A sheep model was also used to assess in vivo the radiopacity and precipitation properties of a highly concentrated
solution of a
cellulose acetate 2,3,4-triiodobenzoate mixed
ester. All materials with 4-iodo- and 2,3,5-triiodobenzoyl groups gave sufficient radiopacity to be regarded as possible embolization materials, whereas iododeoxycellulose and iododeoxycellulose
acetate were not radiopaque because of their low
iodine content.
Esters synthesized using
cellulose as starting material were not soluble in the selected organic
solvents due to the presence of many residual
hydroxyl groups, but could be used for other biomedical applications where insoluble radiopaque materials are used. In contrast, solubility of the materials as well as satisfactory precipitation properties were ensured using
cellulose acetate as the starting material. In conclusion,
cellulose acetate iodobenzoate mixed
esters dissolved in
diglyme or
dimethyl isosorbide (
dimethyl sulfoxide is probably less appropriate because of its toxicity and hemolytic properties) could be useful embolic liquids for the treatment of
cerebral aneurysms or
arteriovenous malformations.