Gelling process differences in reverse emulsion, in situ gelling polymeric materials for intracranial aneurysm embolization, formulated with injectable contrast agents

Abstract The use of liquid‐to‐solid curing materials for brain aneurysm embolization has become increasingly attractive, as liquid embolics can be delivered noninvasively and can potentially achieve a higher degree of aneurysm volume occlusion. This study was aimed at characterizing differences in the gelling process of a reverse emulsion, crosslinking polymer system formulated with different types of injectable contrast agents. The polymeric system consists of poly(propylene glycol) diacrylate (PPODA) and pentaerythritol tetrakis(3‐mercaptopropionate) (QT). These monomers undergo Michael‐type addition upon initiation by a basic, aqueous solution. Conray™ and Omnipaque™ 300, commercially available contrast agents, were pH‐adjusted to basic conditions and used as initiating solutions with the PPODA‐QT system. Material characteristics were identified through rheology and scanning electron microscopy (SEM). Results showed that Conray‐ and Omnipaque‐formulated materials progress through the gelling process uniquely, evidenced by distinctly different viscosity profiles and droplet distributions. These results indicate that Conray is more miscible with the PPODA‐QT organic phase. Greater solubility in the organic phase allows Conray‐formulated gels to have faster and more widespread reaction initiation kinetics when Conray and Omnipaque have the same pH. Omnipaque‐formulated gels require a higher pH for the material to solidify in a time frame comparable to Conray‐formulated gels. This discrepancy arises because the majority of reaction initiation sites in Omnipaque‐formulated gels occur at phase boundaries via hydroxide ion flux from emulsified droplets rather than from hydroxide ions that are solubilized and integrated within the PPODA‐QT organic phase. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.