Liposome-loaded microspheres as a magnetic susceptibility agent for PH sensing

Abstract

MR susceptibility contrast agents have been used for imaging of vasculature and tumors, such as microbubbles and iron oxides. We have developed a susceptibility agent for pH sensing, especially for acidic tumor environment, increasing sensitivity around physiological pH using liposome-loaded microspheres. Our in vitro data showed that both R2 and R2* decreased at low pH, and the percentage change in R2* is larger when compared to controls at pH 6.8-7.2. Liposome-loaded microspheres showed a substantial increase in pH-dependence of R2*, which favoured by localization of liposomes on microspheres, and is first demonstrated to an improve pH sensitivity at 7T.