Liposome-loaded Microspheres as A Magnetic Susceptibility Agent for pH Sensing

. We found that the liposome-loaded microspheres resulted in a larger percentage change in R2* than that in R2, and their decrease in R2* at low pH is more pronounce than that of liposomes. The slope of HMS increased ~ 70% as compared with Liposome2. This increase in the slope supported our hypothesis that the lost of paramagnetic complexes led to a significant change in R2* at different pH by localization of liposomes, hence stronger pH dependence. This preliminary in vitro data showed an improved pH sensitivity, and microspheres with high liposome loading are favourable for R2* contrast enhancement. Liposomes that enclose a large amount of paramagnetic contrast agents increase R2* enhancement. The amount of contrast agent could be reduced during the process of phantom preparation. To increase the percentage change in R2* further, experiments are underway to increase the amount of contrast agent in liposomes and to prepare more porous microspheres for liposome loading.