Jochen Keupp1, Sander Langereis2, Inge de Roos2, Dirk Burdinski2, Jeroen Pikkemaat2, Holger Gruell2,3
1Philips Research Europe, Hamburg, Germany; 2Philips Research Europe, Eindhoven, Netherlands; 3Eindhoven University of Technology, Eindhoven, Netherlands
Localized delivery of anti-cancer drugs by external stimulation of nanocarriers (temperature, pH) promises a larger therapeutic window with reduced side effects of the treatment. The present imaging study is based on a new type of temperature-responsive liposomes, which are dually labeled for 1H-CEST and 19F MR imaging and release an encapsulated payload near the melting temperature (Tm) of their lipid membrane (38 C). In their lumen, a chemical shift agent for 1H-lipoCEST imaging and NH4PF6 for 19F detection is contained. Inside the liposome, the 19F spectral lines are strongly broadened and not detectable. Upon reaching Tm, the lipoCEST contrast vanishes, due to the release of the chemical shift agent and, simultaneously, the 19F MR signal becomes visible. Hence, the 19F signal could be used to quantify the amount of released drug payload, while the CEST signal could measure the local nanocarrier concentration before the release. The study demonstrates the potential of the new liposomal nanocarriers for MRI-guided drug delivery in cancer therapy.