Gadolinium containing photochromic micelles as potential magnetic resonance imaging traceable drug carriers

Novel photochromic amphipathic molecules, KMR‐AZn (Gd‐DTPA‐AZCn), composed of hydrophilic Gd‐DTPA and hydrophobic alkylated azobenzene were prepared. In aqueous environment, KMR‐AZn indicated self‐assembly. The resulting aggregates were demonstrated to be able to include a hydrophobic drug substitute (hydrophobic fluorescent dye) into the internal core, and to release the included compound upon photoirradiation within 10 min through the influence of azobenzene photoisomerization. This micellar MRI contrast agent exhibited three‐ to four‐fold higher r₁ relaxivity (r₁ = 14.5–16.5 mm ^?1 s^?1, 0.47 T at 40°C) than the widely applied small molecule contrast agent Gd‐DTPA (Magnevist^®r₁ = 4.1 mm ^?1 s^?1, 0.47 T at 40°C). This dual functionality of encapsulated compound release and increased MR imaging contrast indicates that KMR‐AZn is a potential candidate for application as a lipid‐based MRI‐traceable drug carrier.