Fabrication of uniform, biocompatible and multifunctional PCL-b-PAA copolymer-based hybrid micelles for magnetic resonance imaging

In this paper, a simple strategy was developed to fabricate a novel kind of uniform, biocompatible and PEGylated multifunctional hybrid micelles with multiple magnetite nanocrystal loaded cores and dye-doped silica cross-linked shells based on the self-assembly between poly(ε-caprolactone)-b- poly(acrylic acid) copolymer and inorganic nanoparticles. The loading of multiple magnetite nanoparticles in the core part of the hybrid micelles endows them with T2-weighted MR imaging functionalities. Small dye molecules (Rhodamine B) were directly incorporated into the silica layer framework during the cross-linking process, imparting the hybrid micelles with fluorescent imaging modality. Poly(ethylene glycol) (PEG) was grafted to reduce the phagocytic capture of nanoparticles by cellular components of the immune system. Importantly, the potential application of magnetite incorporated PEGylated hybrid micelles as T2 contrast agents for MRI was demonstrated both in vitro and in vivo, with the passive targeting behavior via EPR effect due to the leaky vasculature and poor lymphatic drainage in tumors.