RGD-targeted MnO nanoparticles as T1 contrast agents for cancer imaging - the effect of PEG length in vivo.

As magnetic resonance imaging (MRI) contrast agents, T1 Gd3+ chelates are generally the preferred option for radiologists over T2 iron oxide nanoparticles. The main reason for the popularity of T1 agents is the easier interpretation of T1-weighted MR images. However, the chemical versatility of nanoparticulate platforms makes them ideal candidates for the next generation of targeted MRI contrast agents. In this context, we present herein the design and preparation of a nanoparticulate contrast agent based on MnO, which presents T1 contrast enhancement properties as well as nanoparticle formulation. Functionalization of MnO nanoparticles with the extensively studied RGD peptide was used to target tumours over-expressing the αvβ3 integrin. PEG (polyethylene glycol) molecules were used to increase the blood half-life of the nanoparticles in vivo, and the effect of different PEG lengths on the final contrast on MR images was investigated.