Magnetic Resonance Imaging for Monitoring of Magnetic Polyelectrolyte Capsule In Vivo Delivery

Abstract

Layer-by-layer (LbL) assembled polyelectrolyte capsules have been widely studied as promising delivery systems due to their well-controlled architectures. Although their potential applications in vitro have been widely investigated, at present, it is still a challenging task to track their real-time delivery in vivo, where and how they would be located following their administration. In this work, the noninvasive magnetic resonance imaging (MRI) technique was applied to monitor the delivery of polyelectrolyte capsules in vivo, incorporating magnetite nanoparticles as imaging components. First, MRI scan was performed over 6 h after sample administration at the magnetic field of 3.0 T; magnetic capsules, both poly(allylamine hydrochloride)/poly(styrenesulfonate sodium salt)-based and poly-l-arginine hydrochloride/dextran sulfate (Parg/DS)-based, were detected mostly in the liver region, where the transverse relaxation time (T2) was shortened and hypointense images were visualized, demonstrating a contrast-enhanced MRI effect between liver and adjacent tissue. A continuous MRI scan found that the contrast-enhanced MRI effect can last up to 30 h; in the mean time, the Parg/DS-based capsules with smaller diameter were found to have a pronounced clearance effect, which resulted in a weakened MRI effect in the liver. No obvious toxicity was found in animal studies, and all mice survived after MRI scans. Histology study provided evidences to support the MRI results, and also revealed the destination of these magnetic capsules over 30 h after administration.