Biodegradable nanopolymersomes with an ultrahigh iodine content for high-performance CT imaging in vivo were designed. To obtain iodine-rich nanopolymersomes, we devised and prepared a new iodine-functionalized trimethylene carbonate (IC) monomer in two straight steps with an overall yield of 25% by the Finkelstein reaction. Gel permeation chromatography displayed a unimodal distribution with a moderate Mw/Mn of 1.40, confirming successful synthesis of PEG-b-PIC. Interestingly, PEG-b-PIC had an ultrahigh iodine content of 60.4 wt%, which is significantly higher than iohexol and all reported iodinated nanoparticle platforms. Remarkably, the PEG-b-PIC diblock copolymer was readily self-assembled into stable nanopolymersomes. Dynamic light scattering (DLS) showed a small hydrodynamic size of =100 nm with a low polydispersity index =0.10. Transmission electron microscopy (TEM) image confirmed their small size and vesicle structure, likely due to their thick membrane and the inherent PEG stealth ability. The stability of iodine conjugated with an aliphatic chain is usually weaker than that conjugated with aromatic derivatives. However, unlike traditional small molecules, all iodine atoms in IPs are sequestered in the hydrophobic membrane of polymersomes, which would effectively protect iodine from leakage. The in vivo SPECT/CT images showed that in sharp contrast to fast accumulation of Na125I in the thyroid and bladder, I-labeled IPs had a long circulation time and predominantly accumulated in the RES like spleen and liver, further corroborating that IPs are stable in circulation and iodine leakage is negligible.
|Publication status||Published - 14 Mar 2017|
- computed tomography
- contrast agents
- targeted imaging