Thermally adaptive iohexol-loaded microcages for local computerized tomography.

As one of the most used non-invasive imaging modalities, X-ray computed tomography (CT) has many outstanding advantages, but its wide application is still limited owing to various defects of its contrast agents, such as their short in vivo retention time, non-specific distribution, and potential nephrotoxicity. Herein, a non-ionic poly(acrylamide-co-acrylonitrile) copolymer with an upper critical solution temperature (UCST) was utilized to construct novel thermo-responsive microcages (MCs) with a hydrodynamic size of 5-10 μm, which is slightly less than the diameter of a blood vessel, for targeted CT imaging. These MCs exhibited excellent thermo-responsive capability, featuring the appropriate UCST value between 35-40 °C. A reversible UCST-type phase transition endowed these MCs with dramatic expansion above UCST for local embolization in hyperthermia site, and good recovery was observed below UCST for elimination from microvessels after treatments. As a micro-sized carrier, they also exhibited high loading (14.3%) and encapsulation efficiency of iohexol (16.6%) and heat-enhanced release (29.54% in 48 hours), favoring CT imaging with weak signal attenuation. Given their good biocompatibility and biosecurity, these smart MCs are anticipated to develop into facile, effective, safe, and targeted CT contrast agents.