AND-logic MRI contrast by water flux modulation.

Stimuli-responsive MRI agents enable disease-specific imaging by selectively modulating generated contrast in pathological microenvironments. To date, these moieties have been largely limited to those that respond to one specific (potentially false positive) trigger. This work reports AND-logic gated silica nanoparticles modified with a pH-responsive poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) shell, tethered to the particles via a reducible 4,4'-diaminoazobenzene (AZO) cross-linker. These nanoparticles support very high levels of contrast switching exclusively under concurrent mildly acidic and reducing conditions, which are hallmarks of solid tumours, myocardial ischemia, and chronic inflammation.