Caveat Emptor: Commercialized Manganese Oxide Nanoparticles Exhibit Unintended Properties.

Nano-encapsulated manganese oxide (NEMO) particles are noteworthy contrast agents for magnetic resonance imaging (MRI) due to their bright, pH-switchable signal ("OFF" to "ON" at low pH), high metal loading, and targeting capability for increased specificity. For the first time, we performed a head-to-head comparison of NEMO particles from In-house and commercialized sources (US Nano vs Nanoshel) to assess their potential as bright T MRI contrast agents. Manganese oxide nanocrystals (MnO, MnO, and MnO) were systematically evaluated for size, chemistry, release of manganese ions, and MRI signal pre- and post-encapsulation within poly(lactic--glycolic acid) (PLGA).