Monodisperse Hollow MnO₂ with Biodegradability for Efficient Targeted Drug Delivery

The development of new nanocarriers with desired degradability and targeted ability is of great significance for efficient drug delivery. In this work, a monodisperse hollow structured MnO₂ (H-MnO₂) with a mesoporous shell is prepared and functionalized for efficient targeted drug delivery. The highly monodisperse H-MnO₂ with a uniform morphology was obtained by in situ growing MnO₂ on solid silica nanoparticles and subsequently removing the silica core. Then, the H-MnO₂ is successively modified with polyethylene glycol and targeted molecule folate (FA). The resultant H-MnO₂-FA shows excellent colloidal stability and high drug-loading content (∼58.2%) of the antitumor drug doxorubicin hydrochloride (DOX). The H-MnO₂-FA possesses acid-responsive T₁-weighted magnetic resonance imaging ability. The pH-dependent biodegradation behavior of H-MnO₂-FA is directly observed in vitro and confirmed by in vivo imaging, which is expected to favor the potential clearance of this hollow structured nanocarrier and eliminate its long-term toxicity. In addition, the DOX-loaded H-MnO₂-FA also demonstrates excellent cancer cell-killing effect and tumor inhibition efficacy.