Facile synthesis of ultra-small hollow manganese silicate nanoparticles as pH/GSH-responsive T1-MRI contrast agents

Manganese silicate nanoparticles have recently attracted great attention due to the effectiveness of T-1-weighted magnetic resonance imaging (MRI) contrast agents (CAs) in the mildly acidic and high glutathione (GSH) conditions of the tumor microenvironment. Herein, ultra-small hollow manganese silicate (UHMS) nanoparticles were prepared via a facile, economical, and eco-friendly method based on a hydrothermal process using small silica nanoparticles as both the silicon source and templates. The nanoparticles showed remarkable biocompatibility and dispersion stability after modification with polyethylene glycol (PEG). Owing to their ultra-high longitudinal relaxation rate (r(1)) at low pH values and high GSH levels, the UHMS@PEG nanoparticles have performed an excellent pH/GSH-responsive T-1 -weighted MRI. Meanwhile, the nanoparticles showed insignificant cytotoxicity in vitro and in vivo. Therefore, the UHMS@PEG nanoparticles show promise as T-1 -MRI CAs in the tumor microenvironment and may be used to assist in clinical cancer diagnosis.