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Abstract
A novel kind of monodisperse mesoporous manganese silicate coated silica nanoparticle
(MMSSN) as a highly efficient T1-weighted MRI contrast agent (CA) and drug carrier
for cancer diagnosis and chemotherapy has been constructed by a modified "SiO2 sacrifice
and in situ silicate growth" approach under a relatively low hydrothermal temperature
and alkali-free condition. The mesoporous manganese silicate shell provides a large
specific surface area and abundant exposed Mn paramagnetic centers to water molecules,
which endows the MMSSNs with extraordinarily high longitudinal relaxivity. Meanwhile,
the MMSSNs presented an efficient pH/redox-responsive T1-MRI feature based on the
significant enhancement of relaxation rate (r1) stimulated by mild acidic environment
or reducing agent (GSH) both in vitro and in vivo. Furthermore, the mesoporous structure
and negatively charged pore surface of the manganese silicate shell enable the MMSSNs
to attain anti-cancer drug (DOX) storage and a pH-responsive release, which is suitable
for on-demand drug release for the chemotherapy of tumors. Therefore, the mesoporous
manganese silicate-based nanomaterial is a promising candidate as T1-MRI CAs and anticancer-drug
delivery carriers for the theranostics of tumor in an intelligent and on-demand manner.