Facile preparation of coating fluorescent hollow mesoporous silica nanoparticles with pH-sensitive amphiphilic diblock copolymer for controlled drug release and cell imaging

A smart fluorescent drug carrier based on hollow mesoporous silica (HMS) nanoparticles was prepared step by step. First, HMS nanoparticles were doped with lanthanide rare-earth nanocrystals (YVO4:Eu3+). Then the surface of HMS@YVO4:Eu3+ was modified by octadecyltrimethoxysilane (C18). Afterwards, it was coated by designed pH-sensitive amphiphilic diblock copolymer (poly(MPEG-b-DBAM), PMD) through hydrophobic van der Waals interactions. The results of characterization such as transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) reveal that the material shows excellent monodisperse spherical morphology and narrow size distribution (180 nm) with hollow-core@mesoporous-silica-shell@thin-polymer-film structure. The multifunctional system HMS@YVO4:Eu3+@C18@PMD was utilized to deliver the model drug ibuprofen (IBU), and the drug loading content of the system is as high as 834 mg/g (drug/carrier). Due to the coated pH-sensitive polymer film, the loaded drug is selectively released in mildly acidic environment. The time of release of about 80% drug was however prolonged from 50 to 150 h (at pH = 5.0) by the effect of modified C18, which has thus achieved longer-term release. Besides, the prepared material is easily imported into human mouth epidermal carcinoma (KB) cells and showed good and stable red fluorescence, which is suitable for cell imaging.