pH-sensitive polymer-gated multifunctional upconversion NaYF 4 :Yb/Er@mSiO 2 nanocomposite for oral drug delivery

Multifunctional nanocomposite have received much attention due to their potential applications in controlled drug delivery systems. Herein, multifunctional UCNPs@mSiO2-PAA nanocomposite with UCNPs as core and poly (acrylic acid) (PAA)-gated mesoporous silica as shell were fabricated for oral drug delivery. The results demonstrated that the mesoporous silica shell (∼20 nm) uniformly coated on the UCNPs, and the PAA brushes were covalently attached on the pore mouths of mesoporous silica shell. The in vitro drug release results exhibited that the doxorubicin (DOX) molecules were almost encapsulated in the locked pores in simulated gastric fluid (SGF, pH = 1.2) due to the capping effect of PAA brushes, while the DOX could easily diffuse from the opened pores in phosphate buffer solution (PBS, pH = 7.4) due to the removing of the capping. These results indicating that the PAA brushes can be employed as gatekeepers to control the drug transport in and out of the pore channels of UCNPs@mSiO2-PAA. Moreover, the drug release process can be monitored by the changes of fluorescence intensity under the NIR light laser excitation. We anticipate that the multifunctional nanocomposite can be used as nanocarrier for control and tracking of drug release in oral drug delivery systems.