Core-shell structured polypyrrole/mesoporous SiO2 nanocomposite capped with graphene quantum dots as gatekeeper for irradiation-controlled release of methotrexate.

A core-shell structured nanocomposite of polypyrrole/mesoporous SiO2 (PPy/mSiO2) is rationally designed as the nanocarrier for methotrexate (MTX), a chemotherapeutic drug for cancer treatment. Graphene quantum dots (GQDs) are introduced to the outer surface of PPy/mSiO2, and it functions as a gatekeeper for the loaded MTX through the formation of H-bonds with the functionalized mSiO2. In the proposed nanocarrier for MTX, the mesopores in mSiO2 are beneficial for the accommodation of MTX, resulting in enhanced encapsulation capacity of the nanocarrier; on the other hand, PPy can effectively convert the near-infrared (NIR) light to heat. Under the irradiation of NIR light, the H-bonds between GQDs and mSiO2 are broken due to the gradually increased temperature, and therefore the GQDs cap is removed and consequently the encapsulated MTX is released from the nanocarrier. In this study, NIR irradiation-controlled drug delivery is achieved successfully owing to the synergistic effects of PPy, mSiO2 and GQDs, which opens a new window for the construction of smart drug delivery systems.