Quantum Dots Conjugated with Fe3O4-Filled Carbon Nanotubes for Cancer-Targeted Imaging and Magnetically Guided Drug Delivery

A novel and specific nanoplatform for in vitro simultaneous cancer-targeted optical imaging and magnetically guided drug delivery is developed by conjugating CdTe quantum dots with Fe3O4-filled carbon nanotubes (CNTs) for the first time. Fe3O4 is filled into the interior of the CNTs, which facilitates magnetically guided delivery and improves the synergetic targeting efficiency. In comparison with that immobilized on the external surface of CNTs, the magnetite nanocrystals inside the CNTs protect it from agglomeration, enhance its chemical stability, and improve the drug loading capacity. It also avoids magnetic nanocrystals-induced quenching of fluorescence of the quantum dots. The SiO2-coated quantum dots (HQDs) attached on the surface of CNTs exhibit favorable fluorescence as the hybrid SiO2 shells on the QDs surface prevent its fluorescence quenching caused by the CNTs. In addition, the hybrid SiO2 shells also mitigate the toxicity of the CdTe QDs. By coating transferrin on the surface of the herein modified CNTs, it provides a dual-targeted drug delivery system to transport the doxorubicin hydrochloride (DOX) into He la cells by means of an external magnetic field. The nanocarrier based on the multifunctional nanoplatform exhibits an excellent drug loading capability of ca. 110%, in addition to cancer-targeted optical imaging as well as magnetically guided drug delivery.