Nanodiamonds conjugated upconversion nanoparticles for bio-imaging and drug delivery.

A multifunctional nanoplatform with simultaneous imaging and therapeutic capacities has been fabricated by covalently conjugating nanodiamonds (NDs) with upconversion NaYF4:Yb,Er nanoparticles (UCNPs). Green emission can be observed for the UCNP-NDs composites under 980 nm excitation, and in vitro imaging was carried out towards HeLa cells. The UCNP-NDs also shows good drug storage capability toward anticancer drug doxorubicin (Dox) and exhibits significant pH-dependent drug-release behavior. Dox-loaded UCNP-NDs shows higher therapy efficiency towards Hela cells than free Dox when the equivalent concentration of the Dox is more than 10 μg/mL. Thus, a favorable strategy may be provided to decrease the side effects of Dox, minimize drug dose, and improve its efficacy. These findings highlight the fascinating features of UCNP-NDs nanocomposites as upconversion fluorescence imaging contrast agents and doxorubicin loading carrier. In addition, this work may also provide a novel strategy for the design of multifunctional nanoplatforms.