Synthesis of magnetic and upconversion nanocapsules as multifunctional drug delivery system

Multifunctional hollow nanocapsules with magnetic and upconversion luminescence properties were synthesized. Hollow Fe3O4@SiO2 was firstly prepared by using rodlike beta-FeOOH as the template followed by silica coating, calcinations and reduction. Then Fe3O4@SiO2@alpha-NaYF4:Yb3+,Er3+ nanocapsules (FeS-iUCHP) were synthesized by the hydrothermal transformation of the Y(Yb3+, Er3+)(OH)CO3 (YOC) deposited onto the surface of nanocapsules through a urea-assisted homogeneous precipitation method. The hollow nanocapsules with porous structure provide space and entrance for the drug molecules. Due to the outside shell of alpha-NaYF4:Yb3+, Er3+, the nanomaterial shows upconverting red emission upon 980 nm NIR-light excitation. Moreover, the nanocomposites with hollow magnetite core exhibit a high relaxivity with r(2) value of 183 mM(-1) s(-1), which reveal the potential as T-2-weighted contrast agents for magnetic resonance imaging (MRI). The as-prepared nanocapsules can be performed as anti-cancer drug carriers for investigation of drug loading/release properties, which demonstrated a sustained drug release pattern and a comparable cytotoxicity with free doxorubicin (DOX). The multifunctional nanocapsules incorporated upconverting luminescence, T-2-weighted MRI imaging and drug targeting delivery modalities have great potential for theranostic applications in cancer treatment. (C) 2015 Elsevier Inc. All rights reserved.