title: Optimization of upconversion luminescence of Nd(3+)-sensitized BaGdF5-based nanostructures and their application in dual-modality imaging and drug delivery.
abstract: 808 nm excited upconversion nanoparticles (UCNPs) have received extensive attention in the biomedical areas. However, one of the limitations of UCNPs is their lower luminescence efficiency. Aimed at this problem, a series of BaGdF5-based UCNPs were prepared by a layer-by-layer procedure. And UC luminescence properties are optimized by varying the doping concentration of rare earth ions, amount and types of shells. It is found that if the amount of core BaGdF5:20%Yb(3+)/2%Er(3+) was fixed at 0.5 mmol, the optimized conditions of three shell layers are 0.3 mmol of BaGdF5:10%Yb(3+), 0.5 mmol of BaNdF5 and 0.5 mmol of BaGdF5. Thus the UC luminescence intensity of the resultant nanoparticles BaGdF5:20%Yb(3+)/2%Er(3+)@BaGdF5:10%Yb(3+)@BaNdF5@BaGdF5 (Er@Yb@Nd@Gd) is enhanced more than four times compared with that of BaGdF5:20%Yb(3+)/2%Er(3+)@BaGdF5:10%Yb(3+)@BaNdF5 (Er@Yb@Nd). To further improve the biocompatibility and applications in the biological field, carboxymethyl chitosan (CMC), a type of biocompatible water-transfer agent, was used as a capping ligand to modify the surface of Er@Yb@Nd@Gd. An antitumor drug doxorubicin (DOX) was loaded to the CMC-modified Er@Yb@Nd@Gd nanocarriers by electrostatic interactions. The DOX can be selectively released in an acidic environment, which shows a pH-triggered drug release behavior. On the other hand, Er@Yb@Nd@Gd nanoparticles have excellent magnetic properties due to the presence of Gd components. T1-weighted magnetic resonance imaging (MRI) reveals the concentration-dependent brightening effect with longitudinal relaxivity (r1) as high as 43.77 s(-1) (mM)(-1), much higher than that of previous Gd(3+)-based counterparts. The results indicate that this multifunctional drug delivery system is expected to be a promising platform for simultaneous cancer therapy and bioimaging.
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. cxli@ciac.ac.cn jlin@ciac.ac.cn and University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
authors.forename: Fei
authors.initials: F
authors.lastname: He
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. cxli@ciac.ac.cn jlin@ciac.ac.cn.
authors.forename: Chunxia
authors.initials: C
authors.lastname: Li
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. cxli@ciac.ac.cn jlin@ciac.ac.cn.
authors.forename: Xinyang
authors.initials: X
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. cxli@ciac.ac.cn jlin@ciac.ac.cn and University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
authors.forename: Yinyin
authors.initials: Y
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. cxli@ciac.ac.cn jlin@ciac.ac.cn and University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
authors.forename: Xiaoran
authors.initials: X
authors.lastname: Deng
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. cxli@ciac.ac.cn jlin@ciac.ac.cn and University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
authors.forename: Bei
authors.initials: B
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. cxli@ciac.ac.cn jlin@ciac.ac.cn.
authors.forename: Zhiyao
authors.initials: Z
authors.lastname: Hou
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. cxli@ciac.ac.cn jlin@ciac.ac.cn.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Huang
authors.affiliation: Institute for Biomedical Materials and Devices, Faculty of Science, University of Technology Sydney, NSW 2007, Australia.
authors.forename: Dayong
authors.initials: D
authors.lastname: Jin
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. cxli@ciac.ac.cn jlin@ciac.ac.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Lin
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry; D001464:Barium / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry; D004317:Doxorubicin / Q000737:chemistry; D016503:Drug Delivery Systems; D005461:Fluorine / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D049449:Luminescence; D008279:Magnetic Resonance Imaging; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D009354:Neodymium / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D000970:Antineoplastic Agents; D001464:Barium; D005461:Fluorine; D009354:Neodymium; D004317:Doxorubicin; D048271:Chitosan; D005682:Gadolinium