title: Labeling and long-term tracking of bone marrow mesenchymal stem cells in vitro using NaYF4:Yb(3+),Er(3+) upconversion nanoparticles.
abstract: Mesenchymal stem cells (MSCs) hold great promise as cell therapy candidate in clinics. However, the underlying mechanisms remain elusive due to the lack of effective cell tracking approaches during therapeutic processes. In this study, we successfully synthesized and utilized NaYF4:Yb(3+),Er(3+) upconversion nanoparticles (UCNPs) to label and track rabbit bone marrow mesenchymal stem cells (rBMSCs) during the osteogenic differentiation in vitro. To improve their biocompatibility and cellular uptake, we modified the UCNPs with negatively-charged poly(acrylic acid) and positively-charged poly(allylamine hydrochloride) in turns (i.e., PAH-PAA-UCNPs). The effect of cellular uptake of UCNPs on the osteogenic differentiation of rBMSCs was systematically evaluated, and no significant difference was found between rBMSCs labeled with UCNPs (concentration range of 0-50μg/mL) and UCNPs-free rBMSCs in terms of cell viability, ALP activity, osteogenic protein expressions and production of mineralized nodules. Moreover, the PAH-PAA-UCNPs at a concentration of 50μg/mL exhibited the highest biocompatibility and stability, which could well track rBMSCs during the osteogenesis process. These results would provide a positive reference for the application of these lanthanide-doped UCNPs as fluorescent nanoprobes for stem cell tracking to further understand the mechanism of stem cell fate in tissue engineering and stem cell therapy.
  
  
  
  Upconversion nanoparticles (UCNPs) have attracted increasing attention as alternative probes for tracking various types of cells including stem cells. The reported fluorapatite-based UCNPs with the needle-like morphology showed a little poor performance on stem cell tracking, which was possibly attributed to the low upconversion efficiency and cell labeling efficiency potentially due to nanomaterial composition, crystal structure and shape. Here, we synthesized the positively-charged NaYF4:Yb(3+),Er(3+) UCNPs with hexagonal phase and sphere-like morphology to enhance their upconversion efficiency, biocompatibility and cellular uptake, leading to a successful tracking of rBMSCs in osteogenesis process without impairing cell viability and differentiation capacity. This study provided a necessary reference for the application of UCNPs in stem cell tracking to better understand the mechanism of stem cell fate in tissue engineering, stem cell therapy, etc.
authors.affiliation: The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China.
authors.forename: Yufei
authors.initials: Y
authors.lastname: Ma
authors.affiliation: The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ji
authors.affiliation: The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China.
authors.forename: Minli
authors.initials: M
authors.lastname: You
authors.affiliation: The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China.
authors.forename: Shurui
authors.initials: S
authors.lastname: Wang
authors.affiliation: The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Dong
authors.affiliation: The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China.
authors.forename: Guorui
authors.initials: G
authors.lastname: Jin
authors.affiliation: The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China.
authors.forename: Min
authors.initials: M
authors.lastname: Lin
authors.affiliation: Department of Endocrinology and Metabolism, Xijing Hospital, Fourth Military Medical University, 710032 Xi'an, PR China.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, College of Stomatology, Xi'an Jiaotong University, Xi'an 710049, PR China.
authors.forename: Ang
authors.initials: A
authors.lastname: Li
authors.affiliation: The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China. Electronic address: xiaohuizhang@mail.xjtu.edu.cn.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Zhang
authors.affiliation: The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China. Electronic address: fengxu@mail.xjtu.edu.cn.
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism*; D002452:Cell Count; D002453:Cell Cycle; D002454:Cell Differentiation; D002470:Cell Survival; D058948:Cell Tracking / Q000379:methods*; D004705:Endocytosis; D004871:Erbium / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D053758:Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D010012:Osteogenesis; D011073:Polyamines / Q000737:chemistry; D011817:Rabbits; D013194:Staining and Labeling; D013997:Time Factors; D015018:Ytterbium / Q000737:chemistry*; D015019:Yttrium / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D011073:Polyamines; C525362:sodium yttriumtetrafluoride; C063994:polyallylamine; C006903:carbopol 940; D015019:Yttrium; D004871:Erbium; D015018:Ytterbium; D005459:Fluorides
keywords: Cell tracking; Mesenchymal stem cells; Osteogenic differentiation; Upconversion nanoparticles