title: Nanodiamonds act as Trojan horse for intracellular delivery of metal ions to trigger cytotoxicity.
abstract: BACKGROUND
  Nanomaterials hold great promise for applications in the delivery of various molecules with poor cell penetration, yet its potential for delivery of metal ions is rarely considered. Particularly, there is limited insight about the cytotoxicity triggered by nanoparticle-ion interactions. Oxidative stress is one of the major toxicological mechanisms for nanomaterials, and we propose that it may also contribute to nanoparticle-ion complexes induced cytotoxicity.
  
  
  METHODS
  To explore the potential of nanodiamonds (NDs) as vehicles for metal ion delivery, we used a broad range of experimental techniques that aimed at getting a comprehensive assessment of cell responses after exposure of NDs, metal ions, or ND-ion mixture: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Trypan blue exclusion text, optical microscope observation, synchrotron-based scanning transmission X-ray microscopy (STXM) and micro X-ray fluorescence (μXRF) microscopy, inductively coupled plasma-mass spectrometry (ICP-MS), reactive oxygen species (ROS) assay and transmission electron microscopy (TEM) observation. In addition, theoretical calculation and molecular dynamics (MD) computation were used to illustrate the adsorption properties of different metal ion on NDs as well as release profile of ion from ND-ion complexes at different pH values.
  
  
  RESULTS
  The adsorption capacity of NDs for different metal ions was different, and the adsorption for Cu2+ was the most strong among divalent metal ions. These different ND-ion complexes then had different cytotoxicity by influencing the subsequent cellular responses. Detailed investigation of ND-Cu2+ interaction showed that the amount of released Cu2+ from ND-Cu2+ complexes at acidic lysosomal conditions was much higher than that at neutral conditions, leading to the elevation of intracellular ROS level, which triggered cytotoxicity. By theoretical approaches, we demonstrated that the functional carbon surface and cluster structures of NDs made them good vehicles for metal ions delivery.
  
  
  CONCLUSIONS
  NDs played the Trojan horse role by allowing large amounts of metal ions accumulate into living cells followed by subsequent release of ions in the interior of cells, which then led to cytotoxicity. The present experimental and theoretical results provide useful insight into understanding of cytotoxicity triggered by nanoparticle-ion interactions, and open new ways in the interpretation of nanotoxicity.
authors: Division of Physical Biology, and Bioimaging Center, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. zhuying@sinap.ac.cn.
authors: Ying
authors: Y
authors: Zhu
authors: Division of Physical Biology, and Bioimaging Center, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. zy20051209@163.com.|Graduate School of the Chinese Academy of Sciences, Beijing, 100049, China. zy20051209@163.com.
authors: Yu
authors: Y
authors: Zhang
authors: Laboratory of Water Science and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. shiguosheng@sinap.ac.cn.
authors: Guosheng
authors: G
authors: Shi
authors: Graduate School of the Chinese Academy of Sciences, Beijing, 100049, China. yangjinrong@sinap.ac.cn.|Laboratory of Water Science and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. yangjinrong@sinap.ac.cn.
authors: Jinrong
authors: J
authors: Yang
authors: Division of Physical Biology, and Bioimaging Center, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. zhangjichao@sinap.ac.cn.
authors: Jichao
authors: J
authors: Zhang
authors: Division of Physical Biology, and Bioimaging Center, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. liwenxin@sinap.ac.cn.
authors: Wenxin
authors: W
authors: Li
authors: Shanghai Synchrotron Radiation Facility, Shanghai, 201203, China. liaiguo@sinap.ac.cn.
authors: Aiguo
authors: A
authors: Li
authors: Shanghai Synchrotron Radiation Facility, Shanghai, 201203, China. tairenzhong@sinap.ac.cn.
authors: Renzhong
authors: R
authors: Tai
authors: Laboratory of Water Science and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. fanghaiping@sinap.ac.cn.
authors: Haiping
authors: H
authors: Fang
authors: Division of Physical Biology, and Bioimaging Center, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. fchh@sinap.ac.cn.|School of Life Science and Technology, ShanghaiTech University, Shanghai, 200031, China. fchh@sinap.ac.cn.
authors: Chunhai
authors: C
authors: Fan
authors: Division of Physical Biology, and Bioimaging Center, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. huangqing@sinap.ac.cn.
authors: Qing
authors: Q
authors: Huang
mesh_terms: D000327:Adsorption; D000818:Animals; D002413:Cations, Divalent; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004705:Endocytosis; D006801:Humans; D019216:Metals, Heavy / Q000008:administration & dosage* / Q000737:chemistry / Q000633:toxicity*; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D056004:Molecular Dynamics Simulation; D058612:Nanodiamonds / Q000008:administration & dosage* / Q000737:chemistry / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013054:Spectrophotometry, Atomic
chemical_list: D002413:Cations, Divalent; D019216:Metals, Heavy; D058612:Nanodiamonds; D017382:Reactive Oxygen Species
references: Proc Natl Acad Sci U S A. 2005 Aug 9;102(32):11179-84
references: 16061820
references: Nanoscale. 2011 Feb;3(2):435-45
references: 20877788
references: BMC Cancer. 2006;6:267
references: 17107616
references: Langmuir. 2004 Jul 6;20(14):5879-84
references: 16459604
references: J Phys Chem B. 2007 Jan 11;111(1):2-7
references: 17201422
references: Dent Mater. 2009 Dec;25(12):1551-5
references: 19682734
references: Nat Nanotechnol. 2007 Dec;2(12):751-60
references: 18654426
references: Nat Nanotechnol. 2012 Jan;7(1):11-23
references: 22179567
references: ACS Nano. 2013 Aug 27;7(8):6735-46
references: 23829596
references: Environ Pollut. 2003;124(3):457-69
references: 12758026
references: Small. 2011 Nov 4;7(21):3087-95
references: 21913326
references: Toxicology. 2001 Feb 21;159(1-2):23-31
references: 11250052
references: Biomaterials. 2010 Feb;31(5):1007-16
references: 19880174
references: Chem Commun (Camb). 2010 Oct 7;46(37):6909-11
references: 20730162
references: Theranostics. 2012;2(3):302-12
references: 22509196
references: J Am Chem Soc. 2004 Jun 9;126(22):6850-1
references: 15174838
references: J Am Chem Soc. 2009 Aug 5;131(30):10637-44
references: 19722635
references: Nano Lett. 2007 Nov;7(11):3305-14
references: 17918903
references: J Am Chem Soc. 2005 Apr 27;127(16):6021-6
references: 15839702
references: J Synchrotron Radiat. 2010 Nov;17(6):804-9
references: 20975228
references: Environ Sci Technol. 2009 Jun 1;43(11):4169-74
references: 19569347
references: Science. 2006 May 19;312(5776):1027-30
references: 16709779
references: Nat Nanotechnol. 2008 Jun;3(6):363-8
references: 18654548
references: Sci Transl Med. 2013 Oct 30;5(209):209ra152
references: 24174328
references: ACS Nano. 2007 Aug;1(1):50-6
references: 19203129
references: Small. 2012 Jun 11;8(11):1771-9
references: 22434708
references: ACS Nano. 2009 Jul 28;3(7):2016-22
references: 19534485
references: Sci Total Environ. 2003 Jun 1;308(1-3):247-56
references: 12738217
references: Phys Rev A Gen Phys. 1988 Sep 15;38(6):3098-3100
references: 9900728
references: Nat Nanotechnol. 2008 May;3(5):284-8
references: 18654525
references: ACS Nano. 2009 Sep 22;3(9):2609-16
references: 19719152
references: Mater Sci Eng C Mater Biol Appl. 2013 May 1;33(4):1993-2001
references: 23498224
references: Biomaterials. 2010 Nov;31(32):8410-8
references: 20692696
references: Analyst. 2014 Mar 7;139(5):943-53
references: 24260774
references: Phys Rev Lett. 2005 Aug 26;95(9):096801
references: 16197235
references: Sci Transl Med. 2011 Mar 9;3(73):73ra21
references: 21389265