title: Quantitative analysis of nanoparticle internalization in mammalian cells by high resolution X-ray microscopy.
abstract: BACKGROUND
  Quantitative analysis of nanoparticle uptake at the cellular level is critical to nanomedicine procedures. In particular, it is required for a realistic evaluation of their effects. Unfortunately, quantitative measurements of nanoparticle uptake still pose a formidable technical challenge. We present here a method to tackle this problem and analyze the number of metal nanoparticles present in different types of cells. The method relies on high-lateral-resolution (better than 30 nm) transmission x-ray microimages with both absorption contrast and phase contrast -- including two-dimensional (2D) projection images and three-dimensional (3D) tomographic reconstructions that directly show the nanoparticles.
  
  
  RESULTS
  Practical tests were successfully conducted on bare and polyethylene glycol (PEG) coated gold nanoparticles obtained by x-ray irradiation. Using two different cell lines, EMT and HeLa, we obtained the number of nanoparticle clusters uptaken by each cell and the cluster size. Furthermore, the analysis revealed interesting differences between 2D and 3D cultured cells as well as between 2D and 3D data for the same 3D specimen.
  
  
  CONCLUSIONS
  We demonstrated the feasibility and effectiveness of our method, proving that it is accurate enough to measure the nanoparticle uptake differences between cells as well as the sizes of the formed nanoparticle clusters. The differences between 2D and 3D cultures and 2D and 3D images stress the importance of the 3D analysis which is made possible by our approach.
authors.affiliation: Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan.
authors.forename: Hsiang-Hsin
authors.initials: HH
authors.lastname: Chen
authors.forename: Chia-Chi
authors.initials: CC
authors.lastname: Chien
authors.forename: Cyril
authors.initials: C
authors.lastname: Petibois
authors.forename: Cheng-Liang
authors.initials: CL
authors.lastname: Wang
authors.forename: Yong S
authors.initials: YS
authors.lastname: Chu
authors.forename: Sheng-Feng
authors.initials: SF
authors.lastname: Lai
authors.forename: Tzu-En
authors.initials: TE
authors.lastname: Hua
authors.forename: Yi-Yun
authors.initials: YY
authors.lastname: Chen
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Cai
authors.forename: Ivan M
authors.initials: IM
authors.lastname: Kempson
authors.forename: Yeukuang
authors.initials: Y
authors.lastname: Hwu
authors.forename: Giorgio
authors.initials: G
authors.lastname: Margaritondo
mesh_terms: D017209:Apoptosis; D045744:Cell Line, Tumor; D004705:Endocytosis / Q000187:drug effects*; D006046:Gold / Q000008:administration & dosage / Q000009:adverse effects; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D053768:Metal Nanoparticles / Q000008:administration & dosage* / Q000009:adverse effects / Q000737:chemistry; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008858:Microscopy, Phase-Contrast / Q000379:methods; D011092:Polyethylene Glycols / Q000737:chemistry; D013194:Staining and Labeling; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D011092:Polyethylene Glycols; D006046:Gold