Quantitative analysis of nanoparticle internalization in mammalian cells by high resolution X-ray microscopy
1 Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan
2 Department of Engineering and System Science, National Tsing Hua University, Hsinchu 300, Taiwan
3 Université de Bordeaux, CNRS UMR 5248, B8 Avenue des faculties, 33402 Talence-Cedex, France
4 National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY 11973, USA
5 Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 202, Taiwan
6 Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
Journal of Nanobiotechnology 2011, 9:14 doi:10.1186/1477-3155-9-14Published: 10 April 2011
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.
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.
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.