Poster Presentation 2014 International Biophysics Congress

A multimodal approach to the study of magnetic nanoparticles interaction with breast cancer cells (#272)

Michele Chiappi 1 , Jose J. Conesa 1 , Eva Pereiro 2 , Maria J. Rodriguez 1 , Francisco J. Chichon 1 , Jose L. Carrascosa 1 3
  1. Structure of Macromolecules, Centro Nacional de Biotecnologia (CNB-CSIC), Madrid, Spain
  2. MISTRAL Beamline - Experiments division, ALBA Synchrotron Light Source, Cerdanyola del Vallès, Barcelona, Spain
  3. Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia), Madrid, Spain.

We have analyzed the internalization and accumulation of dimercaptosuccinic acid-coated superparamagnetic iron oxide nanoparticles (DMSA-SPIONs), with an average diameter of 15 nm and negative surface charge, in MCF-7 breast cancer cells. Cells were incubated with 0.25 mg Fe ml-1 DMSA-SPIONs for different time intervals ranging from 0 to 24 h. Time-dependent uptake studies showed maximum accumulation of SPIONs after 24 h of incubation.

Light microscopy, Transmission Electron Microscopy and Soft X-ray cryo-tomography (SXT) were used to characterize the interaction and accumulation of magnetic nanoparticles (DMSA-SPIONs) inside MCF-7 cells, and to study the reorganization of the intracellular environment derived from this treatment. Cryo SXT technique allowed us to visualize, at nanometric 3D resolution, the whole cell without chemical fixation or staining agents. Correlative microscopy was used to locate the cells to be imaged by SXT which contained nanoparticles accumulated in endosomes. Reconstructed volumes show the SPION-containing endosomes accumulating near the Golgi area close to the nucleus. This accumulation excludes from this area other organelles like mitochondria, which are displaced to the cellular periphery.

To discriminate unambiguously the iron absorption signal inside the cells from the presence of highly carbon absorbing vesicles in all cells, including control cells without SPION incubation, we performed soft X-ray spectroscopic 2D and 3D imaging around the L3 Fe absorption edge. Acquisition of 2D energy stacks between 690 eV and 730 eV, and tomographic tilted series before (700eV) and above the edge (707 eV), have allowed us to obtain a quantitative three dimensional map of the distribution of iron within the cells.