title: In vitro investigation of silica nanoparticle uptake into human endothelial cells under physiological cyclic stretch.
abstract: BACKGROUND
  In general the prediction of the toxicity and therapeutic efficacy of engineered nanoparticles in humans is initially determined using in vitro static cell culture assays. However, such test systems may not be sufficient for testing nanoparticles intended for intravenous application. Once injected, these nanoparticles are caught up in the blood stream in vivo and are therefore in continuous movement. Physical forces such as shear stress and cyclic stretch caused by the pulsatile blood flow are known to change the phenotype of endothelial cells which line the luminal side of the vasculature and thus may be able to affect cell-nanoparticle interactions.
  
  
  METHODS
  In this study we investigated the uptake of amorphous silica nanoparticles in primary endothelial cells (HUVEC) cultured under physiological cyclic stretch conditions (1 Hz, 5% stretch) and compared this to cells in a standard static cell culture system. The toxicity of varying concentrations was assessed using cell viability and cytotoxicity studies. Nanoparticles were also characterized for the induction of an inflammatory response. Changes to cell morphology was evaluated in cells by examining actin and PECAM staining patterns and the amounts of nanoparticles taken up under the different culture conditions by evaluation of intracellular fluorescence. The expression profile of 26 stress-related was determined by microarray analysis.
  
  
  RESULTS
  The results show that cytotoxicity to endothelial cells caused by silica nanoparticles is not significantly altered under stretch compared to static culture conditions. Nevertheless, cells cultured under stretch internalize fewer nanoparticles. The data indicate that the decrease of nanoparticle content in stretched cells was not due to the induction of cell stress, inflammation processes or an enhanced exocytosis but rather a result of decreased endocytosis.
  
  
  CONCLUSIONS
  In conclusion, this study shows that while the toxic impact of silica nanoparticles is not altered by stretch this dynamic model demonstrates altered cellular uptake of nanoparticles under physiologically relevant in vitro cell culture models. In particular for the development of nanoparticles for biomedical applications such improved in vitro cell culture models may play a pivotal role in the reduction of animal experiments and development costs.
authors.affiliation: REPAIR-lab, Institute of Pathology, University Medical Center of the Johannes Gutenberg University Mainz, European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Mainz, Germany. freesec@uni-mainz.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Freese
authors.affiliation: REPAIR-lab, Institute of Pathology, University Medical Center of the Johannes Gutenberg University Mainz, European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Mainz, Germany. daniel_schreiner@yahoo.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schreiner
authors.affiliation: REPAIR-lab, Institute of Pathology, University Medical Center of the Johannes Gutenberg University Mainz, European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Mainz, Germany. anspach@uni-mainz.de.
authors.forename: Laura
authors.initials: L
authors.lastname: Anspach
authors.affiliation: Fraunhofer ICT-IMM, Mainz, Germany. Christoph.Bantz@imm.fraunhofer.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Bantz
authors.affiliation: Fraunhofer ICT-IMM, Mainz, Germany. maskos@uni-mainz.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Maskos
authors.affiliation: REPAIR-lab, Institute of Pathology, University Medical Center of the Johannes Gutenberg University Mainz, European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Mainz, Germany. runger@uni-mainz.de.
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Unger
authors.affiliation: REPAIR-lab, Institute of Pathology, University Medical Center of the Johannes Gutenberg University Mainz, European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Mainz, Germany. kirkpatrick@uni-mainz.de.
authors.forename: C James
authors.initials: CJ
authors.lastname: Kirkpatrick
mesh_terms: D001692:Biological Transport; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D005089:Exocytosis / Q000187:drug effects; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D053758:Nanoparticles / Q000378:metabolism* / Q000633:toxicity; D020411:Oligonucleotide Array Sequence Analysis; D010316:Particle Size; D011673:Pulsatile Flow; D012822:Silicon Dioxide / Q000378:metabolism* / Q000633:toxicity; D013499:Surface Properties
chemical_list: D016207:Cytokines; D012822:Silicon Dioxide