title: Magnetic assembly of 3D cell clusters: visualizing the formation of an engineered tissue.
abstract: OBJECTIVE
  Contactless magnetic assembly of cells into 3D clusters has been proposed as a novel means for 3D tissue culture that eliminates the need for artificial scaffolds. However, thus far its efficacy has only been studied by comparing expression levels of generic proteins. Here, it has been evaluated by visualizing the evolution of cell clusters assembled by magnetic forces, to examine their resemblance to in vivo tissues.
  
  
  METHODS
  Cells were labeled with magnetic nanoparticles, then assembled into 3D clusters using magnetic force. Scanning electron microscopy was used to image intercellular interactions and morphological features of the clusters.
  
  
  RESULTS
  When cells were held together by magnetic forces for a single day, they formed intercellular contacts through extracellular fibers. These kept the clusters intact once the magnetic forces were removed, thus serving the primary function of scaffolds. The cells self-organized into constructs consistent with the corresponding tissues in vivo. Epithelial cells formed sheets while fibroblasts formed spheroids and exhibited position-dependent morphological heterogeneity. Cells on the periphery of a cluster were flattened while those within were spheroidal, a well-known characteristic of connective tissues in vivo.
  
  
  CONCLUSIONS
  Cells assembled by magnetic forces presented visual features representative of their in vivo states but largely absent in monolayers. This established the efficacy of contactless assembly as a means to fabricate in vitro tissue models.
authors.affiliation: Department of Engineering Physics, McMaster University, Hamilton, ON, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA.
authors.forename: S R P
authors.initials: SR
authors.lastname: Kumar
authors.affiliation: Department of Engineering Physics, McMaster University, Hamilton, ON, Canada.|Department of Mechanical Engineering, McMaster University, Hamilton, ON, Canada.
authors.forename: I K
authors.initials: IK
authors.lastname: Puri
authors.affiliation: Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Elankumaran
mesh_terms: D000818:Animals; D002417:Cattle; D002449:Cell Aggregation; D045744:Cell Line, Tumor; D048430:Cell Shape; D005347:Fibroblasts / Q000166:cytology; D006801:Humans; D008280:Magnetics / Q000379:methods*; D058185:Magnetite Nanoparticles / Q000648:ultrastructure; D012710:Serum Albumin, Bovine / Q000378:metabolism; D018874:Spheroids, Cellular / Q000166:cytology; D023822:Tissue Engineering
chemical_list: D058185:Magnetite Nanoparticles; D012710:Serum Albumin, Bovine
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