title: Magnetic micro-manipulations to probe the local physical properties of porous scaffolds and to confine stem cells.
abstract: The in vitro generation of engineered tissue constructs involves the seeding of cells into porous scaffolds. Ongoing challenges are to design scaffolds to meet biochemical and mechanical requirements and to optimize cell seeding in the constructs. In this context, we have developed a simple method based on a magnetic tweezer set-up to manipulate, probe, and position magnetic objects inside a porous scaffold. The magnetic force acting on magnetic objects of various sizes serves as a control parameter to retrieve the local viscosity of the scaffolds internal channels as well as the stiffness of the scaffolds pores. Labeling of human stem cells with iron oxide magnetic nanoparticles makes it possible to perform the same type of measurement with cells as probes and evaluate their own microenvironment. For 18 microm diameter magnetic beads or magnetically labeled stem cells of similar diameter, the viscosity was equivalently equal to 20 mPa s in average. This apparent viscosity was then found to increase with the magnetic probes sizes. The stiffness probed with 100 microm magnetic beads was found in the 50 Pa range, and was lowered by a factor 5 when probed with cells aggregates. The magnetic forces were also successfully applied to the stem cells to enhance the cell seeding process and impose a well defined spatial organization into the scaffold.
authors.affiliation: Laboratoire Matière et Systèmes Complexes (MSC), UMR 7057 CNRS & Université Paris Diderot, Paris, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Robert
authors.forename: Delphine
authors.initials: D
authors.lastname: Fayol
authors.forename: Catherine
authors.initials: C
authors.lastname: Le Visage
authors.forename: Guillaume
authors.initials: G
authors.lastname: Frasca
authors.forename: Séverine
authors.initials: S
authors.lastname: Brulé
authors.forename: Christine
authors.initials: C
authors.lastname: Ménager
authors.forename: Florence
authors.initials: F
authors.lastname: Gazeau
authors.forename: Didier
authors.initials: D
authors.lastname: Letourneur
authors.forename: Claire
authors.initials: C
authors.lastname: Wilhelm
mesh_terms: D002449:Cell Aggregation; D006801:Humans; D008280:Magnetics / Q000379:methods*; D008863:Microspheres; D009038:Motion; D055585:Physical Phenomena; D016062:Porosity; D013234:Stem Cells / Q000166:cytology*; D054457:Tissue Scaffolds / Q000737:chemistry*; D014783:Viscosity