title: Anisotropic material synthesis by capillary flow in a fluid stripe.
abstract: We present a simple bench-top technique to produce centimeter long concentration gradients in biomaterials incorporating soluble, material, and particle gradients. By patterning hydrophilic regions on a substrate, a stripe of prepolymer solution is held in place on a glass slide by a hydrophobic boundary. Adding a droplet to one end of this "pre-wet" stripe causes a rapid capillary flow that spreads the droplet along the stripe to generate a gradient in the relative concentrations of the droplet and pre-wet solutions. The gradient length and shape are controlled by the pre-wet and droplet volumes, stripe thickness, fluid viscosity and surface tension. Gradient biomaterials are produced by crosslinking gradients of prepolymer solutions. Demonstrated examples include a concentration gradient of cells encapsulated in three dimensions (3D) within a homogeneous biopolymer and a constant concentration of cells encapsulated in 3D within a biomaterial gradient exhibiting a gradient in cell spreading. The technique employs coated glass slides that may be purchased or custom made from tape and hydrophobic spray. The approach is accessible to virtually any researcher or student and should dramatically reduce the time required to synthesize a wide range of gradient biomaterials. Moreover, since the technique employs passive mechanisms it is ideal for remote or resource poor settings.
authors.affiliation: Center for Biomedical Engineering, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA 02139, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Hancock
authors.forename: Francesco
authors.initials: F
authors.lastname: Piraino
authors.forename: Gulden
authors.initials: G
authors.lastname: Camci-Unal
authors.forename: Marco
authors.initials: M
authors.lastname: Rasponi
authors.forename: Ali
authors.initials: A
authors.lastname: Khademhosseini
mesh_terms: D000818:Animals; D016880:Anisotropy; D001672:Biocompatible Materials / Q000138:chemical synthesis*; D051379:Mice; D008863:Microspheres; D041681:NIH 3T3 Cells; D011108:Polymers / Q000494:pharmacology; D012212:Rheology / Q000379:methods*; D012996:Solutions
chemical_list: D001672:Biocompatible Materials; D011108:Polymers; D012996:Solutions