Three-Dimensional Patterning of the ECM Microenvironment Using Magnetic Nanoparticle Self Assembly.

This protocol describes a way to introduce topography to three-dimensional (3D) biomaterials. The self-assembling behavior of magnetic particles can be exploited to form nanoscale to microscale fibers, such that one can dissect the contribution of topography on cell behavior, which is independent of other physical properties of the biomaterial (e.g., stiffness). The magnetic particles are chemically cross-linked with several extracellular matrix (ECM) proteins and then using magnetic force-mediated assembly, one can program aligned nanofibers in a 3D hydrogel. This process allows the creation of diverse topographic patterns in 3D, including isotropic, anisotropic (fibril), or interfaced architectures, without changing the bulk stiffness of the scaffold material. This anisotropic architecture guides the dendritic protrusions of cells, which can be compared to cells grown in an isotropic architecture lacking spatial guidance cues. Several cell types, such as fibroblasts and neurons, have been cultured in this engineered 3D matrix. This technology provides an easy way to construct nano-bio interfaces for various biomedical engineering applications as well as dissect the role of topography in various cell behaviors. © 2016 by John Wiley & Sons, Inc.