Guided Cell Migration on Microtextured Substrates with Variable Local Density and Anisotropy
Kim DH, Seo CH, Han K, Kwon KW, Levchenko A (1), Suh KY (2). – (1) Johns Hopkins University, (2) Seoul National University
Abstract: This work reports the design of and experimentation with a topographically patterned cell culture substrate of variable local density and anisotropy as a facile and efficient platform to guide the organization and migration of cells in spatially desirable patterns. Using UV-assisted capillary force lithography, an optically transparent microstructured layer of a UV curable poly(urethane acrylate) resin is fabricated and employed as a cell-culture substrate after coating with fibronectin. With variable local pattern density and anisotropy present in a single cell-culture substrate, the differential polarization of cell morphology and movement in a single experiment is quantitatively characterized. It is found that cell shape and velocity are exquisitely sensitive to variation in the local anisotropy of the two-dimensional rectangular lattice arrays, with cell elongation and speed decreasing on symmetric lattice patterns. It is also found that cells could integrate orthogonal spatial cues when determining the direction of cell orientation and movement. Furthermore, cells preferentially migrate toward the topographically denser areas from sparser ones. Consistent with these results, it is demonstrated that systematic variation of local densities of rectangular lattice arrays enable a planar assembly of cells into a specified location. It is envisioned that lithographically defined substrates of variable local density and anisotropy not only provide a new route to tailoring the cell-material interface but could serve as a template for advanced tissue engineering.
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Materials & Methods: Silicon wafers were spin-coated with photoresist (Shipley, Marlborough, MA) and then patterned via electron-beam lithography (JBX-9300FS, JEOL). After photoresist development (MF320, Shipley), exposed silicon was deep reactive ion etched (STS ICP Etcher) to form arrays of submicrometer-scale ridges with near-vertical sidewalls. The remaining photoresist on silicon wafers was removed using an ashing process (BMR ICP PR Asher) and then diced into silicon masters for subsequent replica molding. To cast topographic micro- and nanopattern arrays, PUA was used as a mold material from the silicon master as previously described [20]. Briefly, the UV-curable PUA was drop-dispensed onto a silicon master and then a flexible and transparent polyethylene terephthalate (PET) film was brought into contact with the dropped PUA liquid. Subsequently, it was exposed to UV light (λ = 200–400 nm) for 30 s through the transparent backplane (dose = 100 mJ cm−2). After UV curing, the mold was peeled off from the master and additionally cured overnight to terminate the remaining active acrylate groups on the surface prior to use as a first replica. The resulting PUA mold used in the experiment was a thin sheet with a thickness of ≈50 μm.
Microscopic Technique: Time-Lapse Microscopy
Cell Type(s): Fibroblast Cells, NIH 3T3