Paper BI-WeM11
Femtosecond Laser Ablation to Create Nanometer-Scaled Cell Adhesion Ligand Patterns

Wednesday, October 17, 2007, 11:20 am, Room 609

The goal of our project is to fabricate interfaces for mammalian cell culture that control cell fate via the spatial distribution of the individual focal adhesions cells use to interrogate the interface. To create nano-scale cell adhesion sites on a surface, a thin protein adsorption resistant polyethylene glycol (PEG) brush layer was synthesized via surface initiated atom transfer radical polymerization (SI-ATRP). The surface chemistry was verified with XPS, showing strong oxygen and carbon peaks consistent with a PEG film, and thickness of the dry film in air was calculated to be 10nm using a quartz crystal microbalance with dissipation (QCMD). The film was selectively ablated using focused femtosecond laser pulses, exposing the underlying quartz substrate as centers for adsorption or grafting of cell-adhesive molecules. Preliminary results at a wavelength of 400nm with a 50X objective demonstrated spatial resolution approaching 200nm based on atomic force microscopy (AFM) scanning of the ablated features. The practical resolution limit can be further improved (~10-100nm) by utilizing higher magnification lenses at shorter wavelengths or processing in the optical near-field. This technique allows us to generate arbitrary nanoscale protein patterns on the benchtop without specialized processing environments. These nanostructured surfaces will eventually allow us to decouple the effects of cell size and shape, focal adhesion placement, and ligand density on cell fate decision by directly controlling the number and area of focal adhesion complexes formed. Each variable can be modulated independently to determine the effects on cellular function and fate determination.