The effects of protein type and pattern size on cell adhesion, spreading, and focal adhesion development are studied. Fibronectin and vitronectin patterns from 0.1 to 3 μm produced by colloidal lithography reveal important differences in how cells adhere to and bridge focal adhesions across protein nanopatterns versus micropatterns. Vinculin and zyxin in focal adhesions but not integrins are seen to bridge ligand gaps. Differences in protein mechanical properties are implicated as important factors in focal adhesion development.

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The role of ligand spatial distribution on the formation of cadherin mediated cell-cell contacts is studied utilizing nanopatterns of E-cadherin ligands. Protein patches ranging in size from 100 to 800 nm prepared by colloidal lithography critically influence adhesion, spreading, and formation of adherence junctions in epithelial cells. Cells at 100 nm patterns show poor adhesion, while larger pattern sizes show good adhesion, significant spreading, and defined cortical actin. We estimate a threshold of 0.03 μm(2) for epithelial cellular attachment via E-Cadherin.

This paper presents the use of the quartz crystal microbalance with dissipation (QCM-D) combined with surface plasmon resonance (SPR) to probe protein adsorption at nanopatterned surfaces. Three different types of adsorbing materials, representing rigid discrete nanoparticles, dense protein films, and soft low density films have been studied on systematic varied circular nanostructures in the 100-1000 nm size range. Analysis and quantification of the QCM-D response from larger nanostructures could be understood and quantified in the same way as for homogeneous surfaces, while that for nanostructures of 100 and 200 nm diameter was significantly underestimated. Our findings suggest a size limitation of those techniques in analysis of adsorption at nanofeatures.

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