Combining Nonadhesive Materials into Microstructured Composite Surfaces Induces Cell Adhesion and Spreading

The synergistic effects between surface topography and chemical functionality were investigated in order to enhance the adhesion of cells to poorly adhesive materials. It has been established that many cell types are weakly adhesive to thin films of poly(N-isopropylacrylamide), or PNIPAAm, and self-assembled triethylene glycol-terminated alkanethiols (EG3SAM). To enhance adhesion, a topographical cue in the form of electrospun micron-width fibers of PNIPAAm was deposited to each coating. Both coatings, without fibers, supported less than 5% cell adhesion. With the deposition of the PNIPAAm fibers to the PNIPAAm coating, cell adhesion increased to 60% of the theoretical maximum at intermediate fiber coverage before decreasing again; however, cell spreading remained minimal. With the deposition of the PNIPAAm fibers onto the EG3SAM surface, cell adhesion increased to almost 100% at 60% fiber coverage, and unlike the PNIPAAm surface, cell spreading was significantly enhanced. This difference in spreading coincided with the assembly of fiber-associated focal adhesions when the underlying surface was EG3SAM, but not PNIPAAm. These findings indicate that the presence of a sparse topographical feature can stimulate cell adhesion on a typically nonadhesive material, but a chemical dissimilarity between the topographic features and the background is necessary for cell spreading. This work demonstrates for the first time that combining nonadhesive materials into microtextured composites can lead to cell adhesion and spreading on par with strongly adhesive surfaces.