Cell durotaxis on polyelectrolyte multilayers with photogenerated gradients of modulus

Behaviors of rat aortic smooth muscle (A7r5) and human osteosarcoma (U2OS) cells on photo-cross-linked polyelectrolyte multilayers (PEMUs) with uniform, or gradients of, moduli were investigated. The PEMUs were built layer-by-layer with the polycation poly(allylamine hydrochloride) (PAH) and a polyanion poly(acrylic acid) (PAA) that was modified with photoreactive 4-(2-hydroxyethoxy) benzophenone (PAABp). PEMUs with different uniform and gradients of modulus were generated by varying the time of uniform ultraviolet light exposure and by exposure through optical density gradient filters. Analysis of adhesion, morphology, cytoskeletal organization, and motility of the cells on the PEMUs revealed that A7r5 cells established a polarized orientation toward increasing modulus on shallow modulus gradients (approximately 4.7 MPa mm(-1)) and durotaxed toward stiffer regions on steeper gradients (approximately 55 MPa mm(-1)). In contrast, U2OS cells exhibited little orientation or durotaxis on modulus gradients. These results demonstrate the utility of photo-cross-linked PEMUs to direct vascular and osteoblast cell behavior, a potential application for PEMU coatings on biomedical implants.