Optically patternable polymer films as model interfaces to study cellular behaviour on topographically structured materials.

We assessed blood interaction with different micrometer-scale topographies under flow conditions using a micro-fluidic array system. The channels of the micro-fluidic array chip were coated with azobenzene polymer films, which were then topographically structured using a one-step non-contact optical technique. A set of surfaces with different topographies was produced varying laser irradiation duration. These surfaces were then exposed to blood flow. The blood flow rate was measured with a micro-channel array flow analyzer. The measured blood flow rates decreased with time for all the samples, indicating formation of platelet clots which obstruct the channels during flow. This effect appeared enhanced on polymer surfaces having a sinusoidal profile with 200-nm-high ridges and 1.2-μm-grating spacing. The morphology of platelets that adhered on the polymer films was studied by scanning electron microscopy. Platelets adhered on azobenzene surfaces with flat topographies, typically exhibiting filopodia. Platelets adhered on optically structured surfaces also exhibited lamellipodia and appeared flattened on surfaces with the highest ridges. We conclude that surface topography influences blood behaviour on azobenzene polymer films.