Rhodamine labeled fibronectin

Protein adsorption onto the surface of the different PDMS formulations was tested by first preparing rhodamine-labeled fibronectin by diluting 50 μg mL⁻¹ rhodamine-labeled fibronectin (Cytoskeleton Inc) 1 : 20 with 200 ng μL⁻¹ fibronectin (R&D Systems). Spin-coated substrates were cleaned in 70% ethanol and then exposed to UV ozone for 10 minutes with a UV ozone cleaner (Novascan) in order to generate reactive oxygen groups to bind protein. Each substrate was then microcontact printed with 100 μL of the labeled fibronectin using a stamp cut to be 1 cm². After microcontact printing, the substrates were placed in 1× PBS for 30 minutes at 37 °C. After 30 minutes, protein was released from the surface with 2 mL of 0.05% trypsin and incubated at 37 °C for another 30 minutes. Absorbance of the collected samples was quantified using a NanoDrop 2000 spectrophotometer (Thermo Fisher).