a structure on which to attach the microfluidic PDMS slab. Prior to bonding, the well bottoms of the microplate were punched out using a 10 μl pipette tip (the tip head was pressed into the well bottom to punch out the plastic) to provide fluid access to the PDMS slab. To facilitate bonding of the PDMS to the polystyrene plate, the plate was treated with aminopropyltriethoxysilane (APTES), in which the polystyrene plate was first exposed to oxygen plasma (100 W, 60 s, 60% O2). It was then placed in a bath of 5% APTES in distilled water at 80 °C for 20 minutes.23 The polystyrene plate was then washed with distilled water and allowed to fully dry. Lastly, the plate and PDMS were exposed to oxygen plasma at 100 W, 60% O2, for 20 seconds, and then bonded overnight in a 65 °C oven under light weight. To re-oxidize the surface, the completed plate was placed in oxygen plasma at 100 W, 60% O2, for 60 seconds. Immediately following this treatment, sterile distilled water was added to the wells to maintain hydrophilicity. The plate with its lid were then wrapped in Parafilm until sterilization and seeding.
