Therapeutic Micro and Nanotechnology Section: Microwell Array Photoimprint Lithography: Micropost Sensors and Guidance of PC12 Neurite Processes

Abstract

Microwell array photoimprint lithography (PIL) is demonstrated by fabricating a patterned chemical sensing layer that is suitable for use with cultured biological cells and inverted epifluorescence microscopes. A microwell array is a ∼50,000-count, coherent fiber-optic bundle whose distal face was etched chemically. Individual microwells had ∼3 μm depths and ∼8 μm widths. The microwell array PIL process patterned an array of ∼50,000 individual polymeric micropost sensors on a glass coverslip. Individual microposts were ∼3 μm tall and ∼8 μm wide. O2-sensitive micropost array sensors (MPASs) were fabricated using a ruthenium complex encapsulated in a gas permeable photopolymerizable siloxane. pH-sensitive MPASs were fabricated using a fluorescein conjugate encapsulated in a photocrosslinkable poly(vinyl alcohol)-based polymer. PO2 and pH were quantitated by acquiring MPAS luminescence images with an epifluorescence microscope/charge coupled device imaging system. The advantage of a patterned MPAS layer relative to a planar sensing layer is the ability to direct the growth of biological cells. Preliminary data are presented whereby nerve growth factor-differentiated rat pheochromocytoma (PC12) cells grew neurite-like processes that extended along paths defined by the micropost architecture.