Inverted pattern formation of cell microarrays on poly(ethylene glycol) (PEG) gel patterned surface and construction of hepatocyte spheroids on unmodified PEG gel microdomains.

We present herein the novel technique for constructing inverted cell-adhesion patternes on PEG gel modified glass surfaces by photoirradiation using the same photomask and materials. The PEG gel micropatterns were prepared by a photolithographic technique using a photomask with 100 microm aligned cavities after spin-coating of a mixed solution of alpha,omega-dimethacryloyl-PEG (PEG-DMA) and a photoinitiator on glass surfaces. When methanol was used as a casting solvent for the spin-coating (Method A), the circular PEG gel domains with a diameter of 100 microm were fabricated on the surface, and as would be predicted, seeded bovine aortic endothelial cells (BAECs) adhered to the glass area on the constructed surface to form a BAECs sheet with 100 microm aligned cavity. In contrast, it was rather surprising for us that a complete inverted cell pattern was formed when the PEG gel pattern surface was prepared using methanol/water co-solvent (Method B). Furthermore, when hepatoma cancer cells were seeded on the constructed surface prepared by Method B, they formed a spherical multicellular aggregate (spheroid) on the unmodified PEG gel domains without feeder cells. In order to obtain information on this peculiar phenomenon, fluorescence-based protein adsorption experiments, contact angle measurements, and X-ray photospectroscopy (XPS) analysis were carried out.