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Hepatic tissue engineering using primary hepatocytes has been considered a valuable new therapeutic modality for several classes of liver diseases. Recent progress in the development of clinically feasible liver tissue engineering approaches, however, has been hampered mainly by insufficient cell-to-cell contact of the engrafted hepatocytes. We developed a method to engineer a uniformly continuous sheet of hepatic tissue using isolated primary hepatocytes cultured on temperature-responsive surfaces. Sheets of hepatic tissue transplanted into the subcutaneous space resulted in efficient engraftment to the surrounding cells, with the formation of two-dimensional hepatic tissues that stably persisted for longer than 200 d. The engineered hepatic tissues also showed several characteristics of liver-specific functionality. Additionally, when the hepatic tissue sheets were layered in vivo, three-dimensional miniature liver systems having persistent survivability could be also engineered. This technology for liver tissue engineering is simple, minimally invasive and free of potentially immunogenic biodegradable scaffolds.

An approach is presented for the graft copolymerization of acrylamide (AAm) onto the surface of polyethylene films treated with an oxidative plasma or inert gas plasmas, followed by exposure to air. In both cases, peroxides formed by the plasma treatment are likely to be the species responsible for initiating the graft copolymerization. It is shown that the amount of peroxides (~1CT10 mol-cm"2) and grafted PAAm (-10 Mg-cm"2) can be determined with good accuracy by the l,l-diphenyl-2-picrylhydrazyl and the ninhydrin method, respectively. A striking finding is that the amounts of peroxides and the grafted PAAm do not monotonously increase with the plasma exposure time but decrease after passing a maximum. A mechanism is proposed to explain this peculiar dependence of the grafted amount on the exposure time. Optical microscopy on the cross-section of the grafted film reveals the graft copolymerization to be limited to a very thin surface region. Both the merely plasma-treated film and the subsequently grafted film are hydrophilic, but only the grafted film has an invariably low contact angle and a slippery surface when hydrated.

We investigated initial cell adhesion on self-assembled monolayers (SAMs) of alkanethiols carrying different functional groups including methyl (CH 3 ), hydroxyl (OH), carboxylic acid (COOH), and amine (NH 2 ). The combination of a surface plasmon resonance (SPR) instrument and a total internal reflection fluorescence microscope (TIRFM) allowed us to examine the kinetics of protein adsorption and correlating cell adhesion. Upon exposure of the SAM surface to a serum-containing medium, serum proteins rapidly adsorbed, and cells subsequently approached the surface. Adhesion of human umbilical vein endothelial cells (HUVECs) was greatly affected by surface functional groups; HUVECs adhered well to COOH-and NH 2 -SAMs, whereas poorly to CH 3 -and OH-SAMs. The amount of adsorbed protein from the serum-containing medium varied slightly with the terminal groups of the SAMs. On COOH-and NH 2 -SAMs, HUVECs adhered to bovine serum albumin (BSA)-preadsorbed surfaces with a few minutes delay, suggesting that displacement of preadsorbed BSA with cell-adhesive proteins, such as fibronectin or vitronectin, supports cell adhesion to these surfaces. Since the concentration of cell-adhesive proteins is much less than that of non-adhesive proteins such as BSA, displacement of adsorbed proteins with cell-adhesive proteins plays an important role in initial cell adhesion.

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