COVALENT GRAFTING OF FIBRONECTIN AND ASIALOFETUIN AT SURFACE OF POLY(ETHYLENE-TEREPHTHALATE) TRACK-ETCHED MEMBRANES IMPROVES ADHESION BUT NOT DIFFERENTIATION OF RAT HEPATOCYTES

The adhesion and differentiation of rat hepatocytes onto track-etched poly(ethylene terephthalate) (PET) membranes were studied. Native or [ H-3]methylated fibronectin (FN) or asialofetuin (ASF) were immobilized onto oxidized PET membranes, preactivated or not with carbodiimide (W SC). Radiochemical assay and ELISA indicated that upon washing in SDS or in serum-containing medium, significantly less FN was released from WSC-activated membranes than from unactivated ones. These differences were abolished when the NH2 functions of FN were fully acetylated, su ggesting that part of FN was covalently grafted on WSC-activated PET. Although weaker, a comparable effect was observed with ASF. Hepatocyte s adhered faster on membranes on which FN was grafted than adsorbed, r eaching values comparable to collagen-coated PET; after 24 h these dif ferences decreased. Experiments with cycloheximide or at 4 degrees C s uggested that this results from secretion of extracellular matrix adso rbing on PET. Phase I or II biotransformation activities of cells cult ured for 1-4 days on FN-, ASF-, or collagen-treated substrates were no t significantly different. These results indicate that stable immobili zation of FN (covalent grafting) onto PET membranes significantly acce lerates adhesion of hepatocytes but does not affect their differentiat ion. This may result from a progressive surface reconditioning by neos ynthesized extracellular matrix. (C) 1996 John Wiley & Sons, Inc.