IN-VITRO MONOCYTE ADHESION AND ACTIVATION ON MODIFIED FEP COPOLYMER SURFACES

The functional group content and the ionic state of functional groups present on a series of surface modified poly(tetrafluoroethylene/hexaf luoropropylene) (FEP) copolymers were characterized by electron spectr oscopy for chemical analysis (ESCA), contact angle, and attenuated tot al reflection Fourier transform infrared spectroscopy (ATR-FTIR). Addi tionally, after a protein was preadsorbed on these surfaces, in vivo c ell (monocyte) adhesion and activation were analyzed. The two proteins in this study were fibrinogen and immunoglobulin-G (IgG). Four modifi ed FEP surfaces were prepared with increasing concentration of carboxy l groups relative to amide groups; ESCA was used to quantify the funct ional group content. To characterize the ionic state of the functional groups at physiological pH (7.1), the ATR-FTIR spectra were collected at various pH levels. Collectively, the contact angle, ESCA, and ATR- FTIR results suggested that the amide groups were unprotonated and the carboxyl groups were ionized at the physiological pH. The results fro m the in vitro studies showed that on the fibrinogen preadsorbed surfa ces, monocyte adhesion was higher and monocyte activation was lower on the three surfaces that contained carboxyl groups compared to the FEP surface that had only amide groups. Conversely, the results indicated that the surface chemistry had no significant effect on monocyte adhe sion or activation on the IgG preadsorbed surfaces. (C) 1995 John Wile y & Sons, Inc.