X-RAY PHOTOELECTRON-SPECTROSCOPY (XPS) SURFACE-ANALYSIS OF HEMA-MMA MICROCAPSULES

High resolution carbon, C 1s, X-ray photoelectron spectroscopy (XPS) o f the surface of hydroxyethyl methacrylate-methyl methacrylate (HEMA-M MA; 75 mol% HEMA) capsules maintained in PBS for 1 week showed that th e surface was not pure HEMA-MMA. In these spectra, more carbon was bon ded in the C-O form than in the C-C form indicating the presence of th e Pluronic surfactant, L101, adsorbed from the precipitation bath to t he surface during microcapsule preparation. Capsules maintained in med ium containing fetal bovine serum for 1 week showed a nitrogen signal consistent with the presence of adsorbed serum proteins. There was a d ecrease in the amount of nitrogen on the surface after phosphate buffe red saline (PBS) washing, however this did not decrease to zero. These preadsorbed proteins, present on the surface of capsules incubated in serum-containing medium before their implantation, may affect the tis sue response to these capsules. Calcium was not detected on freshly-ma de capsules or capsules maintained in PBS for 1 week but was detected on capsules maintained in medium containing serum. Calcium deposits, i f formed in vitro, could act as nucleation sites for calcification of the polymer in vivo.