as distinct nuclei pseudopodia and polygonal shape fig3 cells were visualized at 200 u00d7 magnification using hoffman modulation contrast optics on a leitz fluovert inverted stage microscope cell growth was also assessed by determining spread cell counts at various time points for cells cultured in media supplemented with 10 calf serum nbd phallacidin 7 nitrobenz 2 oxa 1 3 diazolylphallacidin molecular probes inc eugene ore was employed to visualize actin stress fibers and microfilament bundles in cells attached to the modified surfaces samples were prepared according to the manufacturer 39 s procedure and 1000 u00d7 images were viewed utilizing the fluovert microscope equipped with a leitz e3 excitation filter and uv illumination in the competition studies 3t3 fibroblasts were preincubated for 30 minutes in either serum free medium containing about 90 ug ml rgds or no peptide the cells were then inoculated at a density of about 3000 cells cm 2 on grgd derivatized pet and spreading was determined after three hours incubation under normal culture conditions the grgd derivatized substrates were characterized by their ability to support active adhesion of cells on their surfaces the pet pretreatment was optimized by coupling grgd to tresyl chloride activated films that were hydroxylated for various time periods cell spreading assays using nih 3t3 fibroblasts were performed to determine conditions that supported a maximal response four hours pretreatment appeared to be optimal for maximum cell adhesion and spreading phema films were derivatized with grgd utilizing low concentrations of peptide 80 ng ml which resulted in an increase in cellular adhesion by three orders of magnitude fig4 comparison of grgd coupled pet films with pretreated untresylated films that were incubated with grgd for the normal coupling time demonstrated that either little peptide adsorbed to the latter films.