Laser surface modification of polymers to improve biocompatibility

The effect on neutrophil chemokinesis and fibroblast adhesion of changing surface topography was examined using two polymeric substrates; polycarbonate and polyetherimide, modified by laser treatment to produce pillars of varying dimensions on the surfaces of these materials. The dimensions for the pillars were 7, 25 or 50 mu m square, 0.5, 1.5 or 2.5 mu m deep. Human neutrophils were isolated, by centrifugation, on ficoll from heparinized whole blood obtained from healthy volunteers. Isolated neutrophils were exposed to the surfaces for 20 min and tracked using image processing and analysis techniques. The mean speed for each cell on each surface was calculated and this data statistically analysed using multivariate analysis of variance to determine any significant effect on speed of movement due to the surface topography. Compared to the potent stimulator FMLP all surfaces did not stimulate significant cell movement, but within the groups some surfaces had more effect on cell movement than others, and were stimulating cells to move faster than on the same untextured surface. Surface topography can stimulate neutrophils to move at different speeds across a surface. L929 fibroblasts were incubated on the surfaces for 48 h and then examined using scanning electron microscopy to study fibroblast position and adhesion with respect to the pillars. No pattern of orientation with respect to the pillars were observed and fibroblasts spread and elongated whether in contact with the pillars or on a smooth area of the material.