INFLUENCE OF FLUORESCENT LABELING OF POLYSTYRENE PARTICLES ON PHAGOCYTIC UPTAKE, SURFACE HYDROPHOBICITY, AND PLASMA-PROTEIN ADSORPTION

Purpose. To investigate the influence of fluorescent labelling of poly styrene particles on phagocytic uptake, surface hydrophobicity and pro tein adsorption.Methods. Phagocytic uptake was analysed using chemilum inescence. Hydrophobicity was quantified by adsorption measurements of a hydrophobic dye. Protein adsorption was evaluated by two-dimensiona l electrophoresis. Results. Commercially available fluorescently label led particles showed marked differences when compared to unlabelled pa rticles: phagocytic uptake and surface hydrophobicity of labelled part icles were diminished. Also the plasma protein adsorption pattern was found to be different from the unlabelled particles: for example, the amount of fibrinogen adsorbed was strongly reduced on the labelled par ticles. On the other hand, some unknown proteins could be detected on the fluorescently marked particles. In contrast, plain polystyrene par ticles and labelled ones could be successfully synthesised by Paulke w hich did not show any considerable differences in phagocytic uptake, s urface hydrophobicity and protein adsorption. Polysorbate 20 added as stabilizer to particle suspensions led to completely different behavio ur of the particles: the particles showed altered protein adsorption p atterns, dominated by immunoglobulins and especially by apolipoprotein s. Furthermore, these particles were not phagocytized at all. Conclusi ons. Surface hydrophobicity and phagocytic uptake in vitro as well as the interactions with plasma proteins of commercially available polyst yrene particles were strongly affected by fluorescent labelling. Parti cles synthesised by Paulke remained unchanged after labelling. The res ults show the importance of thorough surface characterization for usin g particles in test systems in vitro and in vivo.