CONTACT-ANGLE STUDIES OF THE SURFACE-PROPERTIES OF COVALENTLY BONDED POLY-L-LYSINE TO SURFACES TREATED BY GLOW-DISCHARGE

Contact angle data, measured by using a sessile drop arrangement in co njunction with Axisymmetric Drop Shape Analysis-contact Diameter (ADSA -CD), were used to quantify the effects of ammonia gas plasma treatmen t on the surface properties of previously untreated polystyrene surfac es. The surface tension of treated polystyrene samples is considerably higher than that of untreated samples. The increase in surface tensio n following plasma treatment is attributed to the addition of amine gr oups to the surface. Next, conformational changes following the attach ment of poly-L-lysine to the untreated samples by simple adsorption an d plasma treated samples by covalent bonding were investigated. Surfac e tension values obtained from contact angle data indicate that confor mational changes to poly-L-lysine occur in both cases, because these v alues are lower than the surface tension of poly-L-lysine in solution. However, contact angle data show that covalently bonded poly-L-lysine undergoes less conformational changes than simply adsorbed poly-L-lys ine.