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Surfaces of polypropylene (PP), polystyrene (PS) and polytetrafluoroethylene (PTFE) were activated with radio frequency plasmas Ar and NH3 to aminate the polymer surface and were subsequently reacted with hyaluronic acid (HA) in one of the three different attachment schemes. Results show that ammonia plasma treated polymers were more reactive toward HA attachment. The three chemistry schemes consisted of two distinct approaches: (1) direct attachment of the HA to the aminated surface, and (2) extending the reactive group away from the surface with succinic anhydride and then reacting the newly formed carboxylic acid group with an adipic dihydrazide modified HA (HA-ADH). The latter scheme proved to be more effective, suggesting that steric effects were involved with the reactivity of the HA with surface groups. These HA-coated polymers are a candidate for cell attachment and growth.

Ultrasonic irradiation at 500 kHz and 10 mW cm-2 of a 24 h old biofilm of P. aeruginosa enhanced the killing of bacteria by gentamicin. To determine whether this bioacoustic effect was caused by ultrasonic-induced changes in the biofilm morphology (biofilm breakup or disruption), the biofilms were examined by confocal scanning laser microscopy (CSLM). Such disruption would be undesirable in the possible ultrasonic treatment of implant infections. The CSLM results showed that the biofilm is a partial monolayer of cells with occasional aggregates of cells, non-cellular materials and extracellular spaces. The aggregates contained large amounts of exopolysaccharide. The structure of biofilm was not changed when the biofilm was exposed to continuous ultrasound at 500 kHz and 10 mW cm-2, the same irradiation parameters that increased cell killing by nearly two orders of magnitude. The observation that low-intensity ultrasound does not disrupt biofilm or disperse the bacteria has significance in the possible use of ultrasound to enhance the action of antibiotics against biofilms.

The protein sticking coefficient, phi, the fraction of collisions that result in adsorption, is a function of the molecular interactions between the protein and the surface. A random walk and diffusion-to-capture model was used to describe the kinetics of protein adsorption. The assumption of a constant sticking coefficient leads to a first-order model of the kinetics. A solution of the problem of adsorption from a semi-infinite medium with first-order kinetics at the boundary was obtained by numerical simulation on the computer. The results of the computer simulations match the time dependence observed experimentally. A correlation was developed to estimate phi from experimental data. phi has been found to be in the range 10(-5)-10(-8) for several protein adsorption kinetic studies reported in the literature.

A hydrophobicity gradient was created by gradually exposing a polydimethylsiloxane film to a radio frequency glow discharge in an oxygen atmosphere. A change in contact angle from 100 to 0 degrees was measured along the gradient surface by means of the Wilhelmy balance technique. The gradient surface was characterized by studying the adsorption from single protein solutions of human albumin, IgG and fibrinogen using total internal reflectance fluorescence (TIRF). Generally, adsorption values similar to monolayer capacities were measured on the hydrophobic side. The adsorption decreased towards the hydrophilic end in correspondence with the change in contact angle. The displacement of proteins with a ethylene oxide-propylene oxide copolymer (EO70PO100EO70) was higher on the hydrophobic side than on the hydrophilic side. Albumin showed an adsorption peak in the wetting transition region, indicating a very strong affinity.

The bulk and surface properties and blood compatibility of a series of polyurethanes based on methylene bis(p-phenyl isocyanate), 1,4-butanediol, and poly(tetramethylene oxide) of molecular weight 1000 were studied. The hard-to-soft segment ratio of these multiphase polymers was varied, and the effect of substituting a poly(dimethylsiloxane)-containing polyol in place of 5% of the polyether soft segment was studied. Bulk properties such as tensile strength and modulus increased with hard segment content, as did surface wettability and ESCA nitrogen content. However, blood compatibility measured by a canine ex vivo blood-contacting experiment was not found to vary with hard/soft segment ratio. The addition of the silicone-containing polyol did not significantly lower the surface wettability, although ESCA-measured silicon content increased and physical properties were unfavourably affected by the incorporation of this co-soft segment. Incorporation of the siloxane-containing component resulted in increased platelet adhesion and fibrinogen deposition at most blood contact times in comparison with the other polyurethanes.

The effect of wall shear rate upon albumin adsorption onto a polyurethaneurea, Biomer, was studied using FTIR-ATR spectroscopy. In these experiments, nondiffusion controlled adsorption was observed from 10 mg/ml solutions at known wall shear rates. Results show that increasing wall shear rate during adsorption does not significantly affect the adsorption kinetics, but does decrease the rate of protein desorption. These results suggest that albumin adsorbed at higher shear rates is more tightly bound to the surface. Comparison of the data to simple mathematical models suggests that more than one layer of protein adsorbs in 2 h.

Linear alkyl chains containing 2, 10 and 18 carbon atoms were grafted to 10% of the urethane nitrogens in a polyether-polyurethane. The polyurethane was synthesized from methylene bis(p-phenyl isocyanate), 1,4-butanediol, and polytetramethylene oxide of 1000 molecular weight in a molar ratio of 3/2/1. Fourier transform infrared spectroscopy and attenuated total reflectance optics were used to study the adsorption of 5.0 mg/ml human serum albumin (HSA) at 37 degrees C to the derivatized and non-derivatized polymers. Both delipidized HSA and HSA containing 6.5 mol stearic acid per mol of albumin were used to study the effect of chain length upon the initial adsorption rate, the total amount adsorbed in 1 h, and the desorption rate. The initial adsorption rates revealed that non-specific adsorption was similar upon all four polymers. An increase in initial adsorption rate upon the C-18 derivatized polymer was attributed to a specific binding interaction between the HSA and the grafted alkyl chains. The conformational stability of the HSA also affected the adsorption rate. The total amount adsorbed after 1 h decreased as the alkyl chain length increased from 2 to 18 methylene groups. The desorption rate decreased in magnitude as the alkyl chain length increased from C-2 to C-18. These results support a hypothesis that alkyl chain length influences the interaction between albumin and an alkylated polymer system.