Thrombosis on blood-contacting medical devices can cause patient fatalities through device failure and unstable thrombi causing embolism. The effect of material wettability on fibrin network formation, structure, and stability is poorly understood. Under static conditions, fibrin fiber network volume and density increase in clots formed on hydrophilic compared to hydrophobic polystyrene surfaces. This correlates with reduced plasma clotting time and increased factor XIIa (FXIIa) activity. These structural differences are consistent up to 50 μm away from the material surface and are FXIIa dependent. Fibrin forms fibers immediately at the material interface on hydrophilic surfaces but are incompletely formed in the first 5 μm above hydrophobic surfaces. Additionally, fibrin clots on hydrophobic surfaces have increased susceptibility to fibrinolysis compared to clots formed on hydrophilic surfaces. Under low-flow conditions, clots are still denser on hydrophilic surfaces, but only 5 μm above the surface, showing the combined effect of the surface wettability and coagulation factor dilution with low flow. Overall, wettability affects fibrin fiber formation at material interfaces, which leads to differences in bulk fibrin clot density and susceptibility to fibrinolysis. These findings have implications for thrombus formed in stagnant or low-flow regions of medical devices and the design of nonthrombogenic materials.
Catheter-associated biofilms are responsible for a large fraction of hospital acquired infections. Antimicrobial surface coating on catheters providing prevention at source is extensively studied to reduce bacterial adhesion. Antimicrobial peptides such as melimine and Mel4, covalently linked to surfaces have shown excellent potential in animal and human studies to suppress infection without toxicity. Covalent binding of the peptides on catheter surfaces improves efficacy but so far has been implemented using multi-step wet chemical coupling that will impede widespread adoption. Here we demonstrate plasma immersion ion implantation (PIII) as a single step treatment that covalently couples antimicrobial peptides to polyvinyl chloride (PVC). Strong antimicrobial activity was demonstrated by higher than 3 log kill of S. aureus. A variant of the process was demonstrated as an antimicrobial treatment for chemically inert glass surfaces. Covalent coupling was rigorously tested by stringent SDS washing. We further demonstrated that the plasma treatment can effectively functionalize both internal and external surfaces of catheter tubing, reducing 99% of bacterial adhesion. The process is feasible as a patient-safe treatment for treating various types of catheters and is suitable for commercial mass production. In a logical extension of the work, the process could be adapted to bone replacement scaffolds of all types including metallic, polymeric and ceramic.
The plasma physics of dielectric barrier discharges (DBD) for carrying out ion implantation in insulators is investigated. A hollow cathode DBD excited by high-voltage pulses is suitable for ion bombardment of the surfaces of insulating tubing, porous material, particles and sheets. Plasma immersion ion implantation of insulating surfaces is useful for many applications in medicine and engineering. The ion bombardment of glass is useful for cleaning and surface modification. The ion implantation of polymers creates radicals that are able to bind molecules to their surfaces for applications in medical procedures and diagnostics. A wire diagnostic probe and optical emission spectroscopy are used for experimental work. A theory based on mutual capacitance is developed to convert data from the probe to give implanted charge as a function of pressure, voltage and pulse duration. We find the operating conditions that allow for charge to be implanted and those that achieve the highest implanted charge.
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