 In the United States over 300 million central venous catheters are used each year  200,000 users of these catheters are subject to life- threatening complications

 Polyurethane catheters can be coated with polyethylene oxide (PEO) brush layers › Hydrophobic association  PEO brush layers can resist adsorption of human blood proteins  Can also resist adhesion of bacteria HYDROPHOBIC HYDROPHILIC PEO PPO HYDROPHOBIC SURFACE

 Brush layers can be loaded with nisin › Lantibiotic › Effective against Gram positive bacteria › Does not give rise to resistant strains

HYDROPHOBIC BACTERIA PROTEIN

 To see if PEO brush layers will retain steric repulsive character when loaded with nisin.  To better understand nisin adsorption and elution behavior based on PEO chain length.

 If PEO chains are in the brush configuration, a nisin-loaded PEO layer will retain its steric-repulsive character.  If the outermost nisin molecules are eluted from a nisin-loaded PEO layer, the PEO segments extending beyond the level of entrapped nisin will regain their ability to provide a steric repulsive barrier to blood protein adsorption.

 Prepare model hydrophobic surfaces by coating (1 micron) silica microspheres with trichlorovinylsilane (TCVS).  Coat derivatized surfaces with PEO- containing triblock polymer chains (BASF Pluronic ® ) of varying lengths, and stabilize with gamma irradiation

 Experimental Design › Contacted with sodium lauryl sulfate (SDS) › Contacted with fibrinogen only › Contacted with nisin and subsequently with fibrinogen  Detect surface changes using zeta potential › Bare silanized surface has a strongly negative charge › Polymer coated surface has a more neutral charge › Nisin has a positive charge › Fibrinogen has a negative charge (lesser)

 Experimental design › Contacted F108 coated spheres with nisin  Can detect surface composition › Uses electron beam to excite electrons of atoms in sample › Energy released indicates presence of specific atoms › Can take images of sample, scanning electron microscope (SEM)

F108 coatedTCVS SilanizedF108 coated w/nisin

 Experimental design › Contacted with nisin  Can detect surface composition › Uses x-ray beam to excite electrons of atoms in sample › Kinetic energy of ejected electrons is indicative of specific elements › More sensitive than EDS › Can differentiate between same atoms with different bond types

 Zeta potential analysis showed: › F108 Pluronic attached in a stable fashion to microspheres › The F108 was in a steric repulsive brush configuration  EDS and SEM analyses showed: › F108 presence on surface of Pluronic coated microspheres › Could not detect nisin adsorption in brush layers  XPS showed: › F108 presence on surface › Nisin adsorption detected

 Continue chain length study using other surface analytical approaches  Study the potency, over time, of nisin against bacteria when loaded in F108 brush layers  Study molecular factors that affect peptide integration into PEO brush layers

Special thanks to:  Dr. Joseph McGuire  Dr. Karl “Rat” Schilke  Ben Steyer  Dr. Woo Kul Lee  Brynn Livesay  Julie Auxier  Steve Golledge (Camcor)  Dr. Kevin Ahern  Dr. Skip Rochefort  Howard Hughes Medical Institute  Johnson Scholars