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

PEO

PPO

HYDROPHOBIC SURFACE

Brush layers can be loaded with nisin› Lantibiotic› Effective against

Gram positive bacteria

› Does not give rise to resistant strains

Nisin

Contact withblood proteins

HYDROPHOBIC

PROT

EI

N

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 Silanized F108 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