Transcript In the United States over 300 million central venous catheters

In the United States
over 300 million
central venous
catheters are used
each year
 200,000 users of
these catheters are
subject to lifethreatening
complications

› Hydrophobic
HYDROPHILIC
PEO
Polyurethane
catheters can be
coated with
polyethylene oxide
(PEO) brush layers
PEO

PPO
HYDROPHOBIC
association
PEO brush layers can
resist adsorption of
human blood proteins
 Can also resist
adhesion of bacteria

HYDROPHOBIC SURFACE

Brush layers can be
loaded with nisin
› Lantibiotic
Nisin
› Effective against
Gram positive
bacteria
› Does not give rise to
resistant strains
Contact with
blood proteins
HYDROPHOBIC
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 PEOcontaining 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)
60
Unchallenged
Zeta Potential (– mV)
50
SDS Wash
40
30
20
10
0
TCVS
Silanized
F108
F68
P105
P65
L101
L61
55
Unchallenged
45
Challenge 1
Zeta Potential (– mV)
Challenge 2
35
Challenge 3
25
15
5
-5
-15
TCVS Silanized
F108
60
Zeta Potential (– mV)
50
40
Unchallenged
Nisin
Challenge 1
Challenge 2
Challenge 3
30
20
10
0
-10
F108 - Buffer
F108 - Fibrinogen
TCVS Silanized Buffer
TCVS Silanized
- Fibrinogen

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)
25
Carbon Atomic Percent
Atomic Percentage
20
Nitrogen Atomic Percent
15
10
5
0
TCVS Silanized
F108
F108 w/nisin
TCVS Silanized
F108 coated
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
60
Carbon Atomic
Percentage
Atomic Percentage
50
Nitrogen Atomic
Percentage
40
30
20
10
0
TCVS
TCVS w/ nisin
F108
F108 w/ nisin

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
