Slide 1 - Oregon State University by wulinqing

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									 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                           HYDROPHILIC

    catheters can be




                         PEO




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

  adhesion of bacteria
   Brush layers can be
    loaded with nisin            Nisin

    › Lantibiotic
    › Effective against
      Gram positive
      bacteria
    › Does not give rise to
                              Contact with
                              blood proteins


      resistant strains
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 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)
                        60

                                                                               Unchallenged
                        50                                                     SDS Wash
Zeta Potential (– mV)




                        40



                        30



                        20



                        10



                        0
                             TCVS Silanized   F108   F68   P105   P65   L101          L61
                        55
                                                      Unchallenged
                        45                            Challenge 1
                                                      Challenge 2
                        35
Zeta Potential (– mV)




                                                      Challenge 3

                        25


                        15


                         5


                         -5


                        -15
                              TCVS Silanized   F108
                        60
                              Unchallenged
                        50    Nisin
                              Challenge 1
                              Challenge 2
Zeta Potential (– mV)




                        40
                              Challenge 3

                        30


                        20


                        10


                         0


                        -10
                              F108 - Buffer   F108 - Fibrinogen   TCVS Silanized -   TCVS Silanized
                                                                      Buffer          - 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

                    20   Nitrogen Atomic Percent
Atomic Percentage




                    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
                    50
                         Nitrogen Atomic
                         Percentage

                    40
Atomic Percentage




                    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

								
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