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PemPlant Co.
May 17, 2007
Final Project Presentation
Maricela Delgadillo
Kay Furman
Yushan Kim
Industrial Application: Medical Devices
• Pacemakers and Defibrillators
▪ Correct abnormal heart rhythm
▪ Size: 1.7x1.9x.3 in; 2.4x2x0.6 in
• Potential for Bacteria Exposure
▪ 6% of all vascular surgeries result
in surgery site infection (HPA)
▪ Skin contact, handling, open wound
▪ 1-2 hr surgical procedure
▪ Current standard of care: antibiotics
• Our Solution:
▪ Antibacterial poly-electrolyte multilayer
2
coatings on titanium
PemPlant Co.
Images from http://www.medtronic.com/
Polyelectrolyte Multilayers (PEMs)
• Systems Analyzed
PAA
PAAm
PAH
▪ 3.0/3.0 polyacrylic
acid/polyacrylamide
(PAA/PAAm)
◦ 5.5 Bilayers
◦ Crosslink 130ºC for 2 hrs
▪ 2.0/2.0 polyacrylic
acid/polyallylamine
hydrochloride (PAA/PAH)
◦ 9.5 Bilayers
◦ Crosslink 80ºC for 30 min
Michael C. Berg March 2005
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PemPlant Co.
Validation: Methylene Blue
bare Ti
3.0/3.0
2.0/2.0
PAAm/PAA
PAH/PAA
• Solution of 1 M pH 7.0
• Binds carboxylates
• Indicates adhesion of
polymer on Ti
substrates
PemPlant Co.
Modulus by AFM
PAA/PAH 2.0/2.0 on Ti
• Si3N4 nitride probe on
cantilever to measure F vs
s upon approach
• E obtained by linear
regression of Hertzian
contact model
Fp  C  s1.5
• Ti substrate: E = 123 KPa
• Glass: E = 500 Kpa1
• Surface roughness
challenges
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PemPlant Co.
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Thompson et al., Biomaterials 26 (2005) 6836–6845
Bacteria Experiment: Methods
2 h, 4 h, or 8 h
37°C incubation
for cell adhesion
Samples in Staph.
epidermidis bacteria
solution [106 cells/mL]
Microscopy
Glass
Whole-slide
photography
Remove
sample, lay agar
gel on top
Approx. 24 h
incubation for
growth of attached
cells
Ti
Visible colonies:
1 per adhered cell
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PemPlant Co.
Bacteria Experiment: Methods
Whole-slide image analysis
(WCIF ImageJ)
PemPlant Co.
Bacteria Results
Bacterial attachment on Ti PEM
50
2h
4h
40
Colonies / sq cm
• Ti performs well as a
PEM substrate
• Effects withstand
time-course test of 4
hours
• Decreased bacteria
viability over time:
8 hour adhesion
incubation yielded no
viable bacteria
30
20
10
*
0
bare
2.0/2.0
3.0/3.0
Surface on Ti Substrate
PemPlant Co.
Bacterial Adhesion
Bare substrate
2.0/2.0
3.0/3.0
Glass
40 μm
Ti
5 mm
• Surface features
▪ Bacteria settle in imperfections on bare Ti
▪ PEMs even prevent colony formation on features
PemPlant Co.
Wear Testing Apparatus/Procedure
• Finger Pressure ~
50g-100 g
• Probe mass: 61.3 g
▪ 50 g weight
▪ Rubber ball
▪ Casting wax
• Wore samples for 10
min at 2 rpm  20
swipes
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PemPlant Co.
Wear Assessment: Contact Angle
• Increased contact angle values after wearing
Contact angle wear assesment
90
80
70
60
50
worn
40
30
20
10
0
Bare Ti
2.0/2.0
3.0/3.0
nitrile glove
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PemPlant Co.
Wear Assessment: Bacteria
• Worn Ti samples remained bacterial resistant
Wear testing
20
Worn
18
Control
Colonies / sq. cm
16
14
12
10
8
6
4
2
0
bare
2.0/2.0
3.0/3.0
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PemPlant Co.
Stability in Buffer Solution
• 1 week in Phosphate-Buffered Saline (PBS)
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• Demonstrated bacteria resistant after PemPlant
1 wk in
Co.
model biological fluid (n=3)
Conclusion
• Primary deliverables:
▪ PEM deposited on titanium
▪ Demonstrated bacteria resistant properties
▪ Sustained properties at 4 h bacteria exposure
▪ Properties retained after handling simulation,
after 1 week in model fluid environment
• Recommend 2.0/2.0 system
• Ready for animal studies, industrial
implementation
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PemPlant Co.
Acknowledgements
•
•
•
•
•
Prof. Chiang, Todd Thompson
Joe Parse, Yin-Lin Xie, Mike Tarkanian
Prof. Van Vliet, Prof. Rubner
Jenny Lichter, Alan Scwartzman, David Bono
3.042 Classmates
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PemPlant Co.
Questions?
• Visit our website for more information:
http://web.mit.edu/3.042/team1_07/
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• Thank you!
M
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PemPlant Co.
Backup
PemPlant Co.
Wear Assessment: Profilometry
• Profilometry conducted on Tencor P-10 surface profiler
• 2 μm radius diamond stylus scans at 6.0 mg
• 590 μm scan on a scratched film:
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PemPlant Co.