may 17, 2007 final project presentation p e m pemplant co. maricela delgadillo kay furman yushan kim
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May 17, 2007Final Project Presentation
PE
M
PemPlant Co.
Maricela DelgadilloKay FurmanYushan Kim
PemPlant Co.2
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
coatings on titanium Images from http://www.medtronic.com/
Polyelectrolyte Multilayers (PEMs)
• Systems Analyzed▪ 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
PemPlant Co.3
Michael C. Berg March 2005
PAA PAAm PAH
PemPlant Co.
Validation: Methylene Blue
bare Ti
3.0/3.0
PAAm/PAA
• Solution of 1 M pH 7.0• Binds carboxylates
• Indicates adhesion of polymer on Ti substrates
2.0/2.0
PAH/PAA
PemPlant Co.PemPlant Co.5
Modulus by AFM
• Si3N4 nitride probe on cantilever to measure F vs s upon approach
• E obtained by linear regression of Hertzian contact model
• Ti substrate: E = 123 KPa• Glass: E = 500 Kpa1
• Surface roughness challenges
PAA/PAH 2.0/2.0 on Ti
1 Thompson et al., Biomaterials 26 (2005) 6836–6845
5.1sCFp
PemPlant Co.PemPlant Co.6
Bacteria Experiment: Methods
Samples in Staph. epidermidis bacteria solution [106 cells/mL]
2 h, 4 h, or 8 h 37°C incubation for cell adhesion
Remove sample, lay agar gel on top
Approx. 24 h incubation for growth of attached cells
Visible colonies:1 per adhered cell
TiGlass
Whole-slide photographyMicroscopy
PemPlant Co.
Whole-slide image analysis (WCIF ImageJ)
Bacteria Experiment: Methods
PemPlant Co.
Bacteria Results
Bacterial attachment on Ti PEM
0
10
20
30
40
50
bare 2.0/2.0 3.0/3.0
Surface on Ti Substrate
Col
onie
s /
sq c
m
2 h 4 h
*
• 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
PemPlant Co.
Bacterial Adhesion
Bare substrate 2.0/2.0 3.0/3.0Glass
Ti
• Surface features▪ Bacteria settle in imperfections on bare Ti▪ PEMs even prevent colony formation on features
40 μm
5 mm
PemPlant Co.10
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
Wear Assessment: Contact Angle
PemPlant Co.11
• Increased contact angle values after wearing
Contact angle wear assesment
0
10
20
30
40
50
60
70
80
90
worn
Bare Ti 2.0/2.0 3.0/3.0 nitrile glove
Wear Assessment: Bacteria
PemPlant Co.12
• Worn Ti samples remained bacterial resistantWear testing
0
2
4
6
8
10
12
14
16
18
20
bare 2.0/2.0 3.0/3.0
Col
onie
s /
sq.
cm
Worn Control
Stability in Buffer Solution
• 1 week in Phosphate-Buffered Saline (PBS)
• Demonstrated bacteria resistant after 1 wk in model biological fluid (n=3)
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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
PemPlant Co.14
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
PemPlant Co.15
Questions?
• Visit our website for more information: http://web.mit.edu/3.042/team1_07/
• Thank you!PemPlant Co.
16
PE
M
PemPlant Co.
Backup
PemPlant Co.18
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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