Transcript Polymers In Medicine - University at Buffalo

Polymers In Medicine
Jeremy C. Robinson
Pierre M. Saint Louis
Anoop Padmaraju
Overview
• Introduction
• Brief History
• Applications
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Cellophane
PGA, PLA, PLGA
Polydimethylsiloxane
Polyethylene and PMMA
Polytetrafluoroethylene
Polyurethane
• The Future
Biomaterials
What are they?
• Substances other than food or drugs contained
in therapeutic or diagnostic systems that are in
contact with tissue or biological fluids
Why use Biomaterials?
• Improve patient’s quality of life by replacing a
defective body part with a substitute.
• Physicians were limited to use off-the shelf
supplies.
• Novel biodegradable polymers and modified
natural substances.
Table 1
2
Applications of Biomaterials
Polymer Applications
Polymer
Applications
PDMS
Catheters, heart
Polytetrafluoroe Heart valves
Valves
thylene
Vascular grafts
Nerve repair
Polyurethane ventricular assist
Polyethylene
Devices
Catheters, hip
prostheses
Polymethylmetha Fracture fixation
PGA, PLA, Drug delivery, devices crylate (PMMA)
And PLGA
Cellophane
Dialysis
membranes
History
• Biomaterials not practical till
1860’s
• 1900’s Biomaterials first used
• WWII, PMMA used to replace
damaged cornea
Cellophane
• “Saran Wrap”, Rayon (fiber)
• “Regenerated” Cellulose
• Invented 1908, Jacques E.
Brandenberger
• Kidney Dialysis
• Invented 1959, William J. Kolff
• Vegetable Parchment, Natural Casings
early membranes
Fig. 2 A schematic of an artificial kidney (hemodialysis)
Fig. 3 The regeneration of Cellulose (cellophane).
PGA, PLA, PLGA
PGA, PLA, PLGA
• First synthesized by Dupont from
Glycolic acid
• PGA, originally Dexon, absorbable
suture
• 1963 Schmitt & Polistina Invents
Biodegradable suture
• PLA & PLGA Drug delivery
systems
PGA, PLA, PLGA
• All polymers have low
polydisparity index (PLA 1.6-1.9)
• Depending on structure, polymers
can be fit for different applications
• Amorphous forms used in drug
delivery systems
• Crystalline forms good for
scaffolding, or sutures
PGA, PLA, PLGA
• Two essentials in scaffolding: high
surface to volume ratio, highly
porous
– Allows cells to easily proliferate for
setup of pathways
– Setup of pathways for nutrients
Polydimethylsiloxane
•“Silicon”
•Lubricants and Foaming agents
•Pacemakers and Vaccine Delivery systems
Polydimethylsiloxane
• Discovered 1927, Dr. Frederick Stanley
Kipping
• Vulcanized rubber, can’t be melted or
dissolved
• Low glass transition
• Produced by hydroxyl, groups through
hydrolysis, replace the 2 Cl in the
monomer
• Ring opening polymerization, Higher
MW
Polydimethylsiloxane
• Used in treatment of prostate
carcinoma
• Small biodegradable pellets
(188  m) injected into area of body
where needed.
• Smaller doses, less toxic effects for
patient

Polyethylene and PMMA
• Thermoplastics, exhibit moderate to
high tensile strength with moderate
elongation
• Used for Hip replacement and Fracture
Fixation
• Annual procedures approaching 5
Million
• Metal alternatives have corrosive
problems
PMMA
Fig. 4a PMMA disc over
femoral window during the
molding process
Fig. 4b PMMA template
after polymerization,
showing molded plug
Polytetrafluoroethylene
• High strength and Chemical resistance
• High modulus and tensile properties
with negligible elongation
• Used for orthopedic and dental devices
• Mechanical heart valve and implants
Polytetrafluoroethylene
• Excellent wear and fatigue
resistance
• Vascular grafts patch injured and
diseased areas of arteries
• Must be flexible to allow for the
difficulties of implantation and to
avoid adjacent tissue irritation
Polyurethane
• Shoe soles, tires and foams
• Thermoset, non-condensation step
growth
• Low molecular weight polymer (47,000)
• “Bridges” the gap between rubber and
plastic
Polyurethane
• One of the best load-bearing capacities
• Discovered 1937, Otto Baker
• Major medical uses Ventricular assist
device
• Developed by Dr. Liotta, Baylor, 1950’s
• Redefined by Pierce and Donachy in
1971
Ventricular Assist Device
Polyurethane
• VAD, used during open heart surgery,
postoperatively and in case of extreme
cardiac trauma
• Pierce and Donachy used segmented
polyurethane in their VAD
• Safe contact barrier compressive
properties made function similar to heart
ventricle
Polyurethane
• Obtained through step-growth
polymerization of diisocyanates
and dihydroxl compounds
• Injection molded
• R.I.M.
• Failures attributed to poor
processing, not physical material
properties
The Future
• Opportunities are limitless
• We as scientists and engineers are
faced with big challenges
• Potential and promise are
tremendous
Questions!
References
1.
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5.
6.
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8.
Peppas, N., Langer, R. “New challenges in biomaterials”, Science, Vol. 263, March, 1994
Andreadis, S., “Applications of Biomaterials”,
Tissue engineering handout, February 2001,
University at Buffalo.
“History and Development of Biomaterials”,
www.bae.ncsu.edu/Courses/bae465
Fried, J. R., “Polymer Science and Technology.”,
Prentice Hall, New Jersey 1995
“Cellophane Invention”,
http://inventors.about.com/science/inventors/library
/inventors/blcellophane.htm
“First Dialysis Unit”, www.ucl.ac.uk/uroneph/history/dialysis.htm
“Dialysis and the Artificial Kidney”,
www.chemengineer.about.com/science/chemengineer/libr
ary/weekly/aa120897.htm
www.beyonddiscovery.com
References
9.
Ikada, Y, Yoshihiko, S, “Tissue Engineering for
Therapeutic Use 4.” Elsevier, 2000, New York
10.
Pulverer, G., Schierholz, J. M., “Development of
New CSF-shunt With Sustained Release of Antimicrobial
Broad-Spectrum Combination.”, Baktercologie, Vol. 286,
107-123
11.
Loomes, L. M., Jian Xiong, J., Brook, M. A.,
Underdown, B. J., McDermott, M. R., “Novel Polymergrafted Starch Microparticles for Mucosal Delivery of
Vaccines.”, Immunology, Vol. 56, 162-168, 1996
12.
www.britannica.com, (keyword “polyethylene”)
13.
“Uses of Polymehtylmethacrylate”, www.rcsed.ac.uk
(Feb 2001)
14.
www.britannica.com, (keyword
“Polytetrafluoroethylene”)
References
15.
“Polyurethane – Features and Benefits”,
www.elastchem-ca.com/poly.html
16.
“Pierce-Donachy Ventricular Assist Device”,
www.asme.org/history/Roster/H142.html
17.
Liotta, D. “The Ventricular Assist Device”,
www.fdliotta.org
The End
Thank You!