Polymers In Medicine

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Polymers In Medicine

• Jeremy C. Robinson
• Pierre M. Saint Louis
• Anoop Padmaraju

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Overview

• Introduction
• Brief History
• Applications
• Cellophane
• PGA, PLA, PLGA
• Polydimethylsiloxane
• Polyethylene and PMMA
• Polytetrafluoroethylene
• Polyurethane
• The Future

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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 patients 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.

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History

• Biomaterials not practical till 1860s
• 1900s Biomaterials first used
• WWII, PMMA used to replace damaged cornea

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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

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PGA, PLA, PLGA
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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

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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

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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

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Polydimethylsiloxane

• Silicon
• Lubricants and Foaming agents
• Pacemakers and Vaccine Delivery systems

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Polydimethylsiloxane

• Discovered 1927, Dr. Frederick Stanley Kipping
• Vulcanized rubber, cant 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

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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

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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

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PMMA
Fig. 4b PMMA template after polymerization,
showing molded plug
Fig. 4a PMMA disc over femoral window during the
molding process
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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

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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

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Polyurethane

• Shoe soles, tires and foams
• Thermoset, non-condensation step growth
• Low molecular weight polymer (47,000)
• Bridges the gap between rubber and plastic

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Polyurethane

• One of the best load-bearing capacities
• Discovered 1937, Otto Baker
• Major medical uses Ventricular assist device
• Developed by Dr. Liotta, Baylor, 1950s
• Redefined by Pierce and Donachy in 1971

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Ventricular Assist Device
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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

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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

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The Future

• Opportunities are limitless
• We as scientists and engineers are faced with big
  challenges
• Potential and promise are tremendous
• Questions!

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References

• Peppas, N., Langer, R. New challenges in
  bio-materials, 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/uro-neph/hist
  ory/dialysis.htm
• Dialysis and the Artificial Kidney,
  www.chemengineer.about.com/science/chemengineer/li
  brary/weekly/aa120897.htm
• www.beyonddiscovery.com
•              

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References

• 9. Ikada, Y, Yoshihiko, S, Tissue
  Engineering for Therapeutic Use 4. Elsevier,
  2000, New York
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• 10.         Pulverer, G., Schierholz, J. M.,
  Development of New CSF-shunt With Sustained
  Release of Antimicrobial Broad-Spectrum
  Combination., Baktercologie, Vol. 286, 107-123
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• 11.         Loomes, L. M., Jian Xiong, J., Brook,
  M. A., Underdown, B. J., McDermott, M. R., Novel
  Polymer-grafted Starch Microparticles for Mucosal
  Delivery of Vaccines., Immunology, Vol. 56,
  162-168, 1996
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• 12.         www.britannica.com, (keyword
  polyethylene)
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• 13.         Uses of Polymehtylmethacrylate,
  www.rcsed.ac.uk (Feb 2001)
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• 14.         www.britannica.com, (keyword
  Polytetrafluoroethylene)

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References

• 15.         Polyurethane Features and
  Benefits, www.elastchem-ca.com/poly.html
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• 16.         Pierce-Donachy Ventricular Assist
  Device, www.asme.org/history/Roster/H142.html
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• 17.         Liotta, D. The Ventricular Assist
  Device, www.fdliotta.org
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The EndThank You!