Transcript
Polymers In Medicine
Jeremy C. Robinson
Pierre M. Saint Louis
Anoop Padmaraju
Jeremy C. Robinson
Pierre M. Saint Louis
Anoop Padmaraju
Overview
• Introduction• Brief History• Applications
– 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 Applications of Biomaterials2
Polymer Applications Polymer Applications PDMS Catheters, heart Polytetrafluoroe Heart valves
Valves thylene Vascular grafts
Nerve repair
Polyurethane ventricular assist Polyethylene Catheters, hip
Devices 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!
References1. Peppas, N., Langer, R. “New challenges in bio-
materials”, Science, Vol. 263, March, 19942. Andreadis, S., “Applications of Biomaterials”,
Tissue engineering handout, February 2001, University at Buffalo.
3. “History and Development of Biomaterials”, www.bae.ncsu.edu/Courses/bae465
4. Fried, J. R., “Polymer Science and Technology.”, Prentice Hall, New Jersey 1995
5. “Cellophane Invention”, http://inventors.about.com/science/inventors/library/inventors/blcellophane.htm
6. “First Dialysis Unit”, www.ucl.ac.uk/uro-neph/history/dialysis.htm
7. “Dialysis and the Artificial Kidney”, www.chemengineer.about.com/science/chemengineer/library/weekly/aa120897.htm
8. 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 Polymer-grafted 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 EndThank You!