Polymers In Medicine

1. Polymers In Medicine Jeremy C. Robinson Pierre M. Saint Louis Anoop Padmaraju

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

3. 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.

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

7. 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

10. PGA, PLA, PLGA

11. 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

12. 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

13. 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

14. Polydimethylsiloxane • “Silicon” • Lubricants and Foaming agents • Pacemakers and Vaccine Delivery systems

15. 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

16. 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

17. 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

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

19. 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

20. 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

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

22. 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

23. Ventricular Assist Device

24. 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

25. 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

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

27. 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/history/dialysis.htm • “Dialysis and the Artificial Kidney”, www.chemengineer.about.com/science/chemengineer/library/weekly/aa120897.htm • www.beyonddiscovery.com

28. 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”)

29. 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

30. The EndThank You!