PolymersInMedicine.ppt

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!