Post on 02-Jun-2018
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Medical Biomaterials:From Polymer Implants to Engineered Tissues
Sujata K. BhatiaHarvard University
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Why get involved with medical biomaterials? The incidence of major chronic diseases, including
diabetes, heart disease, and cancer, is rising
The United States has a graying population: in 2030,
over 20% of the U.S. population will be over age 65
(battling degenerative diseases - arthritis, Alzheimers)
These diseases will require innovative medical device
solutions; drugs and lifestyle changes are not enough
Medical devices are extremely beneficial - every $1spent on healthcare returns $3 worth of health gains
Medical devices are valuable a $150 billion industry
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OK, but why shouldI get involved?
Medical biomaterials is a fascinating field,integrating principles of engineering,
biology, chemistry, and medicine
Working in this field allows you to improve
the practice of medicine, and directlyimpact peoples lives
We can be heroesWe can be heroeswhat dwhat dyou say?you say?--David Bowie, 1977David Bowie, 1977
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A person is,A person is,
among all else,among all else,
a material thing,a material thing,easily torn,easily torn,
not easily mended.not easily mended.
--Ian McEwan,Ian McEwan,AtonementAtonement, 2001, 2001
The ParalyticJean-Baptiste Greuze, 1763
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What is a biomaterial anyway?
A biomaterial is a nonviable material usedin a medical device, intended to interact
with biological systems
An essential characteristic of biomaterials is
biocompatibility, the ability of the materialto perform its function without causing an
adverse effect
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Requirements of Biomaterials
Mechanical performance
Mechanical engineering
Desired characteristics of stability or degradability
Chemistry and biochemistry
Biocompatibility and non-toxicity
Molecular biology
Producible at a large scale
Chemical engineering
Clinically beneficial and cost-effective
Medicine
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Clinical Applications ofBiomaterials Orthopedics
Cardiology and Vascular Medicine
Ophthalmology
Dentistry Neurology
General Surgery
Organ Replacement
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Orthopedic Biomaterials Hip replacements
Titanium, polyethylene, ceramic
Knee replacements Titanium, polyethylene
Bone plates (fracture fixation)
Stainless steel Bone cement
Poly(methyl methacrylate)
Bony defect repair Hydroxyapatite
Artificial tendons & ligaments
Dacron, Teflon
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Cardiovascular Biomaterials Blood vessel prostheses
Dacron, Teflon, polyurethane
Heart valves Reprocessed tissue, stainless steel
Intravascular catheters
Polyurethane, Teflon, silicone Pacemakers
Platinum electrodes,
polyurethane, silicone
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Ophthalmic Biomaterials Intra-ocular lens
Poly(methyl methacrylate)
Contact lens Silicone-acrylate, hydrogel
Corneal bandage
Collagen, hydrogel
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Dental Biomaterials Dental implants (tooth fixation)
Titanium, alumina, calcium
phosphate Dental fillings
Ceramic, composites of powdered
glass and plastic resins
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Biomaterials in Neurology Cochlear implants
Platinum electrode
Deep brain stimulation Pacemaker for the brain
Platinum leads
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Biomaterials in General Surgery Skin repair template
Silicone-collagen composite
Surgical sutures Silk, nylon, poly(glycolide-co-
lactide)
Adhesives and sealants Cyanoacrylate, fibrin
Hernia mesh
Polypropylene
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Organ Replacement Biomaterials Heart-lung machine
Silicone rubber
Artificial kidney(hemodialyzer)
Cellulose, polyacrylonitrile
Artificial heart Polyurethane
Hollow-fiber
dialyzer
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Shortcomings of CurrentBiomaterials
Infection Thrombosis (clotting)
Inflammation
Poor healing, leading toencapsulation
Limited durability
Limited adaptability toenvironment
Limited biological activity
Chronic inflammation around wear
debris of polyethylene elbow
prosthesis (top) and knee prosthesis
(bottom)
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The Next Generation ofBiomaterials Surface-modified biomaterials
Dr. Buddy Ratner (University of Washington)
Smart biomaterials
Dr. Nick Peppas (University of Texas, Austin) Bioactive biomaterials
Dr. Elazer Edelman (Harvard/MIT)
Tissue engineered materials
Dr. Robert Langer (MIT)
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Surface-Modified Biomaterials
Attack on a
biomaterial beginswith deposition of
proteins or cells on
the outer surface of
the biomaterial
Maybe attack can be prevented if biomaterialsurfaces are modified to create stealth
surfaces that resist protein & cell adsorption
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Surface-Modified Biomaterials Surface modification can be achieved by
coating with hydrophilic polymer (PEG) Surface-modified biomaterials should be
resistant to clotting, bacterial colonization,
and the foreign body responseU. Washington
Engineered
Biomaterials
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Smart Biomaterials Smart biomaterials
are materials thatrespond to changes
in pH, temperature,
electrical stimuli, orchemical stimuli
These materials can
be made using pH-sensitive or thermo-
sensitive polymers
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Smart Biomaterials Hydrogels with pH-responsive swelling
behavior are made from ionic networks Poly(methacrylic acid) grafted with
poly(ethylene glycol)
Temperature-responsive hydrogels exist also Poly(N-isopropylacrylamide)
Smart biomaterials may have powerfulapplications in drug delivery
An insulin pill that encapsulates drug at pH 2
in the stomach, and swells to release drug at pH 7
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Bioactive Biomaterials Several bioactive biomaterials are already on
the market, with a dramatic clinical impact: Drug-eluting stents for minimally invasive
treatment of coronary artery disease
Chemotherapeutic(BCNU)-eluting wafersfor local treatment of brain cancer
Lupron-releasing implants for local
treatment of prostate cancer Bone-morphogenic protein (BMP)-
releasing implants for spinal surgery and
fracture repair
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Tissue Engineering
Tissue engineering is an
approach to organregeneration in which live
cells are seeded onto a
degradable polymer scaffold
Following implantation,
the polymer constructgradually degrades, and
the live cells grow into
organized tissue
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Tissue Engineering
Tissue engineering has been investigated for
virtually every organ system: Dermal fibroblasts + collagen matrix Skin (in clinical use)
Vascular endothelial cells + tubular scaffold Blood vessels
Vascular endothelial cells + leaflet scaffold
Heart valves Urothelial cells + tubular or flat scaffold Ureters, Bladder
Chondrocytes + molded scaffold Cartilage
Periosteal cells + polymer mesh Bone
Hepatocytes + polymer mesh Liver Enterocytes + tubular scaffold Intestine
Neurons + electrically conducting polymerNerves
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We can rebuild him. WeWe can rebuild him. Wehave the technology. Wehave the technology. We
have the capability to makehave the capability to make
the worldthe worlds first bionic man.s first bionic man.
Steve Austin will be thatSteve Austin will be that
man. Better than he wasman. Better than he wasbefore.before.
BetterBetterstrongerstronger faster.faster.
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Summary Biomaterials have improved
millions of lives by providingmaterial solutions to biomedical
problems
Traditional biomaterials have beenmade from polymers, ceramics, and
metals
The next generation of biomaterials
will incorporate biomolecules,
therapeutic drugs, and living cells
The Agnew Clinic
Thomas Eakins, 1889
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So, do biomaterials make a difference?
50 years ago certain death
25 years ago open bypass surgery
Involves cracking open the chest cavity
Infection, graft clotting, graft failure
15 years agoballoon angioplasty
Vascular injury by balloon; incomplete opening 10 years agobare-metal stent
Risk of re-closure of artery within a few years
Today drug-eluting stent
Combination of drug and device provides lasting solution
Supposeyourdad has a heart attack:
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For More Information Biomedical Engineering Society - www.bmes.org
Society for Biomaterials - www. biomaterials.org
Advanced Medical Technology - www.advamed.org
Science Careers - nextwave.sciencemag.org
Langer, R. and Peppas, N.A. Advances in biomaterials,
drug delivery, and bionanotechnology, AIChE J. 2003;49:2990-3006.
Langer, R. and Tirrell, D.A. Designing materials forbiology and medicine, Nature 2004 Apr 1; 428:487-492.
Bhatia, S.K. and Bhatia, S.R. Biomaterials,Encyclopedia of Chemical Processsing 2005.
Bhatia, S.K. and Bhatia, S.R. Bioactive Devices,Encyclopedia of Chemical Processsing 2009.