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8/11/2019 Bio materials Chapter 10
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www.biomat.net 10/1/20041. Marrow stem cells could heal broken
bones, Betterhumans
2. Newly grown kidneys can sustain life
in rats, Bio.com3. Doctors grow new jaw in man's back ,
CNN
4. FDA approves implanted lens fornearsightedness, CNN
5. Stent recall may raise qualityexpectations, Medical Device Link
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Wright Medical Technology-TN
The REPIPHYSIS® works by inserting anexpandable implant made from titanium in an
aerospace polymer into the child’s healthybone, after which standard recovery andrehabilitation are expected. However, insteadof undergoing repeated surgeries to extend
the bone, the REPIPHYSIS® uses anelectromagnetic field to slowly lengthen theimplant internally.
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A biomaterial is "any substance (other than drugs)or combination of substances synthetic or natural
in origin, which can be used for any period of time,as a whole or as a part of a system which treats,augments, or replaces any tissue, organ, orfunction of the body".
Biocompatibility — The ability of a material toperform with an appropriate host response in aspecific application
Host Response — The response of the host
organism (local and systemic) to the implantedmaterial or device.
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MicroTest Laboratories - example
Our In-vitro toxicity services are
performed by our experienced
and fully trained microbiologists
In- Vivo Services:
Rabbit Pyrogen
USP Class Testing
Sensitization
ImplantationSub-Chronic/Chronic
Toxicity
Intracutaneous Reactivity
Irritation Testing
Necropsy Services
Histology Services
In-Vitro Services:
Cytotoxicity
Hemolysis
Complement Activation
PT/PTT TestingAMES Mutagenicity
Carcinogencity Testing
Methods
USP
ISO
JP
EP/BP
FDA
ASTM
All Animal Testing is
performed in a fully
AAALAC accredited
facility
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Keywords
Metallic/glass/Polymeric/Ceramic/Composite
Fracture/fatigue/creep/corrosion/degradation
Tissue response/healing/biocompatibility/host
response/carcinogenicity
Hard/soft tissue implants
Vascular/Breast/Urological/Art. Organ
Mucosal contacting …
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Material Selection Parameters
Mechanical
Thermal/Electrical Conductivity
Diffusion
Water Absorption
Biostability
Biocompatibility
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Value Location
H 6.8 Intracellular 7.0 Interstitial7.15-7.35 Blood
O2 2-40 Interstitial mm H40 Venous100 Arterial
Tem erature 37 Normal Core
28 Normal SkinMechanical Stress 4x10
7 N m
-2Muscle eak stress
4x108 N m
-2Tendon eak stress
Stress C cles er ear 3x105
Peristalsis5x10
6 - 4x10
7Heart muscle contraction
Test Conditions:
Length of implant: Day: Month: Longer:
Where used: skin/blood/brain/mucosal/etc.
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Bulk
Material
Surface Layer
of Material
Adsorbed layer of
water, ions &
proteins
Cells in
biological
fluid
Biocompatibility is primarily a surface phenomenon…
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Test Animals
• Rabbits – ear, skin, pyrogen
• Guinea Pigs – skin, esp C@
• Mice – genotoxicity• Horseshoe Crab – endotoxins
• Pig – implant
• Bacteria - genotoxicity• Test actual & elutants & extracts…
• People – long term
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Some Commonly Used Biomaterials
Material ApplicationsSilicone rubber Catheters, tubing
Dacron Vascular graftsCellulose Dialysis membranesPoly(methyl methacrylate) Intraocular lenses, bone cementPolyurethanes Catheters, pacemaker leadsHydogels Opthalmological devices, Drug DeliveryStainless steel Orthopedic devices, stents
Titanium Orthopedic and dental devices Alumina Orthopedic and dental devicesHydroxyapatite Orthopedic and dental devicesCollagen (reprocessed) Opthalmologic applications, wound
dressings
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An Interdisciplinary Field
Bioengineers
Material Scientists
Immunologists
Chemists
Biologists
Surgeons
...
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Journals
Biomaterials World News
Materials Today
Nature
Journal of Biomedical Materials Research Cells and Materials
Journal of Biomaterials Science
Artificial Organs
ASAIO Transactions
Tissue Engineering
Annals of Biomedical Engineering
Medical Device Link
… see: http://www.biomat.net/biomatnet.asp?group=1_5
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A Little History on Biomaterials• Romans, Chinese, and Aztecs used gold in
dentistry over 2000 years ago, Cu not good.
• Ivory & wood teeth
• Aseptic surgery 1860 (Lister)• Bone plates 1900, joints 1930
• Turn of the century, synthetic plastics cameinto use
– WWII, shards of PMMA unintentionally got lodgedinto eyes of aviators
– Parachute cloth used for vascular prosthesis
• 1960- Polyethylene and stainless steel being
used for hip implants
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Uses of Biomaterials
• Replace diseased part – dialysis
• Assist in healing – sutures
• Improve function – contacts• Correct function – spinal rods
• Correct cosmetic – nose, ear
• Aid dx – probe
• Aid tx – catheter• Replace rotten – amalgam
• Replace dead - skin
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Problems/test for wBiomaterials
• Acute toxicity (cytotoxicity) arsenic
• Sub chronic/chronic Pb
• Sensitization Ni, Cu• Genotoxicity
• Carcinogenicity
• Reproductive &/or developmental Pb
• Neurotoxicity• Immunotoxicity
• Pyrogen, endotoxins
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FDA & ISO 10993
• FDA mandates tests based on length ofcontact (24 Hr, 1-30 Days, >30 days)
• See table for details• ISO 10993 – required for European
Union Certification – see flowchart for
exemptions• See Device Categories & examples
• Harmonization – in process…
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First Generation Implants
• ―ad hoc‖ implants • specified by physicians using common and borrowed
materials
• most successes were accidental rather than by
design
Examples — First Generation Implants
• gold fillings, wooden teeth, PMMA dental prosthesis
• steel, gold, ivory, etc., bone plates
• glass eyes and other body parts
• dacron and parachute cloth vascular implants
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Intraocular Lens3 basic materials - PMMA, acrylic, silicone
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Vascular Grafts
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Second generation implants
• engineered implants using common and borrowed materials• developed through collaborations of physicians and engineers
• built on first generation experiences
• used advances in materials science (from other fields)
• titanium alloy dental and orthopaedic implants
• cobalt-chromium-molybdinum orthopaedic implants
• UHMW polyethylene bearing surfaces for total joint replacements
• heart valves and pacemakers
Examples — Second generation implants
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Artificial Hip Joints
http://www.totaljoints.info/Hip.jpg
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Third generation implants• bioengineered implants using bioengineered materials
• few examples on the market
• some modified and new polymeric devices
• many under development
Example - Third generation implants
•tissue engineered implants designed to regrow rather than replace tissues
•Integra LifeSciences artificial skin
•Genzyme cartilage cell procedure
•some resorbable bone repair cements•genetically engineered “biological” components (Genetics Institute and
Creative Biomolecules BMPs)
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Substitute Heart Valves
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SEM displaying the cross section of a composite disk,which had been seeded with cultured bone marrow
stromal cells.
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Synthetic polymer scaffolds
... in the shape of a nose (left) is "seeded" with cells called
chondrocytes that replace the polymer with cartilage over time
(right) to make a suitable implant.
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Evolution of Biomaterials
Structural
Functional Tissue
Engineering Constructs
Soft Tissue
Replacements
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Advances inBiomaterials Technology
• Cell matrices for 3-D growth and tissuereconstruction
• Biosensors, Biomimetic , and smart devices• Controlled Drug Delivery/ Targeted delivery
• Biohybrid organs and Cell immunoisolation
– New biomaterials - bioactive, biodegradable,inorganic
– New processing techniques
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Metals
Semiconductor
Materials
Ceramics
Polymers
Synthetic
BIOMATERIALS
Orthopedic
screws/fixation
Dental Implants Dental Implants
Heart
valves
Bone
replacements
Biosensors
Implantable
Microelectrodes
Skin/cartilageDrug Delivery
DevicesOcular
implants
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Biomaterials for TissueReplacements
• Bioresorbablevascular graft
• Biodegradable nerveguidance channel
• Skin Grafts
• Bone Replacements
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Biomaterials - An EmergingIndustry
• Next generation of medical implantsand therapeutic modalities
• Interface of biotechnology andtraditional engineering
• Significant industrial growth in the next
15 years -- potential of a multi-billiondollar industry
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Biomaterials Companies
• BioForma Research & Consulting, Inc., fibrinolytic systems, protein-material interactions
• Baxter International develops technologies related to the blood and circulatory system.
• Biocompatibles Ltd. develops commercial applications for technology in the field of biocompatibility.
• Carmeda makes a biologically active surface that interacts with and supports the bodys own control mechanisms
• Collagen Aesthetics Inc. bovine and human placental sourced collagens, recombinant collagens, and PEG-polymers
• Endura-Tec Systems Corp. bio-mechanical endurance testing ofstents, grafts, and cardiovascular materials
• Howmedica develops and manufactures products in orthopaedics.
• MATECH Biomedical Technologies, development of biomaterials by chemical polymerization methods.
• Medtronic, Inc. is a medical technology company specializing in implantable and invasive therapies.
• Molecular Geodesics Inc., biomimetic materials for biomedical, industrial, and military applications
• Polymer Technology Group is involved in the synthesis, characterization, and manufacture of new polymer products.
• SurModics, offers PhotoLink(R) surface modification technology that can be used to immobilize biomolecules
• W.L. Gore Medical Products Division, PTFE microstructures configured to exclude or accept tissue ingrowth.
• Zimmer, design, manufacture and distribution of orthopaedic implants and related equipment and supplies
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What are some of theChallenges?
• To more closely replicate complex tissuearchitecture and arrangement in vitro
• To better understand extracellular and
intracellular modulators of cell function• To develop novel materials and processing
techniques that are compatible with biological
interfaces• To find better strategies for immune
acceptance