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BioE/ME C117 Structural Aspects of Biomaterials Course Overview Professor Lisa A. Pruitt, Ph.D. Associate Dean of Virtual Learning and Outreach Education Chancellor's Professor of Mechanical Engineering and Bioengineering Adjunct Professor of Orthopaedic Surgery, UCSF Structural Aspects of Biomaterials

Class Structure
CLASS: Tu/Th: 12:30-2pm 203 McLaughlin Hall
http://www.me.berkeley.edu/ME117
http://webcast.berkeley.edu
Discussion: Mondays, 203 Mclaughlin. Mechanics and design will be taught in discussion.
You are responsible for all material presented in discussion.
Office Hrs (Prof. Lisa Pruitt):Tuesdays 3-4:30 or by appointment,5134 EH, lpruitt@me
Teaching Assistants: Arun Chawan, Jevan Furmanski, Shikha Gupta, Sheryl Kane,
and Cheng Li (office hrs TBA)
Course components: HW (25%), EXAMS, April 11/13 (25%), TERM PROJECT (50%)
**No late homework excepted. All HW is to be prepared professionally (typed). Assignments will be marked down for grammatical errors.
This year our class is webcast. Please use microphones when asking questions.
Reader: CopyWorld

Course Goals
Assessment of structure and mechanical functions of load bearing tissues and their replacements.
Examination of biocompatibility of biomaterials and host response to structural implants.
Quantitative treatment of biomechanical issues and constitutive relationships of tissues and their replacements.
Material selection for load bearing applications including orthopedics, dentistry, cardiology and reconstructive surgery.
Mechanical design for longevity of devices
Understanding of legal and ethical aspects of medical devices.

Course topics
Overview of medical devices, FDA regulatory issues, biocompatibility and sterilization technology
Biomechanical properties: isotropy/anisotropy, stiffness,
bending stresses, contact stresses, multiaxial loading,
plasticity, fatigue, fracture, wear, corrosion, design issues.
Orthopedics, Dental, Cardiovascular, and Soft Tissue Reconstruction. Case studies.

Orthopedics
ORTHOPEDICS TISSUES AND BIOMATERIALS: Structure and function of
orthopedic tissues. Bone, cartilage, intervertebral discs. Total joint replacements,
Spinal implants, Fracture Fixation. Mechanisms for damage and disease.
Clinical treatments.
Case Studies:
1. Sulzer recall-good manufacturing practice, legal and ethical issues associated with device recalls
2. Premature failure in metal prostheses due to corrosion
3. Implant failures due to oxidation and aging of the polymer component
4. Stress shielding/ femoral stem design—stresses, bone resorption, evolution of design and materials
5. Clinical case study (Dr. Mike Ries, Orthopedic Surgery, UCSF, Feb 21)- surgical procedures, osteolysis
6. Evolution of materials (UHMWPE)- the effects of microstructural changes on fatigue, fracture, wear
7. Spinal Implants (Dr. Andy Kohm, Kyphon). Design/ clinical aspects.

Dentistry
DENTAL TISSUES AND BIOMATERIALS:
Structure and function of dental tissues. Dental materials/restorative materials
Progression of disease. Clinical treatments.
Case Studies:
1. Fracture in mineralized tissues (Rob Ritchie, March 9)
2. Implant design/materials

Cardiology
CARDIOVASCULAR TISSUES AND BIOMATERIALS: Structure and function of vascular tissue. Etiology of disease. Clinical treatments. Vascular devices. Design issues.
Case Studies:
1. Heart Valves, materials, design philosophies, clinical
2. Stents: Fatigue and Fracture (Scott Robertson, LBL, April 4 th )
3. Stent design (Dr. Alan Pelton, Nitinol Device Company, April 6 th )

Soft Tissue
SOFT TISSUE: Structural Properties, wound healing, stability, biofixation. Design issues.
Case Studies:
1. Dow- Corning Breast implant case
2. Soft implants: facial, occular

Biomaterials
Classifications
Biocompatibility
Applications

Biomaterials and implants
Replace component of living being
Restore Function
Harmonious interaction with host
Biocompatibility
Long-term structural integrity

Structural biological materials
Hard Tissues: Bone, enamel, dentin
Soft Tissues: Cartilage, tendon, ligament, vitreous humor,vasculature,skin, organs
Fluids: Blood, synovial fluid
Problems when used as an implant material: Infection, resorption, inflammation, rejection

Synthetic Biomaterial Classes
METALS: Co-Cr alloys, Stainless steels, Gold, Titanium alloys, Vitallium, Nitinol (shape memory alloys).
Uses: orthopedics, fracture fixation,dental and facial reconstruction, stents.
CERAMICS: Alumina, Zirconia, Calcium Phosphate, Pyrolitic Carbon.
Uses: orthopedics, heart valves, dental reconstruction.
COATINGS: Bioglasses, Hydroxyapatite, Diamond-like carbon, polymers.
Uses: orthopedics, contact lenses, catheters, in-growth.

Evolution of materials in TJR

Biomaterial Classes cont.
POLYMERS: Silicones, Gore-tex (ePTFE), polyurethanes, polyethylenes(LDPE,HDPE,UHMWPE,), Delrin, polysulfone, polymethylmethacrylate.
Uses: orthopedics, artificial tendons,catheters, vascular grafts, facial and soft tissue reconstruction.
HYDROGELS: Cellulose, Acrylic co-polymers.
Uses: drug delivery, vitreous implants,wound healing.
RESORBABLES: Polyglycolic Acid, Polylactic acid, polyesters. Uses: sutures,drug delivery, in-growth, tissue engineering.

Polymers in the body

Implant Factors
Bulk properties: chemical composition, structure, purity and presence of leachables.
Surface properties: smoothness, COF, geometry, hydrophilicity, and surface charge
Mechanical properties: match properties of component being replaced, such as elastic modulus. Stability and fixation.
Long-term structural integrity: design for fatigue and fracture loading, wear, creep, plastic deformation, and stress corrosion cracking

Host Factors
Species (simulated tests in smaller species do not always capture response in humans)
Age and health status
Immunological/metabolic status
Choice of surgeon

Implant reactions in the body

Biocompatibility
Arises from differences between living and non-living materials
Bioimplants trigger inflammation or foreign body response
New biomaterials must be tested prior to implantation according to FDA regulation
WWII: Validated biocompatibility of several materials including PMMA

Bioactivity spectra

Foreign Body Response
Rapid dilation of capillaries, increased permeability of endothelial cell linings and cell reactions
Macrophages release degradative enzymes (lysozymes) that attempt to digest the foreign material
Macrophages multiply (Mitosis) and serve as progenitor to the giant cell
Undigestable: frustrated phagocytosis. Size scale is important.

Inflammation process

Response to inflammation
Decreased tissue mass and formation of new tissue through granulation
Collagen and other molecules are synthesized
Formation of scar tissue
Remodeling process differs for various tissues

Applications of Biomaterials
Orthopedics: artificial hips,knees, shoulders, wrists; intervertebral discs; fracture fixation; bone grafts.
Cardiovascular: heart valves, PTCA balloons, pacemakers, catheters, grafts, stents.
Dental: enamels, fillings,prosthetics, orthodontics.
Soft tissue: wound healing, reconstructive and augmentation, occular.
Surgical: staples, sutures, scalpels.

Orthopedic Implants

Dental Implants

Cardiovascular devices

LVAS: Pump Drive Unit

Soft Tissue Reconstruction

Challenges
Biofixation and stability of an implant
Long-term wear and debris generation
In-vivo degradation through complex bio-chemi-mechanical actions
Inert materials do not elicit “pro-active” responses in the body
Solutions are often temporary for tissue replacement

Current Trends
Interdisciplinary approach: merge engineering, biology, and materials science
Engineer new biological and hybrid materials
Develop “smart” or “pro-active” materials which can assist in tissue regeneration or treatment

Questions?

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