Exam 1 Flashcards
Provide a comprehensive definition of the term “Biomaterial”
any material, natural or synthetic that comes in contact with human tissue blood or bodily fluids and is intended for use in medicine
What are the general applications areas of biomaterials?
Storage of bodily fluids and tissues
Surgery
Biomedical devices and implants
Wound healing
Diagnosis and monitoring
What is meant by the term biocompatibility?
the ability of a biomedical device to perform with an appropriate host response in a specific application. (This should only be used when speaking about devices, not individual materials). It is also an assessment of the risk-to-benefit ratio of a biomedical device that requires, by definition, a functioning device. Biocompatibility testing is device and application specific. Generally condition and time-dependent
Explain how biocompatibility can be conditional.
Hip replacements and intraocular lenses are examples. They can be biocompatible when they are implanted but afteryears of use they can wear down and no longer be biocompatible.
Describe how biomaterials have evolved since the 1950’s.
1950-1975 bioMATERIALS (emphasis on material and material properties, used off the shelf materials like screws and underwear and carpentry tools)
1975-2000 BIOMATERIALS (started to focus a bit more on the biological side of things, an example is developing fixation plates that would begin to degrade over time in the body and never have to be taken out of the body)
2000-present BIOmaterials (materials designed to elicit specific responses in the body, focus more on what is going to happen in the body. An example is extracellular matrix properties of new materials being used there, or another example is bioartifical skin)
5 major steps of device development
Basic research → Design, prototype, bench testing → Preclinicla testing → Regulatory approval, clinical testing → Commercialization and clinical application
What are the different classes of biomaterials?
Scheme 1
Polymers - usually one or more materials together
Metals
Ceramics
Composites
Scheme 2
Synthetic (Man-made) Materials
Natural Materials
All materials fall into either scheme 1 or 2
These materials differ in atomic or elemental composition and structure
Describe the different levels of organization of a biomaterial.
Molecular
(Ultrastructure, Nanostructure which is the 3D organization of atmos in a molecule, tells us about the shape of the molecule)
Microscale
(small scale or fine structure of a material that is revealed with microscopy, the microstructural organization can strongly influence the physical properties and applications of a material)
Macroscale
(The gross structure of a material that is visible with the naked eye)
Describe how the atomic makeup and microstructure of a biomaterial influences design decisions of engineers in the biomedical device industry.
Design logic triangle (One of the slides from lecture today)
Explain what a metal is and how its structure is related to its properties.
Closely packed polycrystalline structure, freely shared electron cloud, high electrical conductivity
Can have fundamental units that are simple cubic structure, body-centered cubic, face-centered cubic
General properties
High density
Strong
High melting point
Ductile/malleable
Conduct electricity (potential issue is that they conduct heat as well)
Smooth surfaces
Stainless steel for example is an alloy with chromium and nickel. Most common is 316L, has orthopedic benefits.
Explain what a ceramic is and provide two examples of how they are used clinically.
Combination of one or more metals with non metallic elements
Binding is a combination of covalent and ionic binding. You heat these elements up and let it cool just like a normal metal.
It has grains like metals, but smaller and more uniform
Electrons are not shared in ceramics
Due to small grain, these materials are much harder but can also be brittle and crack if force is not applied equally
Properties
High stiffness
High melting point
Low ductility (brittle)
Low electrical conductivity (can be modified)
Low heat conductivity
Lustrous
Polishable (Low surface roughness)
Used for artificial teeth because of this
Example: Alumina
Al2O3
Property comparisons
Metal is the strongest
Ceramics have highest modulus
Polymers can be the most flexible
What is a polymer?
A network of entangled chains of repeating monomeric units that are held together by noncovalent molecular interactions (van der walls or ionic) and in some cases by covalent bonding.
Ex: Polyethylene
The elemental composition of polymers is primarily electronegative atoms: C, N, O, F, Si, Cl, H. These make up most of all medical devices using polymers
Two major types:
Thermoplastics (held together by weak forces, their interactions
are determined by the degrees of overlaps)
Can have Amorphous or Semicrystalline
Thermosets (have covalent interactions within them, an
example is silicone caulking material)
Properties of biomaterials
Surface properties
Talking about the depth of ~1 micron of the surface
Bulk properties
Everything deeper than a micron within the material
Mechanical
Electrical
Magnetic
Optical
Thermal
Important role
The vast majority of biomaterials that we use are solids
More hydrophobic and stiffer than bodily tissues
General requirements for selecting a boimaterial
Non-pyrogenic
Non-carcinogenic
Non-toxic
Sterilizable
Manufacturable
Packageable
Storable
Cost-effective
Biomedical device design
Identify application-specific requirements
Concept
Configuration / design requirements
Prototype
Verification testing
In silico tests
Bench tests
Preclinical analysis
Validation testing
Clinical trials
Total hip replacement (THR)
Approx 200k the per year in us
Performed to alleviate pain
Restore mobility
Common causes
Inflammation of the joint
Referred to as arthritis
Trauma
Congenital deformity
Determining mechanical properties
Tensile testing
Stress (y-axis): a force that is induced by a given change in
length (strain)
Strain (x-axis): change in length over original length (deltaL / L)
Elastic deformation - the initial phase of the stress-strain
curve (always linear at the beginning)
Plastic deformation - the second phase of the stress-strain
curve. This portion of the curve occurs after passing the yield
strength. This is irreversible
Fracture - material failure. This is after passing the ultimate
tensile strength, necking, etc (see slides)
Major Definitions
Elastic deformation:
Youngs modulus
Plastic deformation
Yield strength
Necking
Ultimate tensile strength
Total strain: Maximum strain or elongation at faiure
Toughness: Area under the curve
TAH: Properties of the bone
Osteocytes: small structures that make up cortical/compact bone
Osteoclasts:
Spongy bone: usually filled with vasculature and tissue
Mechanical properties of bone
Traditionally orthopedic implants have been overengineered
They use metals like titanium that are so strong that they bear most of the load, thus allowing the bone to weaken and eventually break
THR facts
40-50k revision surgeries per year in US
Number expected to rise by 50% by 2030
$30-50k per revision in direct costs
>$1B lost annually in indirect costs
Two basic surface coating or engineering approaches
Bioinert approach - tries to optimize the existing surface properties of a device for medical use while minimizing toxicity (increase surface roughness, AFM)
Bioactive approach - biological-based approach to cause specific response (hydroxyapatite)
4 major functions of complement
Target foreign bodies
activate microphages
initiates and sustains inflammation
lyses cells
Complement definition
Part of the innate immune system consisting of an enzymatic cascade involving 30 glycoproteins
Role of bone marrow in FBR?
it is hematopoietic.
It generates cells for both adaptive and innate immune system
Innate immune system
a nonspecific evolutionary defense mechanism against microorganism colonization
2 products that stop bloodflow
ECM based - derived from bovine dermal collagen
fibrin based - sealants and adhesives
3 ways intrinsic and extrinsic coagulation cascade differ
extrinsic:
- requires ligand/protein on surface
- 1 factor
- doesn’t need Calcium
intrinsic:
- activated by adsorption
- 3 factors
- requires calcium for all steps
serine protease and their role in blood clotting
All enzymes involved in blood clotting cascade are serine proteases
Role of tissue factor in blood clotting?
Activates the intrinsic pathway
plasminogen and its role in blood clotting
Zymogen - plasmin produced in liver which can degrade fibrin so that platelets cannot attach to fibrin and degranulate
How do calcium chelators stop blood from clotting?
They bind with the Ca2+ and prevents activation of zymogens needed in clotting cascade
what does self assembly have to do with clot formation
thrombin activates fibrinogen and binds to itself, thus stopping the bleeding and activating the clotting process
What molecules are released by platelets that may affect the FBR?
PDGF, VEGF, TGF-beta
what proteins in the blood affect the FBR?
antibodies, clotting cascade, complement cascade
