Exam 1 Flashcards
Provide a comprehensive definition of the term “Biomaterial”.
Any Material, natural or synthetic, that comes in contact with human tissue or bodily fluids and is intended for or used in medicine.
What are the general applications areas of biomaterials?
-Storage of Bodily fluids and tissues
-Diagnosis and Monitoring
-Surgery-
Wound Healing
-Biomedical devices and implants.
Understand what is meant by the term “Biocompatibility”
The ability of a biomedical device to perform with an appropriate host response in a specific application.
Is device and application specific
It is an assessment of the risk benefit ratio that requires, by definition, a functioning device.
Explain how biocompatibility can be conditional.
Biocompatibility can be time dependent. Biocompatibility is determined by the relationship of the risk to benefit ratio of biomedical device function and not a non-functional biomaterial. It can be conditional if the device breaks during operation or if device function is compromised due the changing impact of the biological environment. It is said to be conditional if the risk to benefit ratio changes over during the life-time of the device.
Describe how biomaterials have evolved since the 1950’s
From 1950-1975 Biomaterials were off the shelf materials that were inert or nontoxic that were used for medicinal purposes. (1954 Dr. DeBakey used Dacron underwear to make a vascular graph)
From 1975-2000 Biomaterials began to be engineered to have specific properties, like being degradable, as to improve the quality and performance of the materials and devices that were inserted.
2000-present Biomaterials are being designed to stimulate or simulate specific responses. Now, tissue engineering and regenerative medicine apply the principles of engineering and the life sciences towards the development of biological substitutes that restore, maintain or improve tissue function.
The future is personalized medicine
Explain how medical devices are classified? In your answer provide examples of each classification and describe how the general classification scheme differs from one class to another.
According to Risk!!
Class 1: lowest risk, usually found outside the body. Minimal invasiveness do not contact the user internally I.e. crutches bedpans, tongue depressors
Class 2: Higher degreee of invasiveness and risk, but relatively short duration. I.e. hearing aids, blood pumps, catheters, contact lens
Class 3: Considerably more invasive and can pose immense risk to user-implants. I.e. cardiac pacemakers, intrauterine devices, intraocular lenses, heart valves, orthopedic implants.
What are the different classes of biomaterials?
Two primary Schemes
Scheme 1:
- Metals
- Ceramics
- Polymers
- Composites
Scheme 2:
- Synthetic Materials
- Natural Materials
Describe the different levels of organization of a biomaterial
Atomic–elemental composition-which elements make up the material
molecular– nanostructure or ultrastructure–how the elements of the material bind and bond to one another
microstructure–the small scale structure of a material seen w/ an optical microscope at 25x zoom. Strongly influences the physical properties and its applications.
macrostructure–What can be seen with the naked eye.
Describe how the atomic makeup and microstructure of a biomaterial influences design decisions of engineers in the biomedical device industry.
The atomic and microstructure of a material influences what characteristics the material will have. Certain devices must do and not do certain things, and some materials are better suited for that than others. For example, a cermaic is brittle so it wouldn’t be used in a device that needed to bend, and therefore, the material engineer would have to use materials w/ an atomic and microtstructure suitable for bending.
Grain size and packing influence mechanical properties,
smaller grains lead to stiffer and tougher material (metal)
Explain what a metal is and how its structure is related to its properties
A metal is a material that is composed of nonmetal elements.
It has a closely packed polycrystaliline structure w/ freely shared electron cloud that causes metals to have high electrical conductivity.
Its crystalline structure can be simply cubic, body-centered cubic and face-centered cubic.
Grain size: 1-1000um, size and packing influence mechanical properties
smaller grains=stiffer material
Properties: high density strong high mp ductile malleable conductors lusterous reflective
Explain what a ceramic is and provide an example of how they are used clinically.
Ceramics are a combination of metallic elements w/ one or more nonmetallic elements (C, N, O, P, S)
primarily ionic bonding, some covalent
crystalline structures
grain size is smaller 1 nm-100um
grain boundaries are much shorter
Properties: low conductivity high stiffness high MP low ductility very brittle lustrous polishable low surface roughness
Clinically:
Al2O3
Load bearing
orthopedic and dental applications (hips and crowns)
List two properties and at least 4 general requirements of a biomaterial incorporated in a biomedical device;
Properties: Surface Properties Bulk Properties -mechanical -electrical -magnetic -optical -thermal
Requirements: non-pyrogenic non-carcinogenic non-toxic sterilizable manufacturible/producible packagealbe storable cost effective
Draw a stress strain curve, label its axes, and explain what relevant mechanical characteristics can be determined from a materials stress-strain curve;
Diagram
Stress (y-axis) Pressure Mpa
strain (x-axis) percent elongation
Elastic deformation: reversible deformation
Young’s Modulus: slope of elastic deformation, stiffness/elastic modulus
Plastic Deformation: irreversable deformation
Yield Strength: stress needed to begin causing plastic deformation
Necking: deformation that occurs as large amounts of strain localize in a small region of the material
Ultimate tensile strength: max stress
total strain: max strain or elongation at failure
toughness: area under the curve.
On the same graph, draw an idealized representative stress strain curve for a metal, ceramic and a polymer
diagram
Define the working principle, probe depth (surface sensitivity) and information provided by AFM and optical profilometry;
HELP
provided by optical profiometry: measures surface topography, roughness and height. non-destructive/contact
capable of nm level vertical resolution across large fields of view
uses visible light
DIAGRAM
Differentiate between the concepts of inertness and bioactivity with regard to a surface coating;
Inert: doesn’t purposefully cause anything to happen
Bioactive: intentionally causes a specific biological response to happen.
List and describe the characteristics that are unique to the surface of a biomaterial;
Topography
Microstructure
Atomic/molecular composition- different than bulk phase
Surface Energy- enhanced chemical reactivity that is different than in the bulk phase
Define the working principle, probe depth (surface sensitivity) and information provided by:
Scanning Electron Microscopy (SEM)
Greater resolution and depth of field offers a 2D image w/ 3D perspective 20x to 30,000 x mag allows greater characterization than one gets w/ a light microscope -surface morphology -chemical composition
We see secondary electrons off of sample
Define the working principle, probe depth (surface sensitivity) and information provided by:
IR Spectroscopy
Probe in: infrared radiation (photons)
signal out: infrared radiation (same beam as probe in)
Info: structure and types of covalent bonds; shows functional groups.
depth (between 10-15 um) variable
Measures absorption of IR light by chemical bonds. each bond absorbs different frequencies
Define the working principle, probe depth (surface sensitivity) and information provided by
EDX/EDS
depth: greater than 1 um
electrons are probe in
Characteristic x-rays are probe out
info: elemental analysis or chemical characterization
Define the working principle, probe depth (surface sensitivity) and information provided by:
X-ray photoelectron spectroscopy XPS or ESCA
Probe: x-ray
signal out: photoelectrons (auger electrons)
depth( 100 A)
info: elemental composition and chemical bonding
Define the working principle, probe depth (surface sensitivity) and information provided by:
Secondary Ion Mass Spectroscopy (SIMS)
probe in: Ions (Ar, Ga, Cs, C60)
signal out: Secondary ions (ions of the sample)
depth: 10 A
info: Elemental and molecular composition
is destructive
How is water as a solvent involved during protein adsorption to a biomaterial?
Proteins are surrounded by a hydration shell. The shell contains water molecules that are more ordered than in bulk phase.
Interaction w/ water shapes the protein. the tertiary structure of the protein is determined by intrachain interactions as well as the hydrophobic effect
Provide two examples of surface dynamics
Changing Geometry flat to spherical
Dynamic rearrangement
when polar and non polar side chains rotate to be in appropriate environment.
Describe what is meant by “excess surface free energy”
Surface atoms lack at least one bonding partner compared to atoms in the bulk phase of a material. Therefore, these atoms have an excess of free energy that can be used to bind to other things.
Is protein adsorption energetically favorable? Why or why not
help!!!!!
Protein adsorption is energetically favorable as the slight increase in enthalpy is more than compensated for by a large decrease in free energy. Increases in the system’s entropy contribute to irreversibility.
Surface dynamics lower the free energy.
Protein adsorption reduces the free energy at moderately hydrophobic surfaces.
but also deforms the proteins?
