Sean frågor Flashcards
What is a parenchymal cell?
The cells that make up our organs and have very specific functions
Explain cell regeneration and repair versus fibrosis.
Regeneration: Parenchymal cell death with intact tissue. Restored to normal function.
Repair: Parenchymal cell death with damaged tissue. Scar formation.
Fibrosis: Causes tissue scarring. With long-term liver inflammation, excess fibrous connective tissue thickens the tissue cell walls and lead to reduced O2 supply
Describe ESCA as well as advantages , disadvantages and areas of application
X-rays are directed at a sample which causes the electrons on the surface to emit in a certain pattern that can be analysed to determine the compunds composition. Measures the binding energy of the compunds electrons.
+Surface sensitive, high resolution
-Elemental limitations, expensive, need for strong vacuum chamber
Describe FCC structure
Close packed. ABC|ABC|…. Each corner has a fraction of an atom and each side has the center of an atom. Metals.
Describe HCP structure
7-3-7 layered unit. Metals and large molecules
Describe BCC structure
One atom in middle, fraction of atoms in every corner. Metals.
Descibe diamond structure
FCC but with a 4 extra atoms connected in the middle kinda. Si, C, Ge…
What are the three generations of biomaterials?
First generation: Bio-inert materials, orthodpedic implants and dental materials
Second generation: Bio-active materials. Drug delivery and resorbable.
Third generation: Regenerative materials. Biomimicking and degradable.
What is biocompatibility
A materials ability to perform a certain task in the body and induce an appropriate host response.
Describe the biocompatibility pathway.
Biomaterial and host come in contact –> Initiation of host response –> Progression of host response –> Indaequate resolution (not tolerable) OR resolution of response (tolerable)
What are the main classes of materials used in the body, name their properties.
Polymers - Elastic, easy to produce
Natural materials (proteins, polysaccharides) - bioactivity, may resorb
Metals - Strong, ductile, may corrode
Ceramics - Biocompatible in bone, brittle
Composites - Strong, hard to make
What is nominal stress?
Force applied orthagonal to the cross sectional area of a sample (N/m2 or Pa). Tensile if elongating, compressive if shortening
What is nominal strain?
A measure of deformation as a result of stress
Describe each area of the stress-strain curve for
1. Titanium alloy
2. Al2O3
3. High Density Polyethylene
Kolla L4
Difference between resilience and toughness.
Resilience: Elastic energy that can be stored in a unit of stressed material
Toughness: Energy required to deform a unit volume of material to its breaking point. Hip implant
What is UTS?
Ultimate Tensile Strength. Maximal stress shown in the stress strain curve.
What is ductility?
Formability of a material. All biomaterials
What difference is there between the true and the engineered stress-strain curve?
True stress and strain can be obtained by scaling the applied force with reference to the actual cross-sectional area of the sample
What is hardness?
How successfully a material resist plastic deformation. Dental materials
What is the poisson ratio?
Deformation relation. Tensile stress –> Elongation and thinnification
What is an isotropic material?
Structure and properties do not vary with direction.
What is an anisotropic material?
Structure and property measurements depend on which direction the load is applied to the sample. Biological materials are most often anisotropic.
Explain tensile testing
Tests a material by acting upon it with a force and looking at properties such as toughness or resilience.
Explain wettability and youngs equation
Wettability: Ability of a liquid to establish contact with a surface
Young’s equation: Ysv=Ssl+Ylv*cos(v). Ysv is interfacial tension between surface and air.
Explain ESCA/XPS and SEM
ESCA/XPS: Measure binding energy. Material emits electron cause of x-ray bombing
SEM: Electron gun nips of electrons of material. Scatter plot for elemental identification. Magnifies surface millions of times.
Name the properties which metals excel at
High strength, young’s modulus similar to bone, fatigue properties
Give examples of use of metals in medicine
Stainless steel in bone implants, titanium screws and dental implants.
What is fatigue? How is it measured?
Structrual damage that grows over time. Starts with a small nick and gets progressivly worse. Occurs without plastic deformation (no warning). Measured using rotating cantilever beam test.
Describe the difference between a stress-strain curve of a metal, ceramic, and polymer
Metal: Normal curve
Ceramic: High Youngs modulus, no deformation before fracture (straight line)
Polymer: Very high youngs modulus, followed by a drop and then flatten out before fracture.
What are the five requirements for biometals?
- Stronger than bone
- Modulus close to bone (avoids stress-shielding)
- High strength
- Biocompatibility
- Price
Describe the strength and youngs modulus for bone to titanium and cobalt-chromium
Tensile strength is much higher for the metals but the E-modulus is too high for the metals.
Name one drawback for titanium, cobalt-chromium and stainless steel
Ti: Poor friction qualities
Cobalt-chromium: Prone to fatigue
Stainless steel: Moderate corrosion resistance
Name and explain the 6 types of corrosion
- Pitting (localized corrosion)
- Stress-corrosion cracking (mechanical stress+corrosive environment)
- Intergranular (mass lost–> mech. properties reduced
- Crevice (deposite attack)
- Galvanic (direct contact with liquid)
- Fretting corrosion
What environmental factors cause corrosion?
High oxygen, hydrogen, metallic inert ions. Presence of salt.
In which 4 ways can we avoid corrosion?
- Materials selection
- Coating
- Avoid design with dissimilar metals in contact
- Environmental control. (different parts of the body are different environments)
What are the advantages of titanium in bioapplications?
High reactivity –> protective oxide layer. Inertness. Mechanical properties.
Describe the three main types of biomaterial infections.
Superficial immediate infections - bacteria
Deep immediate infections - After invasive surgery
Deep late infections - months after surgery, bacteria in body colonizing implant
What is sepsis and what are symptoms?
Blood poisoning. Fever, rapid heart rate, sweating
How do we prevent biomaterial associated infections using antibiotics?
Coating or make the biomaterial drug releasing.
What are the 4 steps of biofilm?
Attachment –> expansion –> maturation –> detachment
What does the EPS contain?
Extracellular DNA, polysaccharides, lipids, proteins
Why are biofilms so hard to eradicate?
Bacteria dormant, as well as antibiotics reacting with the EPS
Describe the gram negative and positive cell walls
Negative: Inner and outer lipid membranes
Positive: Inner lipid membrane and outer shell of peptidoglycans
What are some strategies to prevent biofilms?
Non-adhesive surface, tissue integrating surface
What are the 3 types of polymers?
- Thermoplastic: Deformable upon heating, can be melted repeatedly
- Thermoset: Hard and rigid upon heating. Cannot be melted
- Elastomers: Stretchy. Cross linked polymers
Describe the following hydrogels and their properties:
1. chitosan 2.agarose 3.alginate 4.hyaluronic acid 5.gelatin 6.PAA 7.phema
- From crustaceans. Swelling and bioadhesive
- From seaweed. Used in pharmaceutical capsules
- From algae. Used in food
- From rooster comb. Cosmetic and biomedical
- Is a protein. Capsules. Dissolves in body
- Inert. Insoluable. Not absorbed
- Inert. Not absorbed. Withstand sterilization
What are the 5 uses of hydrogels?
Implant coatings, catheter coatings, tissue engineering, wound dressing, contact lenses
What is a gel?
Cotains solvents (hydrogel-water). Contains compund that is swollen and crosslinked with solvent, usually polymer.
What are the advantages and disadvantages of hydrogels?
+Biocompatible, shapes itself after its site, biodegradable if needed
-Loading capacity, low tensile strength
What are the 3 classifications of hydrogels?
Crosslink, charges, structure
What is a smart gel?
A gel that swells up after activation by a specific action by the body
How do we characterize gel functions?
Swelling, mechanical properties, rheology, diffusion, microscopy
What are the 5 types of degradable polymer implants?
- Temporary support device
- Temporary barrier
- drug delivery device
- Tissue-engineering scaffold
- multi-functional implant
Explain the properties of surface and bulk erosion.
Surface: mass loss is faster than the entering of water in the bulk. Bulk and core remains intact
Bulk: Water enters quicker than the rate of degradation. Occurs throughout material, causing uniform degradation
What is sterility assurance level (SAL)?
Probability that a given implant will remain nonsterile after sterilization. Minum for implants is 10^-6
