Quiz 4 Slides (Lecs. 16-18) Flashcards
What is a bioreactor?
a containment device system that gives the right environment for optimal growth and metabolic activity of an organism?
What are 2 tissue engineering processes that a bioreactor can be used for?
can induce mechanical stimulation to encourage differentiation, or improve long term cell distribution in a scaffold
What are 5 functions of bioreactors?
- Provide spatially uniform cell distribution
- Maintain the desired conc. of gases and nutrients in culture medium
- Facilitate mass transport to the tissue
- Expose the construct to physical stimuli
- Provide info about the formation of 3D tissue
What are bioreactors commonly used in tissue engineering?
compression/strain bioreactors, spinner flask, rotating-wall vessel, hydrostatic pressure bioreactors, flow perfusion bioreactor
What are the bioreactor design requirements in TE?
- bioreactor material contacting the media must be biocompatible and bioinert to avoid adverse reaction
- simple as possible - device should avoid the introduction of machine recesses/crevices (breading ground for infections)
- motors/pumps must be able to apply small forces accurately
Spinner flask
bioreactor used for seeding of cells into bioscaffolds; scaffolds are suspended from the end of needles in the flask and are rotated by the motor
Rotating wall vessels
wall of the vessel rotates, providing upward hydrodynamic drag force that balances the downward gravitational force so that bioscaffolds remain suspended in media
Compression bioreactor
used in cartilage tissue engineering and motor/mechanism to provide precise displacement magnitudes and freqeuncies
Strain bioreactor
used in tendon, ligament, bone, cartilage tissue; similar to compression bioreactors, only a tensile force is applied instead
Hydrostatic pressure bioreactor
consists of a chamber that can withstand applied pressure
Flow perfusion bioreactor
provide the best fluid transport; consists of a fluid pump that forces media through the cell seeded scaffold
Stirred Tank bioreactor common use
used for production of antibiotics and enzymes; has a stirrer
Stirred Tank bioreactor advantages
low operating cost, good temperature control, continuous operation
Stirred Tank bioreactor disadvantages
shear forces can break the cells, many working parts that need to periodically replaces, size limited by motor size and shaft length
Airlift bioreactor common use
used for production of antibiotics and enzymes; central draft tube is critical part
Airlift bioreactor advantages
easy sterilization, simple design, low energy vs stirred tank, greater heat removal vs stirred tank
Airlift bioreactor disadvantages
foaming can be an issue
Packed Bed Bioreactor common use
used in waste water treatment; produce proteins and enzymes
Packed Bed Bioreactor advantages
no moving parts to wear out, higher conversion per unit mass of biocatalyst
Packed Bed Bioreactor Disadvantages
poor temperature control, difficult to clean, difficult to replace catalyst
1st Degree Burn
only epidermis involved; healing within a week
2nd Degree Burn
penetrate epidermis and part of dermis; healing in 7-21 days
3rd Degree Burn
destroyed epidermis and dermis; may look black/charred
4th Degree Burn
involves deeper tissues such as bone, tendon, muscle; no feeling since nerves are destroyed
What are the four functions of skin?
- Protection
- Heat Regulation
- Sensation
- Secretion
What are the major layers of skin?
Epidermis, Dermis, Hypodermis (Subcutaneous layer)
What are the 2 main cell types in the epidermis?
keratinocytes (majority) and melanocytes
What is the stratum corneum?
epidermal layer that consists of flattened dead cells called corneocytes that acts as a barrier to protect underlying tissue from infection, dehydration
What is the stratum basale?
epidermal layer that is primarily made up of basal keratinocyte progenitor cells
Differentiation of cells in the stratum basal layer
cells in the stratum basal can either remain as keratinocyte progenitor cells or they can differentiate into spinosum keratinocytes into granular keratinocytes into corneocyte
What are the 5 main components of the dermal layer?
- dermal fibroblasts
- hair (follicle and shaft)
- arrector pili muscles (causes hair to stand erect)
- glands (sebaceous and sweat)
- blood vessels
What is the hypodermis?
deepest part of the skin; subcutaneous fat layer pads and thermally insulates the body
What are the primary cells found in the skin?
keratinocytes, melanocytes, fibroblasts, endothelial cells
What are the types of ECM and structure proteins found in the skin?
collagen, elastin, GAGS, HA, vessels, nerves
What are melanocytes?
neural crest derived cells that are important for skin tone; contain melanosomes that contain melanin
Why is melanin important?
protection against UV radiation; absorbs UV-B light
Cross talk
critical stimulation between fibroblasts and keratinocytes is important to maintain skin homeostasis
What are 2 motivations for creating engineered cardiovascular tissue?
cardiac infarction (leads to necrosis of heart tissue) and high demand for heart transplants
What is the pericardium?
the membrane enclosing the heart; has an outer fibrous layer and inner serous membrane layer
Coronary arteries
the blood supply of the heart muscle which branches off directly from the aorta
Heart valves
4 of them; interconnecting rings of dense connective tissue that all lie on the same plane
What are the 2 approaches to tissue engineer a heart?
decellularize scaffolds from other species and then seed cells onto it
OR
engineer polymeric scaffolds to mimic the structure and mechanical properties of a biological scaffold
What are 2 techniques that can be used to deliver biomaterials in cardiac applications?
- Injectable hydrogels
- Sew on cardiac patches
What cell type would be used to create a cardiac patch?
alginate or collagen type I
What are the 2 purposes for cardiac patches being glutaraldehyde treated?
- crosslinks collagen fibers > improving mechanical strength
- minimizes antigenicity
What are 3 current heart valve treatment options?
- mechanical valves
- bioprosthetics
- Ross procedure
What is the Ross procedure?
taking patients healthy pulmonary valve, using it to replace the diseased aortic valve and a mechanical valve is placed in the weaker (less pressure) pulmonary position
Veins
carry blood toward the heart; less muscular than arteries; valves to prevent blood backflow
Arteries
carry blood away from heart to tissues; muscular walled; not valves
What are the 3 layers of blood vessel anatomy?
tunica intima, tunica media, tunica adventitia
Tunica Intima
very thin blood vessel layer; contains the endothelium and basal membrane; endothelial cell types
Tunica Media
largest layer of a blood vessel containing collagen and elastin fibers; cell types: fibroblasts, smooth muscle cells
Tunica Adventitia
outer most layer of blood vessel made mostly of collagen and acting as a support; cell types: fibroblasts
For blood vessel bioreactors, why do we need to have a physiological pulse rate and pressure?
Pulse rate (60 BPM) and pressure (120/80) because we want the cells we seed to have the correct phenotype
What is compliance?
ability of a hollow organ to increase in volume with increasing pressure (ease of expansion)
Why is compliance important when engineering a blood vessel?
vascular graft success rates are influence by the compliance mismatch; compliance values should match those of the native vessels
