Modeling Mechanical Stimulus. Intro Activity -(Outline Activity Once Determined) -(Questions, etc.)
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Transcript of Modeling Mechanical Stimulus. Intro Activity -(Outline Activity Once Determined) -(Questions, etc.)
![Page 1: Modeling Mechanical Stimulus. Intro Activity -(Outline Activity Once Determined) -(Questions, etc.)](https://reader035.fdocuments.in/reader035/viewer/2022062423/56649ee75503460f94bf7a39/html5/thumbnails/1.jpg)
Modeling Mechanical Stimulus
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Intro Activity
- (Outline Activity Once Determined)- (Questions, etc.)
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Module Objectives
Understand how cells respond to different types of mechanical signals.
Calibrate a syringe pump to perform better analysis.
Examine the effect of flow on a model scaffold.
Compare simulated bone and vessel properties.
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Stiffness
- Stiffness is now much a material deforms when a force is applied.- Bone is very stiff- Ligaments are less stiff- Neural tissue has very little stiffness
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Stresses
- Stress is the amount of force in a unit area.
- When an external force is applied to an object, it experiences internal stresses.- Plastic- Metal- CELLS
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Normal Stresses
- Normal stress result from forces that act through the center of an object.- Compression- Tension
Picture Here
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Shear Stresses
- Shear stresses occur when forces are applied that are parallel to the surface of an object.- Fluid Flow
Picture Here
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Stresses and Cells
- Muscles experience tension and compression during movement.
- Bones develop to provide resistance to compressive forces.
- Vessels experience shear as blood flows within them.
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Tissue engineers are now looking to mimic the mechanical environment of a cell type to
encourage growth.
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Stiffness-Based Differentiation
- Stem cells can differentiate based on matrix stiffness.- Neurons develop on a soft matrix.- Bone cells develop on a very rigid matrix.
- (PICTURE?)
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Strain-Based Differentiation
- Muscle cells grow best when they alternate between tension and compression.
- Bone growth is encouraged by uniform tensile strain.
- Compression encourages chondrocyte growth, leading to increased cartilage in joints.
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Shear-Based Differentiation
- Shear stresses resulting from fluid flow encourage cellular activity.- Increased extracellular matrix formation.- Better cell proliferation on scaffolds.
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Mechanical Signal Transduction
- Though researchers have yet to determine how mechanical signals are transduced in the cell, proteins in the cytoskeleton have been shown to be important.
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Activities
1.) Calibrating the syringe pump
2.) Measuring the effect of flow on ‘cellular growth’
3.) Problems with scaffold wash out
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Operating the Syringe Pump
- Check the pump to make sure it is in working order.
- Fill the syringe with the proper amount of water.
- Attach the catheter to the syringe and centrifuge tube.
- Place the syringe in the pump.- Apply weight to depress syringe.- Remove weight when fully depressed.
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Activity 1 - Objectives
- Familiarize operation of the gravity-powered syringe pump.
- Determine the relation between weight and flow rate for the pump.
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Activity 1 - Procedure
- Time how long the syringe pump takes to depress weights of 2.5, 5, 7.5, 10, 12.5, and 15 pounds.
- Calculate the average flow rate for each weight.
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Activity 1 - Procedure
- Create a calibration curve for the syringe pump.
Sample Calibration Curve
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Activity 2 - Objectives
- Prepare scaffolds by adding ‘cell culture’ and ‘growth differentiation factor.’
- Test the effect of flow rate to see how much ‘flow-dependent growth factor’ is released for different ‘cell’ types.
- Use the spectrophotometer to determine ‘growth factor’ concentration.
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Activity 2 - Procedure
- Prepare ‘scaffold’ by adding 5 mL ‘cell culture’
- Add 1 mL ‘differentiation growth factor’
- Run water through the scaffold after thirty seconds
Diagram
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Activity 2 - Procedure
- Use a spectrophotometer to measure the concentration of ‘growth factor’ released
- Compare the two ‘tissue’ types
Diagram
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Activity 3 - Objectives
- Understand the hazards of excessive flow in tissue engineering.
- Count ‘cells’ that are washed away from a scaffold at various flow rates.
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Activity 3 - Procedure
- Students will create ‘cells by adding ‘cell culture’ to ‘growth factor.’
Visualize process here
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Activity 3 - Procedure
- Populate the scaffold
- Flow water through the system.
- Count the number of cells washed out.
- Repeat the procedure ad different flow rates.
Diagram