4: 4 Flashcards
name from soft to hard tissue types best found in each one
fat > brain >muscle >cartilage > tendon > cortical bone
what gel works for fat + mammary cells
agarose
what gel works for brain + muscle
PA gel
what gel works for muscle + cartilage
PDMS
what gel works for cortical bone
glass
what are gold nanonrods used for
- Digital stiffness writing
Gold nanorods in hydrogel // when hit with laser in specific pattern= creates heat
what is micro contact printing
- Microcontact printing= size/shape variables + which one best works in stiffness
describe elctrospinning
ECM fibre arrangement random // spinning replicates
What can be used to measure ECM properties
AFM
micro indentation
what can be used to measure traction force
TFM
Micropillar
FRET
What is the wettablity test
Hydrophilicity or Hydrophobicity
o Sdd water + see how much contact angle - larger the angle= more hydrophobicity
what can you use to measure topography
Electro microscope= SEM
or AFM
what tests are used to measure the mechanical properties of ECM
A. Compression test: how much force it requires to x%
B. Tensile test: extend to x% (can be till rupture)
C. Rheological force test: how much force wants to go back to original state after rotation
how do Micro indentation test + atomic force micrsopce work generally
- Indent arm/tip goes down in given force on a sample > detects changes in reflection when tip bend (soft sample = longtime till bend)
what’s the differences between Micro-indentation test and AFM
Micro= larger probe = whole cell tested
AFM= smaller probe // one integrin binding type test
what can AFM measure
force, stiffness, rupture, intracellular traction, height, adhesion
how does AFM measure adhesion
when tip comes back up= adhesion/sticky clings to it = greater peak towards neg = more sticky)
how does AFM measure height/topogrpahy
(as you know where you started (lateral height- length from starting point)
On a graph for AFM is the steady rising line softer or harder compared to the quick up change
steady= softer
how does AFM measure rupture
Coats AFM tip with integrin= binds to extracellular matrix > pull to see how integrin interacts with substrate i.e. stiffness
o = to rupture points
o Stiff= high force, low height - soft= low force, high height
how does AFM measure intracellular traction force
uses antibody - protein interaction
o pulling force from cells
o Soft= little stable focal adhesion> little spread + low integrin = little traction force
what does direct cellular measurement measure and what are the two types
- Measures Traction Force
- Types:
1. Micro-Pillar
2. Traction Force Microscopy
pros/negs of Micro-Pillar
vs Traction Force Microscopy
Pillar pro= high res, no FEM beads, cons= no z
TFM pro= xyz data, cons= require confocal, FEM
what is microvillar made from and how to variable it
- Microneedle = made from PDSMs
- Variables: stiffness of PDMS, diameter, length
what happens if you increase the height of a micropillar
- Length Variable: displacement more on top of longer with same force as smaller (which doesn’t move a lot in comparison)
o i.e. shorter force required in long
why optimal aspect ratio exist for micropillar
too high= lateral collapse , too small = sagging
how is TFM measured
2 Image Process:
Image 1: stressed configuration- cell exerting traction toward centre // beads following it inside
Image 2: remove cell (using trypsin) + beads go back
- Measure bead displacement between stressed and unstressed configuration
what is FRET
- Fluorescence Resonance Energy Transfer (FRET)
o Used to determine how “close” to fluorophores are
how does FRET work
- Energy/laser directed at sample (green) > hits (excites+ changes energy stage) > energy released/emission (emits at slightly diff wavelength
- Donor Emission light can excite acceptor (if they are in close proximity)
- // can measure distance
what is an example of something FRET can measure
- Can Measure: Change in conformation= change in distance
o i.e. when fibronectin is pulled apart (Talin/vinculin to attach)
design experiment to identify the effect of stiffness on traction force
. stiffness hydrogel + use beads to measure traction force using TFN
Advantages of human on a chip
Pros=
- low cost alternatives as uses low fluid/med delivery
- mimic complex structures
0 increase success rate + speed of drug development
limitations of human on a chip
- not yet engineered intergrated systems
- finding common cell medium to integrate system hard
- ## limited self-renewal potential
What is one success of lab on a chip
Microstructure - cancer metastasis
• Found that cancer cell can reassemble cancer nucleus after fitting through small holes
o // differentiate between healthy/tumor cells by how fast they move thru holes
