Experimental Methods

Question 1

Challenges in cell measurements

Answer 1

• very small (1-10 micrometers)
• force sensing as it is soooo little
• cell viability

Question 2

Transmission Electron Microscope (TEM)

Answer 2

• 1000x better than light microscope, improves resolution from 0.2um to 0.2nm
• beam of electrons pass through specimen same way a beam of light does in a light microscope

Question 3

Scanning Electron Microscope (SEM)

Answer 3

• narrow beam of electrons move back and forth across surface of specimen when beam hits the surface
• surface emits more elctrons a detailed almost 3D picture of the specimen surface
• requires specimen to be examined in a vacuum

Question 4

key principle in characterizing mechanical properties

Answer 4

applying a force/pressure to generate deformation/displacement

Question 5

Describe the osmotic swelling technique and is it a indirect/direct method?

Answer 5

indirect measurement

• Apply a concentration difference of colloids/ions to generate osmotic pressure
• Causes cell to swell in volume
• By correlating the pressure difference and volume increase the elasticity of cell membrane can be calculated

Question 6

An isotonic solution will cause a red blood cell to….

Answer 6

stay the same shape/size

Question 7

A hypertonic solution will cause a red blood cell to…

Answer 7

shrink!!!!

as there is a higher concentration of ions in solven than in RBC

Question 8

A hypotonic solution will cause a red blood cell to…..

Answer 8

SWELLLLL

as there is a lower concentration of ions in solven than in RBC

Question 9

What is a selectively permeable membrane?

Answer 9

permits the movement of only certain molecules in and out of the cell e.g. plasma membrane

Question 10

How does water act in different types of solutions?

Answer 10

flows in the direction that tends to equalize the solute concentration (occurs on both sides of the membrane)

Question 11

If a solute is impermeable to the membrane, what is its sigma value (van’t hoff law equation)

Answer 11

1

Question 12

What is the importance of the cell contraction force?

Answer 12

1. Physiology - e.g. heart beating
2. Wound healing - fibroblast cell contraction during scar formation
3. Tissue engineering - fibroblast + vascular smooth muscle cells

Question 13

What techniques can be used for the force measurement of single cells? (3)

Answer 13

(A) Deformable membrane
(B) Traction force microscopy
(C) Elastic micro-pillar (EMP) devices

Question 14

What techniques can be used for the force measurement of multiple cells? (2)

Answer 14

(D) Culture force monitor (CFM)

(E) MCEH

Question 15

List techniques that are indirect measurements (3)

Answer 15

(A) Osmotic swelling technique
(B) Fluid shearing technique
(C) Acoustic (ultrasonic) wave method

Question 16

List techniques that are direct measurements (6)

Answer 16

(A) Micropipette aspiration 
(B) Micromanipulation - comrpession method
(C) Micro-upsetting
(D) Micro/nano-indentation
(E) Atomic force microscopy
(F) Optical tweezers