investigating the mechanical properties of living human cells n.
Download
Skip this Video
Download Presentation
INVESTIGATING THE MECHANICAL PROPERTIES OF LIVING HUMAN CELLS

Loading in 2 Seconds...

play fullscreen
1 / 28

INVESTIGATING THE MECHANICAL PROPERTIES OF LIVING HUMAN CELLS - PowerPoint PPT Presentation


  • 75 Views
  • Uploaded on

INVESTIGATING THE MECHANICAL PROPERTIES OF LIVING HUMAN CELLS. Mark Murphy: GERI & BML Catherine Randall: GERI Alexis Guillaume: Université Claude Bernard, Lyon. PROJECT BREAKDOWN. Mark Murphy Cell Biology Atomic Force Microscopy Fluorescence microscopy. Catherine Randall

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'INVESTIGATING THE MECHANICAL PROPERTIES OF LIVING HUMAN CELLS' - simeon


Download Now An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
investigating the mechanical properties of living human cells

INVESTIGATING THE MECHANICAL PROPERTIES OF LIVING HUMAN CELLS

Mark Murphy: GERI & BML

Catherine Randall: GERI

Alexis Guillaume: Université Claude Bernard, Lyon

slide2

PROJECT BREAKDOWN

  • Mark Murphy
  • Cell Biology
  • Atomic Force Microscopy
  • Fluorescence microscopy
  • Catherine Randall
  • Force Data Analysis
  • Image Processing
  • Alexis Guillaume
  • Computer Modelling
  • Simulation
slide3

WHAT DO WE ALREADY KNOW ABOUT CELL MECHANICS?

  • Very Little!
  • Cytoskeleton
  • Microtubules, Actin Filaments, Intermediate Filaments & Associated Proteins
  • Changes in the cytoskeleton occur during most normal cellular processes
slide6
WHY SHOULD WE STUDY CELLMECHANICS?
  • Changes in the cytoskeleton are associated with many human diseases, such as:
  • Cancer
  • Heart Disease
  • Premature Aging
  • Skin Fragility
  • Liver Disease
  • Such pathologies were first interpreted as ‘Mechanical Weakness Disorders’
slide8

Laser

Photo Detector

Z-piezo

Sample

X-Y Stage

Objective Lens

THE ATOMIC FORCE MICROSCOPE

slide10

Indentation (nm)

Deflection (nm)

2

1

Non-contact region

0

0

Z-Movement (µM)

1

2

AFM FORCE CURVES

slide11

LIVE HUMAN LUNG FIBROBLAST CELL

AFM Deflection Image of Human Lung Cell

3-D Image of Human Lung Cell

(Reconstructed From Height Image)

the hertz model1
THE HERTZ MODEL
  • Describes simple elastic deformations for perfectly homogeneous smooth surfaces

Fcone = 2/π · E / (1-v2) · tan(α) · δ2

Fparabola = 4/3 · E / (1-v2) · √R · δ3/2

  • Two Unknown Values
  • Powell's minimization method
results using the hertz model
RESULTS USING THE HERTZ MODEL

Parabolic tip

Conical tip

problems with the hertz model
PROBLEMS WITH THE HERTZ MODEL
  • Cells are not planar and do not extend infinitely in all directions
  • The cantilever is not infinitely stiff
  • Data is not linear
  • Cells are not perfectly elastic

Must consider other possible solutions

viscoelastic cells
VISCOELASTIC CELLS
  • Constitutive equation
  • Linear Elastic
  • Non-Linear Viscous
strain hardening
STRAIN HARDENING
  • Cells get stiffer with increased applied force
  • Possibly a similar mathematical model to those used in materials science
slide18

CELL INDENTATION OVER TIME WITHOUT SPHERE (n=4)

Applied force = Approx 1.5 nN

Time = 8.5 min

Voltage conversion 1 V/65 nm

  • The tip indents the cell (roughly 400 nm) and does not seem to push back but reaches a plateau
  • This trend is consistent and repeatable
cell indentation over time using attached sphere n 4
CELL INDENTATION OVER TIME USING ATTACHED SPHERE (n =4)

Applied force = Approx 1.5 nN

Time = 8.5 min

Voltage conversion 1 V/65 nm

slide20

ADAPTIVE EVIDENCE!

  • The sphere indents the cell and after a couple of minutes the cell seems to be pushing back
  • This trend is consistent and repeatable when using an attached sphere
how a simulation can help
HOW A SIMULATION CAN HELP
  • Similar experiments without bias
  • New experiments
  • Observe what you can not measure
  • Generally : test some hypothesis
what is simulated
WHAT IS SIMULATED?
  • Adhesion with other cells
  • Lipidic bilayer
  • Actin cortex
  • Cytoskeleton
  • Nucleus
  • Cytoskeleton
  • Actin cortex
  • Lipidic bilayer
  • Focal adhesion complex
  • Substrate
how is the cell simulated
HOW IS THE CELL SIMULATED?
  • Continuum Mechanics :
    • Equations describing the behaviour of the smallest amount of matter that can be seen as continous.
  • Finite Elements Method :
    • A node = an equation
    • Huge system to solve
  • Well-known mechanical materials
  • Realism
  • Slow
results
RESULTS
  • Fairly reproduce experimental conditions ;
  • Displacement, speed and acceleration for each node of the simulation
  • The future : from continuous materials to living materials
slide25

CONCLUSIONS

  • The cells in this study exhibit viscoelastic properties and exhibit strain hardening
  • They Show adaptive behaviour over time when an external force is applied
  • The cell behaves differently when a global force is applied compared to a local force
current future work
CURRENT & FUTURE WORK
  • Develop a model to analyse the force data
  • Disrupt cytoskeleton to determine contribution of each filament type
  • Disrupt cytoskeleton to see how the cell behaves over time
current future work1
CURRENT & FUTURE WORK
  • Compare mechanical properties of normal and pathological cells (cancer)
  • Determine mechanical properties of other cellular components
  • Compare mechanical properties of cells growing on different substrates