Micropipette Aspiration of Malaria Infected RBCs

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Micropipette Aspiration of Malaria Infected RBCs

• Zhang Rou
• April 16 2008

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Background

• A vector borne infectious disease
• 300-500 million infected, and 1 to 3 million
  deaths annually
• Mortality of falciparum malaria is 15-20
• Complications
• Anemia
• Cerebral malaria
• Metabolic acidosis
• Acute renal failure
• Jaundice
• Pulmonary oedema

World wide distribution of malaria
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Background

• Blood stages
• Ring form
• Trophozoite
• schizont

Plasmodium life cycle
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Clinical Correlates

• Cerebral malaria
• Sequestration of RBCs in small blood vessels
• Decreased RBC deformability upon infection
• Rosetting, correlation is not clear
• Anemia
• Decreased RBC deformability

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Experimental Techniques
10 pN to 1nN could be provided by micropipette
aspiration
C.T.Lim et al, Materials Science and Engineering
C26 (2006) 1278-88
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Micropipette Aspiration

• Sample size 15
• Flow rate 18ml/h, ramp rate 0.98pa/s
• Inner diameter d around 1um
• dgt2.9um, enter easily
• 2.9umgtdgt2.5um, upon release, cell returns to
  normal biconcave shape
• 2.5umgtdgt1.9um, released cell is crenated
• 1.9umgtdgt0.9um, cells hemolyzed at entry
• dlt0.9um, part of the cell would be pinched off

(a) Schematic of micropipette aspiration and (b)
image of aspiration of RBC
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Micropipette Aspiration

• Viscous continuum models
• Viscosity?is measured

• Continuum models at equilibrium
• Liquid, shear modulusµis measured
• Solid, Youngs modulus E is measured

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Results and Discussion
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Results and Discussion
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Results and Discussion
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Results and Discussion
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Results and Discussion

• Parasites effect
• RBC deformability depends on
• Surface to volume ratio
• Property of cell membrane
• State of the cytoplasm
• Infected RBCs
• Pigmented parasites are rigid and viscous
• Stiffening of the membrane by erythrocyte
  membrane proteins
• PfEMP1 expression is reduced on the surface of
  knobless Plasmodium falciparum infected RBCs

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Results and Discussion

• Temperature effect
• Entropy increases, reduced deformability at
  higher temperature
• Elastomeric transition of hemoglobin from being
  gel-like to a fluid, and of membrane proteins
  such as spectrin at 36.4C

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Future Work

• Completing experiments at febrile temperature
• Comparing experimental data with mathematical
  models
• Increasing sample size for each condition
• Studying viscosity at different ramp rate

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Acknowledgements

• Prof Lim Chwee Teck
• Lee Yeong Yuh
• Collegues in Nanobiomechanics Lab