Implementation of a Device for Assessing Dosage for Platelet

Glycoprotein Inhibitors

Steven A. Jones, Yuri Lvov, Tianhong Cui,Bruce Walters

Sachin Sah, Kanvasri Jonnalagada, Jeremy Klein

PLATELETS

• Blood Coagulation• Vasoconstriction, vessel repair, immune

response• Defects lead to bleeding disorders• Can enhance atherosclerosis, heart attack,

unstable angina, diabetes, stroke, eclampsia

Platelet Anatomy

The Idea

AgonistReservoirs

Substrates

Separator

Channels

PressureFeed

AssayReserAssayReservoir

WasteReservoir

What Does the Cardiologist Want?

• Glycoprotein Inhibitors (e.g. abciximab).

• What is the proper dose for this heart patient?

• Has an appropriate dose been reached?

• Does this patient need GP Inhibitors?

Analysis of Need

• "It is not possible to use in vitro assays for more direct measurement of platelet viability and hemostatic function on a regular basis, because they are difficult to perform, expensive, and time-consuming”

Holme et al., Transfusion, V. 38, 1998

The Current ImplementationInlet Outlet

Plexiglass Plates PDMSChannel

Nano Coating

Fabrication of channels

UV Mask

Silicon Substrate

Thermal Oxide

Negative Photoresist

Develop

Silicon Oxide

Etch Silicon Oxide

Etch Silicon to 150 μm

Cast PDMS mold

Flow Experiment

Early Images of Platelet Adhesion on Fibrinogen

385/s 2091/s

3990/s 6000/s

147/s

7000/s

Platelet Coverage vs. Shear

0

5

10

15

20

0 20 40 60 80

Shear Stress (dynes/cm2)

Per

cen

tag

e C

ove

rag

e

No Fibrinogen

Fibrinogen

Adhesion Patterns at 20 dynes/cm2

vWf

Fibronectin

Fibrinogen

Fibrinogen Vs Fibronectin Vs vWF

0

0.5

1

1.5

2

2.5

3

3.5

4

150 400 1000 2000 4000 6000

Shear Rate ( /sec )

Perc

enta

ge C

over

age

(%)

Fibrinogen

Fibronectin

vWF

Poly. (Fibrinogen)

Poly. (Fibronectin)

Poly. (vWF)

Conclusions

• Adhesion over various proteins can be observed.– LbL Assembly– Fluorescent Staining/Microscopy

• Adhesion is shear dependent.

• Adhesion patterns depend on the protein substrate used.

Future Work

• Other substrates

• Varieties of platelets

• Quantification of adhesion patterns

• In vivo testing

Acknowledgements

• Sachin Sah• Kanvasri Jonnalaggada• Ameya Kantak• Bruce Gale• David Mills• James Spaulding• Mike McShane• Hua Ai• IfM Staff