Rupture Force Data

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Fibrin fibers, the skeleton of a blood clot, essentially perform the mechanical task of creating a blockage that stems blood flow. Thus, a better understanding of the mechanical properties of these fibers, such as the tensile strength and Young's modulus, will enhance our understanding of blood clots. For quantitative stress and strain measurements, we need to image the deformation of the fiber and measure the

Fibrin Fiber Strength MeasurementsCISMM: Computer Integrated Systems for Microscopy and Manipulation

Collaborators: Susan Lord (Pathology), Dorothy Erie (Chemistry)

Project Lead: Martin Guthold (Wake Forest University) Investigators: Louise Jawerth, Mike Falvo, Rich Superfine

http://www.cs.unc.edu/Research/nano/cismm/fibrin/index.html

November 29, 2003

Motivation

Atomic Force and Optical Microscopy

We are able to achieve a more accurate understanding of data through a combination of atomic force microscopy (AFM) and optical microscopy. AFM data alone can oftentimes be ambiguous. By simultaneously using an optical microscope we can see what is going on in the sample. This can be used to obtain direct force information such as stress and strain data. It can also be used to obtain more global force information. For instance, how applied forces affect areas slightly away from the exact location of the applied forces.

Past Results

Using Atomic Force Microscopy Martin Guthold (currently at Wake Forest University) measured the young’s modulus of fibrin fibers on silicon to be roughly 0.4GPa.

Current Results and Data

The fibrin fibers are fluorescently labeled with two alternative methods. The first is a fluorescent dye. The second method is to adhere quantum dots to the fibers. (Fig 1a) In the case of a dye the fiber has uniform coloration. In contrast the quantum dots speckle the fiber. This is particularly advantageous when trying to measure stress and strain because it allows easy measurement of fiber elongation. After labeling, while still in buffer, simultaneous optical and AFM data is taken. The fluorescent data is projected onto the corresponding AFM data to form a joint image. (Fig 1c) The fibrin fibers are then manipulated while the force information is recorded.

Structured Surfaces

Fibrin fibers can be suspended over structured surfaces. This almost eliminates the force of the fibrin adhering to the surface. Therefore there is a clear fibrin fiber rupture force.

Figure 1: a) Quantum dot labeled fibrin fibers b) Corresponding AFM data c) An overlaid picture of the optical data and AFM data as seen in the nanoManipulator

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Quantum Dot Labeled Fibrin Fiber Suspended across a Channel

applied force simultaneously. For this reason, we are combining fluorescent microscopy with atomic force microscopy. Fibrin fibers are fluorescently labeled with streptavidin-coated quantum dots and deposited on a functionalized glass substrate, imaged and manipulated

under buffer.

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Figures A and B are a fibrin fiber before and after manipulation. The two peaks in Fig. C correspond to the fibrin slipping on the surface and

followed by it breaking.