Biomechanical characterzation of endothelial glycocalyx layer

• Concept: glass bead placed on the endothelial cell surface fluctuates around the equilibrium position in vertical direction due to the termal forces.

Schematics of the particle probe RICM technique  to measure micro-mechanical properties of glycocalyx (not drawn to scale) (V. Hlady, unpublished).

• The vertical position fluctuations, measured by reflectance interference contrast microscopy (RICM), can be used to find the potential energy profile and the local stiffness below the glass bead.

Fig 1. The basis of RICM measurements: spherical probe samples the underlying cell structure (upper left; not drawn to scale); the RICM image of the actual glass sphere (r = 5 µm) showing the interference fringes spaced at 1/4 of the wavelength of the light (middle left panel); the intensity profile across the RICM image (lower left panel).  Intensity variation in the linear region between the first bright and dark region in the RICM image reveals the fluctuation in the probe vertical position in time, This intensity variation is converted into vertical position variation h(t) from which the potential energy profile, V(h), is calculated (V. Hlady, unpublished).

• Effective spring constant of endthelial cell glycocalyx before and after digesting the glycocalyx with specific enzymes.

The potential energy profile, V(h), calculated from RICM intensity fluctuations, are used to calculate the effective spring constant of the bead-cell contact region before and after digesting endothelial cell glycocalyx with specific enzymes (Koskimaki, Dull, Hlady, unpublished).