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Comparison to Scratch Assay

The scratch assay is a widely used technique for investigating wound healing and migration processes. After manually scratching the cell surface with a pipet, the generated wound closes by migration and proliferation of the cells.

However, regarding reproducibility, this method has certain drawbacks:

  • The gap width is highly dependent on the pressure applied to the pipet tip.
  • Scratching removes the surface coating.
  • The removed cells form clumps of living and dead cells at the edges of the scratch. The spreading of living cells can overlay the speed of migration.

The ibidi Culture-Inserts Provide Improved Reproducibility,
Compared to a Scratch Assay

Data provided by M. Börries, University Freiburg, Germany

The Culture-Inserts, in combination with the ibiTreat surface of the μ-Dish, overcome the problems associated with the scratch assay. When the insert is removed there is no change to the ibiTreat surface. This has been proven in tests with different types of cells, such as fibroblasts, keratinocytes, and several endothelial cell types.

ibidi Culture-Inserts Scratch Assays
Cell seeding into designated areas Scratching the cell surface with a needle or tip
Defined cell-free gap Varying cell-free gap – i.e., not reproducible
Defined non-coated surface Might contain extra-cellular matrix remains
No cell damage Cell damage
Internal reference* No internal reference*

*Internal Reference

The internal reference may answer the question as to whether two opposite cell fronts influence each other or not. With the defined cell seeding technique, it is possible to measure the speed of:

A: a cell front that is opposite another cell front; and
B: a single cell front that does not have an opposite cell front.

Impedance Measurements

The ECIS Wound Healing Assay replaces the traditional scratch assay. Instead of mechanically disrupting the cell layer with a pipette tip, and then following the migration of cells with a microscope, the ECIS System uses electric signals to both wound and then monitor the healing process.

The advantages of an impedance-based wound healing assay include:

  • up to 96 simultaneous wound healing experiments
  • the direct derivation of time constants and wound healing velocity
  • a cost-efficient approach to screening applications, from low to high throughput

Experimental Example: Healing Function of Serum

Electrical wounding is performed on a small population of cells that are in contact with a 250 μm electrode, thus creating a well-defined wound.

After the wounding, the healthy cells around the electrode immediately migrate and replace the dead cells on the electrode. Depending on the fetal calf serum (FCS) concentration, the original plateau is once again reached after 10, 13, or 20 hours.