The gold ECIS® electrodes are pristine and have no coatings when shipped from Applied BioPhysics. When culture medium is added to these arrays, the proteins and other large molecules in the medium will immediately adsorb to the very wettable gold surface as they do with any uncoated tissue culture dish (note: this will take place even after reacting the gold with cysteine).

Often it is desirable to alter cell behavior by pre-coating the electrodes with fibronectin, laminin or other ECM proteins. We suggest using the following protocol:

(1)     Make up a solution of the desired protein at 100 micrograms per ml or more in 0.15M NaCl. If a buffer is required, a mild Tris solution (e.g. 0.01M) is recommended. The electrode arrays are stable under acidic conditions, so when coating with collagen there is no problem using solutions containing acetic acid.

(2)    To coat the electrode, simply pipet the protein solution into the well with sufficient volume to flood the substrate surface; usually a volume of 200 microliters is sufficient for most well types. If the protein is valuable, with 1E and 1E+ arrays, it is only necessary to coat the small active electrodes, and a small volume can be applied directly to the electrode surfaces.

(3)    Allow adsorption to take place for at least 15 minutes and longer for more dilute solutions.

(4)    Once adsorption is complete, a molecular layer of the protein will be coating the surfaces. You can now remove the protein solution and rinse any residual protein from the well with sterile medium, saline or water without concern of removing the adsorbed protein.

(5)    The arrays are now ready for other solutions (e.g. cysteine) and inoculation.

We do not recommend: 

• Drying protein solutions in place as this may foul or damage the electrodes.
• The use of phosphate buffer (PBS) for adsorption as this has been shown to interfere with the adsorption of some proteins.
• The use of very dilute protein solutions (<50 micrograms per ml). Remember protein may be adsorbing to the walls of the vessels holding solutions at a level as high as 1 microgram/cm². This can significantly reduce the concentration of protein in very dilute solution.