Solvent Spraying

A high-pressure solvent spray can be used to remove macroscopic amounts of surface contamination such as fingerprints. A convenient way to produce a solvent spray is to use an air brush available from most art supply stores. This treatment generally leaves the gold surface hydrophobic, presumably due to a small residual organic surface film.

Plasma Cleaning

An oxygen plasma can be used to remove organic thin films from the gold surface, including surface bound proteins from previous SPR experiments. The entire SPR slide can be placed in the plasma chamber without electrical damage to the sensor surface. This generally leaves the surface hydrophilic, presumably due to the presence of a thin oxide film. This oxide can be removed by subsequent hydrogen plasma, a treatment that also leaves the gold surface hydrophilic.

Chromic Acid

Chromic acid can also be used to clean gold surfaces and leave them hydrophilic. Immerse only the sensing surface of the SPR slide into a 20% solution of chromium trioxide in water.

CAUTION:

Take care when cleaning disposable gold films with this procedure. Prolonged exposure to chromic acid dissolves the chromium adhesion layer between the surface of the glass slide and the gold, resulting in delamination of the gold layer. Recommends soaking disposable slides for no longer than two minutes.

Detergent Scrubbing

If you are careful, you can clean the gold sensor surface by gentle rubbing with a cloth wet with an aqueous detergent solution, such as 4% sodium dodecyl sulfate (SDS). Eventually, the physical contact of this method does remove gold from the surface; but if you are careful, you can clean one gold surface dozens of times.

In Situ Cleaning Using NaOH/Triton X-100

Another method of reproducibly preparing a clean gold SPR slide surface involves exposure to a solution of 0.1 M NaOH and 1% Triton X-100. This method effectively removes small amounts of surface contamination.

 Summary

These procedures may be used singly or in combination to remove surface contamination in preparation for the binding of bio-molecules directly to the gold surface. They can also be used for the removal of bio-molecules and for regeneration of the sensor surface. 

But, in any case, using SPR slide one time is preferred!