ToF-SIMS chemical mapping study of protein adsorption onto stainless steel surfaces immersed in saline aqueous solutions

It is now well established that protein adsorption constitutes the first step of the biofouling process. As sea. water contains several salts (mainly, NaCl, MgCl2 and CaCID and their influence on the protein adsorption is not yet clear, the aim of this contribution was to bring new insight on their role. For this purpose, different aqueous solutions containing salts mixtures have been prepared while keeping the total salt concentration the same as in natural seawater (36 g/l). A model protein, the bovine serum albumin (BSA) was added to these solutions. Stainless steel surfaces were immersed into these different solutions for 24 h then rinsed and freeze-dried. The time-of-flight-secondary ion mass spectrometry (ToF-SIMS) molecular images show that all the salts dissolved in water produce micrometer particles at the sample surfaces. These particles are mainly consist of sodium, magnesium and calcium. Because there are few space correlations with any counter ions (Cl, SO4-, etc.), these particles are not pure salt residues. Moreover, these particles were found to be the preferred adsorption sites for the proteins. Indeed, the images show that the BSA surrounds these metallic spots to form annular shape patterns (diameter 20 mm). (C) 2002 Elsevier Science B.V. All rights reserved.