The effect of inert salt concentration on polyelectrolyte adsorption from aqueous solutions onto oppositely charged surfaces and the interactions between such surfaces were studied experimentally using a surface force technique and compared to theoretical predictions from Monte Carlo simulations. At a polyelectrolyte concentration of 10 ppm and a low inert salt concentration (10-4 M), the polyelectrolytes adsorb in a flat conformation and the force acting between the surfaces is close to zero down to a separation of 10-1 5 nm, where the surfaces jump inward. The attractive force observed at separations below 10 nm is stronger than the expected van der Waals force. The magnitude and range of the attraction agree with forces obtained from Monte Carlo simulation, and we interpret the attraction as being due to bridging polyelectrolytes. When the salt concentration is increased, additional polyelectrolyte adsorption takes place. This again gives rise to a repulsive force, which is significantly larger than what is observed between bare surfaces. The extra repulsion is due to adsorbed polyelectrolytes stretching out from the surfaces and is also predicted from simulations.
Implantation using stainless steels (SS) is an example where an understanding of protein-induced metal release from SS is important when assessing potential toxicological risks. Here, the protein-induced metal release was investigated for austenitic (AISI 304, 310, and 316L), ferritic (AISI 430), and duplex (AISI 2205) grades in a phosphate buffered saline (PBS, pH 7.4) solution containing either bovine serum albumin (BSA) or lysozyme (LSZ). The results show that both BSA and LSZ induce a significant enrichment of chromium in the surface oxide of all stainless steel grades. Both proteins induced an enhanced extent of released iron, chromium, nickel and manganese, very significant in the case of BSA (up to 40-fold increase), whereas both proteins reduced the corrosion resistance of SS, with the reverse situation for iron metal (reduced corrosion rates and reduced metal release in the presence of proteins). A full monolayer coverage is necessary to induce the effects observed.Electronic supplementary materialThe online version of this article (doi:10.1007/s10856-013-4859-8) contains supplementary material, which is available to authorized users.
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