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.

The growth of polysaccharide multilayers consisting of positively charged chitosan (CH) and negatively charged heparin (HEP) was monitored in situ by employing a quartz crystal microbalance (QCM-D) and dual-polarization interferometry (DPI). The main focus was on how the physicochemical properties of the solution affect the growth and structure of the resulting multilayer film. These results showed that when increasing the ionic strength of the polysaccharide solutions at a fixed pH, both the "dry" (optical) (DPI) mass and wet (QCM) mass of the adsorbed multilayer film increased. The same effect was found when increasing the pH while keeping the ionic strength constant. Furthermore, the growth of multilayers showed an exponential-like behavior independent of the solution conditions that were used in this study. It was also established that chitosan was the predominant species present in the chitosan-heparin multilayer film. We discuss the viscoelastic properties of the adsorbed layers and their variation during the multilayer buildup. Interestingly and contrary to common interpretation of the QCM-D results, we found that under one particular solution condition (pH 4.2 and 30 mM NaCl) the increase in the dissipation of oscillation energy from the adsorbed layer was a consequence of layer stiffening rather than indicating a more hydrated and viscous film. On the basis of the widely used Voigt viscoelastic model for an adsorbed layer, we show that it is the film viscosity and shear that define the layer viscoelasticity (structure) of the film and not the absolute value of energy dissipation, which in fact can be very misleading.

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The adsorption of a biologically important glycoprotein, mucin, and mucin-chitosan complex layer formation on negatively charged surfaces, silica and mica, have been investigated employing ellipsometry, the interferometric surface apparatus, and atomic force microscopy techniques. Particular attention has been paid to the effect of an anionic surfactant sodium, dodecyl sulfate (SDS), with respect to the stability of the adsorption layers. It has been shown that mucin adsorbs on negatively charged surfaces to form highly hydrated layers. Such mucin layers readily associate with surfactants and are easily removed from the surfaces by rinsing with solutions of SDS at concentrations > or =0.2 cmc (1 cmc SDS in 30 mM NaCl is equal to 3.3 mM). The mucin adsorption layer is negatively charged, and we show how a positively charged polyelectrolyte, chitosan, associates with the preadsorbed mucin to form mucin-chitosan complexes that resist desorption by SDS even at SDS concentrations as high as 1 cmc. Thus, a method of mucin layer protection against removal by surfactants is offered. Further, we show how mucin-chitosan multilayers can be formed.

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