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This work was devoted to probe, at the entire population level, interactions between mucins and Lactococcus lactis, using QCM-D. Real-time monitoring of adsorption on polystyrene of PGM (Pig Gastric Mucin) and subsequent adhesion of L. lactis was performed for IBB477 and MG1820 strains. Measuring simultaneously shifts in resonance frequency and dissipation on the polystyrene-coated crystal demonstrated a two-phase process for PGM adsorption. XPS analysis confirmed the presence of adsorbed mucin. The Voigt-based model was used to describe the QCM-D outputs. The predicted thickness of the PGM layer was consistent with the AFM experimental value. Adhesion of L. lactis to bare or PGM-coated polystyrene was then monitored, in combination with DAPI cell counting. Positive frequency shifts were caused by adhering bacteria. The presence of adsorbed PGM strongly reduced bacterial adhesion. However, adhesion of IBB477 to the PGM coating was greatly increased in comparison with that of MG1820. Muco-adhesion may be a highly variable and valuable phenotypic trait among L. lactis strains. [ABSTRACT FROM PUBLISHER]

The adsorption of a model protein, the bovine serum albumin (BSA), on plasma-deposited silver nanocomposite thin films was investigated in situ by quartz crystal microbalance (QCM) and ex situ by X-ray photoelectron spectroscopy (XPS). For comparison, BSA adsorption was also studied on pure silver sample and on the polymeric matrix without silver nanoparticles. Both techniques showed that BSA adsorption systematically occurred, regardless of the chemical composition of the solid surface. BSA adsorption was found to be a fast and irreversible process. For the adsorbed BSA layer characterization, a general island model was considered. The height of the protein islands ( h ) and their surface coverage ( γ ) were estimated from combined QCM and XPS data. On the polymeric matrix, the surface coverage was low whereas on pure silver sample and on the nanocomposite film, it was significantly increased. From QCM measurements, mass loss at a constant rate, ascribed to the release and dissolution of Ag particles from the nanocomposite film into the surrounding solution, was observed before and after BSA adsorption, with two different associated rates. The decrease of the silver release rate after BSA adsorption is explained by silver particles coverage by protein islands. BSA molecules adsorbed on silver nanoparticles have a “blocking” effect, decreased the rate of silver nanoparticle release. However, silver dissolution as Ag + ions may still occur. [ABSTRACT FROM AUTHOR]

Abstract: An XPS investigation was carried out of the surface films, formed by exposure to ultrapure water, on mechanically ground Mg and the two Mg–Al intermetallic compounds: Al3Mg2 and Mg17Al12. The mechanically ground Mg surface had a film of MgO at the Mg metal surface covered by a Mg(OH)2 layer, formed by the reaction of the MgO with water vapour in the air. Upon immersion in ultrapure water, this film converted to a duplex film with an inner MgO layer next to the Mg metal and an external porous hydroxide layer. For both intermetallics, the XPS data is consistent with (i) preferential dissolution of Mg and (ii) a 10nm thick film on the surface after immersion in ultrapure water; the film composition on Al3Mg2 was whilst on Mg17Al12 the composition was . [Copyright &y& Elsevier]