The NAP peptide (H(2)N-(1)NAPVSIPQ(8)-CONH(2)) is a truncated version of the activity-dependent neuroprotective protein. Its neuroprotective activities consist of the inhibition of Aβ(25-35) and Aβ(1-40) fibrillogenesis as well as protection against Aβ-induced neurotoxicity and prevention of microtubule disruption associated with Alzheimer's disease. Therefore, we synthesized NAP and its mutant peptide with the sequence: H(2)N-(1)NAPVCIPQ(8)-COOH (NAPCOH), by replacing serine S(5) with cysteine C(5). Both native and mutant peptides were further used to study their interaction with iron ions. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry, Fourier transform infrared spectroscopy and also atomic force microscopy were used to probe Fe(3+) binding to both peptides. Contrary to the expected results, the investigated peptides underwent different oxidation processes, with resultant reduced Fe(2+) ions. These ions, and not the original Fe(3+) ions, were found to bind to each of non-oxidized peptides.
Plasma polymerized styrene (pPS) films were successfully synthesized by means of atmospheric pressure plasma technique, using a mixture of argon gas and styrene vapor. The morphology and film thickness of the pPS films, deposited on 1 min argon plasma pre-treated glass substrates, were smooth and uniform without any visible features across the whole length of the substrates and displayed a water contact angle of ~83°. X-ray photoelectron spectroscopy (XPS) andFourier transform infrared (FTIR) analysis confirmed the presence of oxygen-containing groups and intact aromatic ring in the pPS coating. The obtained pPS films were stable at least 30 days in air without any visible morphological degradation or chemical changes. However, formation of a topographical pattern with micrometer lateral size and nanometer depth level was observed upon immersion in aqueous media for 72 hours. Micropore formation was believed to originate from the solubility of the low cross-linked oligomers and their subsequent extraction in aqueous media. The influence of the microstructured pPS surface in mediating the attachment of eukaryotic and prokaryotic cells was further investigated. The micro-structured pPS surface influenced the adhesion and proliferation of mammalian cells. Furthermore, we could demonstrate that these films were efficient in the prevention of Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus epidermis (S. epidermis) adhesion and biofilm formation. Importantly, the viability of non-adherent cells and of planktonic bacteria was not affected. Post-coating of microstructured pPS with biocompatible polydopamine did not impact on the antibacterial properties of the surface, suggesting that the polymer topography was the dominant factor. The non-biocidal pPS coating can be useful in applications where microorganism colonization and biofilm formation need to be prevented, such as food packaging and medical equipments.
Is PlasBeam pretreatment an efficient method to improve sealant adhesion onto the enamel surface?The aim of this study isto investigate the effects induced by three pretreatment techniques used to improve sealant adhesion on the enamel surface, respectively standard acid-etching, UV radiations and a new method based on plasma operating at atmospheric pressure, namely the PlasBeam method.The physical-chemical modifications induced onto the enamel surface by the above pretreatments were analyzed using Contact Angle Measurements and Diffuse Reflectance Spectroscopy.The changes in the enamel surface morphology show that the acid-etching pretreatment is mostly efficient in increasing roughness, but this method stimulates the degradation processes that are well-known and turns down the brillianceof the treated surface. On the other hand, the PlasBeam treatment brings a higher roughness at the contact area between sealant and the enamel surface, compared to the UV radiations pretreatments.Moreover, the PlasBeam improves the hydrophilic character of enamel as a practical solution in enhancing the sealant adhesion to the surface. Related to other effects, it has been noticed that thePlasBeam method generates the most reflective enamel surface, whereas the White/Yellow index reaches the minimum level after a 10 second treatment.
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