| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018) | |
| Biomaterial Surfaces & Interfaces | Tuesday Sessions |
| Session BI-TuE |
| Session: | 35 Years of NESAC/BIO II |
| Presenter: | Luca Tortora, National Institute of Nuclear Physics Roma Tre, Italy |
| Authors: | L. Tortora, National Institute of Nuclear Physics Roma Tre, Italy S. De Rosa, National Institute of Nuclear Physics Roma Tre, Italy M. Dettin, University of Padua, Italy V. Secchi, Roma Tre University, Italy C. Battocchio, Roma Tre University, Italy G. Iucci, Roma Tre University, Italy |
| Correspondent: | Click to Email |
The use of short peptide-modified planar gold surfaces or gold nanoparticles is extensively reported in the literature regarding nanoscience and nanotechnology [1]. The mechanism by which these small biomolecules interact to form a film is a crucial information when a solid surface must be functionalized. At the same time, it must be taken into account that the final result in terms of chemical, topological, and functional features is strongly influenced by the orientation of the active layer. Here, a self-assembling peptide (SAP) with a Cys as a terminal residue was used to modify a planar gold surface. The SAP-Cys self-assembled monolayer (SAM) was obtained by o/n incubation of Au surfaces with 1mM SAP-Cys aqueous solution. The presence of alternating positively and negatively charged amino acids (H-Cys-Ala-Glu-Ala-Glu-Ala-Lys-Ala-Lys-Ala-Glu-Ala-Glu-Ala-Lys-Ala-Lys-OH) should guarantee the anchorage of the SAP to the metal surface preserving at the same time the ability of the SAP to self-assemble in antiparallel β-sheet structures. In recent studies [2], XPS analysis has allowed to estimate the film thickness as 4.45 nm and confirm the presence of sulfur atoms of Cys covalently bonded to the metal surface. In addition, an estimate of the mean angle between the peptide bond axis and the substrate surface of about 60° has been calculated by taking advantage of AD-NEXAFS investigations. In this work, we aim to obtain a more detailed understanding of the aggregation mechanism and orientation of SAP-Cys onto the gold surface through ToF-SIMS imaging and depth profiling experiments. Preliminary results obtained in static conditions showed the presence of SH negative ion signal coming from the top surface of the SAM, confirming the self-assembling of the SAP in antiparallel β-sheet structure. The signal intensities of the amino acid fragment ions were used to calculate the following ratios: Ala/Cys, Glu/Cys, Lys/Cys, and AuS/Au. In particular, AuS/Au peak intensity ratio values suggest a gold surface coverage percentage ranging from 8% to 12%. Low values of coverage could be strictly correlated with a strong presence of inorganic ions such as K, Na, spread over the gold substrate, as revealed by ToF-SIMS imaging. Finally, the SAP-Cys film was successfully profiled recording SH-and S-ion signal intensity variations during low energy dual beam depth profiling experiments.
References
1. D.Compagnone et al., Biosens. Bioelectron., 2013, 42, 15, 618-625.
2. V. Secchi et al., J. Phys. Chem. C2018, 122, 6236−6239.