Biological application of water-based electrochemically synthesized CuO leaf-like arrays: SERS response modulated by the positional isomerism and interface type

Highly Sensitive and Stable Copper-Based SERS Chips Prepared by a Chemical Reduction Method

Cu chips are cheaper than Ag and Au chips for practical SERS applications. However, copper substrates generally have weak SERS enhancement effects and poor stability. In the present work, Cu-based SERS chips with high sensitivity and stability were developed by a chemical reduction method. In the preparation process, Cu NPs were densely deposited onto fabric supports. The as-prepared Cu-coated fabric was hydrophobic with fairly good SERS performance. The Cu-coated fabric was able to be used as a SERS chip to detect crystal violet, and it exhibited an enhancement factor of 2.0 × 106 and gave a limit of detection (LOD) as low as 10-8 M. The hydrophobicity of the Cu membrane on the fabric is favorable to cleaning background interference signals and promoting the stability of Cu NPs to environment oxidation. However, this Cu SERS chip was still poor in its long-term stability. The SERS intensity on the chip was decreased to 18% of the original one after it was stored in air for 60 days. A simple introduction of Ag onto the clean Cu surface was achieved by a replacement reaction to further enhance the SERS performances of the Cu chips. The Ag-modified Cu chips showed an increase of the enhancement factor to 7.6 × 106 due to the plasmonic coupling between Cu and Ag in nanoscale, and decreased the LOD of CV to 10-11 M by three orders of magnitude. Owing to the additional protection of Ag shell, the SERS intensity of the Cu-Ag chip after a two-month storing maintained 80% of the original intensity. The Cu-Ag SERS chips were also applied to detect other organics, and showing wide linearity range and low LOD values for the quantitative detection.

Application of Alanine Scanning to Determination of Amino Acids Essential for Peptide Adsorption at the Solid/Solution Interface and Binding to the Receptor: Surface-Enhanced Raman/Infrared Spectroscopy versus Bioactivity Assays

The article describes the application of the alanine-scanning technique used in combination with Raman, surface-enhanced Raman, attenuated total reflection Fourier transform infrared, and surface-enhanced infrared absorption (SEIRA) spectroscopies, which allowed defining the role of individual amino acid residues in the C-terminal 6-14 fragment of the bombesin chain (BN6-14) on the path of its adsorption on the surface of Ag (AgNPs) and Au nanoparticles (AuNPs). A reliable analysis of the SEIRA spectra of these peptides was possible, thanks to a curve fitting of these spectra. By combining alanine-scanning with biological activity studies using cell lines overexpressing bombesin receptors and the intracellular inositol monophosphate assay, it was possible to determine which peptide side chains play a significant role in binding a peptide to membrane-bound G protein-coupled receptors (GPCRs). Based on the analysis of spectral profiles and bioactivity results, conclusions for the specific peptide-metal and peptide-GPCR interactions were drawn and compared.