Monitoring the Interfacial Behavior of Selective Y5 Receptor Antagonist on Colloidal Gold Nanoparticle Surfaces: Surface-Enhanced Vibrational Spectroscopy Studies

This report describes the first detailed characterization of the molecular structure of Lu AA33810, a selective Y5 receptor antagonist, and its behavior at the solid/liquid interface after conjugation with gold nanoparticles (GNPs). Physicochemical characterization, including imaging by scanning electron microscopy as well as electrophoretic mobility and dynamic light scattering measurements, was performed to determine the morphology, electrokinetic properties and range of stability of the GNPs. A comprehensive vibrational analysis, employing Raman spectroscopy, Fourier transform infrared absorption, surface-enhanced Raman spectroscopy, and surface-enhanced infrared absorption methods, is reported. The experimental data are supported by density functional theory calculations. It is implied that the Thz and Phe rings determine the adsorption geometry of Lu AA33810 on the studied GNPs and adopt a tilted orientation, exposing the interaction between the Thz free electron pair and the metallic nanosubstrates. The analysis also provides evidence for strong interaction between the free electron pairs located on the oxygen atoms of the SO2 fragment of methanesulfonarnide and the GNPs. The results provide important insight into designing new compounds with agonistic or antagonistic properties toward the Y5 receptor.