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

Abstract

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 methanesulfonamide and the GNPs. The results provide important insight into designing new compounds with agonistic or antagonistic properties toward the Y5 receptor.

Polarization effect in tip-enhanced infrared nanospectroscopy studies of the selective Y5 receptor antagonist Lu AA33810

“…This phenomenon coupled with the observed strengthening of the aforementioned bands suggest a rather perpendicular orientation of the C-H bonds on the metal surface. However, there are significant differences between the p-polarized TEIRA signal and conventional SEIRA bands recorded in the transmission mode [45]. In particular, the bands at 2,954 and 2,851 cm −1 in the SEIRA spectrum [45], attributed to the asymmetric CH 3 and symmetric CH 2 stretching modes, are not observed in the p-polarized nanoscale signal.…”

“…However, there are significant differences between the p-polarized TEIRA signal and conventional SEIRA bands recorded in the transmission mode [45]. In particular, the bands at 2,954 and 2,851 cm −1 in the SEIRA spectrum [45], attributed to the asymmetric CH 3 and symmetric CH 2 stretching modes, are not observed in the p-polarized nanoscale signal. These findings confirm that the intensities of the C-H bands reveal a strong polarization dependence [36,51].…”

“…, respectively) in comparison to the corresponding SEIRA spectrum [45]. The wavenumber assignments are given in Table 1.…”

“…Lu AA33810 was purchased from Tocris Bioscience (UK) (purity ~ 98.3%) and prepared according to previously published data [45]. A freshly prepared aqueous solution was obtained by dissolving 2.13 mg of the investigated antagonist in the deionized water using the sonification process.…”

“…In the recent study, the molecular structure of Lu AA33810 was determined experimentally (Raman spectroscopy (RS) and FT-IR and theoretically (density functional theory (DFT)) [45]. Furthermore, SERS and SEIRA techniques have been used to discuss the Lu AA33810 interfacial behavior onto GNPs surfaces.…”