Electrochemical and surface plasmon resonance characterization ofβ-cyclodextrin-based self-assembled monolayers and evaluation of their inclusion complexeswith glucocorticoids

Abstract

This paper describes the characterization of a self-assembledβ-cyclodextrin (β-CD)-derivativemonolayer (β-CD-SAM) on a gold surface and the study of their inclusion complexeswith glucocorticoids. To this aim the arrangement of a self-assembledβ-cyclodextrin-derivative monolayer on a gold surface was monitored in situ by meansof surface plasmon resonance (SPR) spectroscopy and double-layer capacitancemeasurements. Film thickness and dielectric constant were evaluated for a monolayer ofβ-CD using one-color-approach SPR. The selectivity of theβ-CD host surface was verified by using electroactive species permeable and impermeable in theβ-CD cavity. The redox probe was selected according to its capacity to permeate theβ-CDmonolayer and its electrochemical behavior. In order to evaluate the feasibility of an inclusion complexbetween β-CD-SAM with some steroids such as cortisol and cortisone, voltammetric experimentsin the presence of the redox probes as molecules competitive with the steroidshave been performed. The formation constant of the surface host–guest byβ-CD-SAM and the steroids under study was calculated.