Thiolated amphiphilic β-cyclodextrin-decorated gold colloids: Synthesis, supramolecular nanoassemblies and controlled release of dopamine

We report a hybrid nanoassembly based on gold colloids decorated with a new thiolated amphiphilic cyclodextrin complexing dopamine (AuNPs@SC16SH/DA). The novel amphiphilic β-cyclodextrin SC16SH, bearing on average one thiol group at the end of an oligoethylene glycol chain per CyD unit, was obtained in a multi-step synthesis and fully characterized by NMR spectroscopy and MALDI analysis. The AuNPs@SC16SH hybrid assembly was prepared by mixing AuNPs and SC16SH in aqueous solution and investigated by UV/Vis and TEM measurements. The AuNPs@SC16SH/DA supramolecular assembly, bearing both thiol-stabilized gold nanoparticles and the neurotransmitter dopamine, has been conceived as stimuli-responsive delivery system able to control the release of dopamine upon proper stimuli. Two redox functionalities (i.e. the Au-S bond and the redox behaviour of dopamine) have been exploited to detach SC16SH/DA complex from the AuNPs@SC16SH/DA progenitor platform, using dithiothreitol (DTT), and to detect the complex by cyclic voltammetry (CV). Following, dopamine was finally released from the SC16SH/DA assembly upon treatment with Brij® S20 and the free dopamine was monitored by CV. Overall, our hybrid nanoassemblies turned out to be able to release dopamine, upon combined action of redox and digestion agents in medium emulating biological environment.