Gold Nanoparticles Interacting with β-Cyclodextrin–Phenylethylamine Inclusion Complex: A Ternary System for Photothermal Drug Release

We report the synthesis of a 1:1 β-cyclodextrin-phenylethylamine (βCD-PhEA) inclusion complex (IC) and the adhesion of gold nanoparticles (AuNPs) onto microcrystals of this complex, which forms a ternary system. The formation of the IC was confirmed by powder X-ray diffraction and NMR analyses ((1)H and ROESY). The stability constant of the IC (760 M(-1)) was determined using the phase solubility method. The adhesion of AuNPs was obtained using the magnetron sputtering technique, and the presence of AuNPs was confirmed using UV-vis spectroscopy (surface plasmon resonance effect), which showed an absorbance at 533 nm. The powder X-ray diffractograms of βCD-PhEA were similar to those of the crystals decorated with AuNPs. A comparison of the one- and two-dimensional NMR spectra of the IC with and without AuNPs suggests partial displacement of the guest to the outside of the βCD due to attraction toward AuNPs, a characteristic tropism effect. The size, morphology, and distribution of the AuNPs were analyzed using TEM and SEM. The average size of the AuNPs was 14 nm. Changes in the IR and Raman spectra were attributed to the formation of the complex and to the specific interactions of this group with the AuNPs. Laser irradiation assays show that the ternary system βCD-PhEA-AuNPs in solution enables the release of the guest.