Structural Properties and Hydrogen-Bond Dynamics of Water Confined in Cyclodextrin-Based Hydrogel

Cyclodextrin nanosponges (CDNS) are a very promising class of cross-linked polymers, made up of cyclodextrins, which can swell in aqueous solution giving rise to an interesting gel-like behavior. These cyclodextrin-based materials show notable properties as systems capable of encapsulating, carrying and releasing a variety of both lipophilic and hydrophilic compounds. As a matter of fact, the presence of cyclodextrin units in the hydrogel network allows to overcome the limited loading of hydrophobic active ingredients in hydrogels and improve the control of drug delivery. Here we present a thorough inspection of the vibrational dynamics of CDNS hydrogel, performed by using Raman scattering experiments, with the aim to give a deep structural and dynamical characterization at molecular level of these polymeric matrices. Particular attention will be devoted to investigating the structural properties and the hydrogen-bond dynamics of the water molecules entrapped in the nano-pores of CDNS. For this purpose, the spectral evolution of the O-H stretching band of the Raman spectra of nanosponges will be followed as increasing the water content of the system, in order to correlate the hydrogen-bond dynamic of water with the swelling ability of the polymers. We believe that these results are a key preliminary step to understand the close relationship between the structural and functional properties of CDNS-hydrogel, also in view of their aforementioned relevant applications as effective organic matrices for molecular encapsulation.