Protein- and Nanoparticle-Loaded Hydrogels Studied by Small-Angle Scattering and Rheology Techniques

Abstract

In the last decades, hydrogels have been used for controlled loading and release in pharmaceutical applications. In tissue engineering, protein–hydrogel hybrid systems play a critical role in wound healing and tissue growth (Vermonden et al. in Chem Rev 112:2853–2888, 2012). At the same time, the mechanical and morphological properties of hydrogels have been modified and tuned by addition of nanoparticles (Haraguchi et al. in Macromolecules 36:5732–5741, 2003). The mechanical properties of hydrogels are one of their key characteristics. For example in injectable hydrogels, shear-thinning behavior is a defining factor (Guvendiren et al. in Soft Matter 8:260–272, 2012). Furthermore, the rheological behavior of a protein- or nanoparticle-loaded hydrogels may be influenced by the presence of the added compound, especially when the last acts as a cross-linking agent. The multi-scale hierarchical structures produced by hydrogel nanocomposites can be resolved by small-angle neutron scattering and X-ray scattering (SANS and SAXS) in the relevant length scales from 1 to 1000 nm (combined with ultra-small-angle X-ray and neutron scattering: USAXS and USANS). The study of such systems under deformation (e.g., Rheo-SANS) gives invaluable insight into the structural details that define mechanical properties (Shibayama in Polym J 43:18–34, 2011). In this chapter, the recent developments in the field of hydrogels and nanoparticle-loaded-hydrogel systems, based mainly on SANS/SAXS and rheological techniques, are presented. A wide range of experimental realizations and examples of promising hydrogel–protein combinations is covered, and the analyses used to connect the structure–rheology properties are demonstrated in a unifying way.