Peptide-based hydrogels with tunable nanostructures for the controlled release of dyes

Hydrogels with different microstructures including nanoribbons, stiff nanofibers, helical ribbons and nanotubes were observed by varying the concentration of oxidized glutathione (OGH) with a fixed concentration of sodium deoxycholate (SD). The self-assembled nanostructures were characterized in detail by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Random coil structures and beta-sheets play important roles in the constructed nanostructures, which were verified by Fourier-transform infrared (FT-IR) spectroscopy and circular dichroism (CD), as well as small angle X-ray diffraction (SXRD) measurements. We proposed a mechanism for these nanostructural transformations. The "weak hydrogels" exhibited irreversible responses to heating and shaking and a reversible response to pH. Furthermore, the hydrogel could be used for the controlled release of dyes. Due to the strong electrostatic attraction between the positively charged dye methylene violet (MV) and the negatively charged nanofibers, methylene violet is released more slowly than the negatively charged dye, methyl orange (MO).