Biodegradable, multiple stimuli-responsive sodium deoxycholate-amino acids-NaCl mixed systems for dye delivery

Supramolecular hydrogels were prepared in mixtures of the biological surfactant sodium deoxycholate (NaDC) and amino acids (glycine (Gly), alanine (Ala), lysine (Lys) and arginine (Arg)) in different pH buffer solutions. We characterized their performance through phase behavior observation, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and rheological measurements. The results demonstrate that the presence of Gly and Ala can enhance the formation of the gels, whereas the addition of Lys and Arg could cause the breakage of the hydrogen bonds and weaken the formation of the gels. The formation of hydrogels with different gelling kinetics and mechanical properties or the behavior of the sol-gel transformation of the systems may be obtained by finely modulating pH. Moreover, the addition of the halide salts (NaCl) can enhance the mechanical strength of the gels. Because of their unique responsiveness to multi-stimuli environments, these biodegradable and pH-sensitive hydrogels hold great promise as versatile vehicles for dye (or drug) delivery.