pH-sensitive nanostructural transformation of a synthetic self-assembling water-soluble tripeptide: nanotube to nanovesicle

Abstract

Construction of various nanostructures using suitable self-assembling molecular building blocks is a challenging issue. Moreover, controlling the formation of a specific nanostructure from self-assembling molecular building blocks by tuning the pH of the solution is interesting. The present study demonstrates pH-responsive nanostructural transformation of a self-assembling water-soluble tripeptide from nanotubes to nanovesicles. In acidic pH (pH 4.3–5.5), hollow nanotubular structures have been observed, while at pH 6.5 (nearly neutral), both nanotubes and nanovesicles coexist uniformly. With an increase in the pH of the solution, only one nanoscopic species, i.e., nanovesicles, has been formed exclusively, and these hollow, fusible nanovesicles are stable within the range pH 7.0–9.2. A further increase in the pH triggers the rupture of these nanovesicles. pH-sensitive nanovesicle formation has been utilized for the entrapment and slow release of a physiological dye, Congo red.