Abstract
<jats:p>We report self-assembled organic nanorods based on an acyl hydrazide low-molecular-weight gelator (LMWG) that undergo stimulus-triggered dynamic evolution. Nanorod fabrication starts from a bulk hydrogel in which the LMWG is self-assembled into molecular-scale fibrils (2.8 nm), that assemble into polydisperse flexible nanofibres (diameter ca. 11 nm) with lengths > 500 nm. Sonicating the gel with supernatant water induces reorganisation, creating a homogeneous solution of rigid nanorods with relatively well-defined lengths of ca. 100 nm. Although underpinned by the same molecular-scale fibrils, the nanorods have a monodisperse diameter of 22 nm, double the original nanofibres. Remarkably, these nanorods are stable in water for extended periods of time (> 1 month). On addition of Au(III), in situ reduction to gold nanoparticles (AuNPs) occurs, with the nanorod acyl hydrazide being oxidised to a carboxylic acid. At low Au(III) loadings, the nanorods become decorated with AuNPs and remain dispersed, but at higher Au(III) loadings, the pH falls below the pKa of the resulting carboxylic acid, triggering aggregation to yield an AuNP-loaded gel-like material. Changing pH switches between aggregation/dispersion via protonation/deprotonation. The nanorods can be functionalised by reacting the acyl hydrazide, for example with the ketone in doxorubicin (Dox). The bulk gel is modified, and sonication gives Dox-loaded nanorods. In summary, we report stable nanorods based on a simple LMWG that evolve in response to stimuli and can be derivatised with bioactive agents – we anticipate future biomedical applications.</jats:p>