pH-Sensitive assembly/disassembly gold nanoparticles with the potential of tumor diagnosis and treatment

Due to the ability to combine the separately unique characteristics of assembled and disassembled nanoparticles (NPs), the stimuli-responsive self-assembly of NPs has attracted considerable interest in functional material applications especially biomaterials. Here we demonstrate a facile and versatile approach to regulate the self-assembly process and transition pH of Au NPs by fine-tuning the co-modified pH-responsive compounds and poly(ethylene glycol) (PEG). Importantly the transition pH (pH=0.4) of the system can be predetermined in the range of 8.2-5.8 (assembled to disassembled) and 8.2-4.2 (disassembled to assembled), which ideally covers the pH of normal tissue, tumor tissue milieu and organelles. The results of fluorescence imaging, Raman spectroscopy and photothermal conversion of the stimuli-responsive Au NPs shows the potential application for tumor specificity theranostics. In a nutshell this study provides a useful toolkit to design tumor-activatable self-assembled NPs with high specificity and universality.