Cyclodextrin as a water-soluble host of azobenzene-based pH probe enables long-term monitoring

Abstract

Azobenzene-based probes have been widely used in biosensing, bioimaging and nanomedicine; however, their water solubility was not good enough, especially for long-term processes. To address the problem, cyclodextrins (CDs) were utilized as water-soluble hosts to facilitate the dispersion of azo molecules separately in the aqueous solution, which avoided aggregation to improve water solubility. In addition, an azobenzene-based pH probe was developed to serve as a model molecule to investigate the influence on responsive performance after host–guest interaction. Compared with α-and β-CD, γ-CD with the biggest cavity size and weakest host–guest interaction displayed the best improvement on water solubility and minimized influence on the pH-responsive performance, providing a universal approach to improve the water solubility of azobenzene-based probes while with a minimal negative effect on the responsive performance, which will be of interest to researchers in the fields of supramolecular chemistry, materials science and nanotechnology.