Supramolecular Assembly Based on Sulfato-β-cyclodextrin for Hypoxia Cell Imaging

Constructing hypoxia fluorescence probes is a developing research field, due to the hypoxic nature of many diseases, caused by an inadequate supply of oxygen. Herein, we reported a noncovalent hypoxia-responsive turn-on fluorescence probe, constructed by biocompatible sulfato-β-cyclodextrin (SCD), azobenzene derivative (1), and fluorochrome rhodamine 123 (Rho123). TEM image and dynamic light scattering (DLS) indicated that negatively multicharged SCD and positively charged 1 aggregated into nanoparticles with an average diameter of 53.8 nm through electrostatic interactions. The critical aggregation concentration (CAC) of 1 in the presence of SCD was obtained as 0.028 mM investigated by optical transmittance experiments quantitatively. The supramolecular assembly (SCD/1) works as both carrier and fluorescent quencher of Rho123. Verified by UV/vis absorption experiments, the azobenzene derivative 1 can be reduced efficiently by chemical reductant with a rate constant of 1.598 min–1. Florescence experiments showed that SCD/1 made a thoroughly quenching of Rho123 and 8-fold recovery of fluorescence intensity after reduced. Under hypoxia condition the azobenzene group of 1 was reduced by azo reductase, accompanying with the release and fluorescence recovery of Rho123. The noncovalent hypoxia-responsive ternary supramolecular assembly was used for hypoxia cell imaging.