Self-assembled ratiometric sensor for specific detection of hypoxia in living cells based on lanthanide-doped upconversion nanoparticles and gold nanoparticles.

We describes the development of a self-assembled nanoprobe for ratiometric sensing of hypoxia in living cells. The probe, UC-AuNPs, is composed of azo-functionalized upconversion nanoparticles (azo-UCNPs) and gold nanoparticles functionalized with β-cyclodextrin (CD-AuNPs). Under hypoxic conditions, reductases reduce azo derivatives on the UCNPs, leading to detachment of the CD-AuNPs and subsequent fluorescence recovery of the green emission. The ratiometric measurement incorporated into the strategy reduces the impact of external factors and improves sensitivity of the probe. The use of NIR excitation effectively minimizes interference from strong luminescence backgrounds in biosystems. The UC-AuNPs nanoprobe is able to effectively sense and monitor hypoxia conditions in living cells and has the potential to distinguish hypoxia-related diseases from healthy tissue, making it a valuable tool for early clinical diagnosis.