Persistent Luminescence Nanosensors: A Generalized Optode-based Platform for Autofluorescence-free Sensing in Biological Systems

Fluorescent nanosensors have drastically progressed our ability to accelerate diagnostics and quantify cellular dynamics in real time. Their modular assembly allows for facile sensor tuning, leading to a large expansion of analytes and systems that can be analyzed. Still, separating sensor signals from background optical signatures remains a major hurdle in the field. Exploiting this modular synthesis, we merged optode-based sensing with near-infrared emitting ZnGa2O4:Cr3+ persistent luminescence nanoparticles (PLNPs) to create functional nanocompo- sites for autofluorescence-free “glow-in-the-dark” sensing. We hydrophobically modified the PLNP surface with covalently bound ligands and incorporated the PLNPs into the polymeric core of optode-based nanoparticles. We demonstrate persistent luminescence nanosensors (PLNs) for five different analytes (K+, Na+, Ca2+, pH, and O2) based on two different sensing mechanisms. The PLNs allowed us to achieve autofluorescence-free quantification of K+ in fetal bovine serum and ratiometric metabolic monitoring of microbial samples with time-resolved luminescence acquisition. We foresee that this approach will allow for high signal-to-noise ratios while sensing in optically challenging samples.