High-efficiency in vitro and in vivo detection of Zn2+ by dye-assembled upconversion nanoparticles

Development of highly sensitive and selective sensing systems of divalent zinc ion (Zn(2+)) in organisms has been a growing interest in the past decades owing to its pivotal role in cellular metabolism, apoptosis, and neurotransmission. Herein, we report the rational design and synthesis of a Zn(2+) fluorescent-based probe by assembling lanthanide-doped upconversion nanoparticles (UCNPs) with chromophores. Specifically, upconversion luminescence (UCL) can be effectively quenched by the chromophores on the surface of nanoparticles via a fluorescence resonant energy transfer (FRET) process and subsequently recovered upon the addition of Zn(2+), thus allowing for quantitative monitoring of Zn(2+). Importantly, the sensing system enables detection of Zn(2+) in real biological samples. We demonstrate that this chromophore-UCNP nanosystem is capable of implementing an efficient in vitro and in vivo detection of Zn(2+) in mouse brain slice with Alzheimer's disease and zebrafish, respectively.