Sensing and imaging of PPi in vivo using lanthanide-based second near-infrared luminescent probes.

Inorganic pyrophosphate (PPi), as a biologically active anion, is closely related to physiological activities and several pathological changes. Here, we reported a luminescent nanoprobe for the detection and imaging of PPi in vivo based on lanthanide nanoparticles with luminescence at the second near-infrared window modified by the tannic acid and Fe3+ complex. A light-harvesting complex was formed after the coordination of colorless tannic acid with Fe3+ and the luminescence of the nanoparticles was quenched through the inner-filter effect. In the presence of PPi, the complex was decomposed due to the stronger coordination affinity of PPi to Fe3+; thus the luminescence of the nanoprobe was recovered. The nanoprobe manifested good linearity with a low detection limit of 3.36 µM. Importantly, in the in vivo study simulating the calcium pyrophosphate deposition disease, the nanoprobe with the second near-infrared luminescence achieved the imaging of the injected PPi at the paw of the mice at a dose of 0.25 mg kg-1. The reported nanoprobe can serve as a convenient tool for the in vivo imaging of PPi and the diagnosis of PPi-related diseases.

A simple paper-based ratiometric luminescent sensor for tetracyclines using copper nanocluster-europium hybrid nanoprobes.

Tetracyclines (TCs), as one of the broad-spectrum antibiotics, are widely used to treat bacterial infections. The residues of TCs in animal-origin foods and drinking water have raised safety concerns and affected the public health. Thus, there is a high demand to develop a simple and rapid method for the detection of TCs. In this work, we developed a ratiometric luminescence probe for the sensitive and visualized detection of TCs. Specifically, tannic acid-stabilized copper nanoclusters (TA-CuNCs) with blue emission at 433 nm were synthesized. The luminescence of TA-CuNCs attenuated partially by the europium ions (Eu3+) due to the aggregation-induced quenching. When TCs were added to the TA-CuNCs-Eu3+ system, the luminescence of TA-CuNCs at 433 nm can be further quenched by the inner-filter effect, and the characteristic luminescence of Eu3+ at 617 nm emerged due to the formation of Eu3+-TCs complex. The ratio of the luminescence at 617 nm-433 nm increased linearly to the concentration of TCs. Additionally, we demonstrated the detection of oxytetracycline in real samples such as tap and lake water, milk, pharmaceutical industry wastewater, honey and soil extract with high recovery rate (97.25%-103.44%). Furthermore, a portable paper device is fabricated by the luminescent probe to conduct the on-site analysis of TCs.