Bimodal persistent luminescence for autofluorescence-free ratiometric biosensing

In optical biosensing, analyte-independent factors such as autofluorescence interference and excitation source fluctuation decrease the sensitivity and accuracy. Herein, we reported a bimodal persistent luminescence strategy to design dual-emissive persistent luminescence nanoparticles (PLNPs) with built-in self-calibration to preclude interference from analyte-independent factors in biosensing. As a proof of concept, ZnGa 2 O 4 :Cr PLNPs with emissions at both 490 nm and 695 nm were designed. The I 490 /I 695 ratio of ZnGa 2 O 4 :Cr was readily adjusted by simply changing the doping concentration of Cr 3+ . The ZnGa 2 O 4 :Cr PLNPs were employed for the ratiometric detection of urinary mesna. A good linear relationship between the I 490 /I 695 ratio of ZnGa 2 O 4 :Cr-based nanoprobe and the concentration of mesna was obtained in the range of 0–40 μM. The limit of detection was about 0.40 μM. Results showed that autofluorescence interference from urine was totally eliminated by collecting the persistent luminescence signal of ZnGa 2 O 4 :Cr after excitation ceased. Moreover, the built-in self-calibration feature of the ratiometric ZnGa 2 O 4 :Cr PLNPs efficiently suppressed the interference from fluctuations in instrumental parameters during urinary mesna detection. The recovery rates of mesna in the spiked urine samples are in the range of 99.1~109.0%, showing the reliability of the ratiometric ZnGa 2 O 4 :Cr PLNPs in urinary mesna detection. ZnGa 2 O 4 :Cr can further be expanded to the detection of other analytes in complex matrices. This study may open new opportunities for the design of dual-emissive PLNPs with tunable ratios of emission intensity, and it can further promote the applications of optical biosensing in disease diagnosis, food safety, and environmental monitoring. Graphical abstract