Molecularly imprinted alginate-PVP membrane for the selective fluorescence detection of flavonoids in foods: A practical case for rutin

Flavonoids benefits have rendered them interesting molecules in the realm of sensing. However, a significant challenge lies in their selective and sensitive detection in complex matrices. One of the most relevant flavonoids is rutin (RU), a flavonoid glycoside. In this work, a novel, straightforward, and green approach is proposed to prepare a selective molecularly imprinted membrane (MIM) for RU based on sodium alginate and polyvinylpyrrolidone, following a central composite design for the optimization of the MIM preparation. The developed membrane was characterized by Fourier transform infrared spectroscopy, thermo-gravimetric analysis, and scanning electron microscopy to assess the functional, thermal, and morphological properties of the membrane, respectively. The developed MIM was successfully applied for the selective and sensitive solid spectro-fluorescence sensing of RU within a concentration range of 0.01–10 µg/mL and a limit of detection (LOD) of 3.6 ng/mL. Furthermore, a new 3D-printed smartphone accessory was designed and applied in smartphone-based solid fluorescence assays. This innovation enabled portable, label-free, rapid, cheap, and green detection of RU across a concentration interval of 0.05–10 µg/mL, with a LOD of 20 ng/mL. Moreover, MIM showed important long-term stability and good reusability (10 regeneration cycles). Finally, the proposed methodology was validated using an accuracy statistical approach. Overall, this study didn’t only demonstrate an innovative and straightforward approach to imprinting technology but also highlighted the promise of the proposed smartphone-based sensing method as a versatile tool with a broad range of applications to automatize the analysis and to enhance portable diagnosis technology.