Isolation of the Flavonoid from Bamboo Residues and Its Application as Metal Ion Sensor in Vitro

Fluorescence sensors prepared from natural polymers have received increasing attention based on their luminescence characteristics for bioimaging, cell imaging, and intracellular detection of inorganic metabolites. In this work, flavonoids isolated from bamboo residues (BRF) were applied as fluorescence sensors for different metal cations' detection in vitro. Results showed the optimal flavonoids extraction condition of solid to liquid ratio, ethanol concentration, extraction time and temperature were determined at 1:25, 50%, 240 min and 90 °C, respectively, resulting in an extraction yield with 104.7 mg/100 g bamboo residues. The BRF is mainly composed of isoorientin, isovitexin, pinosylvin, tricin and isorhamnetin by liquid chromatography-mass spectrometry (LC-MS) analysis. It is found that the BRF displayed strong blue-green emission as well as notable excitation, which can selectively and sensitively detect Fe³⁺ with the limit of detection (LOD) as low as 38.0 nM. In the Fe³⁺ detection was no obvious interference by other cations except for Al³⁺. In addition, the BRF displayed excellent biocompatibility that can be applied to bioimages of the intracellular detection of Fe³⁺ in L02 cells. Finally, it is found that the BRF possessed significant antioxidant properties in scavenging H₂O₂-induced endogenous reactive oxygen species (ROS) in a zebrafish module (in vivo) and L02 cells (in vitro). These results showed that the flavonoid products sustainably isolated from an abundant lignocellulosic waste appear to be effective fluorescent sensors for Fe³⁺ detection in biological systems with excellent biocompatibility and antioxidant activity.