Photo-crosslinked hydrogel as a sensing platform for sensitive detection of free bilirubin in urine samples

In cases of liver lesions or metabolic blockages, the accumulation of bilirubin in the blood can lead to hyperbilirubinemia, resulting in jaundice. Hence, the development of a rapid and highly selective assay strategy for accurately quantifying free bilirubin concentrations in humans is crucial for clinical diagnosis and treatment. In this study, a postsynthetic modification (PSM) strategy was used to obtain UiO-66-PSM (UP) by the aldimine condensation reaction of metal-organic framework UiO-66-NH2 with 2,3,4-trihydroxybenzaldehyde (THBA). UP itself possesses strong fluorescent properties. Subsequently, UiO-66-PSM-Fe (UPF) was synthesized by incorporating Fe3+ onto the UP surface using a one-pot method, where the interaction of Fe3+ with UP induced fluorescence quenching. Bilirubin has a strong binding affinity for Fe3+. Therefore, it can react with the UPF, losing Fe3+ and regaining fluorescence, and thus realizing the detection of bilirubin. In order to further improve the detection outcome and facilitate the application, UPF was loaded onto gelatin methacryloyl hydrogel to construct a fluorescence sensor. This enabled highly sensitive determination of bilirubin with a method limit of detection (LOD) of 5.67 pM. Furthermore, genuine human urine samples were analyzed, demonstrating the practical application of the assay in discovering human health conditions associated with bilirubin.