Hydroxylated Bimetallic MOF Dual-Mode Biosensor: A Platform for Rapid Screening and Accurate Quantitative Detection of Free Bilirubin

Elevated levels of free bilirubin (f-Bil) in the blood can cause neonatal brain damage, making the development of rapid and accurate detection methods critical for diagnosing neonatal jaundice. This study targeted the structural characteristics of f-Bil and synthesized a hydroxylated bimetallic MOF (FeCu-MOF-OH) with high specificity for f-Bil through surface modification using organic small molecules (THBA). Based on its excellent peroxidase-like activity and photochemical properties, a dual-mode detection platform combining colorimetric and molecularly imprinted photoelectrochemical detection was developed. FeCu-MOF-OH exhibits significantly enhanced peroxidase-like activity and photochemical properties due to its high porosity, abundant catalytically active sites, and bimetallic synergistic effects. The electronic structure of the bimetallic nanozyme was studied by using first-principles density functional theory calculations. In colorimetry, the coordination interaction between f-Bil and the Fe³⁺ and Cu²⁺ active sites inhibits the nanozyme's activity, reducing the substrate's colorimetric absorbance and enabling rapid screening of f-Bil within 10 min. To further accurately detect the concentration of f-Bil in blood, a molecularly imprinted photoelectrochemical sensor was constructed on an electrode surface via electropolymerization. Detection was achieved by monitoring changes in photocurrent caused by the elution and rebinding of f-Bil. The detection limits of the two methods were as low as 0.68 nM and 1 pM, respectively. Clinical serum sample testing validated the reliability of this approach. This dual-mode method combines the rapid initial screening capability of colorimetry with the precision of molecular imprinting and is expected to play a significant role in the early diagnosis and treatment monitoring of neonatal jaundice.