Carboxylic Acid–Functionalized β‐Ketoenamine Linked Porous Organic Polymer Based Fluorescent Immunoassay for Prostate Cancer Detection

Prostate-specific antigen (PSA) serves as a critical biomarker for the early diagnosis and monitoring of prostate malignancies. In this work, we report the fabrication of a carboxy-functionalized porous organic polymer (POP) as a highly sensitive and selective fluorescent immunosensor for PSA detection. The POP was synthesized via a solvothermal Schiff base condensation, which bears free -COOH functionalities to facilitate covalent antibody immobilization through classical EDC/NHS coupling chemistry. The resulting POP-antibody bioconjugate exhibited a pronounced fluorescence quenching response upon PSA binding, attributed to static quenching via ground-state complex formation, as confirmed by steady-state and time-resolved photoluminescence studies. Under optimized conditions, the sensor achieved a limit of detection (LOD) of 14 pg/mL, demonstrating a wide linear dynamic range and minimal cross-reactivity with nontarget biomolecules. The high surface area and hierarchical porosity of the POP matrix contributed to enhanced probe-analyte interactions and signal amplification. Notably, the sensor retained excellent performance in complex matrices, with successful PSA quantification in artificial urine and blood samples, highlighting its potential for real-world clinical diagnostics. The synergistic integration of structural surface functionality and photostability in this POP-based platform underscores its promise for ultrasensitive, low-cost, and point-of-care biosensing of cancer biomarkers.