ROMP-Derived Coumarin-Tyrosine Polymeric Chemosensors: A Biomolecule-Inspired Metal-Ion-Free Approach for Arginine Sensing in Artificial Saliva.

The development of noninvasive diagnostic platforms for biomarker detection in complex biological fluids remains a significant challenge. Herein, we report a biomolecule-inspired, metal-ion-free polymeric fluorescence chemosensor in which polymer architecture governs molecular recognition and photophysical response, enabling ultrasensitive detection of arginine (Arg), a clinically relevant biomarker for metabolic and renal disorders. Based on a coumarin-tyrosine-functionalized polynorbornene synthesized via ring-opening metathesis polymerization (ROMP), the system integrates recognition sites within a well-defined macromolecular framework. UV-vis studies reveal a bathochromic shift (350-442 nm) with an isosbestic point at 392 nm upon Arg binding. Both Poly-Cou-Tyr-Boc and Poly-Cou-Tyr-NH 2 exhibit ratiometric fluorescence behavior in DMSO. The polymeric architecture affords enhanced signal amplification over monomeric analogues, achieving a limit of detection (LOD) of 71.42 nM and 103.64 nM, respectively. Systematic evaluation established artificial saliva as the optimal medium due to negligible matrix interference. In this environment, the probes demonstrated matrix-dependent fluorescence sensing. Poly-Cou-Tyr-Boc maintained ratiometric performance, while the deprotected Poly-Cou-Tyr-NH 2 functioned via high-sensitivity intensity-based quenching at 411 nm. This dual-mode capability yielded exceptional LODs of 33.09 nM and 32.45 nM in saliva, respectively. Mechanistic studies, including 1H NMR titration and Job's plot, confirmed a 1:1 interaction mediated by cooperative hydrogen bonding. This work establishes a structure-property-driven polymer design strategy, providing a versatile metal-ion-free platform for next-generation noninvasive diagnostics and real-time metabolic monitoring.