Nanoconfined Polymer Dot Reactors for Ultrasensitive Monitoring of Diverse Metabolites and Point-of-Care Diagnosis.

Polymer dots (Pdots) offer high brightness and tunable electronic properties for point-of-care testing, but conventional sensing often suffers from inefficient stochastic interactions and limited adaptability. Here, we screened Pdots for interactions with the NAD+/NADH redox couple and identified PDFDP Pdots with an NADH detection limit of 2.41 nM. Coupling PDFDP Pdots with NAD+-dependent enzymes enabled detection of multiple metabolites through enzymatically generated NADH. Co-encapsulation of Pdots and enzymes within microreactors further enhanced signal transduction by spatial confinement. Combined with smartphone-based RGB analysis under UV illumination, the platform enabled micromolar detection of lactate, β-hydroxybutyrate, glutamate, alanine, and ethanol. The method was further demonstrated in sweat and urine samples, showing good agreement with established analytical methods and supporting its potential for portable metabolite monitoring and exploratory disease-associated analysis.