Closed-Loop Therapeutic Response Monitoring Using Optical Signatures in Biological Fluids: A Portable Smartphone Software-Defined Alternative to Hardware-Based Diagnostic Systems

Recent advances in consumer and clinical diagnostics have focused on passive measurement systems, including laboratory-based assays, wearable sensors, and hardware-based platforms such as smart toilets. While these systems enable detection of biological signals, they remain limited in their ability to actively guide therapeutic decision-making. This work presents a closed-loop biological monitoring framework that leverages optical signatures in biological fluids to quantify therapeutic response in real time using a smartphone-based imaging system. The approach is based on a generalizable mechanism in which interactions between analytes (e.g., environmental contaminants, metabolic byproducts, or drug metabolites) and therapeutic agents (e.g., polysaccharides, binders, or degradative compounds) produce measurable changes in optical properties, including brightness, turbidity, scattering, and edge dynamics. Unlike traditional diagnostics, the system enables iterative feedback between intervention and measurement, forming a closed-loop cycle of dosing, response assessment, and optimization. Representative experimental data demonstrate dose-dependent optical aggregation behavior in urine following administration of chlorella, with measurable differences in brightness and aggregation kinetics across concentrations. This framework extends beyond conventional biomarkers to include emerging classes such as environmental particulates, including microplastics and nanoplastics, enabling the concept of personal environmental exposure monitoring in biological fluids. The system represents a scalable, software-defined alternative to hardware-centric diagnostic platforms and establishes a foundation for real-time, personalized therapeutic optimization.