Geometry-driven miniaturization of a microfluidic paper-based analytical device for reagent-efficient colorimetric detection of dopamine.

Microfluidic paper-based analytical devices (µPADs) have gained attention for clinical diagnostics due to low cost, simplicity, and suitability for point-of-care testing. However, high reagent and sample consumption, limited analytical efficiency, and non-optimized designs still restrict broader use. To overcome these limitations, we propose a miniaturized and re-optimized µPAD design for colorimetric dopamine that reduces the required assay time and minimizes reagent and sample consumption while maintaining reproducible analytical performance in biological samples. To achieve this goal, six distinct µPAD geometries were designed and evaluated to examine the effect of device architecture on colorimetric signal development, followed by optimization of the selected geometry and reaction conditions. Based on its temporal color development profile and signal intensity, the most suitable configuration was selected for further optimization This optimized platform was further evaluated or reagent consumption, response time, reproducibility, and analytical performance in biological samples. The optimized miniaturized µPAD design achieved more than a six-fold reduction in reagent usage and a two-minute decrease in drying time. The optimized configuration showed an LOQ of 0.0517 µmol/L in buffer, while the selectivity experiments showed signal deviations within ± 3% for the tested interferents. Furthermore, validation in spiked human serum and plasma samples yielded recoveries of 101-102.5%, supporting the feasibility of the proposed µPAD for dopamine analysis in complex biological matrices. Overall, these findings demonstrate the potential of the proposed design as a low-volume and reagent-efficient platform for point-of-care colorimetric sensing and provide a practical basis for further evaluation toward preliminary clinical screening applications.