Dual colorimetric-electrochemical microfluidic paper-based analytical device for point-of-care testing of ischemic stroke

Abstract

A novel microfluidic paper-based analytical device with dual colorimetric and electrochemical detection (dual µPAD) was developed for the assessment of transferrin saturation (TSAT) in samples from ischemic stroke patients. TSAT was calculated by the ratio between transferrin-bound iron, which was colorimetrically measured, and total iron-binding capacity, which was electrochemically measured. To this end, a µPAD was smartly designed with integrated both colorimetric and electrochemical detection reservoirs communicated with and microchannel acting as a chemical reactor and with preloading/storing capabilities (reagent-free device). This approach allowed the dual and simultaneous determination of both parameters, providing an improvement in the reliability and precision of the results benefiting an independent signal principle and processing. µPADs were validated by analyzing a certified reference material showing excellent accuracy (E_r ≤ 5 %) and precision (RSD ≤ 2 %) and then they were applied to the analysis of diagnosed serum samples from ischemic stroke patients. The results were compared to those provided by a free-interference method (urea-PAGE). Impressively, both methods exhibited a good correlation (r = 0.96, p < 0.05), and no significant differences were found between both (slope 1.0 ± 0.1 and the intercept 1 ± 4, p < 0.05), demonstrating the excellent accuracy of our approach during the analysis of complex samples from ischemic stroke patients, using just 90 μL of clinical samples and taking less than 90 min in comparison with the 18 hours required by the urea-PAGE approach. The developed fully integrated colorimetric-electrochemical µPAD is a promising ready to be used reagent-free device for the point-of-care testing of TSAT, which can be used to assist physicians in the fast diagnosis and prognosis of ischemic stroke, where the time to decide is crucial for patient’s survival.