Received: 6 December 2019 Accepted: 12 February 2020
In this study, two important biomarkers, namely glucose and uric acid, were detected in different biological fluids using a highly sensitive and selective chitosan-/nano-based electrochemical microfluidic paper-based analytical device (µPAD). A graphite/chitosan/polyethylene glycol (PEG) mixture was used as bare working electrode and counter electrode with silver ink being used as quasi-reference electrode. Graphene, multiwall carbon nanotubes, and Fe3O4 nanoparticles were used to improve sensitivity as well as selectivity of the working electrodes. The developed chitosan-/nano-based microfluidic analytical system showed apparent redox peaks, and all the three types of nanomaterials improved the performance of the bare graphite/chitosan/PEG electrode with the Fe3O4-modified electrode exhibiting the sharpest signals with the highest selectivity. The linear ranges of glucose and uric acid were 0.01–30 mM and 0.05–15 mM, respectively, where the limits of detection (LOD) were 5 µM and 20 µM for glucose and uric acid, respectively. In comparison with most of previous data reported on μPADs and due to high surface area/volume ratio of NPs and faster electron transfer promoted by chitosan and NPs, the better LODs were found in the current study. The fast, efficient, and low-cost µPADs were successfully applied to highly sensitive and selective detection of glucose and uric acid in serum and urine samples and noninvasive glucose detection in tear samples.