摘要
This paper reports an electrochemical microfluidic paper-based analytical device(EμPAD)for glucose detection,featuring a highly sensitive working electrode(WE)decorated with zinc oxide nanowires(ZnO NWs).In addition to the common features ofμPADs,such as their low costs,high portability/disposability,and ease of operation,the reported EμPAD has three further advantages.(i)It provides higher sensitivity and a lower limit of detection(LOD)than previously reportedμPADs because of the high surface-to-volume ratio and high enzyme-capturing efficiency of the ZnO NWs.(ii)It does not need any light-sensitive electron mediator(as is usually required in enzymatic glucose sensing),which leads to enhanced biosensing stability.(iii)The ZnO NWs are directly synthesized on the paper substrate via low-temperature hydrothermal growth,representing a simple,low-cost,consistent,and mass-producible process.To achieve superior analytical performance,the on-chip stored enzyme(glucose oxidase)dose and the assay incubation time are tuned.More importantly,the critical design parameters of the EμPAD,including the WE area and the ZnO-NW growth level,are adjusted to yield tunable ranges for the assay sensitivity and LOD.The highest sensitivity that we have achieved is 8.24μA·mM^(−1)·cm^(−2),with a corresponding LOD of 59.5μM.By choosing the right combination of design parameters,we constructed EμPADs that cover the range of clinically relevant glucose concentrations(0−15 mM)and fully calibrated these devices using spiked phosphate-buffered saline and human serum.We believe that the reported approach for integrating ZnO NWs on EμPADs could be well utilized in many other designs of EμPADs and provides a facile and inexpensive paradigm for further enhancing the device performance.
