Mask-Free Electro-Addressable Localization of GOx@ZIF-8 on Prussian Blue Microelectrodes for Glucose Biosensing

Precisely integrating MOF powders into patterned electrochemical devices remains a processing challenge, as conventional methods often require masks, manual alignment, or poorly scalable steps and can lead to non-selective deposition and inefficient material use. While electrophoretic and dielectrophoretic deposition methods for particulate materials and GOx@ZIF-8/Prussian Blue (PB) glucose biosensors have been reported independently, low-volume localization of enzyme-loaded MOFs directly onto active microelectrode transducer regions remains challenging. Here, we develop a mask-free, DC-field-assisted microdroplet strategy that selectively localizes GOx@ZIF-8 onto PB-modified interdigitated electrodes (PB@IDEs). The approach uses only 12 µL of GOx@ZIF-8 suspension and, unlike random drop-casting, preferentially confines the biocatalytic MOF to the PB transduction interface, minimizing inactive deposition and improving enzyme utilization. The resulting Nafion/GOx@ZIF-8/PB@IDE biosensor exhibits reproducible spatial localization and approximately threefold higher sensitivity, together with a lower limit of detection, than an otherwise identical drop-cast electrode. The sensor shows a linear amperometric response over 24-175 µM glucose concentration, overlapping concentrations relevant to sweat glucose analysis. These results demonstrate that electro-addressable placement of enzyme@MOF particles can improve reaction-readout coupling while reducing biocatalyst consumption.