Porous hydrogel scaffolds integrating Prussian Blue nanoparticles: A versatile strategy for electrochemical (bio)sensing

Hydrogels have emerged as promising porous soft materials from which to develop a wide range of biosensing platforms due to the possibility to easily engineer their properties and to effectively immobilize enzymes and nanomaterials in their matrix. Despite their attractive properties, the ability to form stable hydrogel films integrating well-dispersed catalytic nanomaterials and enzymes on electrode surfaces is still required to enable their implementation into electrochemical biosensors. Here, we report a facile approach to prepare hydrogel films embedding Prussian Blue nanoparticles (PBNPs) and different enzymes on electrode surfaces for electrochemical biosensing. A one-pot strategy was employed for the synthesis, under mild conditions, of PBNPs and the simultaneous immobilization of enzymes in a highly functionalized carboxymethyl cellulose matrix, yielding homogeneous hydrogel composites. Highly porous hydrogel films were successfully prepared by drop casting the hydrogel composites on the surface of flexible screen-printed electrodes (SPEs). Due to the high loading of well-dispersed PBNPs, the hydrogel films demonstrated good electrocatalytic activity for both the oxidation of NADH and the reduction of hydrogen peroxide resulting in high detection sensitivity. Two amperometric biosensors for the rapid detection of glucose and ethanol in serum were realized by employing hydrogel composites integrating glucose oxidase and alcohol dehydrogenase. By combining the unique features of hydrogels on flexible electrochemical strips, our approach holds great promise for the development of portable electrochemical (bio)sensors, which are easy to fabricate and versatile for the detection of a variety of analytes.