Electrochemical biosensors are promising technologies for detection and monitoring in low-resource settings due to their potential for easy use and low-cost instrumentation. Disposable gold screen-printed electrodes (SPEs) are popular substrates for these biosensors, but necessary dopants in the ink used for their production can interfere with biosensor function and contribute to the heterogeneity of these electrodes. We recently reported an alternative disposable gold electrode made from gold leaf generated using low-cost, equipment-free fabrication. We have directly compared the surface topology, biorecognition element deposition, and functional performance of three disposable gold electrodes: our gold leaf electrodes and two commercial SPEs. Our leaf electrodes significantly outperformed the SPEs for reproducible and effective biosensing in a DNase I assay and are nearly an order of magnitude less expensive than the SPEs. Therefore, these electrodes are promising for further development as point-of-care diagnostics, especially in low-resource settings.
Modification of electrodes with biomolecules is an essential first step for the development of bioelectrochemical systems, which are used in a variety of applications ranging from sensors to fuel cells. Gold is often used because of its ease of modification with thiolated biomolecules, but carbon screen-printed electrodes (SPEs) are gaining popularity due to their low cost and fabrication from abundant resources. However, their effective modification with biomolecules remains a challenge; the majority of work to-date relies on nonspecific adhesion or broad amide bond formation to chemical handles on the electrode surface. By combining facile electrochemical modification to add an aniline handle to electrodes with a specific and biocompatible oxidative coupling reaction, we can readily modify carbon electrodes with a variety of biomolecules. Importantly, both proteins and DNA maintain bioactive conformations following coupling. We have then used biomolecule-modified electrodes to generate microbial monolayers through DNA-directed immobilization. This work provides an easy, general strategy to modify inexpensive carbon electrodes, significantly expanding their potential as bioelectrochemical systems.
Organic waste streams contain a significant amount of latent energy that is difficult to harvest. Microbial electrochemical systems (MESs), which extract electrons through microbial metabolism, are a promising technology to recover this energy. Despite advances in these technologies, microbial electrocatalysis in MESs remains limited by inefficient electron transfer between living cells and electrodes. Here, we demonstrate significant improvement in this interfacial electron transfer through the incorporation of electron- and ion-conductive polymers. We have designed these polymers with a conductive backbone and side chains that mimic ligands of catalytic centers in redox-active enzymes. Specifically, methylimidazolium groups mimic protonated histidines prevalent in enzyme active sites. We show that these polymers substantially enhance mediated electron transfer and overall current generation by Shewanella oneidensis, an electroactive microbe often used in MESs. Our work highlights the importance of materials engineering applied to the biotic-abiotic interface to improve charge transfer in bioelectronic systems.
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