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Electrochemical biosensors based on structure‐switching aptamers offer many advantages because they can operate directly in complex samples and offer the potential to integrate with miniaturized electronics. Unfortunately, these biosensors often suffer from cross‐reactivity problems when measuring a target in samples containing other chemically similar molecules, such as precursors or metabolites. While some progress has been made in selecting highly specific aptamers, the discovery of these reagents remains slow and costly. In this work, a novel strategy is demonstrated to distinguish molecules with miniscule difference in chemical composition (such as a single hydroxyl group)—with cross reactive aptamer probes—by tuning the charge state of the surface on which the aptamer probes are immobilized. As an exemplar, it is shown that the strategy can distinguish between DOX and many structurally similar analytes, including its primary metabolite doxorubicinol (DOXol). Then the ability to accurately quantify mixtures of these two molecules based on their differential response to sensors with different surface‐charge properties is demonstrated. It is believed that this methodology is general and can be extended to a broad range of applications.

 

Pore-based structures occur widely in living organisms. Ion channels embedded in cell membranes, for example, provide pathways, where electron and proton transfer are coupled to the exchange of vital molecules. Learning from mother nature, a recent surge in activity has focused on artificial nanopore architectures to effect electrochemical transformations not accessible in larger structures. Here, we highlight these exciting advances. Starting with a brief overview of nanopore electrodes, including the early history and development of nanopore sensing based on nanopore-confined electrochemistry, we address the core concepts and special characteristics of nanopores in electron transfer. We describe nanopore-based electrochemical sensing and processing, discuss performance limits and challenges, and conclude with an outlook for nextgeneration nanopore electrode sensing platforms and the opportunities they present. 

Detecting and identifying infectious agents and potential pathogens in complex environments and characterizing their mode of action is a critical need. Traditional diagnostics have targeted a single characteristic, e.g. spectral response, surface receptor, mass, intrinsic conductivity, etc. However, advances in detection technologies have identified emerging approaches in which multiple modes of action are combined to obtain enhanced performance characteristics. Particularly appealing in this regard, electrophotonic devices capable of coupling light to electron translocation have experienced rapid recent growth and offer significant advantages for diagnostics. In this chapter, we explore three specific promising approaches that combine electronics and photonics: (a) assays based on closed bipolar electrochemistry coupling electron transfer to color or fluorescence (b) sensors based on localized surface plasmon resonances, and (c) emerging nanophotonics approaches, such as those based on zero-mode waveguides and metamaterials.