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Emerging research indicates that biology routinely uses diffusible redox‐active molecules to mediate communication that can span biological systems (e.g., nervous and immune) and even kingdoms (e.g., a microbiome and its plant/animal host). This redox modality also provides new opportunities to create interactive materials that can communicate with living systems. Here, it is reported that the fabrication of a redox‐active hydrogel film can autonomously synthesize a H₂O₂signaling molecule for communication with a bacterial population. Specifically, a catechol‐conjugated/crosslinked 4‐armed thiolated poly(ethylene glycol) hydrogel film is electrochemically fabricated in which the added catechol moieties confer redox activity: the film can accept electrons from biological reductants (e.g., ascorbate) and donate electrons to O₂to generate H₂O₂. Electron‐transfer from anEscherichia coliculture poises this film to generate the H₂O₂signaling molecule that can induce bacterial gene expression from a redox‐responsive operon. Overall, this work demonstrates that catecholic materials can participate in redox‐based interactions that elicit specific biological responses, and also suggests the possibility that natural phenolics may be a ubiquitous biological example of interactive materials.

Electronic information can be transmitted to cells directly from microelectronics via electrode-activated redox mediators. These transmissions are decoded by redox-responsive promoters which enable user-specified control over biological function. Here, we build on this redox communication modality by establishing an electronic eCRISPR conduit of information exchange. This system acts as a biological signal processor, amplifying signal reception and filtering biological noise. We electronically amplify bacterial quorum sensing (QS) signaling by activating LasI, the autoinducer-1 synthase. Similarly, we filter out unintended noise by inhibiting the native SoxRS-mediated oxidative stress response regulon. We then construct an eCRISPR based redox conduit in bothE. coliandSalmonella enterica. Finally, we display eCRISPR based information processing that allows transmission of spatiotemporal redox commands which are then decoded by gelatin-encapsulatedE. coli. We anticipate that redox communication channels will enable biohybrid microelectronic devices that could transform our abilities to electronically interpret and control biological function.

Process conditions established during the development and manufacture of recombinant protein therapeutics dramatically impacts their quality and clinical efficacy. Technologies that enable rapid assessment of product quality are critically important. Here, we describe the development of sensor interfaces that directly connect to electronics and enable near real‐time assessment of antibody titer and N‐linked galactosylation. We make use of a spatially resolved electroassembled thiolated polyethylene glycol hydrogel that enables electroactivated disulfide linkages. For titer assessment, we constructed a cysteinylated protein G that can be linked to the thiolated hydrogel allowing for robust capture and assessment of antibody concentration. For detecting galactosylation, the hydrogel is linked with thiolated sugars and their corresponding lectins, which enables antibody capture based on glycan pattern. Importantly, we demonstrate linear assessment of total antibody concentration over an industrially relevant range and the selective capture and quantification of antibodies with terminal β‐galactose glycans. We also show that the interfaces can be reused after surface regeneration using a low pH buffer. Our functionalized interfaces offer advantages in their simplicity, rapid assembly, connectivity to electronics, and reusability. As they assemble directly onto electrodes that also serve as I/O registers, we envision incorporation into diagnostic platforms including those in manufacturing settings.

Reduction–oxidation (redox) reactions provide a distinct modality for biological communication that is fundamentally different from the more‐familiar ion‐based electrical modality. Biology uses these two modalities for communication through different systems (immune versus nervous), and uses different mechanisms to control the flow of the charge carriers: the flow of soluble ions is controlled using structural barriers (i.e., membranes) and gates (e.g., membrane‐spanning protein channels), while the flow of insoluble electrons is controlled using redox‐reaction networks. Here, a simple electrochemical approach to pattern catechols onto a flexible polysaccharide hydrogel is reported and it is demonstrated that the patterned catechol regions serve as nodes for the mediated flow of electrons through redox reactions. Electron flow through this node involves the switching of binary redox states (oxidized and reduced) and this node's redox state can be detected (i.e., “read”) by passively observing its optical absorbance, or actively switching its redox‐state electrochemically. Further, this catechol node can be switched through biological mechanisms, and this enables the fabricated catechol node to be embedded within biochemical redox reaction networks to facilitate the spanning of bio‐electronic communication. Thus, it is envisioned that catechols can emerge as a molecular equivalent to a transistor for miniaturize‐able, deployable and sustainable redox‐linked bioelectronics.

Biology uses diffusible oxidants to perform functions that range from signaling to matrix assembly, and these oxidation chemistries offer surprising selectivities. Here, it is reported that mediated electrochemistry can access the richness of such oxidation chemistries. Specifically, electrode‐imposed voltage inputs are used to locally generate oxidized mediators that can diffuse into polymer solutions and induce the formation of covalent bonds for the deposition and functionalization of hydrogels at the electrode surface. Depending on the mediator's redox potential (E⁰), it is possible to “gate” the voltage inputs to target specific residues (e.g., thiols or amines) and oxidation chemistries. Further, mediators of varyingE⁰offer different reactivities and thus allow control of reaction‐diffusion rates to modulate the hydrogel's crosslink density and mechanical properties. Importantly, this mediated oxidation can be performed under physiologically relevant conditions to preserve labile biological functionalities (e.g., cell viability and protein function). Finally, it is demonstrated that protein fusion tags can be engineered to have “targetable” amino acid residues that enable protein function to be oxidatively conjugated to electrodeposited hydrogels. In summary, mediated electrochemistry can engage orthogonal oxidation chemistries to create functionalized matrices and thus mediated electrochemistry should add important capabilities to the electrofabrication toolbox.

Redox is emerging as an alternative modality for bio‐device communication. In contrast to the more familiar ionic electrical modality: (i) redox involves the flow of electrons through oxidation–reduction reactions; (ii) the aqueous medium is an “insulator” to this electron flow since free electrons do not normally exist in water; and (iii) redox states are intrinsically digital (oxidized and reduced). By exploiting these unique features, a catechol‐based molecular memory film is reported. This memory is fabricated by electrochemically grafting catechol to a chitosan–agarose polysaccharide network to generate a redox‐active but non‐conducting matrix. The redox state of the grafted catechol moieties serves as the 2‐state memory. It is shown that these redox states: can be repeatedly switched by diffusible mediators (electron shuttles); can be easily read electrically or optically; are stable for at least 2 h in the absence of energy; are sensitive to biologically relevant oxidizing and reducing contexts; and can be switched enzymatically. This catechol‐based molecular memory film is a simple circuit element for redox linked bioelectronics.

The autoinducer‐2 (AI‐2) quorum sensing system is involved in a range of population‐based bacterial behaviors and has been engineered for cell–cell communication in synthetic biology systems. Investigation into the cellular mechanisms of AI‐2 processing has determined that overexpression of uptake genes increases AI‐2 uptake rate, and genomic deletions of degradation genes lowers the AI‐2 level required for activation of reporter genes. Here, we combine these two strategies to engineer anEscherichia colistrain with enhanced ability to detect and respond to AI‐2. In anE. colistrain that does not produce AI‐2, we monitored AI‐2 uptake and reporter protein expression in a strain that overproduced the AI‐2 uptake or phosphorylation units LsrACDB or LsrK, a strain with the deletion of AI‐2 degradation units LsrF and LsrG, and an “enhanced” strain with both overproduction of AI‐2 uptake and deletion of AI‐2 degradation elements. By adding up to 40 μM AI‐2 to growing cell cultures, we determine that this “enhanced” AI‐2 sensitive strain both uptakes AI‐2 more rapidly and responds with increased reporter protein expression than the others. This work expands the toolbox for manipulating AI‐2 quorum sensing processes both in native environments and for synthetic biology applications.