Xiaocheng Jiang

Exoelectrogens are known to be specialized in reducing various extracellular electron acceptors to form conductive nanomaterials that are integrated with their cell bodies both structurally and functionally. Utilizing this unique capacity, we created a strategy toward the design and fabrication of a biohybrid electronic material by exploiting bioreduced graphene oxide (B-rGO) as the structural and functional linker to facilitate the interaction between the exoelectrogen community and external electronics. The metabolic functions of exoelectrogens encoded in this living hybrid can therefore be effectively translated toward corresponding microbial fuel cell applications. Furthermore, this material can serve as a fundamental building block to be integrated with other microorganisms for constructing various electronic components. Toward a broad impact of this biohybridization strategy, photosynthetic organelles and cells were explored to replace exoelectrogens as the active bioreducing components and as formed materials exhibited 4- and 8-fold improvements in photocurrent intensities as compared with native bioelectrode interfaces. Overall, a biologically driven strategy for the fabrication and assembly of electronic materials is demonstrated, which provides a unique opportunity to precisely probe and modulate desired biofunctions through deterministic electronic inputs/outputs and revolutionize the design and manufacturing of next-generation (bio)electronics.

Significance: We provide insights into the sequence–conformation–property relationship that is central to the mechanical properties of protein elastomers. We find that a high content of glycine residue alone, not including proline, is sufficient for achieving near-perfect resilience. The content of proline residue may be associated with the metastability of random coils. Also, Raman spectroscopy, as a potent tool for investigating the conformation–property relationship, gives rise to a direct correlation between semiquantitative Raman features and the magnitude of elastic resilience. Moreover, metastable conformation or conformational polymorphism is useful to develop continuously and mechanically graded protein materials that may exhibit unique structural merits. This work underlies the exploitation of natural and de novo–designed sequences for protein elastomers and materials.

Electrical impulse generation and its conduction within cells or cellular networks are the cornerstone of electrophysiology. However, the advancement of the field is limited by sensing accuracy and the scalability of current recording technologies. Here we describe a scalable platform that enables accurate recording of transmembrane potentials in electrogenic cells. The platform employs a three-dimensional high-performance field-effect transistor array for minimally invasive cellular interfacing that produces faithful recordings, as validated by the gold standard patch clamp. Leveraging the high spatial and temporal resolutions of the field-effect transistors, we measured the intracellular signal conduction velocity of a cardiomyocyte to be 0.182 m s⁻¹, which is about five times the intercellular velocity. We also demonstrate intracellular recordings in cardiac muscle tissue constructs and reveal the signal conduction paths. This platform could provide new capabilities in probing the electrical behaviours of single cells and cellular networks, which carries broad implications for understanding cellular physiology, pathology and cell–cell interactions.

Living composites comprising of both biotic and abiotic modules are shifting the paradigm of materials science, yet challenges remain in effectively converging their distinctive structural and functional attributes. Here we present a bottom-up hybridization strategy to construct functionally coherent, electrochemically active biohybrids with optimal mass/charge transport, mechanical integrity, and biocatalytic performance. This biohybrid can overcome several key limitations of traditional biocarrier designs and demonstrate superior efficiency in metabolizing low-concentration toxic ions with minimal environmental impact. Overall, this work exemplifies a biointegration strategy that complements existing synthetic biology toolsets to further expand the range of material attributes and functionalities.

Functional hydrogels show great potential for promoting the structural integration and signal transduction at bio/electronic interfaces.

Bottom-up engineering approaches are transforming biological wastewater treatment.

Living electronics that converges the unique functioning modality of biological and electrical circuits has the potential to transform both fundamental biophysical/biochemical inquiries and translational biomedical/engineering applications. This article will review recent progress in overcoming the intrinsic physiochemical and signaling mismatches at biological/electronic interfaces, with specific focus on strategic approaches in forging the functional synergy through: (1) biohybrid electronics, where genetically encoded bio-machineries are hybridized with electronic transducers to facilitate the translation/interpretation of biologically derived signals; and (2) biosynthetic electronics, where biogenic electron pathways are designed and programmed to bridge the gap between internal biological and external electrical circuits. These efforts are reconstructing the way that artificial electronics communicate with living systems, and opening up new possibilities for many cross-disciplinary applications in biosynthesis, sensing, energy transduction, and hybrid information processing.

Electron transport in biological and inorganic systems is mediated through distinct mechanisms and pathways. Their fundamental mismatch in structural and thermodynamic properties has imposed significant challenge on the effective coupling at the biotic/abiotic interface, which is central to the design and development of bioelectronic devices and their translation towards various engineering applications. Using electrochemically active bacteria, such as G. sulfurreducens, as a model system, here we report a bottom-up, bio-synthetic approach to synergize the electron transport and significantly enhance the coupling at the heterogeneous junction. In particular, graphene oxide was exploited as the respiratory electron acceptors, which can be directly reduced by G. sulfurreducens through extracellular electron transfer, closely coupled with outer membrane cytochromes in electroactive conformation, and actively “wire” the redox centers to external electrical contacts. Through this strategy, the contact resistance at the biofilm-electrode interface can be effectively reduced by 90%. Furthermore, the cyclic voltammetry reveals that the electron transfer of DL-1 biofilm transformed from a low-current (~0.36 µA), rate-limited profile to a high-current (~5µA), diffusion-limited profile. These results suggested that the integration of rGO can minimize the charge transfer barriers at the biofilm-electrode interface. The more transparent contact at DL-1/electrode interface also enables unambiguous characterization of the inherent electron transport kinetics across the electroactive biofilm independent of cell-electrode interactions. The current work represents a strategically new approach toward the seamless integration of biological and artificial electronics, which is expected to provide critical insights into the fundamentals of biological electron transport and open up new opportunities for applications in biosensing, biocomputing and bioenergy conversion.

Field-effect transistors (FETs), when functionalized with proper bio-recognition elements (such as antibodies or enzymes), represent a unique platform for real time, specific, label-free transduction of biochemical signals. However, direct immobilization of bio-recognition molecules on FETs imposes limitations on re-programmability, sensor regeneration and robust device handling. Here we demonstrate a modularized design of FET biosensors with separate bio-recognition and transducer modules, which are capable of reversible assembly and disassembly. In particular, hydrogel “stamps” immobilizing bio-receptors have been chosen to build bio-recognition modules to reliably interface with FET transducers structurally and functionally. Successful detection of penicillin down to 0.25 mM has been achieved with penicillinase-encoded hydrogel module, demonstrating effective signal transduction across the hybrid interface. Moreover, sequential integration of urease- and penicillinase-encoded modules on the same FET device allows us to reprogram sensing modality without cross-contamination. In addition to independent bio-receptor encoding, the modular design also fosters sophisticated control of sensing kinetics by modulating the physiochemical microenvironment in the bio-recognition modules. Specifically, the distinction in hydrogel porosity between polyethylene glycol and gelatin enables controlled access and detection of larger molecules, such as poly-L-lysine (MW 150-300 kDa), only through the gelatin module. Bio-recognition modules with standardized interface designs have also been exploited to comply with additive mass fabrication by 3D printing, demonstrating potential for low cost, ease of storage, multiplexing and great customizability for personalized biosensor production. This generic concept presents a unique integration strategy for modularized bioelectronics and could impact broadly hybrid device development.