Nanostructured interfaces for probing and facilitating extracellular electron transfer.

Extracellular electron transfer (EET) is a process performed by electrochemically active bacteria (EAB) to transport metabolically-generated electrons to external solid-phase acceptors through specific molecular pathways. Naturally bridging biotic and abiotic charge transport systems, EET offers ample opportunities in a wide range of bio-interfacing applications, from renewable energy conversion, resource recovery, to bioelectronics. Full exploration of EET fundamentals and applications demands technologies that could seamlessly interface and interrogate with key components and processes at relevant length scales. In this review, we will discuss the recent development of nanoscale platforms that enabled EET investigation from single-cell to network levels. We will further overview research strategies for utilizing rationally designed and integrated nanomaterials for EET facilitation and efficiency enhancement. In the future, EET components such as c-cytochrome based outer membranes and bacterial nanowires along with their assembled structures will present themselves as a whole new category of biosynthetic electroactive materials with genetically encoded functionality and intrinsic biocompatibility, opening up possibilities to revolutionize the way electronic devices communicate with biological systems.

Designed auto-assembly of nanostreptabodies for rapid tissue-specific targeting in vivo.

Molecular medicine can benefit greatly from antibodies that deliver therapeutic and imaging agents to select organs and diseased tissues. Yet the development of complex and defined composite nanostructures remains a challenge that requires both designed stoichiometric assembly and superior in vivo testing ability. Here, we generate nanostructures called nanostreptabodies by controlled sequential assembly of biotin-engineered antibody fragments on a streptavidin scaffold with a defined capacity for additional biotinylated payloads such as other antibodies to create bispecific antibodies as well as organic and non-organic moieties. When injected intravenously, these novel and stable nanostructures exhibit exquisite targeting with tissue-specific imaging and delivery, including rapid transendothelial transport that enhances tissue penetration. This "tinkertoy construction" strategy provides a very flexible and efficient way to link targeting vectors with reporter and/or effector agents, thereby providing virtually endless combinations potentially useful for multipurpose molecular and functional imaging in vivo as well as therapies.