Advances in biosensor engineering have enabled the design of programmable molecular systems to detect a range of pathogens, nucleic acids, and chemicals. Here, we engineer and field-test a biosensor for fluoride, a major groundwater contaminant of global concern. The sensor consists of a cell-free system containing a DNA template that encodes a fluoride-responsive riboswitch regulating genes that produce a fluorescent or colorimetric output. Individual reactions can be lyophilized for long-term storage and detect fluoride at levels above 2 ppm, the Environmental Protection Agency's most stringent regulatory standard, in both laboratory and field conditions. Through onsite detection of fluoride in a real-world water source, this work provides a critical proof-ofprinciple for the future engineering of riboswitches and other biosensors to address challenges for global health and the environment.

Integrating functional self‐propelled Zinc micromotors are created by coup­ling electrodeposition with hard dual‐templating synthesis. The micromotors concurrently possess four robust functions including a remarkably high loading capacity, combinatorial delivery of cargoes, autonomous release of encapsulated payloads, and self‐destruction. This concept could be expanded to simultaneous encapsulation of various payloads for different functionalities such as therapy, diagnostics, and imaging.

Tracking progress towards Target 6.1 of the United Nations Sustainable Development Goals, "achieving universal and equitable access to safe and affordable drinking water for all", necessitates the development of simple, inexpensive tools to monitor water quality. The rapidly growing field of synthetic biology has the potential to address this need by isolating DNA-encoded sensing elements from nature and reassembling them to create field-deployable "biosensors" that can detect pathogenic or chemical water contaminants. Here, we describe current water quality monitoring strategies enabled by synthetic biology and compare them to previous approaches used to detect three priority water contaminants (i.e., fecal pathogens, arsenic, and fluoride), as well as explain the potential for engineered biosensors to simplify and decentralize water quality monitoring. We conclude with an outlook on the future of biosensor development, in which we discuss their adaptability to emerging contaminants (e.g., metals, agricultural products, and pharmaceuticals), outline current limitations, and propose steps to overcome the field's outstanding challenges to facilitate global water quality monitoring.

Advances in biosensor engineering have enabled the design of programmable molecular systems to detect a range of pathogens, nucleic acids, and chemicals. Here, we engineer and field-test a biosensor for fluoride, a major groundwater contaminant of global concern. The sensor consists of a cell-free system containing a DNA template that encodes a fluoride-responsive riboswitch regulating genes that produce a fluorescent or colorimetric output. Individual reactions can be lyophilized for long-term storage and detect fluoride at levels above 2 parts per million, the EPA's most stringent regulatory standard, in both laboratory and field conditions. Through onsite detection of fluoride in a real-world water source, this work provides a critical proof-of-principle for the future engineering of riboswitches and other biosensors to address challenges for global health and the environment.

Transplanting metabolic reactions from one species into another has many uses as a research tool with applications ranging from optogenetics to crop production. Ferredoxin (Fd), the enzyme that most often supplies electrons to these reactions, is often overlooked when transplanting enzymes from one species to another because most cells already contain endogenous Fd. However, we have shown that the production of chromophores used in Phytochrome B (PhyB) optogenetics is greatly enhanced in mammalian cells by expressing bacterial and plant Fds with ferredoxin-NADP+ reductases (FNR). We delineated the rate limiting factors and found that the main metabolic precursor, heme, was not the primary limiting factor for producing either the cyanobacterial or plant chromophores, phycocyanobilin or phytochromobilin, respectively. In fact, Fd is limiting, followed by Fd+FNR and finally heme. Using these findings, we optimized the PCB production system and combined it with a tissue penetrating red/far-red sensing PhyB optogenetic gene switch in animal cells. We further characterized this system in several mammalian cell lines using red and far-red light. Importantly, we found that the light-switchable gene system remains active for several hours upon illumination, even with a short light pulse, and requires very small amounts of light for maximal activation. Boosting chromophore production by matching metabolic pathways with specific ferredoxin systems will enable the unparalleled use of the many PhyB optogenetic tools and has broader implications for optimizing synthetic metabolic pathways.