Lack of access to safe drinking water is a global problem, and methods to reliably and easily detect contaminants could be transformative We report the development of a cell-free in vitro transcription system that uses RNA Output Sensors Activated by Ligand Induction (ROSALIND) to detect contaminants in water A combination of highly processive RNA polymerases, allosteric protein transcription factors and synthetic DNA transcription templates regulates the synthesis of a fluorescence-activating RNA aptamer The presence of a target contaminant induces the transcription of the aptamer, and a fluorescent signal is produced We apply ROSALIND to detect a range of water contaminants, including antibiotics, small molecules and metals We also show that adding RNA circuitry can invert responses, reduce crosstalk and improve sensitivity without protein engineering The ROSALIND system can be freeze-dried for easy storage and distribution, and we apply it in the field to test municipal water supplies, demonstrating its potential use for monitoring water quality

https://www.nature.com/articles/s41587-020-0571-7.pdf?proof=t

Cell-free biosensors for rapid detection of water contaminants

Cell-based biosensors have great potential to detect various toxic and pathogenic contaminants in aqueous environments. However, frequently they cannot meet practical requirements due to insufficient sensing performance. To address this issue, we investigated a modular, cascaded signal amplifying methodology. We first tuned intracellular sensory receptor densities to increase sensitivity, and then engineered multi-layered transcriptional amplifiers to sequentially boost output expression level. We demonstrated these strategies by engineering ultrasensitive bacterial sensors for arsenic and mercury, and improved detection limit and output up to 5,000-fold and 750-fold, respectively. Coupled by leakage regulation approaches, we developed an encapsulated microbial sensor cell array for low-cost, portable and precise field monitoring, where the analyte can be readily quantified via displaying an easy-to-interpret volume bar-like pattern. The ultrasensitive signal amplifying methodology along with the background regulation and the sensing platform will be widely applicable to many other cell-based sensors, paving the way for their real-world applications.

Cascaded amplifying circuits enable ultrasensitive cellular sensors for toxic metals.

Synthetic biology applies genetic tools to engineer living cells and organisms analogous to the programming of machines. In materials synthetic biology, engineering principles from synthetic biology and materials science are integrated to redesign living systems as dynamic and responsive materials with emerging and programmable functionalities. In this Review, we discuss synthetic-biology tools, including genetic circuits, model organisms and design parameters, which can be applied for the construction of smart living materials. We investigate non-living and living self-organizing multifunctional materials, such as intracellular structures and engineered biofilms, and examine the design and applications of hybrid living materials, including living sensors, therapeutics and electronics, as well as energy-conversion materials and living building materials. Finally, we consider prospects and challenges of programmable living materials and identify potential future applications. Materials synthetic biology merges synthetic biology with materials science for the redesign of living systems into smart materials. This Review discusses how synthetic-biology tools can be applied for the engineering of self-organizing functional materials and programmable hybrid living materials.

Materials design by synthetic biology

Narrow linewidth lasers have many applications, such as higher order coherent communications, optical sensing, and metrology. While semiconductor lasers are typically unsuitable for such applications due to relatively low coherence, recent advances in heterogeneous integration of III-V with silicon have shown that this is no longer true. In this tutorial, we discuss in-depth techniques that are used to drastically reduce the linewidth of a laser. The heterogeneous silicon-III/V platform can fully utilize these techniques, and fully integrated lasers with Lorentzian linewidth on the order of 100 Hz and tuning range of 120 nm are shown.

/pdf/tutorial-on-narrow-linewidth-tunable-semiconductor-lasers-8dhr4seov8.pdf

Tutorial on narrow linewidth tunable semiconductor lasers using Si/III-V heterogeneous integration

Synthetic biology will transform how we grow food, what we eat, and where we source materials and medicines. Here I have selected six products that are now on the market, highlighting the underlying technologies and projecting forward to the future that can be expected over the next ten years.

/pdf/synthetic-biology-2020-2030-six-commercially-available-1gg4mi646o.pdf

Synthetic biology 2020-2030: six commercially-available products that are changing our world

VOLUME 35 NUMBER 4 APRIL 2017 NATURE BIOTECHNOLOGY with a novel mode of action is approved for marketing? We submit that three decades of soliciting public engagement has not improved the public acceptance cited by advocates as a justification for the efforts, and that subordinating evidence-based policy making to emotional or political calculations has neither increased public acceptance nor encouraged innovation. We would prefer to heed the caveat of Barbara Keating-Edh, who testified before the National Biotechnology Policy Board in 1991, representing the consumer group Consumer Alert: “For obvious reasons, the consumer views the technologies that are most regulated to be the least safe ones. Heavy involvement by government, no matter how well intended, inevitably sends the wrong signals. Rather than ensuring confidence, it raises suspicion and doubt” [emphasis in original]11. We believe that the current excessive and unscientific regulation at the US Environmental Protection Agency (EPA), USDA and FDA (and other agencies) erodes both public understanding and trust, and exacerbates skepticism about the safety of

Remote detection of buried landmines using a bacterial sensor.

With a new generation of quantum dot (QD) optical gain material comprising atom-like features, the fundamental spectral characteristics of laser emission have been improved significantly. We describe the spectral and power characteristics of continuous wave (CW) single-mode InAs/AlGaInAs/InP QD distributed feedback lasers operating at 1.5 μm. Linewidths as narrow as 60 kHz (30  kHz±10  kHz intrinsic linewidth) at 20°C, which broadens to only 280 kHz (80  kHz±10  kHz intrinsic linewidth) at 80°C, have been achieved. The laser exhibits high output powers of 58 mW at 20°C and 26 mW at 80°C with side mode suppression ratios exceeding 50 dB. These record values stem from high uniformity of the QDs and a large dot density. The linewidth was measured by two techniques that confirm each other: delayed self-heterodyne interferometry and optical frequency comb interferometry. A model fits the experimental results well and enables extraction of the bias and temperature dependent α parameter. At 20°C, α is less than 0.5 at threshold and increases to only 0.9 at 150 mA above threshold. The corresponding values at 80°C are 2 and 2.5. These results imply a great potential of QD lasers for the most demanding applications in terms of spectral purity, such as coherent optical communication systems and optical metrology.

Large linewidth reduction in semiconductor lasers based on atom-like gain material

InP-based quantum dot (QD) material with five QD layers in the active region was used to fabricate distributed feedback (DFB) lasers with a cavity length of ~1.5 mm. QDs enable tailoring of device properties, like gain, bandwidth and low linewidth enhancement factor (alpha-factor) that are favourable for applications in next generation coherent communication. Theoretical considerations taking into account the quasi zero-dimensional nature of the active material, clearly predict a strong reduction of the laser linewidth by appropriate dot design. Previous results on QD DFB lasers using 2 QD layers in the active region exhibited a linewidth of 110 kHz. New results based on 5 QD layers suggest considerably lower linewidth as was predicted by theory. First results suggest linewidths below 50 kHz.

Narrow-linewidth 1.5 μm quantum dot distributed feedback lasers for next generation coherent communication

Narrow linewidth InAs/InP QD DFB lasers with linewidths of less than 50kHz at 20°C which broadens to less than 80kHz at 80°C were demonstrated using delayed self-heterodyne as well as by optical frequency comb interferometry.

Narrow Linewidth InAs/InP Quantum Dot DFB Laser

We report spectral characteristics of InAs/InP QD DFB lasers. Owing to low linewidth enhancement factor and high modal gain, lasers with 5 QD layers exhibit record linewidth of 55 kHz measured by the heterodyne beat note between the laser and an ultra-stable optical frequency comb.

Tali Septon

Papers

Remote detection of buried landmines using a bacterial sensor.

Large linewidth reduction in semiconductor lasers based on atom-like gain material

Narrow-linewidth 1.5 μm quantum dot distributed feedback lasers for next generation coherent communication

Narrow Linewidth InAs/InP Quantum Dot DFB Laser

Spectral Characteristics of Narrow Linewidth InAs/InP Quantum Dot Distributed Feedback Lasers