Engineered Nucleotide Chemicapacitive Microsensor Array Augmented with Physics-Guided Machine Learning for High-Throughput Screening of Cannabidiol.

The recent legalization of cannabidiol (CBD) to treat neurological conditions such as epilepsy has sparked rising interest across global pharmaceuticals and synthetic biology industries to engineer microbes for sustainable synthetic production of medicinal CBD. Since the process involves screening large amounts of samples, the main challenge is often associated with the conventional screening platform that is time consuming, and laborious with high operating costs. Here, a portable, high-throughput Aptamer-based BioSenSing System (ABS3 ) is introduced for label-free, low-cost, fully automated, and highly accurate CBD concentrations' classification in a complex biological environment. The ABS3 comprises an array of interdigitated microelectrode sensors, each functionalized with different engineered aptamers. To further empower the functionality of the ABS3 , unique electrochemical features from each sensor are synergized using physics-guided multidimensional analysis. The capabilities of this ABS3 are demonstrated by achieving excellent CBD concentrations' classification with a high prediction accuracy of 99.98% and a fast testing time of 22 µs per testing sample using the optimized random forest (RF) model. It is foreseen that this approach will be the key to the realistic transformation from fundamental research to system miniaturization for diagnostics of disease biomarkers and drug development in the field of chemical/bioanalytics.

Structure of a Minimal α-Carboxysome-Derived Shell and Its Utility in Enzyme Stabilization.

Bacterial microcompartments are proteinaceous shells that encase specialized metabolic processes in bacteria. Recent advances in simplification of these intricate shells have encouraged bioengineering efforts. Here, we construct minimal shells derived from the Halothiobacillus neapolitanus α-carboxysome, which we term Cso-shell. Using cryogenic electron microscopy, the atomic-level structures of two shell forms were obtained, reinforcing notions of evolutionarily conserved features in bacterial microcompartment shell architecture. Encapsulation peptide sequences that facilitate loading of heterologous protein cargo within the shells were identified. We further provide a first demonstration in utilizing minimal bacterial microcompartment-derived shells for hosting heterologous enzymes. Cso-shells were found to stabilize enzymatic activities against heat shock, presence of methanol co-solvent, consecutive freeze-thawing, and alkaline environments. This study yields insights into α-carboxysome assembly and advances the utility of synthetic bacterial microcompartments as nanoreactors capable of stabilizing enzymes with varied properties and reaction chemistries.

Motion Control of Micro-/Nanomotors.

As we progress towards employing self-propelled micro-/nanomotors in envisioned applications such as cargo delivery, environmental remediation, and therapeutic treatments, precise control of the micro-/nanomotors direction and their speed is essential. In this Review, major emerging approaches utilized for the motion control of micro-/nanomotors have been discussed, together with the lastest publications describing these approaches. Future studies could incorporate investigations on micro-/nanomotors motion control in a real-world environment in which matrix complexity might disrupt successful manipulation of these small-scale devices.

Fe(0) Nanomotors in Ton Quantities (10(20) Units) for Environmental Remediation.

Despite demonstrating potential for environmental remediation and biomedical applications, the practical environmental applications of autonomous self-propelled micro-/nanorobots have been limited by the inability to fabricate these devices in large (kilograms/tons) quantities. In view of the demand for large-scale environmental remediation by micro-/nanomotors, which are easily synthesized and powered by nontoxic fuel, we have developed bubble-propelled Fe(0) Janus nanomotors by a facile thermally induced solid-state procedure and investigated their potential as decontamination agents of pollutants. These Fe(0) Janus nanomotors, stabilized by an ultrathin iron oxide shell, were fuelled by their decomposition in citric acid, leading to the asymmetric bubble propulsion. The degradation of azo-dyes was dramatically increased in the presence of moving self-propelled Fe(0) nanomotors, which acted as reducing agents. Such enhanced pollutant decomposition triggered by biocompatible Fe(0) (nanoscale zero-valent iron motors), which can be handled in the air and fabricated in ton quantities for low cost, will revolutionize the way that environmental remediation is carried out.

Fluorinated Nanocarbons Cytotoxicity.

As the research in nanotechnology progresses, there will eventually be an influx in the number of commercial products containing different types of nanomaterials. This phenomenon might damage our health and environment if the nanomaterials used are found to be toxic and they are released into the waters when the products degrade. In this study, we investigated the cytotoxicity of fluorinated nanocarbons (CXFs), a group of nanomaterials which can find applications in solid lubricants and lithium primary batteries. Our cell viability findings indicated that the toxicological effects induced by the CXF are dependent on the dose, size, shape, and fluorine content of the CXF. In addition, we verified that CXFs have insignificant interactions with the cell viability assays-methylthiazolyldiphenyl-tetrazolium bromide (MTT) and water-soluble tetrazolium salt (WST-8), thus suggesting that the cytotoxicity data obtained are unlikely to be affected by CXF-induced artifacts and the results will be reliable.

The Cytotoxicity of Layered Black Phosphorus.

Black phosphorus (BP), the latest addition to the family of 2D layered materials, has attracted much interest owing to potential optoelectronics, nanoelectronics, and biomedicine applications. Little is known about its toxicity, such as whether it could be as toxic as white phosphorus. In response to the possibility of BP employment into commercial products and biomedical devices, its cytotoxicity to human lung carcinoma epithelial cells (A549) was investigated. Following a 24 h exposure of the cells with different BP concentrations, cell viability assessments were conducted using water-soluble tetrazolium salt (WST-8) and methylthiazolyldiphenyltetrazolium bromide (MTT) assays. The toxicological effects were found to be dose-dependent, with BP reducing cell viabilities to 48% (WST-8) and 34% (MTT) at 50 µg mL(-1) exposure. This toxicity was observed to be generally intermediate between that of graphene oxides and exfoliated transition-metal dichalcogenides (MoS2, WS2, WSe2). The relatively low toxicity paves the way to utilization of black phosphorus.

Cytotoxicity of exfoliated transition-metal dichalcogenides (MoS2 , WS2 , and WSe2 ) is lower than that of graphene and its analogues.

Studies involving transition-metal dichalcogenides (TMDs) have been around for many decades and in recent years, many were focused on using TMDs to synthesize inorganic analogues of carbon nanotubes, fullerene, as well as graphene and its derivatives with the ultimate aim of employing these materials into consumer products. In view of this rising trend, we investigated the cytotoxicity of three common exfoliated TMDs (exTMDs), namely MoS2 , WS2 , and WSe2 , and compared their toxicological effects with graphene oxides and halogenated graphenes to find out whether these inorganic analogues of graphenes and derivatives would show improved biocompatibility. Based on the cell viability assessments using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and water-soluble tetrazolium salt (WST-8) assays on human lung carcinoma epithelial cells (A549) following a 24 h exposure to varying concentrations of the three exTMDs, it was concluded that MoS2 and WS2 nanosheets induced very low cytotoxicity to A549 cells, even at high concentrations. On the other hand, WSe2 exhibited dose-dependent toxicological effects on A549 cells, reducing cell viability to 31.8 % at the maximum concentration of 400 µg mL(-1) ; the higher cytotoxicity displayed by WSe2 might be linked to the identity of the chalcogen. In comparison with graphene oxides and halogenated graphenes, MoS2 and WS2 were much less hazardous, whereas WSe2 showed similar degree of cytotoxicity. Future in-depth studies should be built upon this first work on the in vitro cytotoxicity of MoS2 and WS2 to ensure that they do not pose acute toxicity. Lastly, nanomaterial-induced interference control experiments revealed that exTMDs were capable of reacting with MTT assay viability markers in the absence of cells, but not with WST-8 assay. This suggests that the MTT assay is not suitable for measuring the cytotoxicity of exTMDs because inflated results will be obtained, giving false impressions that the materials are less toxic.

Direct voltammetric determination of redox-active iron in carbon nanotubes.

With the advances in nanotechnology over the past decade, consumer products are increasingly being incorporated with carbon nanotubes (CNTs). As the harmful effects of CNTs are suggested to be primarily due to the bioavailable amounts of metallic impurities, it is vital to detect and quantify these species using sensitive and facile methods. Therefore, in this study, we investigated the possibility of quantifying the amount of redox-available iron-containing impurities in CNTs with voltammetric techniques such as cyclic voltammetry. We examined the electrochemistry of Fe3 O4 nanoparticles in phosphate buffer solution and discovered that its electrochemical behavior could be affected by pH of the electrolyte. By utilizing the unique redox reaction between the iron and phosphate species, the redox available iron content in CNTs was determined successfully using voltammetry.

Engineering a Metal Reductase for the Bioremediation of Anthropogenic Electronic Wastes: From Hg(II) to Au(III) and Ag(I) Enzymatic Reduction.

Recovering precious metals from electronic waste (e-waste) using microbes presents a sustainable methodology that can contribute toward the maintenance of planetary health. To better realize the potential of bioremediation using engineered microbes, enzymes that mediate the reduction of Au(III) to Au(0) have been the subject of intense research. In this study, we report the successful engineering of a metal reductase, MerA, whose cognate substrate is mercury(II), toward other precious metals such as Au(III) and Ag(I). The engineered variant, G415I, exhibited a 15-fold increase in catalytic efficiency (k cat/K M) in Au(III) reduction to Au(0) and a 200-fold increase in catalytic efficiency in Ag(I) reduction to Ag(0) with respect to the wild-type enzyme. The apparent shift in preference toward noncognate metal ions may be attributed to the energetics of valency preference. The improved Au(III) reductase has an apparent increased preference toward monovalent cations such as Au(I) and Ag(I), with respect to divalent cations such as Hg(II), the cognate substrate of the progenitor MerA (an increase in K M of 5.0-fold for Hg(II), compared to a decrease in K M of 5.8-fold for Au(III) and 1.8-fold for Ag(I), respectively). This study further extends the mechanistic understanding of Au(III) bioreduction that could proceed through the stabilization of Au(I) en route to Au(0) and suggests that the biosynthesis of Au nanoparticles with high efficiency can be realized through the engineering of promiscuous metal reductases for precious metal recovery from e-wastes.

Biologically engineered microbes for bioremediation of electronic waste: Wayposts, challenges and future directions.

In the face of a burgeoning stream of e-waste globally, e-waste recycling becomes increasingly imperative, not only to mitigate the environmental and health risks it poses but also as an urban mining strategy for resource recovery of precious metals, rare Earth elements, and even plastics. As part of the continual efforts to develop greener alternatives to conventional approaches of e-waste recycling, biologically assisted degradation of e-waste offers a promising recourse by capitalising on certain microorganisms' innate ability to interact with metals or degrade plastics. By harnessing emerging genetic tools in synthetic biology, the evolution of novel or enhanced capabilities needed to advance bioremediation and resource recovery could be potentially accelerated by improving enzyme catalytic abilities, modifying substrate specificities, and increasing toxicity tolerance. Yet, the management of e-waste presents formidable challenges due to its massive volume, high component complexity, and associated toxicity. Several limitations will need to be addressed before nascent laboratory-scale achievements in bioremediation can be translated to viable industrial applications. Nonetheless, vested groups, involving both start-up and established companies, have taken visionary steps towards deploying microbes for commercial implementation in e-waste recycling.

Beyond platinum: silver-catalyst based bubble-propelled tubular micromotors.

There has been enormous interest in autonomous self-propelled micro-/nanomotors, especially those that relied on the decomposition of hydrogen peroxide fuel to generate oxygen bubbles and usually consisted of platinum on their surface which acts as an efficient catalyst. In this study, we developed Pt-free tubular micromotors by using a less expensive silver catalyst for bubble propulsion.

The gating effect by thousands of bubble-propelled micromotors in macroscale channels.

Increasing interest in the utilization of self-propelled micro-/nanomotors for environmental remediation requires the examination of their efficiency at the macroscale level. As such, we investigated the effect of micro-/nanomotors' propulsion and bubbling on the rate of sodium hydroxide dissolution and the subsequent dispersion of OH(-) ions across more than 30 cm, so as to understand how these factors might affect the dispersion of remediation agents in real systems which might require these agents to travel long distances to reach the pollutants. Experimental results showed that the presence of large numbers of active bubble-propelled tubular bimetallic Cu/Pt micromotors (4.5 × 10(4)) induced a gating effect on the dissolution and dispersion process, slowing down the change in pH of the solution considerably. The retardation was found to be dependent on the number of active micromotors present in the range of 1.5 × 10(4) to 4.5 × 10(4) micromotors. At lower numbers (0.75 × 10(4)), however, propelling micromotors did speed up the dissolution and dispersion process. The understanding of the combined effects of large number of micro-/nanomotors' motion and bubbling on its macroscale mixing behavior is of significant importance for future applications of these devices.

Cytotoxicity of halogenated graphenes.

Graphene and its family of derivatives possess unique and remarkable physicochemical properties which make them valuable materials for applications in many areas like electronics, energy storage and biomedicine. In response to the possibility of its large-scale manufacturing as commercial products in the future, an investigation was conducted to determine the cytotoxicity of one particular family of graphene derivatives, the halogenated graphenes, for the first time. Halogenated graphenes were prepared through thermal exfoliation of graphite oxide in gaseous chlorine, bromine or iodine atmospheres to yield chlorine- (TRGO-Cl), bromine- (TRGO-Br) and iodine-doped graphene (TRGO-I) respectively. 24 h exposure of human lung carcinoma epithelial cells (A549) to the three halogenated graphenes and subsequent cell viability assessments using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and water-soluble tetrazolium salt (WST-8) assays revealed that all the halogenated graphenes examined are rather cytotoxic at the concentrations tested (3.125 µg mL(-1) to 200 µg mL(-1)) and the effects are dose-dependent, with TRGO-Cl reducing the cell viability to as low as 25.7% at the maximum concentration of 200 µg mL(-1). Their levels of cytotoxicity can be arranged in the order of TRGO-Cl > TRGO-Br > TRGO-I, and it is suggested that the amount of halogen present in the graphene material is the determining factor for the observed trend. Control experiments were carried out to test for possible nanomaterial-induced interference as a consequence of reaction between the halogenated graphenes and the viability markers (MTT/WST-8 reagent) or binding of the formazan products under cell-free conditions. The data obtained eliminate the probability of significant influence by these interferents as the change in the normalized percentage of formazan formed is relatively small and thorough washings were performed prior to the viability assessments to reduce the amount of halogenated graphenes that could eventually interact with the MTT/WST-8 assays. More studies need to be carried out in the future to complement the results obtained in this initial study in an attempt to develop a better understanding of the health hazards that the halogenated graphenes pose.