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We designed a paper-based analytical device by integrating horseradish peroxidase (HRP)-encapsulated 3D DNA for visual detection of alkaline phosphatase (ALP).

Terminal deoxynucleotidyl transferase (TdT) catalyzes template-independent DNA synthesis in a well-controllable mode on paper, allowing absolute quantification of polymetric labeling of a single 3′-OH present on genomic DNA.

ConspectusPathogens have long presented a significant threat to human lives, and hence the rapid detection of infectious pathogens is vital for improving human health. Current detection methods lack the means to detect infectious pathogens in a simple, rapid, and reliable manner at the time and point of need. Functional nucleic acids (FNAs) have the potential to overcome these limitations by acting as key components for point-of-care (POC) biosensors due to their distinctive advantages that include high binding affinities and specificities, excellent chemical stability, ease of synthesis and modification, and compatibility with a variety of signal-amplification and signal-transduction mechanisms.This Account summarizes the work completed in our groups toward developing FNA-based biosensors for detecting bacteria. In vitro selection has led to the isolation of many RNA-cleaving fluorogenic DNAzymes (RFDs) and DNA aptamers that can recognize infectious pathogens, including Escherichia coli, Clostridium difficile, Helicobacter pylori, and Legionella pneumophila. In most cases, a "many-against-many" approach was employed using a DNA library against a crude cellular mixture of an infectious pathogen containing diverse biomarkers as the target to isolate RFDs, with combined counter and positive selections ensuring high specificity toward the desired target. This procedure allows for the isolation of pathogen-specific FNAs without first identifying a suitable biomarker. Multiple target-specific DNA aptamers, including anti-glutamate dehydrogenase (GDH) circular aptamers, anti-degraded toxin B aptamers, and anti-RNase HII aptamers, have also been isolated for the detection of bacteria such as Clostridium difficile. The isolated FNAs have been integrated into fluorescent, colorimetric, and electrochemical biosensors using various signal transduction mechanisms. Both simple-to-use paper-based analytical devices and hand-held electrical devices with integrated FNAs have been developed for POC applications. In addition, signal-amplification strategies, including DNA catenane enabled rolling circle amplification (RCA), DNAzyme feedback RCA, and an all-DNA amplification system using a four-way junction and catalytic hairpin assembly (CHA), have been designed and applied to these systems to further increase their detection sensitivity. The use of these FNA-based biosensors to detect pathogens directly in clinical samples, such as urine, blood, and stool, has now been demonstrated with an outstanding sensitivity of as low as 10 cells per milliliter, highlighting the tremendous potential of using FNA-based sensors in clinical applications. We further describe strategies to overcome the challenges of using FNA-based biosensors in clinical applications, including strategies to improve the stability of FNAs in biological samples and prevent their nonspecific degradation from nucleases and strategies to deal with issues such as signal loss caused by nonspecific binding and biofouling. Finally, the remaining roadblocks for employing FNA-based biosensors in clinical applications are discussed.

Bioaerosols could carry and spread harmful microorganisms, thus posing a continuous threat to human beings and livestock health. Early warning and management are crucial for controlling the spread of bioaerosols. Herein, we developed a split aptamer (SA)-based electrochemical nanosensor chip (denoted SAE-nChip) for rapid and sensitive detection of adenosine triphosphate (ATP) in bioaerosols. The platform features two components: split DNA aptamers for their ability to bind ATP and undergo target-induced assembly on the chip surface and ZIF-8@MXene composites for their ability to provide a high surface density of aptamer-binding sites and facilitate the electron transfer at the biointerface. The SAE-nChip was capable of detecting ATP with a detection limit of 10 pM. Furthermore, this assay allowed the detection of ATP in cultured microorganisms and collected real bioaerosols. Overall, this strategy of interfacing DNA aptamers with MXene-based composite materials represents a versatile approach for the ubiquitous detection of biochemical targets in bioaerosols.

Adenosine 5'-triphosphate (ATP) is a central extracellular signaling agent involved in various physiological and pathological processes. However, precise measurements of the temporal and spatial components of ATP dynamics are lacking due primarily to the limitations of available methods for ATP detection. Here, we report on the first effort to design a self-phosphorylating DNAzyme (SPDz) sensor for fluorescence imaging of ATP. In response to ATP, SPDz sensors exhibit subsecond response kinetics, extremely high specificity, and micromolar affinities. In particular, we demonstrate cell-surface-anchored SPDz sensors for fluorescence imaging of both stress-induced endogenous ATP release in astrocytes and mechanical stimulation-evoked ATP release at the single-cell level. We also validated their utility for visualizing the rapid dynamic properties of ATP signaling upon electrical stimulation in astrocytes. Thus, SPDz sensors are robust tools for monitoring ATP signaling underlying diverse cellular processes.

We described a new system termed droplet DNAzyme-coupled rolling circle amplification (dDRCA) that can selectively detect bacteria from clinical urine samples with single-cell sensitivity within 1.5 h compared with the several hours needed for traditionally used culture-based methods.

φ29 DNA polymerase (Polφ29) is capable of synthesizing long-chain single-stranded (ss) DNA molecules by copying the sequence of a small ss circular DNA template (ssCDT) in a process known as rolling circle amplification (RCA). The use of a ssCDT in RCA, however, comes with a key drawback: the rate of DNA synthesis is significantly reduced. We hypothesize that this issue can be overcome using a very long linear ssDNA template with a repeating sequence. To test this idea, we engineered a DNA assembly, which we denote "micrometer-sized DNA track" (μDT). This μDT, with an average length of ≈13.5 μm, is made of a long chain DNA with a primer-binding domain at its 3' end and ≈1000 repeating sequence units at its 5' end, each carrying a DNA anchor. We find that Polφ29 copies μDT at a speed ≈5-time faster than it does a related ssCDT. We use this to design a simple all-in-one printed paper device for rapid and sensitive detection of microRNA let-7. This paper sensor is capable of detecting 1 pM let-7a in 10 minutes.

Protein biomarkers often exist as degradation fragments in biological samples, and affinity agents derived using a purified protein may not recognize them, limiting their value for clinical diagnosis. Herein, we present a method to overcome this issue, by selecting aptamers against a degraded form of the toxin B protein, which is a marker for diagnosing toxigenic Clostridium difficile infections. This approach has led to isolation of a DNA aptamer that recognizes degraded toxin B, fresh toxin B, and toxin B spiked into human stool samples. DNA aptamers selected using intact recombinant toxin B failed to recognize degraded toxin B, which is the form present in stored stool samples. Using this new aptamer, we produced a simple paper-based analytical device for colorimetric detection of toxin B in stool samples, or in the NAP1 strain of Clostridium difficile. The combined aptamer-selection and paper-sensing strategy can expand the practical utility of DNA aptamers in clinical diagnosis.

A large number of nanomaterials can strongly adsorb DNA and quench fluorescence, such as graphene oxide, gold nanoparticles, and most metal oxides. On the other hand, noncationic nanomaterials that adsorb DNA but cannot quench fluorescence are less known. These materials are attractive for studying the mechanism of DNA-based surface reactions. Y

Nanozymes are nanomaterials with enzyme-like activities. Compared to natural enzymes, nanozymes are more stable and cost-effective, and they have unique properties due to their nanoscale size and surface chemistry. In this review, we summarize 'signal-on' nanozyme-based sensors for detecting metal ions, anions, small molecules and proteins. Since protein-based enzymes are already highly active, they were used to detect their inhibitors, resulting in 'signal-off' sensors. On the other hand, for nanozymes, target molecules were detected either as a promotor of nanozyme activity or for its ability to selectively remove nanozyme inhibitors. In both cases, 'signal-on' detection was achieved. We classify the commonly used nanozymes based on their composition such as metal oxide, gold nanoparticles and other nanomaterials, most of which belong to the oxidase, peroxidase and catalase mimics. The nanozymes can catalyze the oxidation of colorless or non-fluorescent substrates to produce a visual or fluorescent signal. Based on this, this article presents some typical 'turn-on' and 'turn-off-on' sensors, and we critically review their design principles. At the end, further perspectives for the nanozyme-based sensors are outlined.

MXene Ti3C2Tx adsorb human plasma proteins to form protein corona. Opsonin proteins are highly enriched in the corona. The first main driving forces between MXene Ti3C2Tx nanosheets and human plasma proteins are hydrogen bonding.

Superoxide and other reactive oxygen species (ROS) shape microbial communities and drive the transformation of metals and inorganic/organic matter. Taxonomically diverse bacteria and phytoplankton produce extracellular superoxide during laboratory cultivation. Understanding the physiological reasons for extracellular superoxide production by aerobes in the environment is a crucial question yet not fully solved. Here, we showed that iron-starving Arthrobacter sp. QXT-31 (A. QXT-31) secreted a type of siderophore [deferoxamine (DFO)], which provoked extracellular superoxide production by A. QXT-31 during carbon sources-level fluctuation. Several other siderophores also demonstrated similar effects to A. QXT-31. RNA-Seq data hinted that DFO stripped iron from iron-bearing proteins in electron transfer chain (ETC) of metabolically active A. QXT-31, resulting in electron leakage from the electron-rich (resulting from carbon sources metabolism by A. QXT-31) ETC and superoxide production. Considering that most aerobes secrete siderophore(s) and undergo carbon sources-level fluctuation, the superoxide-generation pathway is likely a common pathway by which aerobes produce extracellular superoxide in the environment, thus influencing the microbial community and cycling of elements. Our results pointed that the ubiquitous siderophore might be the potential driving force for the microbial generation of superoxide and other ROS and revealed the important role of iron physiology in microbial ROS generation.

Detection and characterization of DNA damage plays a critical role in genotoxicity testing, drug screening, and environmental health. We developed a fully integrated origami paper-based analytical device (oPAD) for measuring DNA damage. This simple device allows on-paper cell lysis, DNA extraction, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) reaction and signal readout with simple operation steps, enabling rapid (within 30 min) and high throughput assessment of multiple DNA damages induced by exogenous chemical agents.

We report on a paper-based sensor capable of performing template-independent DNA synthesis by terminal deoxynucleotidyl transferase (TdT). Importantly, we observed that TdT efficiently incorporates fluorescently labeled dUTP on to 3'-OH ends of DNA strands in a strictly controllable manner on cellulose paper, in comparison to its distributive mode of DNA synthesis in solution. Due to the high roughness and porous nature of cellulose paper, we attribute this controllable DNA polymerization to the pore confinement effect on the catalytic behaviour of TdT. Taking advantage of this finding, we proposed a paper-assisted TdT (PAT) assay for absolute quantification of alkylated DNA lesions (N7-methylguanine), DNA deamination (cytosine-to-uracil) and DNA oxidation (8-oxo-7,8-dihydroguanine) by combining various DNA glycosylases. This PAT assay provides a low-cost, high throughput and easy to use method for quantifying the absolute levels of various types of DNA lesions, thus making it well-suited for drug development, genotoxicity testing, and environmental toxicology.

Fluorescent metal sensors based on DNA often rely on changes in end-to-end distance or local environmental near fluorophore labels. Because metal ions can also nonspecifically interact with DNA through various mechanisms, such as charge screening, base binding, and increase or decrease in duplex stability, robust and specific sensing of metal ions has been quite challenging. In this work, a side-by-side comparison of two signaling strategies on a Na+ -specific DNAzyme that contained a Na+ -binding aptamer was performed. The duplex regions of the DNAzyme was systematically shortened and its effect was studied by using a 2-aminopurine (2AP)-labeled substrate strand. Na+ binding affected the local environmental of the 2AP label and increased its fluorescence. A synergistic process of Na+ binding and forming the duplex on the 5'-end of the enzyme strand was observed, and this end was close to the aptamer loop. Effective Na+ binding was achieved with a five base-pair stem. The effect on the 3'-end is more continuous, and the stem needs to form first before Na+ can bind. With an optimized substrate binding arm, a FRET-based sensor has been designed by labeling the two ends of a cis form of the DNAzyme with two fluorophores. In this case, Na+ failed to show a distinct difference from that of Li+ or K+ ; thus indicating that probing changes to the local environment allows more robust sensing of metal ions.

Increasing micropollutant and cyanobacterial contamination of drinking water threatens human health worldwide. However, these contaminates are not efficiently removed by common drinking water treatment processes, and thus additional treatments are frequently required. Recent investigations have demonstrated that KMnO4 pre-oxidation can efficiently remove some micropollutants and cyanobacteria but the release of cyanobacterial toxins and Mn2+ limit its use. To overcome these problems, we proposed a KMnO4 pre-oxidation coupled with bioaugmentation (e.g., sand filtration) method to treat micropollutant- and cyanobacteria-laden water. We used 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (BP-4, a common micropollutant in drinking water sources) and Microcystis aeruginosa (a widely distributed cyanobacterial species) as model pollutants to verify the feasibility of the proposed method. Results revealed that KMnO4 pre-oxidation efficiently removed existing natural organic matter and Microcystis aeruginosa but failed to remove BP-4 and released Mn2+ and microcystin-LR (MC-LR) during treatment. Following the addition of a manganese-oxidizing bacterial strain (Pseudomonas sp. QJX-1) to the KMnO4-treated solution, we found that the bacteria could transform Mn2+ to Mn(III&IV) oxides, with the formed Mn oxides then able to remove BP-4 and MC-LR. Overall, the proposed method exhibited advantages in the removal of natural organic matter (i.e., decreasing disinfection byproduct formation), micropollutants, and cyanobacteria as well as preventing the release of Mn2+, and thus may be considered a good alternative for treating polluted drinking water.

Paper-based sensor technology represents a new class of point-of-care (POC) diagnostic devices that is affordable, portable, rapid and scalable for manufacturing. One of the goals of developing new paper-based POC diagnostics is the need to recognize targets with high specificity and sensitivity. Herein, a graphene oxide-circular aptamer based assay is described for highly specific and sensitive detection of a target protein on bioactive paper. The circular aptamer was self-assembled onto graphene oxide to generate the biorecognition moieties, followed by the desorption reaction induced by the specific binding of the target. The released circular aptamer then hybridizes to paper-bound DNA primers, thus initiating the rolling circle amplification reaction to produce a long DNA molecule containing multiple horseradish peroxidase-mimicking DNAzyme units, which further catalyze the oxidation of substrates by H2O2 in the presence of hemin to yield a distinct colorimetric signal on paper. Under the optimal conditions, this dual amplification method can achieve detection of platelet-derived growth factor (PDGF) at a concentration as low as 100 pM. Overall, this strategy of paper-based nanobiosensors may hold great potential for rapid, accurate and inexpensive biomarker detection in POC applications.

There is currently a great need for developing a simple and effective biosensing platform for the detection of single biomolecules (e.g., DNAs, RNAs, or proteins) in the biological, medical, and environmental fields. Here, we show a versatile and sensitive fluorescence counting strategy for quantifying proteins and microRNAs by employing functional DNA superstructures (denoted as 3D DNA). A 3D DNA biolabel was first engineered to become highly fluorescent and carry recognition elements for the target of interest. The presence of a target cross-links the resultant of the 3D DNA biolabel and a surface-bound capturing antibody or DNA oligonucleotide, thus forming a sandwich complex that can be easily resolved using traditional fluorescence microscopy. The broad utility of this platform is illustrated by engineering two different 3D DNA biolabels that enable the quantification of β-lactamase (one secreted bacterial hydrolase) and miR-21 (one overexpressed microRNA in cancer cells) with detection limits of 100 aM and 1 fM, respectively. We envision that the approach described herein will find useful applications in chemical biology, medical diagnostics, and biosensing.

Effective detection of pollutant gases is vital for protection of natural environment and human health. There is an increasing demand for sensing devices that are equipped with high sensitivity, fast response/recovery speed, and remarkable selectivity. Particularly, attention is given to the designability of sensing materials with porous structures. Among diverse kinds of porous materials, metal-organic frameworks (MOFs) exhibit high porosity, high degree of crystallinity and exceptional chemical activity. Their strong host-guest interactions with guest molecules facilitate the application of MOFs in adsorption, catalysis and sensing systems. In particular, the tailorable framework/composition and potential for post-synthetic modification of MOFs endow them with widely promising application in gas sensing devices. In this review, we outlined the fundamental aspects and applications of MOFs for gas sensors, and discussed various techniques of monitoring gases based on MOFs as functional materials. Insights and perspectives for further challenges faced by MOFs are discussed in the end.

Superoxide and other reactive oxygen species (ROS) in the environment shape microbial communities1 and drive transformation of metals2,3 and inorganic/organic matter4,5. Taxonomically diverse bacteria and phytoplankton can produce extracellular superoxide during laboratory cultivation6-11. Understanding the physiological reasons for extracellular superoxide production by aerobes in the environment is a crucial question yet not fully solved. Here, we showed that iron-starving Arthrobacter sp. QXT-31 (referred to as A. QXT-31 hereafter) secreted a type of siderophore (deferoxamine, DFO), which provoked extracellular superoxide production by carbon-starving A. QXT-31 when carbon sources were recovered. Several other siderophores also demonstrated similar effects. RNA-Seq data hinted that DFO stripped iron from iron-bearing proteins in the electron transfer chain (ETC) of metabolically active A. QXT-31, resulting in electron leakage from the electron-rich (resulting from carbons source metabolism) ETC and superoxide production. Considering that most aerobes secrete siderophore(s)12 and often suffer from carbon starvation in the environment, certain aerobes are expected to produce extracellular superoxide when carbon source(s) recover/fluctuate, thus influencing the microbial community and cycling of many elements. In addition, an artificial iron-chelator (diethylenetriamine pentaacetic acid, DTPA) was widely used in microbial superoxide quantification. Our results showed that DTPA provoked superoxide production by A. QXT-31 and highlighted its potential interference in microbial superoxide quantification.

Phosphorus is a key element responsible for eutrophication, and its measurement and speciation is a critical topic in analytical chemistry. Most research efforts have been devoted to detecting phosphate (P(V)), while few reports on phosphite (P(III)) are available, making it difficult for sensor-based understanding of the phosphorus cycle. This study presents a fluorescent "turn-on" sensor for quantitative and highly selective analysis of phosphite based on the different coordination strength of N and P lone-pair electrons toward nickel oxide (NiO). A few N-containing compounds (mainly Good's buffers) were screened as inhibitors for the oxidase-like activity of NiO nanoparticles for the oxidation of Amplex red (AR). HEPES was found to be most effective for inhibiting the formation of fluorescent resorufin, the oxidation product of AR. Among various phosphorus-, arsenic-, selenium-, and sulfur-containing species, along with various cations, phosphite was the only one that could restore the activity, likely due to its stronger affinity with the surface, and it is not an inhibitor. Under the optimum condition, the sensor detected P(III) up to 1 mM with a detection limit of 1.46 μM. The phosphite analysis with recovery rates ranged from 74.2 ± 2.6% to 107.5 ± 0.5% in real water and biological samples, suggesting the potential applicability of this sensor.

Technologies capable of linking DNA amplification to molecular recognition are very desirable for ultrasensitive biosensing applications. We have developed a simple but powerful isothermal DNA amplification method, termed DNAzyme feedback amplification (DFA), that is capable of relaying molecular recognition to exponential DNA amplification. The method incorporates both an RNA-cleaving DNAzyme (RCD) and rolling circle amplification (RCA) carried out by a special DNA polymerase using a circular DNA template. DFA begins with a stimulus-dependent RCA reaction, producing tandemly linked RCDs in long-chain DNA products. These RCDs cleave an RNA-containing DNA sequence to form additional primers that hybridize to the circular DNA molecule, giving rise to DNA assemblies that act as the new inputs for RCA. The RCA reaction and the cleavage event keep on feeding each other autonomously, resulting in exponential growth of repetitive DNA sequences that can be easily detected. This method can be used for the detection of both nucleic acid based targets and non-nucleic acid analytes. In this article, we discuss the conceptual framework of the feedback amplification approach, the essential features of this method as well as remaining challenges and possible solutions.

Nanoparticles are massively discharged into the aquatic environment leading to adverse health effects. Considering their adsorption of small molecules and polymers, it is important to study the effect of aqueous system composition on NPs’ behavior and toxicity. Nanomaterials with enzyme-like activities have caught a lot of recent research interest. Since nanozyme reactions take place on the surface of nanomaterials, their catalytic activities often show significant influence by adsorption of small molecules and polymers. CeO2 and Fe3O4 nanoparticles are two classic nanozymes, showing oxidase and peroxidase like activities, respectively. Inorganic arsenic species are critical for environmental and catalytic research. In this study, we used 3,3′,5,5′-tetramethylbenzidine (TMB) as a model substrate to examine the effect of inorganic arsenic species (As(III) and As(V)) on the activity of CeO2 and Fe3O4. The oxidation capacity of nanoceria was decreased to one third with the addition of 1 mM As(III), but was improved by 3-fold in the presence of 0.1 mM As(V). The former is mainly due to the reducing power of As(III), while the latter is attributable to the adsorption of As(V) on the nanoceria surface decreasing the electrostatic repulsion between nanoceria and TMB. For Fe3O4, its activity was first promoted and later inhibited by both As(III) and As(V). Therefore, nanomaterials not only affect arsenic species through redox chemistry and adsorption, but in turn arsenic can affect the catalytic activity of nanomaterials.

We have developed an effective chemical-vapor-deposition method to fabricate large-scale cerium hexaboride nanowire arrays on flexible carbon substates. The nanowires show diameters of 80–200 nm and lengths of 5–30 μm. The high resolution transmission electron microcopy (HRTEM) indicates that the nanowire is of high crystalline with the growth orientation of [001]. The field emission of these nanowires shows favorable electron emission properties, including the turn-on fields of 1.76 V μm −1 , threshold fields of 3.60 V μm −1 and high field emission enhancement factors of 2203 ± 27, respectively. The field emission properties depending on the gap between the anode and cathode are also investigated. The results show that the turn-on fields and threshold fields decrease from 1.76 and 3.60 V μm −1 to 1.28 and 2.77 V μm −1 , respectively; whereas the field emission enhancement factors increase from 2203 ± 27 to 4012 ± 66 with the anode-cathode distance increasing from 500 to 700 μm. The excellent field emission performances indicate the promising application prospects of this material in flexible electronics and optoelectronics, such as high light electron sources, flat panel displays and thermal electrical power converters.

The toxicity of disinfection by-products (DBPs) from a single precursor was studied intensively. Here we examined the genotoxicity when two precursors (tyrosine (Tyr) and benzophenone-4 (BP-4)) were chlorinated together and separately. We sought to examine whether the genotoxicity of the mixture (GCM) could be estimated from the sum of the genotoxicities of the individual precursors (GCI), which were chlorinated separately. We determined the genotoxicity using the SOS/umu test. The results revealed that GCM was not identical to GCI. The difference in genotoxicity between GCM and GCI (G Δ ) was observed to decrease with increasing pH. GCM was higher than GCI (G Δ > 0) at pH 5.0–6.1, and lower than GCI (G Δ (chlorinated mixture) /TON (the sum of chlorinated individuals) , is useful to estimate G Δ .

High concentrations of iron (Fe(II)) and manganese (Mn(II)) often occur simultaneously in groundwater. Previously, we demonstrated that Fe(II) and Mn(II) could be oxidized to biogenic Fe-Mn oxides (BFMO) via aeration and microbial oxidation, and the formed BFMO could further oxidize and adsorb other pollutants (e.g., arsenic (As(III)) and antimony (Sb(III))). To apply this finding to groundwater remediation, we established four quartz-sand columns for treating groundwater containing Fe(II), Mn(II), As(III), and Sb(III). A Mn-oxidizing bacterium (Pseudomonas sp. QJX-1) was inoculated into two parallel bioaugmented columns. Long-term treatment (120 d) showed that bioaugmentation accelerated the formation of Fe-Mn oxides, resulting in an increase in As and Sb removal. The bioaugmented columns also exhibited higher overall treatment effect and anti-shock load capacity than that of the non-bioaugmented columns. To clarify the causal relationship between the microbial community and treatment effect, we compared the biomass of active bacteria (reverse-transcribed real-time PCR), bacterial community composition (Miseq 16S rRNA sequencing) and community function (metagenomic sequencing) between the bioaugmented and non-bioaugmented columns. Results indicated that the QJX1 strain grew steadily and attached onto the filter material surface in the bioaugmented columns. In general, the inoculated strain did not significantly alter the composition of the indigenous bacterial community, but did improve the relative abundances of xenobiotic metabolism genes and Mn oxidation gene. Thus, bioaugmentation intensified microbial degradation/utilization for the direct removal of pollutants and increased the formation of Fe-Mn oxides for the indirect removal of pollutants. Our study provides an alternative method for the treatment of groundwater containing high Fe(II), Mn(II) and As/Sb.

In order for deep learning applications to run efficiently on low-power edge devices, including mobile and internet-of-things systems, it is important to reduce their computational and memory requirements. Binarized neural networks have shown promise in this area, but these are typically designed using existing architectures based on floating-point number representations. A more promising approach is to apply network architecture search algorithms to find optimized binarized architectures. In this paper, encoding schemes for the genetic algorithm search of binarized networks are described. The simulation results demonstrate the effectiveness of the proposed method.

Rapid detection of pathogenic bacteria is extremely important for public health and safety. Here, we describe for the first time an integrated origami paper-based analytical device (PAD) incorporating cell lysis, molecular recognition, amplification and visual detection of Escherichia coli (E. coli). The device features three components: paper for its ability to extract protein molecules nonspecifically from cells, DNA superstructures for their ability to immobilize RNA-cleaving DNAzymes (RCDs) but undergo target-induced RNA cleavage on paper, and isothermal rolling circle amplification (RCA) for its ability to amplify each cleavage event into repetitive sequence units that can be detected by naked eye. This device can achieve detection of E. coli K12 with a detection limit of as low as 103 CFU&middot, mL&minus, 1 in a total turnaround time of 35 min. Furthermore, this device allowed the sensitive detection of E. coli in complex sample matrices such as juice and milk. Given that more specific RCDs can be evolved for diverse bacteria, the integrated PAD holds great potential for rapid, sensitive and highly selective detection of pathogenic bacteria in resource-limited settings.

Fluorescent metal sensors based on DNA often rely on changes in end-to-end distance or local environmental near fluorophore labels. Because metal ions can also nonspecifically interact with DNA through various mechanisms, such as charge screening, base binding, and increase or decrease in duplex stability, robust and specific sensing of metal ions has been quite challenging. In this work, a side-by-side comparison of two signaling strategies on a Na

The increasing needs for developing biosensors for various applications in infectious disease diagnosis, environmental monitoring, and food safety put forth challenges on sensor performances such as sensitivity, selectivity, assay time, and operation cost. The CRISPR-Cas systems, regarded as molecular scissors, present an extremely high accuracy toward cleaving the targeted DNA and RNA. The presence of a target triggers the activation of CRISPR-Cas system to cleave the specific nucleic acid sequence and generate a signal. Recent studies have demonstrated the establishment of various facile and versatile CRISPR-Cas-based biosensing platforms. In this review, we will briefly introduce the general characteristics and mechanisms of the class II CRISPR-Cas systems, and highlight the biosensing strategies for a wide variety nucleic acid and non-nucleic acid analytes.

The early detection of cancer in both healthy and high-risk populations offers increased opportunity for treatment and curative intent. In this paper, we propose a hybrid classifier that produces an efficient classification system for cancer detection in cell datasets. The first part of this work investigates the performance of artificial neural networks (ANN) such as Self-Organizing Feature Map (SOM) and Learning Vector Quantization (LVQ), while in the second part, we present our investigation on the performances of Decision Tree (DT) and its pruning model. We also, in the third part, present our proposal for a new hybrid classifier that is based on the Random Forest (RF) and the combination of the LVQ and DT. Experimental results of the proposed hybrid classifier indicate that the hybrid classifier effectively avoids the drawbacks of individual classifiers and has high anti-noise performance.

Tramadol (TRA) is one of the most detected analgesics in environmental matrices, and it is of high significance to study the reactivity of TRA during chlorination considering its potential toxicity to the environment. The chlorine/TRA reaction is first order with respect to the TRA concentration, and a combination of first-order and second-order with respect to chlorine concentration. The pH dependence of the observed rate constants (kobs) showed that the TRA oxidation reactivity increased with increasing pH. kobs can be quantitatively described by considering all active species including Cl2, Cl2O and HOCl, and the individual rate constants of HOCl/TRA(0), HOCl/TRAH(+), Cl2/TRA and Cl2O/TRA reactions were calculated to be (2.61±0.29)×10(3)M(-1)s(-1), 14.73±4.17M(-1)s(-1), (3.93±0.34)×10(5)M(-1)s(-1) and (5.66±1.83)×10(6)M(-1)s(-1), respectively. Eleven degradation products were detected with UPLC-Q-TOF-MS, and the corresponding structures of eight products found under various pH conditions were proposed. The amine group was proposed to be the initial attack site under alkaline pH conditions, where reaction of the deprotonated amine group with HOCl is favorable. Under acidic and neutral pH conditions, however, two possible reaction pathways were proposed. One is an electrophilic substitution on the aromatic ring, and another is an electrophilic substitution on the nitrogen, leading to an N-chlorinated intermediate, which can be further oxidized. Finally, the SOS/umu test showed that the genotoxicity of TRA chlorination products increased with increasing dosage of chlorine, which was mostly attributed to the formation of some chlorine substitution products.