Peng Zuo

A low-cost and simple paper-based microfluidic device for simultaneous multiplex determination of different types of chemical contaminants in food.

It is difficult to carry out multiple detection of different type of chemicals because of the different chemical microenvironment requirements. Herein, a low-cost and simple paper-based microfluidic device integrated with fluorescence labeled single-stranded DNA (ssDNA) functionalized graphene oxide sensor was developed for the multiplex determination of different types of chemical contaminants in food. In this work, Cy5 labeled corresponding functional ssDNA for different analytes associated with graphene oxide (ssDNA-GO) were employed as core detection sensors to sensitively report the presence of the different type of chemicals as well as enlarge the chemical compatibility, which made it possible to simultaneous detect multiple chemicals under a same chemical microenvironment. Paper microfluidic device can be easily fabricated and paper substrate also facilitated the integration of ssDNA-GO sensors via physical absorption. This device has been successfully applied in multiplex detection of heavy metal mercury (II) ion (Hg(2+)) and silver (I) ion (Ag(+)) and aminoglycoside antibiotics residues in food. It also provided enormous potential for applications of environmental monitoring and clinical diagnosis.

Label-free electrochemical impedance spectroscopy biosensor for direct detection of cancer cells based on the interaction between carbohydrate and lectin.

A novel label-free electrochemical impedance spectroscopy (EIS) biosensor for direct cancer cell detection based on the interaction between carbohydrate and lectin has been developed with good sensitivity and selectivity. In the present work, concanavalin A (Con A), a mannose specific lectin, was immobilized on a gold disk electrode to fabricate the Con A sensor. This sensor was incubated with the cancer cell sample, and the binding of cancer cells with Con A resulted in a change of charge transfer resistance (Rct). EIS measurement was employed to measure the impedance change which reveals the concentration of cancer cells. This method has been successfully applied in human liver cancer cell Bel-7404 for direct and sensitive detection with a detection limit of 234cells/mL. This method could be extended to carry out multi-component diagnosis applications, thus providing enormous potential for applications of cancer monitoring and therapy.

Supportless electrochemical sensor based on molecularly imprinted polymer modified nanoporous microrod for determination of dopamine at trace level

In this work, we developed a novel freestanding metallic microrod as working electrode for highly sensitive and selective electrochemical detection of trace dopamine (DA). The electrode was facilely fabricated via first dealloying smooth Au-Ag alloy microrod (AMR) into nanoporous Au-Ag alloy microrod (NPAMR) and further modifying with electro-polymerized molecularly imprinted polymer (MIP). Influencing factors during electro-polymerization process including pH value and molar ratio of monomer to template molecule were optimized. Under the optimal conditions, a linear range from 2 × 10(-13) to 2 × 10(-8)M for measuring DA was obtained with an ultralow detection limit of 7.63 × 10(-14)M (S/N=3). In addition, the MIP-modified electrode (MIP/NPAMR) was successfully employed to test DA in serum and brain samples.

DNAzyme-based microarray for highly sensitive determination of metal ions.

A novel microarray for the multiplex determination of heavy metal ions in aqueous solution based on DNAzymes has been developed with good sensitivity and selectivity. In the present work, metal ion dependent DNAzymes of copper (Cu-Enz) and lead (Pb-Enz) were first associated with their corresponding DNA substrates (Cu-Sub and Pb-Sub) immobilized on the surface of aldehyde-coated slides. After introducing the corresponding metal ions, the DNA cleavage of the substrates caused by the DNAzymes took place, resulting in a dramatic change in fluorescent signal intensity. The proposed microarray method, which can be used as a multi-component assay with high efficiency, combines the high sensitivity and selectivity of DNAzymes with the high throughput and parallel analysis of microarray technology. The method reveals a sensitivity corresponding to 0.6ppb and 2ppb for Cu(2+) and Pb(2+), respectively, which is sufficient to detect them in drinking water. This approach may find potential applications in environmental monitoring, food safety monitoring, clinical toxicology, waste treatment, the cosmetic industry and industrial process monitoring.

A cost-effective Z-folding controlled liquid handling microfluidic paper analysis device for pathogen detection via ATP quantification

A cost-effective microfluidic paper analysis device (μPAD) was developed with a special Z-folding design for controlling the fluidic flowing and substrate transportation. This presented μPAD can be easily fabricated through wax printing by using a solid ink printer which deposits wax onto the surface of a chromatographic paper, and then baked on a hotplate by penetrating the molten wax into the paper to create a hydrophobic barrier. After μPAD fabrication, liquid control and substrate transportation can be easily carried out by twice folding the μPAD following Z shape. The Z folding made two separated reagent holding zone connected while the detection reaction occurred with the connection. In this paper, a pathogens detection indicated by ATP quantification was took as a proof-in-principle application of using this presented μPAD, the limit of detection (LOD) was 1 μM for ATP detection and 2.6×10(7) CFU/mL for Salmonella live cell detection, which showed a great potential for Point-of-Care Testing (POCT) applications.

Ultrasensitive and selective assay of glutathione species in arsenic trioxide-treated leukemia HL-60 cell line by molecularly imprinted polymer decorated electrochemical sensors.

Herein a pair of molecularly imprinted polymer (MIP) modified electrochemical sensors were reported to detect glutathione (GSH) and glutathione disulfide (GSSG) in arsenic trioxide-treated HL-60 cells. MIP film was in situ synthesized onto electrode surface via electro-polymerization in a facile way. The characteristics of the obtained sensors were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Both GSH-MIP and GSSG-MIP sensors exhibit the relatively wide linear detection range and low detection limit of 1.33 × 10(-10) M (S/N=3). It is found that N-acetylcysteine and DL-homocysteine, the precursors of GSH, show little influence on the detection of glutathione species, nor did the reactants of arsenite and GSH. Such strategies were successfully applied to discriminate GSH and GSSG in cell samples with acceptable recoveries of 92.0-109.1%, and the results are comparable with classic o-phthalaldehyde fluorospectrophotometry. Moreover, the presented sensors allow for easy disclosure of the reversion of malignant phenotype in leukemia cells via glutathione species analysis.

Sirtuin-dependent reversible lysine acetylation of glutamine synthetases reveals an autofeedback loop in nitrogen metabolism

Significance Nitrogen availability influences morphogenesis, antibiotic production, and virulence/pathogenicity in actinomycetes. This work provides novel insights into the molecular mechanisms underlying nitrogen metabolism regulation. Glutamine synthetases (GlnA) were acetylated by the acetyltransferase AcuA, which was regulated by the nitrogen regulator GlnR. Acetylation inactivated GlnA4 (GSII). Acetylated GSI-β (GlnA1) exhibited a remarkable ability to directly interact with GlnR and enhance GlnR–DNA binding, thereby modulating target gene transcription in response to nitrogen availability. The results indicated that GSI-β plays a central and essential role in nitrogen metabolism through not only controlling glutamine synthesis but also serving as the nitrogen signal for GlnR activation. These findings substantively extend our understanding of the regulatory mechanisms underlying nitrogen metabolism in actinobacteria, which include antibiotic-producing actinomycetes and pathogenic mycobacteria. In cells of all domains of life, reversible lysine acetylation modulates the function of proteins involved in central cellular processes such as metabolism. In this study, we demonstrate that the nitrogen regulator GlnR of the actinomycete Saccharopolyspora erythraea directly regulates transcription of the acuA gene (SACE_5148), which encodes a Gcn5-type lysine acetyltransferase. We found that AcuA acetylates two glutamine synthetases (GlnA1 and GlnA4) and that this lysine acetylation inactivated GlnA4 (GSII) but had no significant effect on GlnA1 (GSI-β) activity under the conditions tested. Instead, acetylation of GlnA1 led to a gain-of-function that modulated its interaction with the GlnR regulator and enhanced GlnR–DNA binding. It was observed that this regulatory function of acetylated GSI-β enzymes is highly conserved across actinomycetes. In turn, GlnR controls the catalytic and regulatory activities (intracellular acetylation levels) of glutamine synthetases at the transcriptional and posttranslational levels, indicating an autofeedback loop that regulates nitrogen metabolism in response to environmental change. Thus, this GlnR-mediated acetylation pathway provides a signaling cascade that acts from nutrient sensing to acetylation of proteins to feedback regulation. This work presents significant new insights at the molecular level into the mechanisms underlying the regulation of protein acetylation and nitrogen metabolism in actinomycetes.

Electrochemical sensor based on molecularly imprinted polymer for sensitive and selective determination of metronidazole via two different approaches

AbstractA molecularly imprinted polymer decorated glassy carbon electrode (MIP/GCE) is facilely developed into an electrochemical sensing platform for detection of metronidazole (MNZ). MIP preparation was carried out via in situ electropolymerization and o-phenylenediamine was selected as the optimal functional monomer. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize and assess the performance of the so-obtained sensor. In particular, two assay methods, which are based on different principles, were involved in the detection procedure. One is based on MIP/catalysis (Method І) and the other is MIP/gate effect (Method II). Comparison of these two methods was made in the aspects including detection range, sensitivity, accuracy, selectivity, repeatability, and long-term stability. It is found that Method І affords a lower detection limit of 3.33 × 10−10 M (S/N = 3) while the detection limit of Method II is 6.67 × 10−10 M (S/N = 3). The linear range of Method І and II is 1.0 × 10−9 to 1.0 × 10−8 M and 2.0 × 10−9 to 1.0 × 10−7 M, respectively. The MIP/GCE exhibits good recognition ability towards the template molecule-MNZ in the presence of the analogues of MNZ and other interferents, which can be ascribed to the successful imprinting effect during MIP membrane preparation. Graphical AbstractProcedure for fabricating MIP/GCE and its application in detecting metronidazole in serum

Multicomponent mesofluidic system for the detection of veterinary drug residues based on competitive immunoassay.

An automated multicomponent mesofluidic system (MCMS) based on biorecognitions carried out on meso-scale glass beads in polydimethylsiloxane (PDMS) channels was developed. The constructed MCMS consisted of five modules: a bead introduction module, a bioreaction module, a solution handling module, a liquid driving module, and a signal collection module. The integration of these modules enables the assay to be automated and reduces it to a one-step protocol. The MCMS has successfully been applied toward the detection of veterinary drug residues in animal-derived foods. The drug antigen-coated beads (varphi250 microm) were arrayed in the PDMS channels (varphi300 microm). The competitive immunoassay was then carried out on the surface of the glass beads. After washing, the Cy3-labeled secondary antibody was introduced to probe the antigen-antibody complex anchored to the beads. The fluorescence intensity of each bead was measured and used to determine the residual drug concentration. The MCMS is highly sensitive, with its detection limits ranging from 0.02 (salbutamol) to 3.5 microg/L (sulfamethazine), and has a short assay time of 45 min or less. The experimental results demonstrate that the MCMS proves to be an economic, efficient, and sensitive platform for multicomponent detection of compound residues for contamination in foods or the environment.