22 research outputs found
Complete removal of heavy metals with simultaneous efficient treatment of etching terminal wastewater using scaled-up microbial electrolysis cells
The treatment of actual low and high strengths etching terminal wastewater (ETW) from plating and electronic industry meeting national discharge standards is demonstrated in laboratory scale (1 L) and in scaled-up (40 L) microbial electrolysis cells (MECs). Both cylindrical single-chamber MECs achieved complete removal of heavy metals and efficient treatment of organics using either low strength ETW at an hydraulic retention time (HRT) of 5 d, or high strength wastewater at HRTs of 7 d (1 L) or 9 d (40 L). The removal rate of organics and heavy metals increased by 36-fold and scaled almost with the reactor volume ratio of 40. Electrode potentials in the scaled-up MECs (40 L) were resilient to the wastewater strength. Bacterial communities on both anodes and cathodes of the 1 L and the 40 L reactors experienced a selective shock and a significant community change after switching from low to high strengths wastewater, although reactor performance was effectively maintained. This study demonstrates complete removal of multiple heavy metals with simultaneous efficient wastewater treatment in MECs of different scales meeting China national discharge standards and provides a plausible approach for simultaneous removal of value-added products (e.g., heavy metals) and efficient treatment of practical etching terminal wastewater
Efficient conversion of bicarbonate (HCO3<sup>ā</sup>) to acetate and simultaneous heavy metal Cr(VI) removal in photo-assisted microbial electrosynthesis systems combining WO3/MoO3/g-C3N4 heterojunctions and Serratia marcescens electrotroph
The removal of the hazardous heavy metal Cr(VI) in water and the simultaneous production of acetate from the reduction of inorganic carbon (HCO3ā) is demonstrated in a photo-assisted microbial electrosynthesis (MES) system incorporating WO3/MoO3/g-C3N4 Z-scheme heterojunctions and Serratia marcescens Q1 electrotroph cathode. The rates of acetate production (6.1 Ā± 0.3 mg/L/h) and Cr(VI) removal (4.5 Ā± 0.1 mg/L/h) recorded at a circuital current of 2.8 Ā± 0.1 A/m2 were 2.4-fold (acetate production), 1.7-time (Cr(VI) removal) and 1.6-fold (circuital current) of those in the controls recorded in the absence of WO3/MoO3/g-C3N4, and 1.6-fold (acetate production) and 1.8-time (circuital current) of those in the absence of both Cr(VI) and WO3/MoO3/g-C3N4. Photogenerated WO3/MoO3/g-C3N4 conduction bands electrons favored both direct or indirect (via S. marcescens) reductions of Cr(VI) and H+, with the latter producing H2 which was further metabolized by S. marcescens with HCO3ā to yield acetate. The higher circuital current drawn under photoirradiation conditions refilled the photo-generated valence band holes in the semiconductor and provided the driving force for the reduction reactions. This study provides an alternative and feasible approach for achieving complete removal of toxic heavy metal from water and industrial waters with simultaneous conversion of inorganic carbon to key block chemicals
High-Sensitivity and High-Efficiency Detection of DNA Hydroxymethylation in Genomic DNA by Multiplexing Electrochemical Biosensing
DNA
hydroxymethylation (5-hmC) is a kind of new epigenetic modification,
which plays key roles in DNA demethylation, genomic reprogramming,
and the gene expression in mammals. For further exploring the functions
of 5-hmC, it is necessary to develop sensitive and selective methods
for detecting 5-hmC. Herein, we developed a novel multiplexing electrochemical
(MEC) biosensor for 5-hmC detection based on the glycosylation modification
of 5-hmC and enzymatic signal amplification. The 5-hmC was first glycosylated
by T4 Ī²-glucosyltransferase and then oxidated by sodium periodate.
The resulting glucosyl-modified 5-hmC (5-ghmC) was incubated with
ARP-biotin and was bound to avidin-HRP. The 5-hmC can be detected
at the subnanogram level. Finally, we performed 5-hmC detection for
mouse tissue samples and cancer cell lines. The limit of detection
of the MEC biosensor is 20 times lower than that of commercial kits
based on optical meaurement. Also, the biosensor presented high detection
specificity because the chemical reaction for 5-hmC modification can
not happen at any other unhydroxymethylated nucleic acid bases. Importantly,
benefited by its multiplexing capacity, the developed MEC biosensor
showed excellent high efficiency, which was time-saving and cost less
DNA Nanostructure-Based Universal Microarray Platform for High-Efficiency Multiplex Bioanalysis in Biofluids
Microarrays of biomolecules have
greatly promoted the development of the fields of genomics, proteomics,
and clinical assays because of their remarkably parallel and high-throughput
assay capability. Immobilization strategies for biomolecules on a
solid support surface play a crucial role in the fabrication of high-performance
biological microarrays. In this study, rationally designed DNA tetrahedra
carrying three amino groups and one single-stranded DNA extension
were synthesized by the self-assembly of four oligonucleotides, followed
by high-performance liquid chromatography purification. We fabricated
DNA tetrahedron-based microarrays by covalently coupling the DNA tetrahedron
onto glass substrates. After their biorecognition capability was evaluated,
DNA tetrahedron microarrays were utilized for the analysis of different
types of bioactive molecules. The gap hybridization strategy, the
sandwich configuration, and the engineering aptamer strategy were
employed for the assay of miRNA biomarkers, protein cancer biomarkers,
and small molecules, respectively. The arrays showed good capability
to anchor capture biomolecules for improving biorecognition. Addressable
and high-throughput analysis with improved sensitivity and specificity
had been achieved. The limit of detection for let-7a miRNA, prostate
specific antigen, and cocaine were 10 fM, 40 pg/mL, and 100 nM, respectively.
More importantly, we demonstrated that the microarray platform worked
well with clinical serum samples and showed good relativity with conventional
chemical luminescent immunoassay. We have developed a novel approach
for the fabrication of DNA tetrahedron-based microarrays and a universal
DNA tetrahedron-based microarray platform for the detection of different
types of bioactive molecules. The microarray platform shows great
potential for clinical diagnosis
Highly Stable Graphene-Based Nanocomposite (GOāPEIāAg) with Broad-Spectrum, Long-Term Antimicrobial Activity and Antibiofilm Effects
Various
silver nanoparticle (AgNP)-decorated graphene oxide (GO) nanocomposites
(GOāAg) have received increasing attention owing to their antimicrobial
activity and biocompatibility; however, their aggregation in physiological
solutions and the generally complex synthesis methods warrant improvement.
This study aimed to synthesize a polyethyleneimine (PEI)-modified
and AgNP-decorated GO nanocomposite (GOāPEIāAg) through
a facile approach through microwave irradiation without any extra
reductants and surfactants; its antimicrobial activity was investigated
on Gram-negative/-positive bacteria (including drug-resistant bacteria)
and fungi. Compared with GOāAg, GOāPEIāAg acquired
excellent stability in physiological solutions and electropositivity,
showing substantially higher antimicrobial efficacy. Moreover, GOāPEIāAg
exhibited particularly excellent long-term effects, presenting no
obvious decline in antimicrobial activity after 1 week storage in
physiological saline and repeated use for three times and the lasting
inhibition of bacterial growth in nutrient-rich culture medium. In
contrast, GOāAg exhibited a >60% decline in antimicrobial
activity after storage. Importantly, GOāPEIāAg effectively
eliminated adhered bacteria, thereby preventing biofilm formation.
The primary antimicrobial mechanisms of GOāPEIāAg were
evidenced as physical damage to the pathogen structure, causing cytoplasmic
leakage. Hence, stable GOāPEIāAg with robust, long-term
antimicrobial activity holds promise in combating public-health threats
posed by drug-resistant bacteria and biofilms
Gold Nanoparticle-Based Enzyme-Linked Antibody-Aptamer Sandwich Assay for Detection of <i>Salmonella</i> Typhimurium
Enzyme-linked immunosorbent assay
(ELISA) provides a convenient means for the detection of <i>Salmonella
enterica</i> serovar Typhimurium (STM), which is important for
rapid diagnosis of foodborne pathogens. However, conventional ELISA
is limited by antibodyāantigen immunoreactions and suffers
from poor sensitivity and tedious sample pretreatment. Therefore,
development of novel ELISA remains challenging. Herein, we designed
a comprehensive strategy for rapid, sensitive, and quantitative detection
of STM with high specificity by gold nanoparticle-based enzyme-linked
antibody-aptamer sandwich (nano-ELAAS) method. STM was captured and
preconcentrated from samples with aptamer-modified magnetic particles,
followed by binding with detector antibodies. Then nanoprobes carrying
a large amount of reporter antibodies and horseradish peroxidase molecules
were used for colorimetric signal amplification. Under the optimized
reaction conditions, the nano-ELAAS assay had a quantitative detection
range from 1 Ć 10<sup>3</sup> to 1 Ć 10<sup>8</sup> CFU
mL<sup>ā1</sup>, a limit of detection of 1 Ć 10<sup>3</sup> CFU mL<sup>ā1</sup>, and a selectivity of >10-fold for
STM in samples containing other bacteria at higher concentration with
an assay time less than 3 h. In addition, the developed nanoprobes
were improved in terms of detection range and/or sensitivity when
compared with two commercial enzyme-labeled antibody signal reporters.
Finally, the nano-ELAAS method was demonstrated to work well in milk
samples, a common source of STM contamination
Electrochemical DNA Biosensor Based on a Tetrahedral Nanostructure Probe for the Detection of Avian Influenza A (H7N9) Virus
A DNA tetrahedral nanostructure-based
electrochemical biosensor was developed to detect avian influenza
A (H7N9) virus through recognizing a fragment of the hemagglutinin
gene sequence. The DNA tetrahedral probe was immobilized onto a gold
electrode surface based on self-assembly between three thiolated nucleotide
sequences and a longer nucleotide sequence containing complementary
DNA to hybridize with the target single-stranded (ss)ĀDNA. The captured
target sequence was hybridized with a biotinylated-ssDNA oligonucleotide
as a detection probe, and then avidin-horseradish peroxidase was introduced
to produce an amperometric signal through the interaction with 3,3ā²,5,5ā²-tetramethylbenzidine
substrate. The target ssDNA was obtained by asymmetric polymerase
chain reaction (PCR) of the cDNA template, reversely transcribed from
the viral lysate of influenza A (H7N9) virus in throat swabs. The
results showed that this electrochemical biosensor could specifically
recognize the target DNA fragment of influenza A (H7N9) virus from
other types of influenza viruses, such as influenza A (H1N1) and (H3N2)
viruses, and even from single-base mismatches of oligonucleotides.
Its detection limit could reach a magnitude of 100 fM for target nucleotide
sequences. Moreover, the cycle number of the asymmetric PCR could
be reduced below three with the electrochemical biosensor still distinguishing
the target sequence from the negative control. To the best of our
knowledge, this is the first report of the detection of target DNA
from clinical samples using a tetrahedral DNA probe functionalized
electrochemical biosensor. It displays that the DNA tetrahedra has
a great potential application as a probe of the electrochemical biosensor
to detect avian influenza A (H7N9) virus and other pathogens at the
gene level, which will potentially aid the prevention and control
of the disease caused by such pathogens
Nano Rolling-Circle Amplification for Enhanced SERS Hot Spots in Protein Microarray Analysis
Although āhot spotsā have been proved to
contribute to surface enhanced Raman scattering (SERS), less attention
was paid to increase the number of the āhot spotā to
directly enhance the Raman signals in bioanalytical systems. Here
we report a new strategy based on nano rolling-circle amplification
(nanoRCA) and nano hyperbranched rolling-circle amplification (nanoHRCA)
to increase āhot spotā groups for protein microarrays.
First, protein and ssDNA are coassembled on gold nanoparticles, making
the assembled probe have both binding ability and hybridization ability.
Second, the ssDNAs act as primers to initiate in situ RCA reaction
to produced long ssDNAs. Third, a large number of SERS probes are
loaded on the long ssDNA templetes, allowing thousands of SERS probes
involved in each biomolecular recognition event. The strategy offered
high-efficiency Raman enhancement and could detect less than 10 zeptomolar
protein molecules in protein microarray analysis
Graphene Nanoprobes for Real-Time Monitoring of Isothermal Nucleic Acid Amplification
Isothermal amplification
is an efficient way to amplify DNA with high accuracy; however, the
real-time monitoring for quantification analysis mostly relied on
expensive and precisely designed probes. In the present study, a graphene
oxide (GO)-based nanoprobe was used to real-time monitor the isothermal
amplification process. The interaction between GO and different DNA
structures was systematically investigated, including single-stranded
DNA (ssDNA), double-stranded DNA (dsDNA), DNA 3-helix, and long rolling
circle amplification (RCA) and hybridization chain reaction (HCR)
products, which existed in one-, two-, and three-dimensional structures.
It was found that the high rigid structures exhibited much lower affinity
with GO than soft ssDNA, and generally the rigidity was dependent
on the length of targets and the hybridization position with probe
DNA. On the basis of these results, we successfully monitored HCR
amplification process, RCA process, and the enzyme restriction of
RCA products with GO nanoprobe; other applications including the detection
of the assembly/disassembly of DNA 3-helix structures were also performed.
Compared to the widely used end-point detection methods, the GO-based
sensing platform is simple, sensitive, cost-effective, and especially
in a real-time monitoring mode. We believe such studies can provide
comprehensive understandings and evocation on design of GO-based biosensors
for broad application in various fields
Multicolor GoldāSilver Nano-Mushrooms as Ready-to-Use SERS Probes for Ultrasensitive and Multiplex DNA/miRNA Detection
Uniform
silver-containing metal nanostructures with strong and
stable surface-enhanced Raman scattering (SERS) signals hold great
promise for developing ultrasensitive probes for biodetection. Nevertheless,
the direct synthesis of such ready-to-use nanoprobes remains extremely
challenging. Herein we report a DNA-mediated goldāsilver nanomushroom
with interior nanogaps directly synthesized and used for multiplex
and simultaneous SERS detection of various DNA and RNA targets. The
DNA involved in the nanostructures can act as not only gap DNA (mediated
DNA) but also probe DNA (hybridized DNA), and DNAās involvement
enables the nanostructures to have the inherent ability to recognize
DNA and RNA targets. Importantly, we were the first to establish a
new method for the generation of multicolor SERS probes using two
different strategies. First Raman-labeled alkanethiol probe DNA was
assembled on gold nanoparticles, and second, thiol-containing Raman
reporters were coassembled with the probe DNA. The ready-to-use probes
also give great potential to develop ultrasensitive detection methods
for various biological molecules