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The adsorption and cleavage behavior of DNA molecules by graphene oxide under UV irradiation were investigated in detail. It will provide novel insights into the potential environmental risk of graphene oxide in the aquatic environment.

In this study, 7 Pseudomonas strains were isolated from a wastewater treatment plant, and the alginate production of Pseudomonas strains under different environmental conditions was evaluated. Subsequently, alginate-biomass hydrogel beads were prepared using alginate and biomass of Pseudomonas, and their adsorption performances and mechanism to Pb

In this work, a novel method for the synthesis of copper nanoclusters is developed using nucleosides as templates and hydroxylamine hydrochloride as the reductant. Various nucleosides can regulate the catalytic activity of copper nanoclusters.

Advanced oxidation processes-based catalysis system as the most typical pollutant degradation technology always suffer from poor durability and photo-dependent. Inspired by the fact that some nanomaterials exhibit catalytic properties closer to natural enzymes, a high peroxidase-like activity and stability CeO

Recovery of microbial synthetic polymers with high economic value and market demand in activated sludge has attracted extensive attention. This work analyzed the synthesis of cyanophycin granule peptide (CGP) in activated sludge and its adsorption capacity for heavy metals and dyes. The distribution and expression of synthetic genes for eight biopolymers in two wastewater treatment plants (WWTPs) were analyzed by metagenomics and metatranscriptomics. The results indicate that the abundance and expression level of CGP synthase (cphA) are similar to those of polyhydroxyalkanoate polymerase, implying high synthesis of CGP in activated sludges. CGP in activated sludge is mainly polymerized from aspartic acid and arginine, and its secondary structure is mainly β-sheet. The crude yields of CGP are as high as 104 ± 26 and 76 ± 13 mg/g dry sludge in winter and in summer, respectively, comparable to those of polyhydroxyalkanoate and alginate. CGP has a stronger adsorption capacity for anionic pollutants (Cr (VI) and methyl orange) than for cationic pollutants because it is rich in guanidine groups. This study highlights prospects for recovery and application of CGP from WWTPs. IMPORTANCE The conversion of organic pollutants into bioresources by activated sludge can reduce the carbon dioxide emission of wastewater treatment plants. Identification of new high value-added biopolymers produced by activated sludge is beneficial to recover bioresources. Cyanophycin granule polypeptide (CGP), first discovered in cyanobacteria, has unique chemical and material properties suitable for industrial food, medicine, cosmetics, water treatment, and agriculture applications. Here, we revealed for the first time that activated sludge has a remarkable ability to produce CGP. These findings could further facilitate the conversion of wastewater treatment plants into resource recycling plants.

Thiocyanate (SCN−) is a metabolite of cyanide detoxification, which is considered to be a biomarker of environmental tobacco smoke exposure. Herein, a simple, fast and label-free fluorescent sensor was developed to determine SCN− based on the in situ formation of DNA-templated fluorescent copper nanoclusters (CuNCs). Without SCN−, the Cu(II) ions in buffer were reduced by ascorbic acid and then accumulated on the DNA template, showing a high fluorescence. However, in the presence of SCN−, the Cu(II) ions reacted with thiocyanate and then the remaining unreacted Cu(II) ions were reduced by ascorbic acid, producing a small amount of the CuNCs and a weak fluorescence. Several important parameters such as the concentrations of DNA, Cu(II) ions and ascorbic acid were optimized. Under the optimized conditions, the linear range was 10–100 μM and the limit of detection (LOD) was 4.94 μM for thiocyanate assay. Due to the strong chelation between SCN− and the Cu(II) ions, high selectivity was achieved for SCN− detection by this sensor, with practical applications in real water and artificial saliva. The operation process is simple and the signal response of this method to thiocyanate is fast, within a few minutes. Therefore, the developed assay has great potential to determine thiocyanate for the assessment of water safety and human health.

With the increasing concerns regarding bacterial adaption to nanomaterials, it is critical to explore the main mechanism behind the adaptive morphogenesis of microorganisms. In this work, the biofilms formed from activated sludge exposed to 5 and 50 mg/L nTiO

The generic of antibiotics is considered to be a main reason for the generation of antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs). However, little has been reported about the antibiotic biosynthesis by activated sludge. In this study, the distribution and expression of antibiotic biosynthetic genes (ABGs) in the floc sludge and biofilm from two WWTPs were deciphered using metagenomics and metatranscriptomics. The results showed that 2% of the community were in general well-linked to antibiotic production, indicating a non-negligible antibiotic synthetic ability of WWTPs. 93 ABGs belonging to 26 antibiotics were determined, among which aminoglycosides, β-lactams, ansamycins, peptides, macrolides were majority. The relative abundances of detected ABGs had a large interval, ranging from 0.000006% to 0.042%. The predominant antibiotic types of synthetic genes with higher relative expression levels were monobactams, penicillincephalosporins and streptomycin, primarily belonging to β-lactams and aminoglycosides. The hypothetical synthetic pathways of streptomycin synthesis and penicillincephalosporin synthesis were proposed. And the coexistence of ABGs and ARGs for these two antibiotics was also pronounced in activated sludge from meta-omics data. These findings for the first time demonstrated the antibiotic synthetic potential in activated sludges, revealing new sources of antibiotics and resistance genes in WWTPs, and thereby aggravating environmental pollution.

Enzyme-free amplification techniques based on dynamic DNA self-assembly (DDSA) have recently been developed for the in situ detection of mRNA in living cells. However, signal generation in traditional DDSA amplifiers is mainly dependent on the random diffusion of dissociative probes in a bulk solution, which is generally accompanied by poor kinetics and interference from complex biological systems. In this work, a new amplifier based on the design of an intramolecular catalytic hairpin assembly (intra-CHA) is proposed for the FRET imaging of mRNA in living cells. Compared with that in the free catalytic hairpin assembly (free-CHA), probes H1 and H2 in intra-CHA were simultaneously fixed on a DNA tetrahedron. The distance between them was closer, the local concentration of H1 and H2 in intra-CHA was theoretically approximately 808-times higher than that in free-CHA, and the initial reaction rate was enhanced 15.6 fold. Due to the spatial confinement effect, the reaction kinetics for target-catalyzed signal generation were significantly improved. By virtue of the three-dimensional nanostructure, H1 and H2 in the intra-CHA amplifier entered cells without any transfection or nanocarrier, and the probes and their products were free from biological interference, providing much higher signal stability for the reliable imaging of mRNA in living cells., An intramolecular catalytic hairpin assembly is implemented on a DNA tetrahedron for mRNA imaging in living cells. The spatial confinement effect enables the acceleration of target-triggered signal generation, with excellent cell permeability and FRET signal stability.

Herein, we developed a simple and rapid strategy to synthesize gold/silver bimetallic nanoclusters (Au/Ag NCs) with highly biochemical stability by a one-pot route. The Au/Ag NCs were obtained via a chemical reduction procedure in alkaline aqueous solution at 75 °C within only 20 min by employing bovine serum albumin (BSA) as both ligand and reductant. The as-obtained Au/Ag NCs displayed bright orange fluorescence with an emission peak located at 570 nm and temperature-dependent fluorescence property, which were utilized as fluorescent thermometer directly. More intriguingly, the Au/Ag NCs were very stable against various pH values, ions, biothiols, H2O2, fetal bovine serum (FBS), RPMI 1640 medium and amino acids. Taking advantage of the excellent biochemical stability, a ratiometric fluorescence biosensor, fluorescein-5-isothiocyanate (FITC)-Au/Ag NCs, was constructed for pH sensing based on the incorporation of FITC into the Au/Ag NCs. Furthermore, the ratiometric pH sensor was also successfully applied on the model of HeLa cells.

Ascorbic acid (AA) plays an important role in many physiological and biochemical processes. Herein, a novel, rapid and label-free fluorescence strategy was proposed to detect ascorbic acid based on the in situ formation of copper nanoclusters (CuNCs). When reducing ascorbic acid was present, the Cu(II) ions in 3-(N-morpholino) propanesulfonic acid (MOPS) buffer were transformed into CuNCs and showed high fluorescence. The excitation and emission peaks of CuNCs were 340 nm and 580 nm, respectively. The fluorescence intensity was proportional to the concentration of ascorbic acid. Under optimized conditions, the linear range of ascorbic acid detection is 50 to 1000 μM, and the detection limit is 41.94 μM. In addition, this method is successfully applied to the determination of ascorbic acid in real samples (serum samples and vitamin C tablets) and has shown satisfactory results. Besides the simple operation and good detection capability, the signal response of this method to ascorbic acid is fast and can reach maximum saturation in a few minutes. There is no background interference due to the in situ formation of the signal unit (CuNCs). Therefore, the proposed strategy has a strong potential to detect ascorbic acid in medical diagnosis and food safety due to its excellent analytical sensitivity and high selectivity.

A facile and eco-friendly approach for synthesizing fluorescent tungsten disulfide (WS2) nanosheets was developed via nitrogen atom doping using melamine as the nitrogen source. After nitrogen atom doping, the WS2 showed excellent ultraviolet emission and good stability. Further, the fluorescent WS2 was used as a fluorescent probe for mercury(II) (Hg2+) detection, with a detection limit of 0.02 μM. Finally, this fluorescent nanoprobe was applied to the determination of Hg2+ in real water samples and demonstrated satisfactory results.

Tetracycline (TC) is widely used to treat bacterial infections in humans and animals due to its low price and good antibacterial properties. The abuse of tetracycline has led to TC residues in daily food that could seriously affect human health. Thus, it is imperative to develop highly sensitive and selective methods for TC detection. In this work, we developed a colorimetric method for TC detection based on an enzyme-linked aptamer assay (ELAA) with multivalent HRP-mimicking DNAzyme. An aptamer was used as an alternative recognition element in the enzyme-linked immunosorbent assay (ELISA). Multivalent HRP-mimicking DNAzyme, assembled via hybridization chain reactions (HCR), was used for catalytic substrate color rendering in ELAA. The multivalent HRP-mimicking DNAzyme exhibited enhanced catalytic capacity and improved the detection sensitivity greatly. The limit of detection was 8.1 × 10-2 ng mL-1 with a linear range from 1.0 × 10-2 ng mL-1 to 1.0 × 104 ng mL-1 toward TC in buffer. To challenge the practical application capability of this strategy, the detection of TC in milk samples was also investigated and showed similar linear relationships. Due to the introduction of an aptamer, this ELAA strategy shows high selectivity towards TC and has potential for the detection of a wide spectrum of analytes.

Pyrolysis can not only effectively dispose of plastic wastes but also reclaim valuable chemicals and biochar. However, the production and release of second pollutants, particularly chlorine-containing products, have been neglected. The mechanism for the transformation of chlorine during the pyrolysis of plastic wastes remains unclear. Herein, a thermogravimetric Fourier transform infrared mass spectrometry technology was used to investigate the migration and transformation of substances during the pyrolysis of polyvinyl chloride (PVC) plastic from 200 °C to 900 °C with heating rates of 5, 50, 100, 150, and 200 K min−1. Results show the first stage of weight loss is at 200 °C-360 °C, where the dehydrochlorination of PVC mainly occurred, accompanied by the formation of conjugated double bonds and a small number of hydrocarbon compounds. The second stage of weight loss is at 360 °C-550 °C, where the breakage and rearrangement of the long polyethene chain may occur. Kinetics analysis shows the higher activation energy value is in the second stage, which indicates that the second stage reaction is less likely to occur and the Flynn–Wall–Ozawa method is more suitable for the study of plastic pyrolysis kinetics. This study suggests that second pollutants can be minimized during controllable pyrolysis.

Tetracyclines (TC) are a common antibiotic for using in livestock breeding and healthcare; however, due to the inappropriate application of TCs, more than 75% of TCs are excreted and released into the environment in an active form through human and animal urine and feces, which results in high levels of TCs in the ecological system, causing adverse effects on the food safety and human health. Thus, the high-performance monitoring of TC pollution is necessary. In this work, a highly sensitive fluorescent aptasensor was developed that was based on graphene oxide (GO) regulation of low background signal and target-induced fluorescence restoration. In the absence of analyte, the DNA probe (TC aptamer) was adsorbed completely by GO and failed to enhance the fluorescence of SYBR gold (SG), thereby resulting in a low background signal. When the TC-included samples were added, the DNA probe formed an aptamer-TC complex, thereby separating from the surface of the GO and inducing the fluorescence of SG. Under optimal conditions, the proposed strategy could detect TC concentrations of less than 6.2 × 10−3 ng mL−1, which is four orders of magnitude better than the detection limit of the “turn off” mode (53.9511 ng mL−1). Moreover, this aptasensor has been used to detect TC from milk samples and wastewater samples, and its satisfactory performances demonstrate that the proposed strategy can be applied in practice for TC monitor in food safety and environmental protection. Therefore, we believe that this work is meaningful in pollution monitoring, environment restoration and emergency treatment.

A large amount of tetracycline (TC) persists in water, soil, food, and feed due to the overuse of antibiotics, causing serious environmental problems such as damage to ecosystems and posing risks to human health. Thus, there is an urgent need to find a method to detect TC that is practical, rapid, sensitive, and offers ready visualization of TC levels so that adequate remediation measures can be immediately implemented. Herein, we report a fluorescent and colorimetric dual-mode nanosensor for the detection of TC based on reduced state carbon dots (r-CDs). In the presence of TC, the emission fluorescence of r-CDs was quenched by the Forster resonance energy transfer mechanism to achieve high-sensitivity detection of TC with a low limit of detection (LOD) of 1.73 nM. Moreover, TC was also detected by r-CDs via a noticeable color change of the solution (from colorless to red) with the naked eye, having an LOD of 0.46 μM. Furthermore, r-CDs have excellent selectivity and sensitivity in detecting TC in wastewater, and therefore, have practical applications in wastewater treatment. The fluorescent and colorimetric dual-mode proposed in this work may offer a unique idea for the detection of TC, with great prospects for environmental wastewater applications.

The breast cancer 1 (BRCA1) gene is a tumor suppressor gene, whose mutation is closely related to breast cancer. Therefore, the sensitive detection of the BRCA1 gene is extremely important for human health, particularly for women. In this study, a label-free fluorescent method based on hairpin DNA-templated copper nanoclusters (CuNCs) was for the first time developed for the detection of the BRCA1 gene. In the absence of target DNA, the detection system showed a strong red emission and produced a high emission peak. However, in the presence of the BRCA1 gene, the DNA probe hybridized with the BRCA1 gene and conformation of the DNA probe changed. As a result, the amount of produced CuNCs decreased and a low emission peak was obtained. The fluorescence intensity of the detection system was linearly correlated with the concentration of the BRCA1 gene ranging from 2 nM to 600 nM. The detectable limit was 2 nM for the BRCA1 gene assay, which was comparable with those reported by other non-amplifying sensors. Moreover, the developed method showed satisfactory recoveries for the BRCA1 gene assay in the bovine serum. The DNA-templated CuNC-based fluorescent assay thus offered a promising platform for the diagnosis of a breast cancer biomarker.

Water pollution arising from heavy metal ions continues to be a major environmental problem, which represents a serious threat to human beings and animals worldwide. New materials that can simultaneously detect and remove these toxic ions are urgently required. Herein, nitrogen and sulfur co-doped molybdenum selenide nanosheets (N, S-MoSe

Microbial extracellular polymeric substances (EPS) coating nanoparticles (NPs) surface can form NPs-EPS corona, which significantly affect the adsorption of NPs to toxic substances and alter the ecotoxicological effect of NPs. In this work, the EPS coronas on TiO2 NPs (TNPs) and CeO2 NPs (CNPs) were characterized and the adsorption characteristics of NPs with and without EPS corona to five heavy metals were investigated in single-metal and multiple-metal systems. The results of spectral analysis showed that NPs-EPS corona exhibited new crystalline phases and abundant functional groups. Moreover, 42 and 13 proteins were identified in the TNPs-EPS and CNPs-EPS coronas, respectively. The rates of Cd2+, Pb2+, Cu2+, Ni2+ and Ag+ adsorption by NPs-EPS corona increased to values that were 6.7-7.6, 4.4-5.1, 4.2-5.5, 3.9-4.9 and 8.5-8.8 times those of NPs without EPS corona, respectively, in single-metal system. NPs-EPS coronas are effective in absorbing Ag+, Pb2+ and Cu2+ compared with Cd2+and Ni2+ in multiple metal adsorption. These results indicated that NPs-EPS corona effectively adsorb and remove heavy metals by forming NPs-EPS-metal complexes and inducing precipitation. However, NPs-EPS corona can enhance the toxicity of NPs by accumulating highly-toxic heavy metals in aquatic environments.

Improper dosage of Bleomycin (BLM) can easily lead to a series of side effects such as pulmonary fibrosis and pulmonary toxicity. Therefore, detecting the content of BLM in actual sample is very helpful to make full use of its therapeutic efficacy and reduce its toxicity. Herein, we constructed a copper ion and G-quadruplex mediated label-free sensor to detect BLM. The strategy mainly relies on the chelation of BLM to copper ions, which makes the copper ions lose the quenching ability to the fluorescent dye N-methylmesoporphyrin (NMM) after chelation. With the assistance of the G-quadruplex, the BLM content in the sample can be detected by observing the change in fluorescence. A good linear relationship can be clearly observed within the BLM concentration range of 0.1 nM-75 nM, and the limit of detection was derived as 0.1 nM. This sensor did not involve any labeling or addition of Fe2+, even in the presence of 10 different antibiotics and 11 different metal ions, it still has a good monitoring effect, and can be successfully applied to the detection of BLM in serum and wastewater. Thus, we believe that this work hold great potential in antibiotic monitoring and environmental protection.

Intracellular pH (pHi) is an important parameter associated with cellular behaviors and pathological conditions. Sensing pHi and monitoring its changes are essential but challenging due to the lack of high-sensitive probes. Herein, a ratiometric fluorescent probe with ultra pH-sensitivity is developed based on hairpin-contained i-motif strand (I-strand, labeled with Rhodamine Green and BHQ2 at two termini) and complementary strand (C-strand, labeled with Rhodamine Red at its 5′-end). At neutral pH, both I-strand and C-strand hybridize into a rigid duplex (I–C), which holds the Rhodamine Red and the BHQ2 in close proximity. As a result, the fluorescence emission (F597 nm) of the Rhodamine Red is strongly suppressed, while the Rhodamine Green (F542 nm) is in a “signal on” state. However, the slightly acidic pH enforced the I-strand to form an intramolecular i-motif and initiated the dehybridization of I–C duplex, leading to Rhodamine Red in a “signal on” state and a decreased fluorescence of Rhodamine Green...

Mercury ions (Hg2+) owing to excessive discharge cause serious damage to human health and the water ecosystem via bioaccumulation in food chains. Novel materials employed for the high-performance monitoring of Hg2+ are urgently required. Herein, using sucrose, boric acid, and melamine as raw materials, a new nanomaterial sensor, namely boron and nitrogen co-doped carbon dots (B, N-CDs), was designed for fluorescent and colorimetric dual-mode detection of Hg2+. Because of the occurrence of both dynamic and static quenching, B, N-CDs were utilized to function as fluorescent sensors for detecting Hg2+ with a limit of detection (LOD) of 5.3 nM. B, N-CDs performed an action for catalytic oxidation of 3,3',5,5'-Tetramethylbenzidine (TMB) to a blue cationic radical via peroxidase mimetic activity. By sequentially adding cysteine and Hg2+ to control the emergence of the TMB cation radical, a sensor for the Hg2+ assay was established through the colorimetric "on-off-on" signal and the LOD was as low as 7.8 nM. Moreover, the application potential of B, N-CDs for complex water environments was demonstrated to be excellent. In summary, the dual-mode detection method delivers some valid strategies for the detection of mercury in aqueous solutions employing the functional nanomaterials mentioned, and opens new avenues in tackling the problem of heavy metal ion pollution for environmental monitoring and remediation.

A novel and adjustable lamp based on competitive interaction among dsDNA-SYBR Green I (SGI), ion quencher, and analyte was designed for bioanalysis. The "filament" and switch of the lamp could be customized by employing different dsDNA and ion quencher. The poly(AT/TA) dsDNA was successfully screened as the most effective filament of the lamp. Two common ions, Hg2+ and Fe3+, were selected as the model switch, and the corresponding ligand molecules cysteine (Cys) and pyrophosphate ions (PPi) were selected as the targets. When the fluorescence-quenched dsDNA/SGI-ion complex was introduced into a target-containing system, ions could be bound by competitive molecules and separate from the complex, thereby lighting the lamp. However, no light was observed if the biomolecule could not snatch the metal ions from the complex. Under the optimal conditions, sensitive and selective detection of Cys and PPi was achieved by the lamp, with practical applications in fetal bovine serum and human urine. This ion quencher regulated lamp for fluorescent bioassays is simple in design, fast in operation, and is more convenient than other methods. Significantly, as many molecules could form stable complexes with metal ions selectively, this ion quencher operated lamp has potential for the detection of a wide spectrum of analytes. Graphical abstract A novel and adjustable lamp on the basis of competitive interaction among dsDNA-SYBR Green I, ions quencher and analyte was designed for bioanalysis. The filament and switch of lamp could be customized by employing different dsDNA and ions quencher.

Water pollution arising from heavy metal ions continues to be a major environmental problem, which represents a serious threat to human beings and animals worldwide. New materials that can simultaneously detect and remove these toxic ions are urgently required. Herein, nitrogen and sulfur co-doped molybdenum selenide nanosheets (N, S-MoSe2) were prepared and found to be fluorescently responsive to mercury (II) with an improved adsorption capacity (208.33 mg g−1), thereby providing the possibility for the simultaneous detection and removal of mercury (II) in water samples. The great affinity was the result of the complexation of mercury (II) with Se and S atoms in N, S-MoSe2 as well as the electrostatic adsorption of cation mercury (II) on negatively charged N, S-MoSe2. Besides good sensitivity and selectivity toward mercury (II), N, S-MoSe2 displayed a relatively consistent performance under a wide pH range from 3 to 10. The removal efficiency reached 87.5% with fast adsorption kinetics, and N, S-MoSe2 could be reused after simple treatment. Thus, this work is expected to provide new material for the detection and removal of mercury (II) in an aqueous solution and offer an insight into the interaction between heavy metal ions and inorganic nanomaterials.

Measuring the levels of Fe3+ in human body has attracted considerable attention for health monitoring as it plays an essential role in many physiological processes. In this work, we reported a selective fluorescent nanoprobe for Fe3+ detection in biological samples based on ultrabright N/P codoped carbon dots. By employing adenosine 5′-triphosphate (ATP) as the carbon, nitrogen, and phosphorus source, the N/P codoped carbon dots could be simply prepared through hydrothermal treatment. The obtained carbon dots exhibited high quantum yields up to 43.2%, as well as excellent photostability, low toxicity, and water solubility. Because of the Fe–O–P bonds formed between Fe3+ and the N/P codoped carbon dots, this nanoprobe showed high selectivity toward Fe3+ against various potential interfering substances in the presence of EDTA. The fluorescence quenching of as-fabricated carbon dots was observed with the increasing Fe3+ concentration, and the calibration curve displayed a wide linear region over the range of...

Copper pollution has become a very serious problem in modern society with the increasing industrial emission and the acid mine drainage. Copper deficiency or excess copper accumulation in human and animal livers can bring both oxidative stress and severe disorders. Thus, the development of a simple and efficient strategy for Cu2+ ion detection in water and blood samples is very necessary and meaningful. In this study, a simple, fast, and sensitive fluorescence method was put forward to detect Cu2+ ions based on C5 DNA-templated gold nanoclusters (AuNCs) and Fenton-like reactions. Under aerobic conditions, ascorbic acid is not only involved in the reduction of Cu2+, but also reacts with O2 to produce H2O2. Then, hydroxyl radical (˙OH), yielded by H2O2 and Cu+, can seriously quench the fluorescence of AuNCs. Attributed to the unique Fenton-like reaction between ascorbic acid and the Cu2+ ions, high selectivity was achieved for Cu2+ ion monitoring using this nanosensor, and the practical applications of this nanosensor in real water and blood samples were realized.

In this work, we developed a simple, rapid and mild strategy for synthesis of DNA-templated fluorescent gold nanoclusters (AuNCs) through association of gold ions to DNA templates and reduction with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES). After systematical investigation on the formation of fluorescent AuNCs by using different DNA templates, C5 DNA was found as the best template for the formation of fluorescent AuNCs in this system. This process could be completed within 5min after the reaction beginning under ambient conditions. The prepared C5-AuNCs displayed good blue emission and photostability. Furthermore, this C5-AuNCs could be applied to detecting Hg2+ ions specifically based on the specific and strong interaction between Hg2+ and Au+. The C5-AuNCs provided excellent selectivity for Hg2+ ions over other metal ions, and also high sensitivity, with a detection limit of 50nM. As biocompatible, environmentally-friendly, and synthesis-rapid, this C5-AuNCs probe appears to be promising candidate for biochemical sensing via simple modification of template DNA.

Due to its unique programmability, nanosized structure, and biocompatible properties, deoxyribonucleic acid (DNA) has attracted increasing attention for the construction of versatile nanostructures and nanomaterials. This review summarizes the recent developments in DNA-templated fluorescent nanomaterials, including DNA-stabilized quantum dots (QDs) and DNA-templated metal nanoclusters (NCs), as well as their applications in bioanalysis. These fluorescent nanomaterials not only have good fluorescence properties but also exhibit excellent performance in DNA recognition, which greatly expands the range of their bioanalytical applications. Finally, we discuss some current challenges and future work in this field, with the goal of further promoting the potential applications and developments of DNA-templated fluorescent nanomaterials in biochemical analysis.

Copper nanoclusters (CuNCs) are an attractive alternative to other metal nanoclusters. The synthesis of CuNCs is highly efficient and fast, with low-cost and without any complicated manipulation. Because of their tunable fluorescence and low toxicity, CuNCs have been highly exploited for biochemical sensing. This review (with 172 refs.) summarizes the progress that has been made in the field in the past years. Following an introduction into the fundamentals of CuNCs, the review first focuses on synthetic methods and the fluorescence properties of CuNCs (with subsections on the use of proteins, peptides, DNA and other molecules as templates). This is followed by a section on the use of CuNCs in fluorometric assays, with subsections on the detection of small molecules, proteins, nucleic acids, various other biomolecules including drugs, and of pH values. A further large chapter summarizes the work related to environmental analyses, specifically on determination of metal ions, anions and pollutants. Graphical abstract Schematic representation of the synthesis and potential applications of copper nanocluster (CuNCs) in biochemical analysis, emphatically reflected in some vital areas such as small molecule analysis, biomacromolecule monitoring, cell imaging, ions detection, toxic pollutant, etc.

Micrococcal nuclease (MNase) is a naturally-secreted nucleic acid degrading enzyme with important role in the spread of the bacteria in an infected host. The content of MNase can be used to estimate the pathogenicity of Staphylococcus aureus (S. aureus). A fluorometric method is described here for determination of the activity of MNase and for identification of S. aureus using DNA templated fluorescent copper nanoclusters (CuNC). A double-stranded DNA (dsDNA) with AT-rich regions and protruding 3′-termini was identified as a high-selectivity substrate for MNase and as a template for CuNC. In the absence of MNase, the long AT-rich dsDNA templates the formation of CuNC that display bright yellow fluorescence, with excitation/emission peaks at 340/570 nm. However, the substrates are enzymatically digested to mononucleotides or short-oligonucleotide fragments, which fail to synthesize fluorescent CuNC. The method works in the 1.0 × 10−3 - 5.0 × 10−2 U mL−1 MNase activity range, has a 1.0 mU mL−1 detection limit, and is highly selective over other exonucleases. The assay was successfully applied to the detection of MNase secreted by S. aureus and to the identification of S. aureus.

Micrococcal nuclease (MNase) is a nonspecific endo-exonuclease that digests single-stranded/double-stranded DNA and RNA. The existence of MNase can serves as an important diagnostic biomarker of Staphylococcus aureus (S. aureus) infection. However, most of the substrates in MNase-based sensors are single-stranded DNA, which could also be digested by exonuclease I or S1 nuclease and interfere the MNase detection. In this work, we developed a highly selective fluorescent method for MNase detection using a specific dsDNA and nucleic acid dye SYBR Green I (SGI) as the indicator. After rational design, an AT-rich dsDNA with 3′ protruding termini was screened as the high-specific substrate of MNase assay and efficient enhancer of SGI. The AT-rich dsDNA substrate can resist the digestion of other exonuclease and greatly enhance the fluorescence of SGI. This high-specific substrate-based probe can detect MNase in buffer as well as biological sample with highly selectivity. Moreover, this method was also applied to monitor the MNase secreted by S. aureus. Thus, the proposed MNase-based assay has a strong potential to identify S. aureus in food safety and microbial infection due to its excellent analytical sensitivity and high selectivity.

Fluorescent metal nanoclusters (MNCs), composed of a few to hundreds of noble metal atoms, are a type of sub-nanometer scale transitional material between atoms and nanoparticles. The special structure and size endow MNCs with a series of excellent fluorescence properties, such as strong fluorescence, high quantum yield, good anti-photobleaching, and mega-Stokes shift. In addition, MNCs show advantageous properties with respect to good biocompatibility and water solubility. These properties have made MNCs new metal nano-fluorophores (MNFs) that are widely used in biochemical analysis and bioimaging. Among the various scaffolds for the stabilization of MNCs, deoxyribonucleic acid (DNA) is an interesting ligand due to its unique structure and programmable sequences. The properties of DNA-templated MNCs, such as the excitation/emission wavelength, fluorescence intensity, and the sizes of the MNCs, can be controlled by DNA templates with different sequences, lengths or configurations. We call DNA-templated MNCs “DNA-coded MNFs” here. In this review, based on our previous studies on DNA-templated MNCs, we focus on systematically summarizing the preparations, property regulations and applications of DNA-coded MNFs in biosensing and bioimaging. Finally, the current challenges, research emphases and prospects of DNA-coded MNFs are also discussed. We believe that this review will promote the development of this fertile research area in the future.

With the development of carbon-based nanomaterials, carbon dots (CDs) have recently received increasing attention owing to their unique optical properties, low toxicity, facile synthesis, abundance and inexpensive precursors. Along with the demonstrated applications in bioimaging, photocatalysis, and biochemical sensing, CDs are expected to have novel applications in different environmental fields. This work aims to review the recent developments in the use of CDs for environmental pollution control and remediation, such as sensing of environmental pollutants, contaminant adsorption, membrane separation, pollutant degradation, and as antimicrobial agents. Different synthesis methods of CDs as well as properties relevant to environmental applications are also discussed. Compared with other carbon-based nanomaterials, the unique nanostructures and properties of CDs enable exceptional environmental capabilities. Moreover, the challenges and research direction for future environmental applications of CDs are also highlighted. We believe this review will provide new direction to the development of environmental pollution control and remediation using CDs.

In this work, a universal and sensitive “signal-on” electrochemical aptasensor platform has been developed based on a triple-helix molecular switch (THMS)-induced hybridization chain reaction (HCR) amplification. This aptasensor platform system consists of a THMS-based molecular recognition process in a homogeneous solution and a HCR amplification on a gold electrode. In the absence of a target, the aptamer sequence is flanked by two arm segments (APT) and the triplex-forming oligonucleotide (TFO), forming a rigid THMS. It is in the eT off state. However, upon the introduction of a target, the interaction between the target and the APT leads to the dissociation of the THMS and thereby liberates the TFO, allowing the TFO to hybridize with the capture probe (CP) DNA and trigger the formation of dsDNA polymers through in situ HCR amplification. The dsDNA polymers cause the electrostatic attraction of numerous electroactive indicators [Ru(NH3)6]3+, resulting in significantly amplified electrochemical signal output. It is in the eT on state. As proof-of-principle, we use this approach to detect adenosine and human α-thrombin (Tmb), achieving lowest limit of detection values of 0.6 nM and 70.9 pM, respectively. As an electrochemical aptasensor platform, its universality can be easily realized by altering only the sequence of the APT, which provides a promising alternative to the electrochemical detection of a variety of analytes and may have potential applications in biomedical research and clinical diagnosis.

Owing to their highly efficient catalytic effects and substrate specificity, the nucleic acid tool enzymes are applied as 'nano-tools' for manipulating different nucleic acid substrates both in the test-tube and in living organisms. In addition to the function as molecular scissors and molecular glue in genetic engineering, the application of nucleic acid tool enzymes in biochemical analysis has also been extensively developed in the past few decades. Used as amplifying labels for biorecognition events, the nucleic acid tool enzymes are mainly applied in nucleic acids amplification sensing, as well as the amplification sensing of biorelated variations of nucleic acids. With the introduction of aptamers, which can bind different target molecules, the nucleic acid tool enzymes-aided signal amplification strategies can also be used to sense non-nucleic targets (e.g., ions, small molecules, proteins, and cells). This review describes and discusses the amplification strategies of nucleic acid tool enzymes-aided biosensors for biochemical analysis applications. Various analytes, including nucleic acids, ions, small molecules, proteins, and cells, are reviewed briefly. This work also addresses the future trends and outlooks for signal amplification in nucleic acid tool enzymes-aided biosensors.

DNA templated fluorescent copper nanoclusters (DNA-CuNCs) have demonstrated enormous potential for biochemical analysis. However, most of them are focused on DNA-related sensing. Here, we designed a hairpin DNA/RNA chimeric chain for the formation of fluorescent CuNCs and further applied it to detect reverse transcription-associated ribonuclease H (RNase H). The DNA/RNA chimera templated copper nanoclusters (DNA/RNA-CuNCs) exhibited similar spectral properties with DNA-CuNCs. In the presence of RNase H, the RNA segment in chimera is hydrolyzed and release short oligonucleotides, which fail to synthsize fluorescent CuNCs. The capabilities for RNase H detection from complex samples and screening of inhibitors were verified. This strategy exhibited high sensitivity for RNase H with a detectable minimum concentration of 5.5 × 10−4 U mL-1, which is lower than the developed fluorescent methods. This work will open up new thoughts to design new template for metal nanoclusters and broaden their application in RNA-related sensing.

The infection and spread of pathogens (e.g., COVID-19) pose an enormous threat to the safety of human beings and animals all over the world. The rapid and accurate monitoring and determination of pathogens are of great significance to clinical diagnosis, food safety and environmental evaluation. In recent years, with the evolution of nanotechnology, nano-sized graphene and graphene derivatives have been frequently introduced into the construction of biosensors due to their unique physicochemical properties and biocompatibility. The combination of biomolecules with specific recognition capabilities and graphene materials provides a promising strategy to construct more stable and sensitive biosensors for the detection of pathogens. This review tracks the development of graphene biosensors for the detection of bacterial and viral pathogens, mainly including the preparation of graphene biosensors and their working mechanism. The challenges involved in this field have been discussed, and the perspective for further development has been put forward, aiming to promote the development of pathogens sensing and the contribution to epidemic prevention., Highlights • The infection and spread of pathogens threaten human health, the development of effective detection strategies is highly important and essential. • Graphene biosensor as one of effective nano-platforms is reviewed in the field of pathogen detection. • The preparation of graphene biosensors and their sensing mechanism are introduced and discussed. • The current challenges in this field and the perspective for further development are presented, which will be meaningful for pathogens sensing and epidemic prevention.

Carbon dots (CDs) have wide applications in chemical sensor, electrocatalysis, and photocatalysis, but most preparations of carbon dots need high temperature and long reaction time. In this work, a chemical oxidation and surface passivation approach was introduced to synthesize fluorescent CDs in low-temperature condition using phosphoric acid and ammonium hydroxide as the oxidant and passivator, respectively. The as-prepared CDs exhibited two emission bands at 356 nm and 440 nm with different excited wavelengths, and high quantum yield (25.51%). More important, the fluorescent CDs display good water-solubility and high biocompatibility even under broad pH range or high ionic strengths. Moreover, this high-stable fluorescent CDs was also employed as a ratiometric fluorescence probe for ascorbic acid sensing based on the inner filter effect (IFE) between ascorbic acid and CDs. This strategy represented excellent sensitivity and selectivity for ascorbic acid analysis both in buffer and biological samples, providing a valuable platform for ascorbic acid detection in clinic diagnosis.

Microbial extracellular proteins serve as important functions in wastewater treatment process. Analysis of their compositions and properties is crucial to probe their specific functions. However, conventional analytical techniques cannot obtain interest protein information from complex proteins. Recently, the extracellular proteomics method has been applied to resolve the composition of extracellular proteins. In order to better understand the roles of extracellular protein in wastewater treatment process, this review provides the information on the proteomics methods and their application in investigating extracellular proteins involved in microbial attachment/aggregation, biodegradation of pollutants, and response to environmental stresses. Future work needs to exploit the full capability of the proteome.

As an important member of the tool enzymes, exonuclease is a kind of hydrolytic enzymes without strict base sequence dependence. In recent years, by taking advantage of different hydrolysis ways of exonuclease and nanotechnology, cycle effect of enzyme digestion, aptamer, non Watson-Crick base pairing system by metal ions, fluorescent nucleic acid probes, electrochemical methods etc., a series of exonuclease-assisted signal amplification strategies have been developed, which have played a key role in improving the sensitivity of detection method. Therefore, exonucleases have been widely used in highly sensitive detection of nucleic acids, proteins, ions, small molecules and so on. To understand it better and apply it well in the future, the application progresses of exonuclease-assisted signal amplification strategies in biochemical analysis have been summarized in this review.