SIRT1 regulates mitochondrial fission to alleviate high altitude hypoxia inducedcardiac dysfunction in rats via the PGC-1α-DRP1/FIS1/MFF pathway.

High-altitude exposure has been linked to cardiac dysfunction. Silent information regulator factor 2-related enzyme 1 (sirtuin 1, SIRT1), a nicotinamide adenine dinucleotide-dependent deacetylase, plays a crucial role in regulating numerous cardiovascular diseases. However, the relationship between SIRT1 and cardiac dysfunction induced by hypobaric hypoxia (HH) remains unexplored. This study aims to assess the impact of SIRT1 on HH-induced cardiac dysfunction and delve into the underlying mechanisms, both in vivo and in vitro. In this study, we have demonstrated that exposure to HH results in cardiomyocyte injury, along with the downregulation of SIRT1 and mitochondrial dysfunction. Upregulating SIRT1 significantly inhibits mitochondrial fission, improves mitochondrial function, reduces cardiomyocyte injury, and consequently enhances cardiac function in HH-exposed rats. Additionally, HH exposure triggers aberrant expression of mitochondrial fission-regulated proteins, with a decrease in PPARγ coactivator 1 alpha (PGC-1α) and mitochondrial fission factor (MFF) and an increase in mitochondrial fission 1 (FIS1) and dynamin-related protein 1 (DRP1), all of which are mitigated by SIRT1 upregulation. Furthermore, inhibiting PGC-1α diminishes the positive effects of SIRT1 regulation on the expression of DRP1, MFF, and FIS1, as well as mitochondrial fission. These findings demonstrate that SIRT1 alleviates HHinduced cardiac dysfunction by preventing mitochondrial fission through the PGC-1α-DRP1/FIS1/MFF pathway.

TMEM56 deficiency impairs the haem metabolism and cell cycle progression during human erythropoiesis.

TMEM56, a gene coding a transmembrane protein, is abundantly expressed in erythroid cells. Despite this, its role in erythropoiesis has not been well characterized. In this study, we sought to clarify the function of TMEM56 in erythroid development, focusing specifically on its involvement in haem biosynthesis and cell cycle progression. To do this, we used CD34+ haematopoietic stem cells derived from umbilical cord blood and differentiated them into erythroid cells in an ex vivo model. Our results indicate that the loss of TMEM56 disrupts haem biosynthesis and impairs erythroid differentiation. Furthermore, deletion of Tmem56 in the erythroid lineage in murine models using erythropoietin receptor (EpoR)-Cre revealed defects in erythroid progenitors within the bone marrow under both normal conditions and during haemolytic anaemia. These observations underscore the regulatory role of TMEM56 in maintaining erythroid lineage homeostasis. Taken together, our results unveil a previously unrecognized function of TMEM56 in erythroid differentiation and suggest its potential as an unfounded target for therapeutic strategies in the treatment of erythropoietic disorders.

ACSL1 positively regulates adipogenic differentiation.

Aberrant adipogenic differentiation is strongly associated with obesity and related metabolic diseases. Elucidating the key factors driving adipogenesis is an effective strategy for identifying novel therapeutic targets for treating metabolic diseases represented by obesity. In this study, transcriptomic techniques were employed to investigate the functional genes that regulate adipogenic differentiation in OP9 cells and 3T3-L1 cells. The findings indicated a notable upregulation of Acsl1 expression throughout the adipogenic differentiation process. Knocking down Acsl1 led to a decrease in the expression of genes associated with adipogenesis and a reduction in triglyceride accumulation. Additionally, Acsl1 overexpression promoted adipocyte differentiation and adipose-specific overexpression of Acsl1 markedly aggravated steatosis induced by a high-fat diet. Mechanistically, Cyp2f2, Dusp23 and Gstm2 are the crucial genes implicated in Acsl1-induced adipogenic differentiation. The findings of this study indicate that Acsl1 promotes adipogenesis and could serve as a potential therapeutic target for treating obesity and related metabolic disorders.

Primer exchange reaction assisted CRISPR/Cas9 cleavage for detection of dual microRNAs with electrochemistry method.

An electrochemical sensor assisted by primer exchange reaction (PER) and CRISPR/Cas9 system (PER-CRISPR/Cas9-E) was established for the sensitive detection of dual microRNAs (miRNAs). Two PER hairpin (HP) were designed to produce a lot of extended PER products, which could hybridize with two kinds of hairpin probes modified on the electrode and initiate the cleavage of two CRISPR/Cas9 systems guided by single guide RNAs (sgRNAs) with different recognition sequences. The decrease of the two electrochemical redox signals indicated the presence of dual-target miRNAs. With the robustness and high specificity of PER amplification and CRISPR/Cas9 cleavage system, simultaneous detection of two targets was achieved and the detection limits for miRNA-21 and miRNA-155 were 0.43 fM and 0.12 fM, respectively. The developed biosensor has the advantages of low cost, easy operation, and in-situ detection, providing a promising platform for point-of-care detection of multiple miRNAs.

Chemiluminescence Sensor for miRNA-21 Detection Based on CRISPR-Cas12a and Cation Exchange Reaction.

Herein, a chemiluminescence (CL) biosensor based on CRISPR-Cas12a and cation exchange reaction was constructed to detect the biomarker microRNA-21 (miRNA-21). The rolling circle amplification (RCA) reaction was introduced to convert each target RNA strand into a long single-stranded DNA with repeated sequences, which acted as triggers to initiate the transcleavage activity of CRISPR-Cas12a. The activated Cas12a could cleave the biotinylated linker DNA of CuS nanoparticles (NPs) to inhibit the binding of CuS NPs to streptavidin immobilized on the surface of the microplate, which strongly reduced the generation of Cu2+ from a cation exchange between CuS NPs and AgNO3, and thus efficiently suppressed the CL of Cu2+-luminol-H2O2 system, giving a "signal off" biosensor. With the multiple amplification, the detection limit of the developed sensor for miRNA-21 reached 16 aM. In addition, this biosensor is not only suitable for a professional chemiluminescence instrument but also for a smartphone used as a detection tool for the purpose of portable and low-cost assay. This method could be used to specifically detect quite a low level of miRNA-21 in human serum samples and various cancer cells, indicating its potential in ultrasensitive molecular diagnostics.

Nickel-induced transcriptional memory in lung epithelial cells promotes interferon signaling upon nicotine exposure.

Exposure to nickel, an environmental respiratory toxicant, is associated with lung diseases including asthma, pulmonary fibrosis, bronchitis and cancers. Our previous studies have shown that a majority of the nickel-induced transcriptional changes are persistent and do not reverse even after the termination of exposure. This suggested transcriptional memory, wherein the cell 'remembers' past nickel exposure. Transcriptional memory, due to which the cells respond more robustly to a previously encountered stimulus has been identified in a number of organisms. Therefore, transcriptional memory has been described as an adaptive mechanism. However, transcriptional memory caused by environmental toxicant exposures has not been well investigated. Moreover, how the transcriptional memory caused by an environmental toxicant might influence the outcome of exposure to a second toxicant has not been explored. In this study, we investigated whether nickel-induced transcriptional memory influences the outcome of the cell's response to a second respiratory toxicant, nicotine. Nicotine, an addictive compound in tobacco, is associated with the development of chronic lung diseases including chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis. Our results show that nicotine exposure upregulated a subset of genes only in the cells previously exposed to nickel. Furthermore, our analyses indicate robust activation of interferon (IFN) signaling in these cells. IFN signaling is a driver of inflammation, which is associated with many chronic lung diseases. Therefore, our results suggest that nicotine exposure of lung cells that retain the transcriptional memory of previous nickel exposure could result in increased susceptibility to developing chronic inflammatory lung diseases.

DNA-Au Janus Nanoparticles for In Situ SERS Detection and Targeted Chemo-photodynamic Synergistic Therapy.

Cancer theranostics is of great significance in the personalized therapy. In this work, stable Janus nanoparticles (JNPs) containing PEG and two kinds of DNAs were prepared by means of "click chemistry". In response to ATP or acid condition, the prepared JNPs could form Au NP dimers, which facilitate in situ SERS detection and SERS imaging analysis of cancer cells due to the formation of "hot spots" in the nanogap between the Au NP dimers. A detection limit of 2.3 × 10-9 M was obtained for ATP. As for a pH sensor, the SERS signals increased with the decrease of pH value from 8.0 to 4.0. In situ monitoring of ATP or acid condition in cancer cells by SERS can improve the accuracy and sensitivity of diagnosis. Moreover, drugs and photosensitizers loaded on the other side of JNPs led to the chemotherapy/photodynamic therapy synergistic antitumor effect, which was verified by in vitro and in vivo experiments. Given the excellent performance in SERS detection and cancer therapy, the developed JNPs hold considerable potential in cancer theranostics.

Transcriptional repression of E-cadherin in nickel-exposed lung epithelial cells mediated by loss of Sp1 binding at the promoter.

E-cadherin plays a central role in the stability of epithelial tissues by facilitating cell-cell adhesion. Loss of E-cadherin expression is a hallmark of epithelial-mesenchymal transition (EMT), a major event in the pathogenesis of several lung diseases. Our earlier studies showed that nickel, a ubiquitous environmental toxicant, induced EMT by persistently downregulating E-cadherin expression in human lung epithelial cells and that the EMT remained irreversible postexposure. However, the molecular basis of persistent E-cadherin downregulation by nickel exposure is not understood. Here, our studies show that the binding of transcription factor Sp1 to the promoter of E-cadherin encoding gene, CDH1, is essential for its expression. Nickel exposure caused a loss of Sp1 binding at the CDH1 promoter, resulting in its downregulation and EMT induction. Loss of Sp1 binding at the CDH1 promoter was associated with an increase in the binding of ZEB1 adjacent to the Sp1 binding site. ZEB1, an EMT master regulator persistently upregulated by nickel exposure, is a negative regulator of CDH1. CRISPR-Cas9-mediated knockout of ZEB1 restored Sp1 binding at the CDH1 promoter. Furthermore, ZEB1 knockout rescued E-cadherin expression and re-established the epithelial phenotype. Since EMT is associated with a number of nickel-exposure-associated chronic inflammatory lung diseases including asthma, fibrosis and cancer and metastasis, our findings provide new insights into the mechanisms associated with nickel pathogenesis.

Downregulation of hedgehog-interacting protein (HHIP) contributes to hexavalent chromium-induced malignant transformation of human bronchial epithelial cells.

Hexavalent chromium [Cr(VI)] is a potent human lung carcinogen. Multiple mechanisms have been proposed that contribute to Cr(VI)-induced lung carcinogenesis including oxidative stress, DNA damage, genomic instability and epigenetic modulation. However, the molecular mechanisms and pathways mediating Cr(VI) carcinogenicity have not been fully elucidated. Hedgehog (Hh) signaling is a key pathway that plays important roles in the formation of multiple tissues during embryogenesis and in the maintenance of stem cell populations in adults. Dysregulation of Hh signaling pathway has been reported in many human cancers. Here, we report a drastic reduction in both mRNA and protein levels of hedgehog-interacting protein (HHIP), a downstream target and a negative regulator of Hh signaling, in Cr(VI)-transformed cells. These findings point to a potential role of Hh signaling in Cr(VI)-induced malignant transformation and lung carcinogenesis. Cr(VI)-transformed cells exhibited DNA hypermethylation and silencing histone marks in the promoter region of HHIP, indicating that an epigenetic mechanism mediates Cr(VI)-induced silencing of HHIP. In addition, the major targets of Hh signaling (GLI1-3 and PTCH1) were significantly increased in Cr(VI)-transformed cells, suggesting an aberrant activation of Hh signaling in these cells. Moreover, ectopically expressing HHIP not only suppressed Hh signaling but also inhibited cell proliferation and anchorage-independent growth in Cr(VI)-transformed cells. In conclusion, these findings establish a novel regulatory mechanism underlying Cr(VI)-induced lung carcinogenesis and provide new insights for developing a better diagnostic and prognostic strategy for Cr(VI)-related human lung cancer.

Cathodic photoelectrochemical aptasensor based on NiO/BiOI/Au NP composite sensitized with CdSe for determination of exosomes.

A cathodic photoelectrochemical sensor has been developed for the determination of exosomes, based on a dual-signal reduction strategy. A heterostructure of NiO/BiOI/Au NP/CdSe was synthesized as a photoelectrochemical sensing interface, which is able to suppress the recombination of electron-hole pairs and produce a higher photocurrent. The obtained materials were characterized, and the mechanism for the generation of the cathodic photocurrent was proposed. CdSe QDs (quantum dots) modified with DNA2 were assembled on the electrode through the hybridization with EpCAM aptamer on the surface of ITO/NiO/BiOI/Au NP. The introduction of CdSe QDs to the electrode increases the photocurrent.The recognition of exosomes with aptamer DNA led to the separation of CdSe QDs from the electrode, which in turn caused the decrease of photocurrents. Meanwhile, the big volume of exosomes hinders the electron transfer between the electrode and electrolyte. Due to the dual reduction effect, a sensitive PEC sensor was obtained with a detection limit of 1.2 × 102 particles/µL exosomes (λex = 430 nm, bias voltage = - 0.1 V). The cathodic photoelectrochemical sensor showed good selectivity, performed well in a complex biological environment and could be used to distinguishbreast cancer patients from healthy individuals.

Activated Plasmonic Nanoaggregates for Dark-Field in Situ Imaging for HER2 Protein Imaging on Cell Surfaces.

Dark-field microscopy (DFM) based on localized surface plasmon resonance (LSPR) was used for observation of experimental phenomena, which is a hopeful nondamaging and non-photobleaching biological imaging technique. In this strategy, plasma nanoaggregates with stronger scattering efficiency were formed in the presence of the target, causing a "turn-on" phenomenon, when asymmetry modified AuNPs were introduced as probes with zero LSPR background. First, Au1-N3 probe and Au2-C≡C probe were designed for the cycloaddition between azide and alkyne to form AuNP dimers under catalytic action by Cu+, which was obtained from the reduction of Cu2+ by sodium ascorbate. The two kinds of probes were successfully used for the detection of Cu2+ in rat serum. Then, to apply this concept to protein on cells, DNA and antibody were modified on the probes. DNA1/Au1-N3 probe and anti-HER2/Au2-C≡C probe were proposed for HER2 protein DFM on cells. By designing an aptamer sequence in primer, the rolling circle amplification (RCA) was introduced in HER2 DFM on cells, and the image signal was much brighter than that from no-RCA. The unique design made it easier to discriminate the target signal from background noise in cell DFM. This method might be used in the fields of molecular diagnostics and cell imaging.

Regulation of trehalose, a typical stress protectant, on central metabolisms, cell growth and division of Saccharomyces cerevisiae CEN.PK113-7D.

Trehalose could protect the typical food microorganism Saccharomyces cerevisiae cell against environmental stresses; however, the other regulation effects of trehalose on yeast cells during the fermentation are still poorly understood. In this manuscript, different concentrations (i.e., 0, 2 and 5% g/v) of trehalose were respectively added into the medium to evaluate the effect of trehalose on growth, central metabolisms and division of S. cerevisiae CEN.PK113-7D strain that could uptake exogenous trehalose. Results indicated that addition of trehalose could inhibit yeast cell growth in the presence or absence of 8% v/v ethanol stress. Exogenous trehalose inhibited the glucose transporting efficiency and reduced intracellular glucose content. Simultaneously, increased intracellular trehalose content destroyed the steady state of trehalose cycle and caused the imbalance between the upper glycolysis part and the lower part, thereby leading to the dysfunction of glycolysis and further inhibiting the normal yeast cell growth. Moreover, energy metabolisms were impaired and the ATP production was reduced by addition of trehalose. Finally, exogenous trehalose-associated inhibition on yeast cell growth and metabolisms delayed cell cycle. These results also highlighted our knowledge about relationship between trehalose and growth, metabolisms and division of S. cerevisiae cells during fermentation.

Ultrasensitive Detection of Exosomes by Target-Triggered Three-Dimensional DNA Walking Machine and Exonuclease III-Assisted Electrochemical Ratiometric Biosensing.

Exosomes are membrane-enclosed phospholipid extracellular vesicles. In spite of their great promise as noninvasive biomarkers for cancer diagnosis, sensitive detection of exosomes is still challenging. Herein, the detection of exosomes was changed to the detection of DNA after recognition of exosomes with its aptamers. CD63 aptamer and EpCAM aptamer were used for the detection of MCF-7 cell-secreted exosome. The recognition process was amplified through the movements of a three-dimensional DNA walker. And then, Exonuclease III- assisted electrochemical ratiometric sensor was applied for further signal amplification. Under optimal conditions, the detection limit of 1.3 × 104 particles/mL was obtained with excellent selectivity. Furthermore, clinical application test for the detection of exosomes in human serum was also verified.

Cadmium exposure upregulates SNAIL through miR-30 repression in human lung epithelial cells.

Cadmium (Cd) is a known human lung carcinogen. In addition, Cd exposure is associated with several lung diseases including emphysema, chronic obstructive pulmonary disease (COPD), asthma and fibrosis. Although earlier studies have identified several processes dysregulated by Cd exposure, the underlying mechanisms remain unclear. Here, we examined the transcriptome of lung epithelial cells exposed to Cd to understand the molecular basis of Cd-induced diseases. Computational analysis of the transcriptome predicted a significant number of Cd-upregulated genes to be targets of miR-30 family miRNAs. Experimental validation showed downregulation of all the miR-30 family members in Cd exposed cells. We found SNAIL, an EMT master regulator, to be the most upregulated among the miR-30 targets. Furthermore, we found decrease in the levels of epithelial marker E- cadherin (CDH1) and increase in the levels of mesenchymal markers, ZEB1 and vimentin. This suggested induction of EMT in Cd exposed cells. Luciferase reporter assays showed that miR-30 repressed SNAIL by directly targeting its 3' UTR. Over expression of miR-30e and transfection of miR-30e mimics reduced Cd-induced SNAIL upregulation. Our results suggest that miR-30 negatively regulates SNAIL in lung epithelial cells and that Cd-induced downregulation of miR-30 relieves this repression, resulting in SNAIL upregulation and EMT induction. EMT plays a major role in many diseases associated with Cd exposure including fibrosis, COPD, and cancer and metastasis. Therefore, our identification of miR-30 downregulation in Cd exposed cells and the consequent activation of SNAIL provides important mechanistic insights into lung diseases associated with Cd exposure.

Dual cycle amplification and dual signal enhancement assisted sensitive SERS assay of MicroRNA.

A sensitive surface-enhanced Raman scattering (SERS) approach has been developed for detection of microRNA (miRNA) based on target-triggered dual signal amplification including strand displancement amplification (SDA) and hybridization chain reaction (HCR). With the assistant of polymerase and nicking endonuclease (NEase), target miRNA combines with the single stranded template DNA to generate a great amount of trigger DNA which can induce HCR. Coupled the dual cycle amplification of SDA and HCR with the dual enhancement of gold nanoparticles (AuNPs), a low detection limit of 0.5 fM for miRNA is obtained using the proposed strategy. With high sensitivity, universality, rapid analysis, and high selectivity, this method has a great potential for detecting biomolecules with trace amounts in bioanalysis and clinical biomedicine.

Intracellular dark-field imaging of ATP and photothermal therapy using a colorimetric assay based on gold nanoparticle aggregation via tetrazine/trans-cyclooctene cycloaddition.

In this study, we developed a colorimetric ATP assay based on the ATP-induced aggregation of Au nanoparticles (AuNPs). This aggregation modified the local surface plasmon resonance (LSPR) of the AuNPs, which was used to detect and localize ATP in cells via dark-field imaging. The AuNP aggregation process involved the reaction of two types of functionalized AuNPs with each other: tetrazine-modified AuNPs (Au3-N4) and asymmetrically functionalized trans-cyclooctene-modified AuNPs (Au1-(E)-cyclooctene). This cycloaddition reaction occurs without the need for a catalyst such as the Cu ions that are used in the "click" reactions often employed in assays of this type. Initially, we asymmetrically functionalized both types of AuNPs and let them dimerize, which permitted us to explore the resulting wavelength shift in the LSPR of the AuNPs. Then, to facilitate the specific recognition of ATP, a designed DNA (DNA1) containing an ATP aptamer sequence was attached to carboxyl polystyrene microbeads (MBs). After attaching a different DNA (DNA2, which hybridizes with DNA1) to Au1-(E)-cyclooctene, the assay probe MB/DNA1/DNA2/Au1-(E)-cyclooctene (MB/Au1) was generated. While bound to MB/DNA1, the DNA2/Au1-(E)-cyclooctene cannot react with Au3-N4 due to steric hindrance from the MB. However, in the presence of ATP, the probe MB/Au1 dissociates, and the resulting free DNA2/Au1-(E)-cyclooctene can then react with the Au3-N4, leading to the formation of AuNP aggregates. Dark-field microscopy (DFM) images showed that the LSPR of the AuNPs shifted from the green region (AuNP monomers) to the orange-red region (AuNP aggregates) in the presence of intracellular ATP. Moreover, the AuNP aggregates were found to exhibit significant photothermal effects under 808-nm laser irradiation. Upon introducing the probe MB/Au1 and Au3-N4 into HeLa cells in vitro and in vivo, and then irradiating the cells with a 808-nm NIR laser, the resulting AuNP aggregates showed promising photothermal cancer therapy performance. This assay therefore has the potential to be widely used for the identification and determination of nanoparticles in biological DFM and in tumor theranostics. Graphical abstract.

TOTAL BODY ADIPOSITY, TRIGLYCERIDES, AND LEG FAT ARE INDEPENDENT RISK FACTORS FOR DIABETIC PERIPHERAL NEUROPATHY IN CHINESE PATIENTS WITH TYPE 2 DIABETES MELLITUS.

OBJECTIVE: To evaluate the risk factors associated with diabetic peripheral neuropathy (DPN) in Chinese patients with type 2 diabetes mellitus (T2DM). METHODS: Between January 2014 and December 2017, 107 participants who had obesity with T2DM and 349 participants who had normal weight with T2DM, matched for age, sex, and duration of diabetes, were recruited. The clinical and biochemical parameters were measured in each patient. DPN was diagnosed based on neuropathy symptom score and neuropathy deficit score. Motor and sensory nerve conduction velocities were measured by electromyography. Body fat mass was estimated by dual-energy X-ray absorptiometry, while hepatic steatosis was evaluated by ultrasonography. RESULTS: The group with obesity had a significant higher prevalence of DPN (66.62%) than that (46.99%) of the group with normal weight. Compared to the patients with normal weight, the sural sensory nerve in the right lower limbs of the patients with obesity was more susceptible to damage. Hypertriglyceridemia in the patients with obesity was a significant independent risk factor for DPN (odds ratio [OR], 3.90 [95% confidence interval (CI), 1.01 to 15.02]; P = .04), while the duration of diabetes (OR, 1.33 [95% CI, 1.07 to 1.65]; P<.01) and leg subcutaneous fat mass (OR, 0.72 [95% CI, 0.57 to 0.90]; P<.01) in the patients with normal weight were independent risk factors for DPN. The presence of obesity alone in patients with T2DM could predict high DPN risk (OR, 3.09 [95% CI, 1.11 to 8.65]; P = .04). CONCLUSION: Reducing total body adiposity and triglyceride levels, as well as avoiding leg subcutaneous fat atrophy, could be new prevention strategies for DPN in Chinese patients with T2DM. ABBREVIATIONS: ALB = albumin; ALT = alanine transaminase; AST = aspartate transaminase; AUC = area under the curve; AUCc-p/AUCglu = AUC of C-peptide/AUC of glucose; BMI = body mass index; BP = blood pressure; CI = confidence interval; Cr = creatinine; DBP = diastolic blood pressure; DPN = diabetic peripheral neuropathy; FC-P = fasting C-peptide; FPG = fasting plasma glucose; FFA = free fatty acid; γ-GGT = γ-glutamyl transferase; HbA1c = glycated hemoglobin A1c; HDL-C = high-density-lipoprotein cholesterol; ISI = insulin sensitivity index; ISSI-2 = insulin secretion-sensitivity index-2; LDL-C = low-density-lipoprotein cholesterol; MNCS = motor nerve conduction velocity; OGTT = oral glucose tolerance test; PG = plasma glucose; SAT = subcutaneous adipose tissue; SBP = systolic blood pressure; SNCS = sensory nerve conduction velocity; T2DM = type 2 diabetes mellitus; TC = total cholesterol; TG = triglyceride; UA = uric acid; VAT = visceral adipose tissue; WC = waist circumference.

Fluorometric determination of mercury(II) by using thymine-thymine mismatches as recognition elements, toehold binding, and enzyme-assisted signal amplification.

A highly sensitive fluorometric method is described for the determination of mercury(II) ions. It is based on (a) the use of a DNA probe containing thymine-thymine mismatches that are employed as Hg(II) recognition elements, (b) subsequent toehold binding, and (c) endocuclease-assisted signal amplification. Target recycling is triggered by exonuclease III. This produces a large amount of ssDNA (defined as primer). Then, the generated primer-initiated strand displacement reaction with the help of polymerase and nicking endonuclease releases the free fluorophore-labelled probe. Under excitation at 532 nm, the fluorescent probe displays emission with a peak at 582 nm. The sensitivity of this method is improved by introduction of nicking endonuclease. The working range of the assay extends from 20 pM to 10 nM, and the detection limit is as low as 6 pM of Hg(II). Graphical abstract Schematic presentation of the fluorometric method for determination of mercury(II). By using a special structure of thymine-thymine mismatches, target-induced toehold binding and enzyme-assisted signal amplification strategy were employed. This method is selective and good performance in real sample application.

An CuInS2 photocathode for the sensitive photoelectrochemical determination of microRNA-21 based on DNA-protein interaction and exonuclease III assisted target recycling amplification.

A photocathode is described for the determination of microRNA-21 by using CuInS2 as an active photocathode material. Exonuclease III assisted target recycling amplification was employed to enhance the detection sensitivity. The TATA-binding protein (TBP) was applied to enhance steric hindrance which decreases the photoelectrochemical intensity. This strategy is designed by combining the anti-interference photocathode material, enzyme assisted target recycling amplification and TBP induced signal off, showing remarkable amplification efficiency. Under the optimized conditions, the detection limit for microRNA-21 is as low as 0.47 fM, and a linear range was got from 1.0 × 10-15 M to 1.0 × 10-6 M. Graphical abstract Schematic representation of sensitive photoelectrochemical detection of microRNA-21.CuInS2 is used as an active photocathode material. Combined Exonuclease III assisted target recycling amplification and TATA-binding protein decreased of photoelectrochemical intensity, the detection limit was 0.47 fM with good selectivity. (miR-21: microRNA-21; CS: chitosan).

A DNA functionalized porphyrinic metal-organic framework as a peroxidase mimicking catalyst for amperometric determination of the activity of T4 polynucleotide kinase.

An electrochemical method is described for the sensitive detection of the activity of the enzyme T4 polynucleotide kinase (PNK) by using a DNA functionalized porphyrinic metal-organic framework (L/(Fe-P)n-MOF). In the presence of PNK, the hairpin oligonucleotide (HP1) becomes phosphorylated, and the trigger is released by lambda exonuclease (λ exo). The trigger DNA hybridizes with hairpin probe (immobilized on the gold electrode) to form a nicking endonuclease cleavage site. Thus, a single-strand capture probe is employed to hybridize with L/(Fe-P)n-MOF. The (Fe-P)n-MOF is a peroxidase mimicking material with high catalytic efficiency. By using this amplification strategy, an electrochemical signal is procured that allows for the determination of T4 PNK in the 1.0 mU·mL-1 to 1.0 U·mL-1 with a detection limit of 0.62 mU·mL-1. The method is selective and can be used to screen for enzyme inhibitors. Conceivably, the (Fe-P)n-MOF can also be used to detect other analytes via its peroxidase-mimicking activity. Graphical abstract Schematic presentation of T4 polynucleotide kinase (PNK) detection. Two hairpin DNAs (HP) and a porphyrinic metal-organic framework with peroxidase-mimicking activity are used. The detection limit is 0.62 mU mL-1 with enzyme assisted signal amplification. This method is selective and can be used to screen for enzyme inhibitors.