Glucan polysaccharides isolated from Lactarius hatsudake Tanaka mushroom: Structural characterization and in vitro bioactivities.

Commercially available mushroom polysaccharides have found widespread use as adjuvant tumor treatments. However, the bioactivity of polysaccharides in Lactarius hatsudake Tanaka (L. hatsudake), a mushroom with both edible and medicinal uses, remains relatively unexplored. To address this gap, five L. hatsudake polysaccharides with varying molecular weights were isolated, named LHP-1 (898 kDa), LHP-2 (677 kDa), LHP-3 (385 kDa), LHP-4 (20 kDa), and LHP-5 (4.9 kDa). Gas chromatography-mass spectrometry, nuclear magnetic resonance, and atomic force microscopy, etc., were employed to determine their structural characteristics. The results confirmed that spherical aggregates with amorphous flexible fiber chains dominated the conformation of the LHP. LHP-1 and LHP-2 were identified as glucans with α-(1,4)-Glcp as the main chain; LHP-3 and LHP-4 were classified as galactans with varying molecular weights but with α-(1,6)-Galp as the main chain; LHP-5 was a glucan with ß-(1,3)-Glcp as the main chain and ß-(1,6)-Glcp connecting to the side chains. Significant differences were observed in inhibiting tumor cell cytotoxicity and the antioxidant activity of the LHPs, with LHP-5 and LHP-4 identified as the principal bioactive components. These findings provide a theoretical foundation for the valuable use of L. hatsudake and emphasize the potential application of LHPs in therapeutic tumor treatments.

Total Infectome Characterization of Respiratory Infections during the 2022-23 COVID-19 Outbreak in China Revealed Extensive Coinfections with Links to SARS-CoV-2 Status, Age, and Disease Severity.

Between 7 December 2022 and 28 February 2023, China experienced a new wave of COVID-19 that swept across the entire country and resulted in an increasing amount of respiratory infections and hospitalizations. The purpose of this study is to reveal the intensity and composition of coinfecting microbial agents. In total, 196 inpatients were recruited from The Third People's Hospital of Shenzhen, and 169 respiratory and 73 blood samples were collected for metagenomic next-generation sequencing. The total "Infectome" was characterized and compared across different groups defined by the SARS-CoV-2 detection status, age groups, and severity of disease. Our results revealed a total of 22 species of pathogenic microbes (4 viruses, 13 bacteria, and 5 fungi), and more were discovered in the respiratory tract than in blood. The diversity of the total infectome was highly distinguished between respiratory and blood samples, and it was generally higher in patients that were SARS-CoV-2-positive, older in age, and with more severe disease. At the individual pathogen level, HSV-1 seemed to be the major contributor to these differences observed in the overall comparisons. Collectively, this study reveals the highly complex respiratory infectome and high-intensity coinfection in patients admitted to the hospital during the period of the 2023 COVID-19 pandemic in China.

Potential osteoporosis-blocker Sparassis crispa polysaccharide: Isolation, purification and structure elucidation.

This study aimed to investigate the structural characterization of water-soluble polysaccharides from Sparassis crispa and their effects on the proliferation and differentiation of mouse osteoblasts. Three fractions (F-1, F-2, and F-3) were obtained from crude polysaccharides by a DEAE-52 cellulose column. The main fraction (F-1) was further purified by polysaccharide gel purification systems to obtain purified water-soluble Sparassis crispa polysaccharide (SCPS). The chemical structure of SCPS was analyzed by gas chromatography, Fourier transform infrared spectroscopy, methylation analysis, and nuclear magnetic resonance spectroscopy. The monosaccharide compositional analysis revealed that SCPS consisted of fucose, arabinose, galactose, glucose, xylose, mannose, ribose, galacturonic acid, glucuronic acid, and mannuronic acid in a molar ratio of 17.37:1.94:25.52:30.83:1.14:0.30:4.98:2.87:2.65. Moreover, the backbone of SCPS was composed of →3)-ß-d-Glcp-(1→4)-ß-d-Glcp-(1→, with side chains attached to the backbone at the O-6 positions through the →3,6)-ß-d-Glcp-(1→ linkage. The in vitro experiments were conducted to investigate the effects of SCPS on the proliferation and differentiation of mouse osteoblasts. The results showed that SCPS significantly enhanced the proliferation and differentiation of mouse osteoblasts, indicating their potential as a pharmaceutical agent for promoting osteoblast proliferation and differentiation.

Protists play important roles in the assembly and stability of denitrifying bacterial communities in copper-tailings drainage.

Unraveling the drivers controlling the assembly and stability of functional communities is a central issue in ecology. Despite extensive research and data, relatively little attention has been paid on the importance of biotic factors and, in particular, on the trophic interaction for explaining the assembly of microbial community. Here, we examined the diversity, assembly, and stability of nirS-, nirK-, and nosZ-type denitrifying bacterial communities in copper-tailings drainages of the Shibahe tailings reservoir in Zhongtiao Mountain, China's. We found that components of nirS-, nirK-, and nosZ-type denitrifying bacterial community diversity, such as taxon relative abundance, richness, and copy number, were strongly correlated with protist community composition and diversity. Assembly of the nirK-type denitrifying bacterial community was governed by dispersal limitation, whereas those of nirS- and nosZ-type communities were controlled by homogeneous selection. The relative importance of protist diversity in the assembly of nirK- and nosZ-type denitrifying bacterial communities was greater than that in nirS-type assembly. In addition, protists reduced the stability of the co-occurrence network of the nosZ-type denitrifying bacterial community. Compared with eukaryotic algae, protozoa had a greater impact on the stability of denitrifying bacterial community co-occurrence networks. Generally, protists affected the assembly and community stability of denitrifying bacteria in copper-tailings drainages. Our findings thus emphasize the importance of protists on affecting the assembly and community stability of denitrifying bacteria in copper-tailings drainages and may be useful for predicting changes in the ecological functions of microorganisms.

Fluorescent aptasensor for highly sensitive detection of Staphylococcus aureus based on dual-amplification strategy by integrating DNA walking and hybridization chain reaction.

Food-borne diseases caused by bacteria threaten human health. Herein, we presented a new fluorescent aptasensor by coupling DNA walking and hybridization chain reaction (HCR) for convenient and sensitive quantification of bacteria. Staphylococcus aureus (S. aureus) was selected as target. When there was target in the system, the binding of S. aureus with its aptamer caused the disintegration of aptamer/DNA walker on the surface of AuNPs and released DNA walker. With the help of Nt.BsmAI, DNA walker moved along the surface of AuNPs and trigger probe was detached from AuNPs. The trigger probe could initiate hybridization chain reaction (HCR) and opened the stems of H1@AuNPs probe and H2@AuNPs probe. After the addition of nicking endonuclease, the adjacent upconversion nanoparticles (UCNPs, NaYF4:Yb3+, Er3+) were further away from the quenchers (AuNPs) of H1 and H2. Therefore, the fluorescence intensity of UCNPs could be restored via fluorescence resonance energy transfer (FRET). Bacteria were thus detected by recording the fluorescence intensity of UCNPs. This method is simple, rapid and sensitive. It can directly detect bacteria in a low background signal. The limit of detection (LOD) was 10 CFU/mL, detection time was less than 3 h. Recovery rates in simulated milk, honey and human serum samples ranged from 93.6 % to 105.8 %. The strategy opens up new paths for early diagnosis of diseases and food monitoring.

Effects of curcumin on non-alcoholic fatty liver disease: A scientific metrogy study.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases encountered in clinical practice. Curcumin can alleviate insulin resistance, inhibit oxidative stress response, reduce inflammation, reduce liver fat deposition, and effectively improve NAFLD through various modalities, inhibiting the progression into cirrhosis and fibrosis. PURPOSE: To explore the current status, hot spots, and developing trends of curcumin in NAFLD treatment through quantitative scientific analysis to serve as a reference for subsequent studies. STUDY DESIGN: A comprehensive analysis of the mechanism of action of curcumin in the treatment of NAFLD and methods to increase curcumin bioavailability using bibliometric analysis and literature review. METHODS: This study used VOSviewer software to analyze the literature related to curcumin treatment of NAFLD in the Web of Science (WOS) core set database. A comprehensive and in-depth review was conducted based on the results of scientific econometric research and literature review. RESULTS: The review observed that curcumin can activate various signaling pathways such as AMPK and NF-κB to inhibit oxidative stress and apoptosis, thereby reflecting its pharmacological effects: lowering lipid, anti-inflammatory, reducing insulin resistance, and anti-fibrosis. These mechanisms improve or even reverse the complex pathological features of lipid metabolism disorders associated with NAFLD. Curcumin also can potentially serve as a primary regulatory target for treating hepatic steatosis using gut microbiota. However, these pharmacological effects of curcumin were limited owing to its low bioavailability. CONCLUSION: This review discusses NAFLD treatment with curcumin, analyzes the reasons for its low bioavailability, and introduces models for studying and methods for improving curcumin bioavailability. As research on NAFLD grows, future research should capture the trend of basic research, pay attention to clinical research, and continuously explore the therapeutic potential of curcumin.

Advances in embedding techniques of anthocyanins: Improving stability, bioactivity and bioavailability.

The health benefits of anthocyanins have attracted extensive research interest. However, anthocyanins are sensitive to certain environmental and gastrointestinal conditions and have low oral bioavailability. It has been reported that delivery systems made in different ways could improve the stability, bioavailability and bioactivity of anthocyanins. This present review summarizes the factors affecting the stability of anthocyanins and the reasons for poor bioavailability, and various technologies for encapsulation of anthocyanins including microcapsules, nanoemulsions, microemulsions, Pickering emulsions, nanoliposomes, nanoparticles, hydrogels and co-assembly with amphiphilic peptides were discussed. In particular, the effects of these encapsulation technologies on the stability, bioavailability and bioactivities of anthocyanins in vitro and in vivo experiments are reviewed in detail, which provided scientific insights for anthocyanins encapsulation methods. However, the application of anthocyanins in food industry as well as the biological fate and functional pathways in vivo still need to be further explored.

Regulation mechanism of lipids for extracellular yellow pigments production by Monascus purpureus BWY-5.

The biosynthesis and secretion of Monascus pigments are closely related to the integrity of the cell membrane, which determines the composition of lipids and its content in cell membrane. The present study aimed to thoroughly describe the changes of lipid profiling in Monascus purpureus BWY-5, which was screened by carbon ion beam irradiation (12C6+) to almost single yield extracellular Monascus yellow pigments (extra-MYPs), by absolute quantitative lipidomics and tandem mass tags (TMT) based quantitative proteomic. 12C6+ irradiation caused non-lipid oxidation damage to Monascus cell membrane, leading to an imbalance in cell membrane lipid homeostasis. This imbalance was attributed to significant changes not only in the composition but also in the content of lipids in Monascus, especially the inhibition of glycerophospholipid biosynthesis. Integrity of plasma membrane was maintained by the increased production of ergosterol, monogalactosylmonoacylglycerol (MGMG) and sulfoquinovosylmonoacylglycerol (SQMG), while mitochondrial membrane homeostasis was maintained by the increase of cardiolipin production. The growth and extra-MYPs production of Monascus BWY-5 have been regulated by the promotion of sphingolipids (ceramide and sulfatide) biosynthesis. Simultaneous, energy homeostasis may be achieved by increase of TG synthesis and Ca2+/Mg2+-ATPase activity. These finding suggest ergosterol, cardiolipin, sphingolipids, MGMG and SQMG play a key facilitating role in cytomembrane lipid homeostasis maintaining for Monascus purpureus BWY-5, and then it is closely related to cell growth and extra-MYPs production. KEY POINTS: 1. Energy homeostasis in Monascus purpureus BWY-5 was achieved by increase of TG synthesis and Ca2+/Mg2+-ATPase activity. 2. Integrity of plasma membrane in Monascus purpureus BWY-5 was maintained by the increased production of ergosterol. 3. Mitochondrial membrane homeostasis in Monascus purpureus BWY-5 was maintaed by the increase of cardiolipin synthesis.

Enzyme-targeted near-infrared fluorescent probe for organophosphorus pesticide residue detection.

Pesticide residues significantly affect food safety and harm human health. In this work, a series of near-infrared fluorescent probes were designed and developed by acylating the hydroxyl group of the hemicyanine skeleton with a quenching moiety for monitoring the presence of organophosphorus pesticides in food and live cells. The carboxylic ester bond on the probe was hydrolyzed catalytically in the presence of carboxylesterase and thereby the fluorophore was released with near-infrared emission. Notably, the proposed probe 1 exhibited excellent sensitivity against organophosphorus based on the carboxylesterase inhibition mechanism and the detection limit for isocarbophos achieved 0.1734 µg/L in the fresh vegetable sample. More importantly, probe 1 allowed for situ visualization of organophosphorus in live cells and bacteria, meaning great potential for tracking the organophosphorus in biological systems. Consequently, this study presents a promising strategy for tracking pesticide residues in food and biological systems.

Covalent organic frameworks assisted for food safety analysis.

Food safety incidents threaten human health and life safety. It is an effective method to prevent and control the occurrence of food safety events by enhancing the rapid and sensitive detection of food contaminants. Emerging porous materials provide for the development of efficient and stable detection methods. Covalent organic frameworks (COFs) are favored by researchers for their highly ordered pore structure, large specific surface area, and good structural and functional designability. Especially in the sensing field, COFs play the roles of carriers, conductors, quenchers, and reporters, and have broad application prospects. To better understand COFs-based sensing studies, this review briefly introduces the characteristics and different functional roles of COFs in food safety analysis, focusing on the applications of COFs in the detection of various food contaminants (including foodborne pathogens, mycotoxins, pesticides, antibiotics, heavy metals, and others). Finally, the challenges and opportunities for COFs-based sensing are discussed to facilitate further applications and development of COFs in food safety.

Preparation of blue fluorescent copper nanoclusters for sensitive and selective sensing of apigenin in pharmaceutical samples.

One-pot means was performed for the rapid preparation of copper nanoclusters (Cu NCs), which were employed as a fluorescence system for the sensitive apigenin measurement in pharmaceutical samples. Herein, CuCl2 aqueous solution was reduced to Cu NCs through ascorbic acid and the Cu NCs were protected through trypsin under 65 ℃ for 4 h. The entire preparation process was rapid, facile and environmentally friendly. The trypsin-capped Cu NCs were demonstrated through ultraviolet-visible spectroscopy, fluorescence spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and fluorescence lifetime, respectively. The Cu NCs revealed blue fluorescence with emission wavelength around 465 nm under the excitation wavelength of 380 nm. The fluorescence weakening feature of Cu NCs with apigenin was observed. On this basis, a facile and sensitive turn-off fluorescent nanoprobe for the sensing of apigenin in real samples was developed. The logarithm of relative fluorescence intensity revealed a good linear relationship with apigenin contents from 0.5 µM to 300 µM with the detection limit of 0.079 µM. The Cu NCs-based fluorescent nanosensor have been employed to measure the apigenin amounts in real samples such as medical saline, bovine and human serum. The results revealed excellent potential of this Cu NCs-based fluorescent nanoprobe for the convention computation of apigenin amounts in real samples.

Solvent-free oxidation of benzyl C-H to ketone with Co-Ni layered double hydroxide as the catalyst and O2 as the sole oxidant.

The aerobic oxidation of ethylbenzene is an effective way to produce acetophenone, in which solvent-free conditions and oxygen as the sole oxidant are the best choice. At present, the catalytic activity and selectivity are still at an unsatisfactory level, because efficient catalysts need to achieve both C-H bond activation and O2 activation. In this work, the 2-methylimidazole-induced hydrolysis strategy was used to prepare a new class of CoNi-layered double hydroxide (CoNi-LDH) materials with different metal ratios. High-Resolution Transmission Electron Microscopy (HRTEM) showed that CoNi-LDH had obvious weak crystallinity and a thin lamellar structure. X-ray Photoelectron Spectroscopy (XPS) reveals the consistency between the content of the M-O component in the host layer and the proportion of Co3+, among which CoNi-LDH with a feed ratio (Co : Ni) of 2 : 1 (Co2Ni-LDH) has the highest M-O content and Co3+ ratio. The formation of M-O is due to the H-vacancy generated by the breaking of the hydroxyl group, which can be used for the H abstraction of C-H bonds. The redox effect caused by M2+/M3+ facilitates the transfer of electrons, which promotes the activation of O2 to the superoxide radical anion (˙O2-). Thereby, Co2Ni-LDH shows the highest catalytic activity for the oxidation of ethylbenzene. Under solvent-free conditions and with oxygen as the sole oxidant, 97.8% conversion of ethylbenzene and 98.8% selectivity of acetophenone can be obtained. The excellent catalytic performance is related to the structure of CoNi-LDH, and is also the best when compared with the reported results. Various types of aromatic hydrocarbons containing benzyl C-H bonds can be effectively oxidized by CoNi-LDH to produce the corresponding ketone products.

The construction of CRISPR/Cas9-mediated FRET 16S rDNA sensor for detection of Mycobacterium tuberculosis.

The simple and efficient detection of nucleic acids is important in the diagnosis of tuberculosis (TB) caused by Mycobacterium tuberculosis (M. tuberculosis). However, base mismatch will lead to false positive and false negative nucleic acid test, which seriously interferes with the accuracy of the final results. Herein, we demonstrated a CRISPR/Cas-9-mediated fluorescent strategy utilizing fluorescence resonance energy transfer (FRET) for the detection of bacteria. High-variable region of M. tuberculosis 16S rDNA fragment was used as the target, and CRISPR/Cas9 was used as the recognition element. The binding of the P1 probe of upconversion nanoparticles (UCNPs) @SiO2-P1 and the P2 probe of Fe3O4@Au-P2 caused the fluorescence quenching of UCNPs. In the presence of the target, the P2 probe hybridized with the target to form double-stranded DNA (dsDNA), which was recognized and cleaved by CRISPR/Cas9, resulting in the breaking of the P1-P2 duplex linkage. UCNPs moved away from Fe3O4@Au under a magnetic field, and the fluorescence signal was restored; bacteria were detected under the excitation of a 980 nm laser source. Using the CRISPR/Cas-9-mediated system, the sensor could distinguish single-base mismatches in 10 bases from the protospacer adjacent motif (PAM) region. The limit of detection (LOD) was 20 CFU mL-1 and the detection time was 2 h. It developed a new way of accurate nucleic acid detection for disease diagnosis.

Recent advances of fluorescent sensors for bacteria detection-A review.

Bacterial infections have become a global public health problem. Rapid and sensitive bacterial detection is of great importance for human health. Among various sensor systems, fluorescence sensor is rapid, portable, multiplexed, and cost-efficient. Herein, we reviewed the current trends of fluorescent sensors for bacterial detection from three aspects (response materials, target and recognition way). The fluorescent materials have the advantages of high fluorescent strength, high stability, and good biocompatibility. They provide a new path for bacterial detection. Several recent fluorescent nanomaterials for bacterial detection, including semiconductor quantum dots (QDs), carbon dots (CDs), up-conversion nanoparticles (UCNPs) and metal organic frameworks (MOFs), were introduced. Their optical properties and detection mechanisms were analyzed and compared. For different response targets in the detection process, we studied the fluorescence strategy using DNA, bacteria, and metabolites as the response target. In addition, we classified the recognition way between nanomaterial and target, including specific recognition methods based on aptamers, antibodies, bacteriophages, and non-specific recognition methods based on biological functional materials. The characteristics of different recognition methods were summarized. Finally, the weaknesses and future development of bacterial fluorescence sensor were discussed. This review provides new insights into the application of fluorescent sensing systems as an important tool for bacterial detection.

Sustainable production of astaxanthin in microorganisms: the past, present, and future.

Astaxanthin (3,3'-dihydroxy-4,4'-diketo-ß-carotene) is a type of C40 carotenoid with remarkable antioxidant characteristics, showing significant application prospects in many fields. Traditionally, the astaxanthin is mainly obtained from chemical synthesis and natural acquisition, with both approaches having many limitations and not capable of meeting the growing market demand. In order to cope with these challenges, novel techniques, e.g., the innovative cell engineering strategies, have been developed to increase the astaxanthin production. In this review, we first elaborated the biosynthetic pathway of astaxanthin, with the key enzymes and their functions discussed in the metabolic process. Then, we summarized the conventional, non-genetic strategies to promote the production of astaxanthin, including the methods of exogenous additives, mutagenesis, and adaptive evolution. Lastly, we reviewed comprehensively the latest studies on the synthesis of astaxanthin in various recombinant microorganisms based on the concept of microbial cell factory. Furthermore, we have proposed several novel technologies for improving the astaxanthin accumulation in several model species of microorganisms.

A mutant of Monascus purpureus obtained by carbon ion beam irradiation yielded yellow pigments using various nitrogen sources.

The industrial production of monascus yellow pigments (MYPs) has not yet been done due to the lack of high-quality industrial Monascus strains. In this work, we employed carbon ion beam (12C6+) irradiation to screen Monascus strains that produce high-quality extracellular MYPs (extr-MYPs). One genetically stable M. purpureus mutant of BWY-5 with extr-MYPs accumulation was obtained under 12C6+ irradiation (80 MeV/u, 200 Gy). M. purpureus BWY-5 could use various nitrogen sources to produce single pH stable extr-MYPs (around 80 AU at 370 nm). Moreover, citrinin was not detected by HPLC method. Transcriptomics of the MYP production strain suggested that Carbon ion beam irradiation led to deletion (MpigF, MpigG and MpigH), downregulation (CtnE, CtnH and CtnI) and upregulation (MpigM) of genes related with biosynthesis of MOPs and MRPs, citrinin, and extr-MYPs, respectively. The results showed that M. purpureus BWY-5 has the potential to be used as an industrial Monascus strain and platform for extr-MYPs production and monascus polyketide synthetic pathway studies, respectively.

Genomic characterization of two metagenome-assembled genomes of Tropheryma whipplei from China.

Whipple's disease is a rare chronic systemic disease that affects almost any organ system of the body caused by the intracellular bacterium Tropheryma whipplei, which is found ubiquitously in the environment. Sequencing of the T. whipplei genome has revealed that it has a reduced genome (0.93 Mbp), a characteristic shared with other intracellular bacteria. Until our research started, 19 T. whipplei strains had been sequenced from cultures originated in France, Canada, and Germany. The genome of T. whipplei bacterium has not been studied in Asia yet. Here, two metagenome-assembled genomes (MAGs) of T. whipplei from China were reconstructed through metagenomic next-generation sequencing (mNGS) and genome binning. We also provided genomic insights into the geographical role and genomic features by analyzing the whole genome. The whole-genome phylogenetic tree was constructed based on single-nucleotide polymorphism (SNP) distance calculations and then grouped by distance similarity. The phylogenetic tree shows inconsistencies with geographic origins, thus suggesting that the variations in geographical origins cannot explain the phylogenetic relationships among the 21 T. whipplei strains. The two Chinese strains were closely related to each other, and also found to be related to strains from Germany (T. whipplei TW08/27) and France (T. whipplei Bcu26 and T. whipplei Neuro1). Furthermore, the Average Nucleotide Identity (ANI) matrix also showed no association between geographic origins and genomic similarities. The pan-genome analysis revealed that T. whipplei has a closed pan-genome composed of big core-genomes and small accessory genomes, like other intracellular bacteria. By examining the genotypes of the sequenced strains, all 21 T. whipplei strains were found to be resistant to fluoroquinolones, due to the genetic mutations in genes gyrA, gyrB, parC, and parE. The 21 T. Whipplei strains shared the same virulence factors, except for the alpC gene, which existed in 7 out of the 21 T. whipplei strains. When comparing 21 entire T. whipplei pan-genomes from various nations, it was discovered that the bacterium also possessed a closed genome, which was a trait shared by intracellular pathogens.

Cascade signal enhancement by integrating DNA walking and RCA reaction-assisted "silver-link" crossing electrode for ultrasensitive electrochemical detection of Staphylococcus aureus.

The key factor to control the incidence rate of diseases caused by bacteria is rapid detection and early diagnosis. Herein, we proposed a new electrochemical bacterial sensor by coupling DNA walking and rolling circle amplification (RCA) reaction-assisted "silver-link" crossing electrode. Staphylococcus aureus (S. aureus) was detected using this proof-of concept strategy. Aptamer/DNA walker and auxiliary sequence (AS)/RCA reaction probe (RP) duplexes were modified on the electrode surface. The binding of S. aureus with its aptamer caused the disintegration of aptamer/DNA walker and released DNA walker. With the help of Exo III, DNA walker moved along the electrode surface and AS in AS/RP duplex was continuously digested to release RP. By introducing phi29 DNA polymerase, RCA reaction was performed using RP as the reaction primer to form long single-strand RCA extension products between the electrodes. The "silver-link" crossing electrode was formed by metallization of "gene-link", significant conductivity was thus acquired for bacteria detection. The limit of detection (LOD) was 10 CFU/mL and detection time was 2 h. The proposed sensor has high efficiency, good stability and low background signal, human serum and milk samples were successfully detected, which emerged a promising potential in the food monitoring and clinical diagnosis.

A G-quadruplex/hemin structure-undamaged method to inhibit peroxidase-mimic DNAzyme activity for biosensing development.

Damaging the structure of the G-quadruplex (G4) to prevent the formation of the G4/hemin complex is presently the only available method to inhibit the activity of the peroxidase-mimic DNAzyme. In this study, a unique intramolecular inhibitory effect of the adjacent base-pair (InE(N:N)), by installing a rationally adjacent base-pair of the G4 core sequence, is proposed for the inhibition of the DNAzyme activity, which eliminates the need to damage the entire G4 structure. Various base pairs show different abilities to inhibit DNAzyme activity. The adjacent adenine: thymine pair possesses the best inhibitory efficiency (17 times). Through detailed investigations of the InE(N:N), it was revealed that the adjacent adenine: thymine pair downregulated the formation of compound I in the catalytic process, thus inhibiting the G4 DNAzyme activity. The mechanism of inhibition indicated that the carbonyl group on the hexatomic ring of the complementary base played an important role. To further reflect the advantages of the proposed strategy, two InE(N:N)-based biosensors were developed for DNA analysis and Uracil-DNA glycosylase (UDG) detection. Compared with existing DNAzyme-based methods, the application of InE(N: N) facilitates the real-time assay and simplifies the design difficulty. Therefore, InE(N:N) provides new insights into the regulation of the DNAzyme activity and offers an efficient approach for the future application of DNAzyme.