A direct electrochemical sensor based on covalent organic frameworks/platinum nanoparticles for the detection of ofloxacin in water.

A direct electrochemical sensor based on covalent organic frameworks (COFs)/platinum nanoparticles (PtNPs) composite was fabricated for the detection of ofloxacin (OFX) in water. Firstly, the COF material was synthesized via the condensation reaction of 1,3,5-tris(4-aminophenyl)benzene (TAPB) with terephthalaldehyde (TPA) and integrated with PtNPs by in situ reduction. Then, TAPB-TPA-COFs/PtNPs composite was loaded onto the surface of the glassy carbon electrode (GCE) by drip coating to construct the working electrode (TAPB-TPA-COFs/PtNPs/GCE). The electrochemical performance of TAPB-TPA-COFs/PtNPs/GCE showed a significant improvement compared with that of TAPB-TPA-COFs/GCE, leading to a 3.2-fold increase in the electrochemical signal for 0.01 mM OFX. Under optimal conditions, the TAPB-TPA-COFs/PtNPs/GCE exhibited a wide linear range of 9.901 × 10-3-1.406 µM and 2.024-15.19 µM with a detection limit of 2.184 × 10-3 µM. The TAPB-TPA-COFs/PtNPs/GCE-based electrochemical sensor with excellent performance provides great potential for the rapid and trace detection of residual OFX.

The Predictive Value of CD3+/CD8+ Lymphocyte Infiltration and PD-L1 Expression in Colorectal Cancer.

AIM: The immune system plays an important role in tumor development and treatment. In this study, we aimed to determine the relationships among the expressions of PD-L1, CD3, CD8, MMR proteins, clinicopathological features, and prognosis of CRC. METHODS: Immunohistochemistry was used to determine the expression of PD-L1, CD3, and CD8 in 771 patients with CRC. RESULTS: The expression of PD-L1 in TC was related to the right colon, adenocarcinoma, and dMMR, and in IC, it was related to younger CRC patients and the TNM stage. The expression of CD3 and CD8 in tumor-infiltrating lymphocytes was related to lymph node metastasis and the TNM stage. The expression of PD-L1 in TC and IC was correlated with the infiltration of CD3+ and CD8+ lymphocytes. Univariate survival analysis showed that the expression of PD-L1 in TC, IC, and dMMR was related to a better prognosis. Multivariate survival analysis showed that age, TNM stage, and dMMR were independent prognostic factors for CRC. The OS of the chemotherapy was significantly higher than that of the non-chemotherapy in III-IV TNM stage patients; CRC patients with positive PD-L1 expression in TC or IC and dMMR did not benefit from chemotherapy. CONCLUSIONS: PD-L1 expression in TC and IC was closely related to the density of CD3 and CD8 infiltration in tumor-infiltrating lymphocytes. The expression of CD3 and CD8 in tumor-infiltrating lymphocytes and the expression of PD-L1 in IC were linked to the TNM stage of CRC patients. PD-L1 expression in TC and IC and MMR status may act as an important biomarker for guiding the postoperative treatment of III-IV TNM stage CRC patients.

Eco-friendly fabrication of multifunctional magnetic plasmonic photocatalyst for adsorption, SERS monitoring and photodegradation of residual fluoroquinolone antibiotics in water.

In this work, a kind of multifunctional magnetic plasmonic photocatalyst was prepared by a green and efficient process. Magnetic mesoporous anatase titanium dioxide (Fe3O4@mTiO2) was synthesized by microwave-assisted hydrothermal, and Ag NPs were simultaneously in-situ grown on Fe3O4@mTiO2 (Fe3O4@mTiO2@Ag), graphene oxide (GO) was then wrapped on Fe3O4@mTiO2@Ag (Fe3O4@mTiO2@Ag@GO) to increase its adsorption capacity for fluoroquinolone antibiotics (FQs). Owing to the localized surface plasmon resonance (LSPR) effect of Ag, as well as the photocatalytic capacity of TiO2, a multifunctional platform based on Fe3O4@mTiO2@Ag@GO was constructed for adsorption, surface-enhanced Raman spectroscopy (SERS) monitoring and photodegradation of FQs in water. The quantitative SERS detection of norfloxacin (NOR), ciprofloxacin (CIP), and enrofloxacin (ENR) was demonstrated with LOD of 0.1 µg mL-1, and the qualitative analysis was confirmed by density functional theory (DFT) calculation. The photocatalytic degradation rate of NOR over Fe3O4@mTiO2@Ag@GO was about 4.6 and 1.4 times faster than that of Fe3O4@mTiO2 and Fe3O4@mTiO2@Ag, indicating the synergetic effects of Ag NPs and GO, the used Fe3O4@mTiO2@Ag@GO can be easily recovered and recycled for at least 5 times. Thus, the eco-friendly magnetic plasmonic photocatalyst provided a potential solution for the removal and monitoring of residual FQs in environmental water.

An accuracy improved ratiometric SERS sensor for rhodamine 6G in chili powder using a metal-organic framework support.

Internal standard molecule 4-mercaptobenzoic acid (4-MBA) embedded Au core-Ag shell nanorods (Au-MBA@Ag NRs) were prepared by a seed-mediated growth method, then loaded on octahedral MIL-88B-NH2 to obtain a novel ratiometric SERS substrate of Au-MBA@Ag NRs/PSS/MIL-88B-NH2 (AMAPM) for detecting rhodamine 6G (R6G) in chili powder. The porous structure and excellent adsorption ability of MIL-88B-NH2, allowed for increased loading of Au-MBA@Ag NRs, thereby shortening the distance between adsorbed R6G and the "hot spot" resulting from local surface plasmon resonance (LSPR) of Au-MBA@Ag NRs. Based on the SERS characteristic peak ratio of R6G to 4-MBA, the ratiometric SERS substrate displayed improved accuracy and excellent performance for R6G detection, with a wide linear range of 5-320 nM and a low detection limit of 2.29 nM as well as fine stability, reproducibility and specificity. The proposed ratiometric SERS substrate offered a simple, fast and sensitive sensing strategy for R6G detection in chili powder, which demonstrated potential applications in food safety and the analysis of trace analytes in complex matrices.

Spatial heterogeneity of soil available medium- and micro-elements in evergreen-deciduous broadleaved forest in karst.

Understanding the spatial heterogeneity of soil available medium- and micro-elements in karst area can provide a valuable theoretical guideline for soil nutrient management of karst ecosystem. We collected soil samples at a soil depth of 0-10 cm using grid sampling (20 m×20 m) in a 25 hm2 (500 m×500 m) dynamic monitoring plot. We further analyzed the spatial variability of soil medium- and micro-elements and their drivers, with classic statistics analysis and geo-statistics analysis. The results showed that the average contents of exchangeable Ca and Mg and available Fe, Mn, Cu, Zn, and B were 7870, 1490, 30.24, 149.12, 1.77, 13.54, and 0.65 mg·kg-1, respectively. The coefficient of variation of the nutrients ranged from 34.5% to 68.8%, showing a medium degree of their spatial variation. The coefficient of determination of the best-fit semi-variogram models of each nutrient was higher than 0.90, except for available Zn (0.78), indicating a strong predictive power for the spatial variation of the nutrients. The nugget coefficients for all the nutrients were less than 50%, showing a moderate spatial correlation, and the structural factors played a pivotal role. The spatially autocorrelated variation was within the range of 60.3-485.1 m, among which available Zn showed the lowest range and the deepest fragmentation degree. The spatial distribution of exchangeable Ca, Mg, and available B were consistent, with contents in the depression being significantly lower than that in other habitats. The contents of available Fe, Mn, and Cu declined with the increases of altitude and were significantly lower on the hilltop than in other habitats. The spatial variation of soil medium- and micro-elements was closely related to topographic factors in karst forest. Elevation, slope, soil thickness, and rock exposure rate were the primary drivers of spatial variation of soil elements and need to be considered in soil nutrient management of karst forestlands.

A multifunctional integrated carbon nanotubes/polyphenylene sulfide composite: preparation, properties and applications.

Although great progress has been achieved in polyphenylene sulfide (PPS) composites by the use of carbon nanotubes (CNTs), the development of cost-efficient, well dispersive and multifunctional integrated PPS composites has yet to be achieved because of the strong solvent resistance of PPS. In this work, a CNTs-PPS/PVA composite material has been prepared by mucus dispersion-annealing, which employed polyvinyl alcohol (PVA) to disperse PPS particles and CNTs at room temperature. Dispersion and scanning electron microscopy observations revealed that PVA mucus can uniformly suspend and disperse micron-sized PPS particles, promoting the interpenetration of the micro-nano scale between PPS and CNTs. During the annealing process, PPS particles deformed and then crosslinked with CNTs and PVA to form a CNTs-PPS/PVA composite. The as-prepared CNTs-PPS/PVA composite possesses outstanding versatility, including excellent heat stability with resistant temperatures up to 350 °C, corrosion resistance against strong acids and alkalis for up to 30 days, and distinguished electrical conductivity with 2941 S m-1. Besides, a well-dispersed CNTs-PPS/PVA suspension could be used to 3D print microcircuits. Hence, such multifunctional integrated composites will be highly promising in the future of new materials. This research also develops a simple and meaningful method to construct composites for solvent resistant polymers.

Sensitive detection of 4-nitrophenol based on pyridine diketopyrrolopyrrole-functionalized graphene oxide direct electrochemical sensor.

For highly sensitive detection of 4-nitrophenol (4-NP) in the environment, a novel pyridine diketopyrrolopyrrole-functionalized graphene oxide (PDPP-GO) composite was constructed for the first time by an improved Hummers' method. Herein, PDPP was completely dissolved in sulfuric acid (6 mol L-1) and reacted with GO, promoting PDPP evenly adhering to the GO surface. Moreover, the specific surface area increased from 15.51 to 22.033 m2 g-1. Infrared spectroscopy and X-ray photoelectron spectroscopy simultaneously demonstrated that PDPP was bound to GO by the strong intermolecular hydrogen bonding and π-π stacking conjugation. During the cyclic voltammetry test, the PDPP-GO coated glassy carbon electrode (PDPP-GO/GCE) direct electrochemical sensor gave expression to the best electrocatalytic activity for 4-nitrophenol detection than GO/GCE and bare GCE. Under optimization conditions, the as-prepared PDPP-GO/GCE sensor brought out remarkable sensitivities of 18.54 (0.5-50 µM) and 6.61 µA µM-1 cm-2 (50-163 µM) in the linear detection of 4-NP. Besides, a low detection limit of 0.10 µM, reliable long-term stability, excellent selectivity, and reproducibility were obtained. In the real sample test, the PDPP-GO/GCE demonstrated sensitive and reliable determination.

A Pyridine Diketopyrrolopyrrole-Grafted Graphene Oxide Nanocomposite for the Sensitive Detection of Chloramphenicol by a Direct Electrochemical Method.

A novel direct electrochemical sensor, based on a pyridine diketopyrrolopyrrole/graphene oxide nanocomposite-modified glass carbon electrode (PDPP/GO/GCE), was developed herein for chloramphenicol (CAP) detection. In this research, PDPP was grafted onto GO by C-N bonds and π-π conjugation, which were synergistically confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The morphology study shows that PDPP was uniformly dispersed on the GO in the form of particles. The constructed PDPP/GO/GCE showed the strongest response signal to CAP in the evaluation of electrocatalytic activity by cyclic voltammetry compared to that of GO-modified and unmodified GCE, revealing that the introduction of PDPP can effectively improve the electrocatalytic activity of sensors. Moreover, PDPP/GO/GCE had a noticeable current signal when the concentration of CAP was as low as 0.001 uM and had a wide line range (0.01-780 uM) with a low limit of detection (1.64 nM). The sensor properties of the as-obtained PDPP/GO/GCE involved anti-interference, reproducibility, and stability, which were also evaluated and revealed satisfactory results.

Molecularly imprinted 3D SERS sensor with inorganic frameworks for specific and recyclable SERS sensing application.

Poor selectivity and reusability of Au/Ag nanostructures are the main challenges for surface-enhanced Raman spectroscopy (SERS) in real sample detection. Herein, a novel specific and reusable three-dimensional (3D) SERS sensor with dual functions of selective trapping and photocatalytic degradation was designed. Firstly, Au-Ag bimetallic nanoparticles decorated silicon nanowires array (SiNWs-AuAg) were prepared as 3D SERS substrate. Then, silicon-based inorganic-framework molecularly imprinted TiO2 (TiO2@SiMIP) was synthesized and immobilized on SiNWs-AuAg by using rhodamine 6G (R6G) as template molecule. Owing to the excellent SERS performance of SiNWs-AuAg and the specific affinity of TiO2@SiMIP to template molecule, the prepared SERS sensor enables sensitive and selective detection of R6G in food samples with a limit of detection (LOD) of 0.27 nM. In addition, due to the photocatalysis of TiO2 and the stability of silicon-based inorganic framework, the residual templates in TiO2@SiMIP can be completely removed by UV irradiation, and the imprinted cavity of regenerated sensors still maintained good selectivity after regeneration by UV irradiation.

[Effects of tree mortality on the spatial patterns and interspecific associations of individuals in karst evergreen deciduous broad-leaved mixed forests]. / å–€æ–¯ç‰¹å¸¸ç»¿è½å¶é˜”å¶æž—ä¸ªä½“æ­»äº¡å¯¹ç©ºé—´æ ¼å±€åŠç§é—´å ³è”æ€§çš„å½±å“.

Tree mortality is an important ecological process in forests. It is crucial to understand how tree mortality affects spatial patterns and interspecific associations for revealing the mechanisms of tree mortality and community dynamics. We employed the correlation method of spatial point pattern analysis to analyse the variations in spatial patterns and interspecific relations before and after mortality using data obtained from two surveys of a 25 hm2 plot in the Mulun National Natural Reserve, China. The results showed that most species had an aggregated distribution both pre- and post-mortality. The proportion of species with aggregated distribution reduced slightly post-mortality compared with that for pre-mortality. Increases in the number of species with random distribution at small scale indicated that tree death was not random. At the species level, there were significant positive associations between dead and live trees of the 13 common species at different levels of 0-30 m range, suggesting weak intraspecific and interspecific competition among dominant species. Pre- and post-mortality interspecific associations were mostly positive, which remained stable during the period of two surveys for most species, indicating that the community had reached a rather stable stage. Following tree mortality, the number of species with positive associations increased at 1-30 m scales, whereas the number of species with negative and no associations decreased at most scales. These results indicated that the pressure of interspecific competition was relieved to some extent after individual death.

[Effects of Organic Materials on Phosphorus Fractions and phoD-harboring Bacterial Community in Karst Soil].

Efficient utilization of organic materials based on the rich resources in the karst region can promote soil fertility. Microorganisms have a crucial influence on soil phosphorus availability. phoD is considered to be the encoding phosphatase gene that can reflect the hydrolysis of organophosphorus compounds for the soil bacterial community. Molecular analysis of the phoD-harboring bacterial gene provides insight into promoting soil phosphorus availability under different fertilization managements. However, the effects of organic materials on soil phosphorus fractions associated with phoD-harboring bacterial communities are poorly understood. This study comprehensively investigated the effects of organic materials on soil phosphorus availability and explored environmental drivers of phoD-harboring bacteria in the Karst region. Here, six treatments were designed in the field as follows:non-fertilized control (CK), inorganic fertilization (NPK), inorganic fertilization combined with straw (NPKS), inorganic fertilization combined with manure (NPKM), inorganic fertilization combined with sludge (NPKL), and inorganic fertilization combined with sugarcane ash (NPKA). The phoD-harboring bacterial community in Karst region soil was analyzed using high-throughput sequencing. The results showed that the content of total P (TP), Olsen-P, and Ca2-P increased with the years after organic material application, whereas the content of CaCl2-P first decreased and then increased. Compared to that under the CK treatment, organic material application, especially NPKL treatment, significantly increased soil total nitrogen (TN), TP, Olsen-P, CaCl2-P, and Ca2-P contents, followed by those in the NPKA and NPKM treatments. Correlation analysis showed that the contents of CaCl2-P, Ca2-P, and Olsen-P were significantly positively correlated with soil exchangeable calcium (Ca-ex) content. Redundancy analysis (RDA) showed that TN, Ca-ex, soil organic carbon (SOC), and total potassium (TK) contents were the key factors affecting soil P fractions. Using high-throughput sequencing, we found that only NPKS increased the richness of phoD-harboring bacteria compared to that under the control treatment. No significant difference was observed in the phoD-harboring bacterial community among all treatments. The RDA model selected the Ca-ex, TK, Olsen-P, pH, and SOC as the key environmental predictors for the phoD-harboring bacterial community. In summary, soil phosphorus availability can be improved through the input of organic materials and inorganic fertilizer combined with manure, sludge, and ash. These additions were suitable for nutrient management and sustainable development in farmland soil in the Karst region of Guangxi.

Stabilizing and upregulating Axin with tankyrase inhibitor reverses 5-fluorouracil chemoresistance and proliferation by targeting the WNT/caveolin-1 axis in colorectal cancer cells.

Chemoresistance is a main obstacle for colorectal cancer treatment. In this study, we evaluated the effects and mechanisms of the WNT/ß-catenin signaling pathway on the chemoresistance of SW480 and SW620 colorectal cancer cells. The activity of ß-catenin was activated/inhibited by the small molecule compound GSK-3 inhibitor 6-bromo-indirubin-3'-oxime and the tankyrase inhibitor XAV939. The downstream target genes of the WNT/ß-catenin signaling pathway were screened using a cDNA microarray and bioinformatics analysis. Apoptosis induced by 5-Fu, cell cycle distribution and expression levels of WNT/ß-catenin/TCF12/caveolin-1 and multidrug resistance proteins were examed by flow cytometry and western blot after ß-catenin activation/inhibition and caveolin-1 overexpression/interference. The effect and mechanism of XAV939 on proliferation and apoptosis induced by 5-Fu in xenograft tumors of nude mice were evaluated by immunohistochemistry and TUNEL staining. 6-Bromo-indirubin-3'-oxime treatment increased ß-catenin expression by regulating GSK-3ß phosphorylation, accompanied by upregulation of TCF12, caveolin-1, P-gp, and MRP2 and downregulation of apoptosis induced by 5-Fu. Conversely, XAV939 treatment decreased ß-catenin expression by upregulating Axin, accompanied by downregulation of TCF12, Caveolin-1, P-gp, and MRP2 and upregulation of apoptosis induced by 5-Fu. The caveolin-1 gene was identified as an important downstream gene of the WNT/ß-catenin signaling pathway. Caveolin-1 overexpression upregulated ß-catenin expression, increased P-gp and MRP2 expression and decreased apoptosis induced by 5-Fu; conversely, caveolin-1 interference caused the opposite effects. In addition, in vivo experiments showed that XAV939 treatment reduced ß-catenin expression, increased apoptosis induced by 5-Fu and repressed xenograft tumor growth. Our findings suggested that inhibition of WNT/ß-catenin/TCF12/caveolin-1 provides a new promising therapeutic strategy for colorectal cancer treatment.

Specific and Sensitive Detection of Tartrazine on the Electrochemical Interface of a Molecularly Imprinted Polydopamine-Coated PtCo Nanoalloy on Graphene Oxide.

A novel electrochemical sensor designed to recognize and detect tartrazine (TZ) was constructed based on a molecularly imprinted polydopamine (MIPDA)-coated nanocomposite of platinum cobalt (PtCo) nanoalloy-functionalized graphene oxide (GO). The nanocomposites were characterized and the TZ electrochemical detection performance of the sensor and various reference electrodes was investigated. Interestingly, the synergistic effect of the strong electrocatalytic activity of the PtCo nanoalloy-decorated GO and the high TZ recognition ability of the imprinted cavities of the MIPDA coating resulted in a large and specific response to TZ. Under the optimized conditions, the sensor displayed linear response ranges of 0.003-0.180 and 0.180-3.950 µM, and its detection limit was 1.1 nM (S/N = 3). The electrochemical sensor displayed high anti-interference ability, good stability, and adequate reproducibility, and was successfully used to detect TZ in spiked food samples. Comparison of important indexes of this sensor with those of previous electrochemical sensors for TZ revealed that this sensor showed improved performance. This surface-imprinted sensor provides an ultrasensitive, highly specific, effective, and low-cost method for TZ determination in foodstuffs.

Accumulation in nutrient acquisition strategies of arbuscular mycorrhizal fungi and plant roots in poor and heterogeneous soils of karst shrub ecosystems.

BACKGROUND: Arbuscular mycorrhizal (AM) fungi and roots play important roles in plant nutrient acquisition, especially in nutrient poor and heterogeneous soils. However, whether an accumulation strategy of AM fungi and root exists in such soils of karst shrubland ecosystems remains unclear. Root traits related to nutrient acquisition (root biomass, AM colonisation, root acid phosphatase activity and N2 fixation) were measured in two N2-fixing plants (i.e. Albizia odoratissima (Linn. f.) Benth. and Cajanus cajan (Linn.) Millsp.) that were grown in heterogeneous or homogeneous nutrient (ammonium) soil with and without AM fungi inoculation. RESULTS: Both of these plants had higher AM colonisation, root biomass and relative growth rate (RGR), but lower N2 fixation and root acid phosphatase activity in the rhizosphere in the heterogeneous soil environment, than that in the homogeneous soil environment. Plants grown in the AM fungi-inoculated heterogeneous soil environment had increased root biomass and root acid phosphatase activity compared with those grown in soil without inoculation. AM colonisation was negatively correlated with the N2 fixation rate of A. odoratissima, while it was not significantly correlated with the root phosphatase activity. CONCLUSIONS: Our results indicated that enhanced AM symbiosis and root biomass increased the absorptive surfaces for nutrient acquisition, highlighting the accumulation strategies of AM and root traits for plant nutrient acquisition in nutrient poor and heterogeneous soils of the karst shrubland ecosystem.

Simple and sensitive nitric oxide biosensor based on the electrocatalysis of horseradish peroxidase on AuNPs@metal-organic framework composite-modified electrode.

Fe-based metal-organic framework (MIL-101(Fe)) was synthesized through a simple solvothermal synthesis and then used to prepare the AuNPs-decorated MIL-101(Fe) nanocomposite (APPPM(Fe)) by a multi-step layer-by-layer assembly process. Benefited from the porous structure of MIL-101(Fe) and the multilayer assemble process, the loading amount of AuNPs on APPPM(Fe) was enhanced and exhibited a fine biocompatible interface and high conductivity. Through the intense Au-S bond, high loading amount of horseradish peroxidase was immobilized on APPPM(Fe) and the native bioactivity of HRP was kept to realize its direct electrochemistry. From the electrochemical kinetics, the constructed biosensor displayed fast electron transfer and good electrocatalysis activity for the detection of nitric oxide (NO) with wide linear range from 0.033 to 5370 µM and a low detection limit of 0.01 µM (3 σ) as well as fine stability, reproducibility and specificity. According to results of real sample analysis, the proposed electrochemical biosensor offers fast and simple detection of NO in real serum. Therefore, the present strategy definitely provided a potential application prospect in NO clinic detection and disease therapy.

The predictive value and correlation of ß-catenin, CMTM6, and PD-L1 expression in colorectal cancer.

CMTM6 is a major regulator of PD-L1 expression. Aberrant Wnt pathway signaling occurs in most sporadic colorectal cancers (CRC). However, the significance and correlation of ß-catenin, CMTM6, and PD-L1 immunohistochemical expression in CRC is still unknown and need to be further verified. We evaluated the expression levels of ß-catenin, CMTM6, PD-L1, and MMR (mismatch repair) proteins by immunohistochemistry in CRC tissue microarray (TMA), and evaluated the association among ß-catenin, CMTM6, PD-L1 expression, MMR status, and clinicopathological features in 704 CRC patients. Positive expression of PD-L1 in tumor cells (TC) is associated with more frequent dMMR (mismatch repair deficient) status, CMTM6 expression, right colon, and younger CRC patients. The expression of PD-L1 in tumor-infiltrating immune cells (IC) is associated with a higher frequency of adenocarcinoma, ß-catenin, and CMTM6 expression. In univariate analysis, age, histological subtype, histologic grade, lymphatic metastasis, TNM stage, MMR status, and expression of PD-L1 protein in IC were significantly associated with the overall survival. In multivariate analysis, age, histologic grade, TNM stage, MMR status, and expression of PD-L1 protein in IC were independent prognostic factors. The overall survival of the adjuvant chemotherapy group was significantly higher than those non-chemotherapy in TNM stage III-IV CRC patients, but no significant overall survival improvement was found in the positive PD-L1 in TC, positive PD-L1 in IC, positive CMTM6, low ß-catenin expression, or dMMR status subgroups. Expression of CMTM6 and PD-L1 in CRC are positively associated with ß-catenin and reliable biomarkers for the prediction of responding to chemotherapy. The expression of ß-catenin/CMTM6/PD-L1 and MMR status may be valuable biomarkers for guiding different treatment strategies in CRC patients.

A capillary-based SERS sensor for ultrasensitive and selective detection of Hg2+ by amalgamation with Au@4-MBA@Ag core-shell nanoparticles.

A capillary-based SERS sensor was fabricated for ultrasensitive and selective detection of Hg2+ in water. Au@Ag core-shell NPs embedded with 4-mercaptobenzoic acid (4-MBA) (Au@4-MBA@Ag) were prepared by a seed growth method and fixed on the inner wall of the glass capillary to obtain the sensor. Owing to the amalgamation between Ag and Hg, the capillary-based SERS sensor can specifically recognize the reduced Hg2+ without any recognition element, and the resulted Ag/Hg amalgam can weaken the SERS activity of Ag shell; thus, the SERS intensity of the embedded 4-MBA at 1075 cm-1 gradually decreased with the increase of Hg2+ concentration. Under the optimum condition, the fabricated sensor can sensitively determine Hg2+ in water with a limit of detection (LOD) as low as 0.03 nM. The capillary-based SERS sensor offers the advantages of simple preparation, superior stability, and high selectivity, which is promising for rapid and on-site detection of Hg2+ in water combined with a portable Raman device.

BP[dG]-induced distortions to DNA polymerase and DNA duplex: A detailed mechanism of BP adducts blocking replication.

As one of the most widespread environmental pollutants, benzo[α]pyrene is metabolized to diol epoxides and then covalently breaks the initial DNA base pairs, which has been closely related to the occurrence and development of many human cancers. High fidelity DNA polymerases play an extremely important role in maintaining the reliability or fidelity of nucleic acid replication, which is generally blocked by BP adducts. To reveal the blocking mechanism of BP, two comparative molecular dynamics simulations were performed for the thermophilic Bacillus stearothermophilus DNA polymerase I large fragment (BF) complexes with normal and BP-bound DNA duplexes. The results of global conformational changes and molecular interactions show that the association of BP leads to the rearrangement of intramolecular hydrogen bonds, impairing the molecular recognition between the polymerase and the DNA duplex. It is also found that the conformation of DNA duplex is distorted, accompanied by an increase in molecular overall rigidity. In terms of possible blocking mechanisms, the BP moiety perfectly integrates itself into the base-paired environment in a special vertical conformation and occupies the space required for the incoming nucleotide. This work provides useful dynamics and structural information for understanding the toxic effect of BP on DNA replication at atomic level.

A dual enhanced anti-bacterial strategy based on high chlorin e6-loaded polyethyleneimine functionalized graphene.

Bacterial infection has always been a long-term problem of human history and has nowadays became a severe threat to human health with the appearance of drug-resistant bacteria due to the abuse of antibiotics. In this study, a high chlorin e6 (Ce6) photosensitizer-loaded polyethyleneimine-functionalized graphene (PEI-G) nanocomposite (PEI-G@Ce6) was prepared. The loading capacity of Ce6 on PEI-G@Ce6 was approximately up to 32.91 wt%, which was higher than that of other nanomaterials. The as-prepared PEI-G@Ce6 not only improves the photostability of free photosensitizer Ce6 molecules but also maintains the ability of singlet oxygen generation. Based on the dual enhancement of the physical antibacterial effects of PEI-G and the photodynamic therapy (PDT) antibacterial effects of loaded photosensitizer Ce6, PEI-G@Ce6 exhibited enhanced antibacterial efficiency towards Staphylococcus aureus. Therefore, the present strategy provided an effective platform to improve antibacterial efficiency for the better treatment of wound infections.

[Straw Returning Plus Nitrogen Fertilizer Affects the Soil Microbial Community and Organic Carbon Mineralization in Karst Farmland].

The use of straw returning plus nitrogen fertilizer on farmland is one of the important agronomic practices for adjusting soil organic carbon (SOC) transformations. To explore the mechanisms of straw and nitrogen fertilizer application on straw and SOC mineralization in long-term fertilized soils, an incubation experiment with the 13C isotope tracing technique was conducted, which involved three long-term fertilized models in typical karst soils (no fertilization, inorganic fertilization, and a combination of inorganic fertilization and straw). To study the mechanisms of 13C-labeled straw and SOC mineralization, four treatments were designed as follows:no straw and nitrogen (control), and straw combined with three levels of nitrogen fertilizer (0, 214.0, and 571.0 mg·kg-1 soil). The results showed that cumulative mineralization amounts of straw-derived organic carbon in long-term fertilized soils were markedly higher than those in non-fertilized soil. Straw-derived organic carbon mineralization was significantly affected by nitrogen fertilizer levels. The positive priming effects (PE) in long-term fertilized soils were much lower than those in non-fertilized soil. The PE was decreased at the low nitrogen fertilizer level but increased at the high nitrogen fertilizer level. The principal component analysis (PCA) of phospholipid fatty acids (PLFAs) indicated that the soil microbial community structure was greatly affected by the long-term fertilization models and combined straw and nitrogen fertilizer application. Moreover, the content of PLFAs in soil microorganisms, namely, bacteria and fungi, were remarkably increased by the straw plus nitrogen fertilizer (values increased by 40.3%-53.0%, 41.1%-62.6%, and 60.5%-148.6% compared with control), but levels were not significantly affected by nitrogen fertilizer levels alone. The ratios between PLFAs of soil gram-positive and gram-negative bacteria (G+/G-) decreased and were stable at around 0.8. The structure equation models (SEM) demonstrated that the combination of straw and nitrogen affected the soil gram-positive and gram-negative bacteria structure and increased the soil DOC content, which promoted the decomposition of straw and affected the mineralization of SOC. These results indicate that straw returning plus low nitrogen fertilizer can improve the SOC sequestration capacity in karst farmland.