The diagnostic value of lower glucose consumption for IDH1 mutated gliomas on FDG-PET.

BACKGROUND: Non-invasive diagnosis of IDH1 mutation for gliomas has great clinical significance, and PET has natural advantage to detect metabolism, as IDH mutated gliomas share lower glucose consumption. METHODS: Clinical data of patients with gliomas and 18F-FDG PET were retrospectively reviewed. Receiver operating characteristic curve (ROC) analysis was conducted, and standard uptake value (SUV) was estimated in combination with grades or IDH1 mutation. The glucose consumption was investigated with U251 cells expressing wild-type or mutated IDH1 by glucose assay. Quantification of glucose was determined by HPLC in clinical tissues. Meanwhile, bioinformatics and western blot were applied to analyze the expression level of metabolic enzymes (e.g. HK1, PKM2, PC) in gliomas. RESULTS: Seventy-one glioma cases were enrolled, including 30 carrying IDH1 mutation. The sensitivity and specificity dependent on SUVmax (3.85) predicting IDH1 mutation reached 73.2 and 86.7%, respectively. The sensitivity and specificity of differentiating grades by SUVmax (3.1) were 92.3 and 64.4%, respectively. Glucose consumption of U251 IDH1 mutant cells (0.209 ± 0.0472 mg/ml) was obviously lower than IDH1wild-type cells (0.978 ± 0.0773 mg/ml, P = 0.0001) and astrocyte controls (0.335 ± 0.0592 mg/ml, P = 0.0451). Meanwhile, the glucose quantity in IDH1mutant glioma samples were significantly lower than those in IDH1 wild-type tissues (1.033 ± 1.19608 vs 6.361 ± 4.3909 mg/g, P = 0.0051). Silico analysis and western blot confirmed that HK1 and PKM2 in IDH1 wild-type gliomas were significantly higher than in IDH1 mutant group, while PC was significantly higher in IDH1 mutant gliomas. CONCLUSION: SUVmax on PET can predict IDH1 mutation with adequate sensitivity and specificity, as is supported by reduced glucose consumption in IDH1 mutant gliomas.

Foliar zinc reduced Cd accumulation in grains by inhibiting Cd mobility in the xylem and increasing Cd retention ability in roots1.

Cadmium (Cd) pollution endangers the safe utilization of paddy soils, and foliar zinc (Zn) can reduce the toxic effects of Cd. However, little is known about the effects of foliar Zn application on the transport and immobilization of Cd in key rice tissues and the physiological state of rice plants. A pot experiment was conducted to explore the effects of spraying 0.2% and 0.4% Zn (ZnSO4) during the early grain-filling stage on Cd transport in rice, photosynthesis, glutathione (GSH) levels, Cd concentrations in xylem sap, and the expression of Zn transporter genes. The results showed that grain Cd concentrations in the 0.2% Zn and 0.4% Zn treatments were 24% and 31% lower, respectively, than those of the control treatments at maturity. Compared with the control treatments, the 0.4% Zn treatment increased Cd by 60%, 69%, 23%, and 22% in husks, rachises, first internodes, and roots, respectively. Application of Zn reduced xylem Cd content by up to 26% and downregulated transporter genes (OSZIP12, OSZIP4, and OSZIP7a) in flag leaves. Foliar Zn increased Cd bioaccumulation in roots while decreasing Cd bioaccumulation in grains. Zn reduced GSH concentration in flag leaves and stems, inhibiting photosynthesis (intercellular CO2 concentration, transpiration rate). Taken together, foliar Zn can reduce the expression of Zn transporter genes and the mobility of Cd in the xylem, promoting the fixation of Cd in husks, rachises, first internodes, and roots, ultimately reducing Cd concentration in rice grains.

Template-Free Try-On Image Synthesis via Semantic-Guided Optimization.

The virtual try-on task is so attractive that it has drawn considerable attention in the field of computer vision. However, presenting the 3-D physical characteristic (e.g., pleat and shadow) based on a 2-D image is very challenging. Although there have been several previous studies on 2-D-based virtual try-on work, most: 1) required user-specified target poses that are not user-friendly and may not be the best for the target clothing and 2) failed to address some problematic cases, including facial details, clothing wrinkles, and body occlusions. To address these two challenges, in this article, we propose an innovative template-free try-on image synthesis (TF-TIS) network. The TF-TIS first synthesizes the target pose according to the user-specified in-shop clothing. Afterward, given an in-shop clothing image, a user image, and a synthesized pose, we propose a novel model for synthesizing a human try-on image with the target clothing in the best fitting pose. The qualitative and quantitative experiments both indicate that the proposed TF-TIS outperforms the state-of-the-art methods, especially for difficult cases.

Vaginal enterocele after cystectomy: A case report.

BACKGROUND: After undergoing radical cystectomy combined with hysterectomy, female patients may suffer from pelvic organ prolapse due to the destruction of pelvic structures, which mainly manifests as the prolapse of tissues of the vulva to varying degrees and can be accompanied by symptoms, such as bleeding and inflammation. Once this complication is present, surgical intervention is needed to resolve it. Therefore, preventing and managing this complication is especially important. CASE SUMMARY: The postoperative occurrence of acute enterocele is rare, and a case of acute small bowel vaginosis 2 mo after radical cystectomy with hysterectomy is reported. When the patient was admitted, physical examination revealed that the small bowel was displaced approximately 20 cm because of vaginocele. A team of gynecological, general surgery, and urological surgeons was employed to return the small bowel and repair the lacerated vaginal wall during the emergency operation. Eventually, the patient recovered, and no recurrence was seen in the half year of follow-up. CONCLUSION: We review the surgical approach for such patients, analyze high-risk factors for the disease and suggest corresponding preventive measures.

Application of a novel computer-assisted surgery system in percutaneous nephrolithotomy: A controlled study.

BACKGROUND: Most complex renal stones are managed primarily with percutaneous nephrolithotomy (PCNL). However, PCNL is still a great challenge for surgeons because of poor comprehension on complex adjacent structures. Novel techniques are required to assist in planning and navigation. AIM: To apply and evaluate the Hisense computer-assisted surgery (CAS) system in PCNL. METHODS: A total of 60 patients with complex renal stones were included. Thirty patients in the CAS group had three-dimensional (3D) virtual models constructed with the CAS system. The model assisted in planning and navigating in the CAS system. Thirty patients in the control group planned and navigated as standard PCNL, without the application of the CAS system. Success rate of one attempt, operation time, initial stone-free rate, decrease in hemoglobin, and complications were collected and analyzed. RESULTS: There were no statistically significant differences in the baseline characteristics or planning characteristics. The success rate of one puncturing attempt (90% vs 67%, P = 0.028) and the initial stone-free rate (87% vs 63%, P = 0.037) were significantly higher in the CAS group. However, there were no statistically significant differences in the operation time (89.20 ± 29.60 min vs 92.33 ± 33.08 min, P = 0.859) or in the decrease in hemoglobin (11.07 ± 8.32 g/L vs 9.03 ± 11.72 g/L, P = 0.300) between the CAS group and the control group. No statistically significant differences in the incidence of complications (Clavien-Dindo grade ≥ 2) were found. CONCLUSION: Compared with standard PCNL, CAS-assisted PCNL had advantages in terms of the puncturing success rate and stone-free rate. The Hisense CAS System was recommended to assist in preoperative planning and intraoperative navigation for an intuitive, precise and convenient PCNL.

Foliar application of Zn reduces Cd accumulation in grains of late rice by regulating the antioxidant system, enhancing Cd chelation onto cell wall of leaves, and inhibiting Cd translocation in rice.

Paddy soil contaminated by cadmium (Cd) has attracted worldwide attention, while foliar spraying of zinc (Zn) could be considered a cost-effective and practical agronomic measure for reducing Cd accumulation in rice grain. However, the effects due to foliar spraying of Zn on different cultivars, as well as the mechanism of subsequent processes taking place are not fully understood up to now. To go a step ahead, a field experiment was conducted with the aim of studying the capability of foliar application of Zn (0.4% ZnSO4) to reduce Cd concentration in grain in five late rice cultivars (here named JLYHZ, FYY272, JY284, CLY7 and LXY130), and the antioxidant activities and subcellular distribution of Cd in the leaves. The results indicate that foliar Zn application significantly decreased grain yield in JY284, CLY7 and JLYHZ, compared to controls. In addition, foliar application of Zn significantly decreased Cd concentration in grain of the five rice cultivars, while increased Zn concentration. The effect of foliar application of Zn on transport coefficients of Cd varied greatly for the different rice cultivars. Foliar application of Zn significantly decreased the malondialdehyde (MDA) concentration in rice leaves, and increased peroxidase (POD) activity. Also, it changed the distribution of Cd in the soluble fraction in leaves (expressed as proportion), which was significantly decreased, and the proportion of Cd in the cell wall increased. The structural equation model (SEM) revealed the positive effects of flag leaf Cd, first node Cd, old leaf Cd, and root Cd concentration on grain Cd concentration. Flag leaf Cd had the highest standardized total effects on grain Cd concentration, followed by old leaf Cd. These results indicated that foliar application of Zn was effective in reducing grain Cd concentration of late rice by enhancing antioxidant activities and Cd chelation onto cell wall of leaves, and reducing Cd concentrations in leaves.

Risk factors for postoperative delayed gastric emptying in ovarian cancer treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.

BACKGROUND: Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) has shown promising results in improving the survival of ovarian cancer patients. Although the safety profiles of CRS-HIPEC exist, more attention should be paid to gastrointestinal complications, as the procedure involves a considerable proportion of bowel resection and anastomosis. AIM: To identify the risk factors for delayed gastric emptying in ovarian cancer treated with CRS-HIPEC. METHODS: A cross-sectional study was conducted. According to the inclusion and exclusion criteria, we retrospectively analyzed 77 patients admitted between March 2014 and April 2018 with advanced and recurrent ovarian cancer treated with CRS-HIPEC in Beijing Shijitan Hospital of Capital Medical University. Risk factors for delayed gastric emptying were analyzed using univariate analysis. All of the statistically significant variables in the univariate analysis were entered into the multivariable logistic regression model to determine factors independently associated with delayed gastric emptying. RESULTS: Among the 77 included patients, 36.4% (28/77) had delayed gastric emptying after CRS-HIPEC. The median age and body mass index of all patients were 59 years and 22.83 kg/m2, respectively. Preoperative chemotherapy was administered in 55 patients (71%). Sixty-two patients (81%) had a history of at least one previous pelvic surgery. The median operation time and intraoperative hemorrhage volume were 630 min and 600 mL, respectively. Omentectomy was performed in 32 cases of primary ovarian cancer and 24 cases of recurrence. The median peritoneal cancer index was 16. The risk factors for delayed gastric emptying from the univariate analysis were body mass index < 23 kg/m2 (X 2 = 5.059, P = 0.025), history of pelvic surgery (X 2 = 4.498, P = 0.034), history of chemotherapy (X 2 = 4.334, P = 0.037), operation time ≥ 7 h (X 2 = 4.827, P = 0.047), and intraoperative hemorrhage ≥ 800 mL (X 2 = 7.112, P = 0.008). Multivariable analysis revealed that age ≥ 70 years (HR = 7.127; 95%CI 1.122-45.264; P = 0.037) and intraoperative hemorrhage ≥ 800 mL (HR = 3.416; 95%CI 1.067-10.939; P = 0.039) were independently associated with postoperative delayed gastric emptying after CRS-HIPEC. CONCLUSION: Postoperative gastrointestinal management, including prolonged nasogastric intubation, should be promoted for patients over 70 years or those with intraoperative bleeding exceeding 800 mL.

[Zonation on non-point source pollution risk in the lower reaches of Zijiang River based on the "source-sink" theory]. / 基于"源-汇"理论的资江下游地区非点源污染风险区划.

Non-point source pollution risk assessment and zonation research are of great significance for the eco-environmental protection and optimization of land use structure. We identified the "source" and "sink" landscape using the "source-sink" landscape pattern theory based on the two phases of land use data in the lower reaches of Zijiang River in 2010 and 2018. We comprehensively considered the non-point source pollution occurrence and migration factors, and used location-weighted landscape contrast index (LCI) and non-point source pollution load index (NPPRI) to analyze non-point source pollution risk spatio-temporal characteristics in the study area. Zonation on non-point source pollution in the lower reaches of Zijiang River was studied by identifying the key factors of non-point source pollution risk. The results showed that the overall risk of non-point source pollution was relatively low. The sub-basin with "sink" landscape was the main type, accounting for 61.2%. Non-point source pollution risk was low in the southwest and was high along the banks of Zhixi River, Taohua River and main stream of Zijiang River, as well as plain in the northeast of the lower Zijiang River. The risk of non-point source pollution from 2010 to 2018 showed an increasing trend. The changes in landscape pattern, especially the expansion of rural settlement, arable land and the shrinkage of forest land had positive and negative responses to the risk of non-point source pollution, respectively. LCI, slope, and distance were the key factors affecting the change of the risk index of non-point source pollution. The lower reaches of the Zijiang River could be divided into four control regions: pollution treatment area near river, low slope pollution control area, ecological restoration-risk prevention and control area, and ecological priority protection area.

Phenotypic characterization of CADASIL patients with the Arg332Cys mutation in the NOTCH3.

BACKGROUND: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary vascular disease caused by mutations in NOTCH3, that are primarily localized in exons 4, 3, and 11. The Arg332Cys mutation in exon 6 has been rarely reported in patients with CADASIL. METHODS: A case study and the results of a comprehensive systemic search of the PubMed database, using the keywords "CADASIL", "Arg332Cys", "R332C", and "exon 6", are reported. The results obtained, combined with the data obtained from the largest published case series on CADASIL, the clinical and imaging characteristics of patients with the Arg332Cys mutation, were compared and analyzed. RESULTS: A 48-year-old woman with a rare Arg332Cys mutation in exon 6 of NOTCH3, who presented with rapidly developing dementia and recurrent ischemic stroke, was investigated herein. Magnetic resonance imaging (MRI) revealed abnormal signals in the cerebral white matter, bilateral thalamus, internal and external capsules, basal ganglia, corpus callosum, and brainstem. Literature review identified an additional 21 individuals, comprising 11 Europeans and 10 Asians, with the Arg332Cys mutation; of these identified individuals, clinical data was available for 2 Italian and 9 Asian patients. Analysis of the clinical characteristics of the 11 patients and the patient we reported showed that their mean age at disease onset was 37.82±9.36 years, much earlier than 57.0±9.36 years reported in literature. The most frequent manifestations were transient ischemic stroke or stroke (83.3%), followed by cognitive impairment (58.3%), psychiatric symptoms (50%), and migraine (33.3%). Among the 10 Asian patients with available imaging data, the characteristic high signals for the external capsule and brainstem accounted for 90% and 71.43% respectively, and anterior temporal high signal took proportion of 60% (higher than 34.5% reported for Asian patients in literature). None of the 6 patients with available gradient echo imaging data had cerebral microbleeding. CONCLUSIONS: CADASIL patients with the Arg332Cys mutation in exon 6 have been reported in Europe and Asia. The majority of patients had early disease onset. Diffuse high signals involving the external capsule, brainstem, and bilateral temporal pole are the main neuroimaging characteristics.

Effectiveness of simultaneous foliar application of Zn and Mn or P to reduce Cd concentration in rice grains: a field study.

Excess cadmium (Cd) in agricultural soils can be taken up by rice plants and concentrated in the grain, presenting a human health risk. In this study, we field tested the effects of three foliar treatments (zinc (Zn) alone, or combined with manganese (ZnMn) or phosphorus (ZnP)) on the Cd concentration and grain yield of six rice cultivars (C Liangyou 7, Fengyuanyou 272, Xiangwanxian 12, Tianyouhuazhan, Xiangwanxian 13, and Jinyou 284) at the grain filling stage. Our results showed that rice yield and Cd, Zn, Mn, P, and K concentrations were significantly different among the cultivars (p < 0.05); for example, Jinyou 284 recorded lower Cd levels than any other cultivar. Application of Zn, ZnMn, and ZnP had no significant effect on rice yield and Mn, P, and K concentrations for all cultivars. Compared with the control, Cd concentrations after treatment with Zn, ZnMn, and ZnP decreased by 19.03-32.55%, 36.63-55.78% (p < 0.05), and 25.72-49.10%, respectively, while Zn concentrations increased by 11.02-29.38%, 10.63-32.67%, and 11.97-36.82%, respectively. There was a significant negative correlation between Cd and Zn concentrations (p < 0.01). All three treatments increased Zn and reduced Cd concentration in rice grains, though ZnMn was most effective. Therefore, cultivar selection and Zn fertilizer application are effective strategies to minimize Cd concentration in rice grains. However, the lowest result still exceeded the Chinese Cd safety limit (0.2 mg Cd kg-1) by a factor of 2.6, demonstrating that additional effective measures should be simultaneously used to further reduce the accumulation of Cd in rice grains.

Molybdenum disulfide sphere-based electrochemical aptasensors for protein detection.

In this work, we report the development of an ultrasensitive sandwich-type electrochemical aptasensor for protein detection. The aptasensor is fabricated by using nitrogen-doped graphene oxide (N-GO) and Au nanoparticles (AuNPs) as sensing substrates, molybdenum disulfide (MoS2) spheres as the hybridization chain reaction (HCR) platform, and thrombin as the model protein. When the hybridization reaction is initiated through two biotinylated hairpin probes, vast horseradish peroxidases are immobilized on the long duplex by the biotin-avidin reaction. An electrochemical-chemical-chemical redox cycling reaction then takes place in the detection system, which contains p-dihydroxybenzene, ferrocene carboxylate and tris(2-carboxyethyl)phosphine. Benefiting from the good conductivity and high specific surface area of N-GO/AuNPs and MoS2 spheres, signal amplification of the HCR and detection system, and excellent selectivity of the aptamer and sandwich-type strategy, the proposed assay shows a wide linear range of 10 fM-0.1 nM towards thrombin with a detection limit of 27 aM (S/N = 3) along with clear distinction from different proteins. The proposed assay is successfully used to detect thrombin in human serum, which would have promising prospects for disease diagnosis and therapy.

Ultrasensitive electrochemical biosensing platform based on spherical silicon dioxide/molybdenum selenide nanohybrids and triggered Hybridization Chain Reaction.

An ultrasensitive sandwich-type electrochemical biosensor for DNA detection is developed based on spherical silicon dioxide/molybdenum selenide (SiO2@MoSe2) and graphene oxide-gold nanoparticles (GO-AuNPs) hybrids as carrier triggered Hybridization Chain Reaction (HCR) coupling with multi-signal amplification. The proposed sensoring assay utilizes a spherical SiO2@MoSe2/AuNPs as sensing platform and GO-AuNPs hybrids as carriers to supply vast binding sites. H2O2+HQ system is used for DNA detection and HCR as the signal and selectivity enhancer. The sensor is designed in sandwich type to increase the specificity. As a result, the present biosensor exhibits a good dynamic range from 0.1fM to 100pM with a low detection limit of 0.068fM (S/N=3). This work shows a considerable potential for quantitative detection of DNA in early clinical diagnostics.

Au nanoparticles/hollow molybdenum disulfide microcubes based biosensor for microRNA-21 detection coupled with duplex-specific nuclease and enzyme signal amplification.

An ultrasensitive electrochemical biosensor for detecting microRNAs is fabricated based on hollow molybdenum disulfide (MoS2) microcubes. Duplex-specific nuclease, enzyme and electrochemical-chemical-chemical redox cycling are used for signal amplification. Hollow MoS2 microcubes constructed by ultrathin nanosheets are synthesized by a facile template-assisted strategy and used as supporting substrate. For biosensor assembling, biotinylated ssDNA capture probes are first immobilized on Au nanoparticles (AuNPs)/MoS2 modified electrode in order to combine with streptavidin-conjugated alkaline phosphatase (SA-ALP). When capture probes hybridize with miRNAs, duplex-specific nuclease cleaves the formative duplexes. At the moment, the biotin group strips from the electrode surface and SA-ALP is incapacitated to attach onto electrode. Then, ascorbic acids induce the electrochemical-chemical-chemical redox cycling to produce electrochemical response in the presence of ferrocene methanol and tris (2-carboxyethyl) phosphine. Under optimum conditions, the proposed biosensor shows a good linear relationship between the current variation and logarithm of the microRNAs concentration ranging from 0.1fM to 0.1pM with a detection limit of 0.086fM (S/N=3). Furthermore, the biosensor is successfully applied to detect target miRNA-21 in human serum samples.

Tetrandrine inhibits the proliferation of human osteosarcoma cells by upregulating the PTEN pathway.

Tetrandrine (TET) is a natural product isolated from the Chinese herb Stephania tetrandra S. Moore and has been reported to have antiproliferation and apoptosis-inducing activity in various malignant tumor cells. However, the exact molecular mechanisms underlying these effects remain unclear. In the present study, we tested the antiproliferation effect of TET on osteosarcoma (OS) 143B cells and explored the possible potential molecular mechanism in this process. Using CCK-8 assay and flow cytometry, we found that TET inhibited proliferation, induced apoptosis and arrested the cell cycle of the 143B cells. Using a xenograft tumor model of human OS, tetrandrine was found to inhibit tumor growth in vivo. TET increased the protein level of phosphatase and tensin homolog (PTEN) and decreased its phosphorylation as detected by western blot analysis and immunohistochemistry.Overexpression of PTEN strengthened the anticancer effect of TET, while knockdown of PTEN attenuated it. Meanwhile, TET activated p38 MAPK and increased its phosphorylation. Our findings suggest that TET may be a potential anticancer drug for OS. In addition, its effects may be mediated by the upregulation of PTEN. Moreover the expression alteration of PTEN and p-PTEN was mediated by the TET-induced activation of p38 MAPK in a direct or indirect manner.

Ultrasensitive sensing platform for platelet-derived growth factor BB detection based on layered molybdenum selenide-graphene composites and Exonuclease III assisted signal amplification.

A highly sensitive and ultrasensitive electrochemical aptasensor for platelet-derived growth factor BB (PDGF-BB) detection is fabricated based on layered molybdenum selenide-graphene (MoSe2-Gr) composites and Exonuclease III (Exo III)-aided signal amplification. MoSe2-Gr is prepared by a simple hydrothermal method and used as a promising sensing platform. Exo III has a specifical exo-deoxyribonuclease activity for duplex DNAs in the direction from 3' to 5' terminus, however its activity is limited on the duplex DNAs with more than 4 mismatched terminal bases at 3' ends. Herein, aptamer and complementary DNA (cDNA) sequences are designed with four thymine bases on 3' ends. In the presence of target protein, the aptamer associates with it and facilitates the formation of duplex DNA between cDNA and signal DNA. The duplex DNA then is digested by Exo III and releases cDNA, which hybridizes with signal DNA to perform a new cleavage process. Nevertheless, in the absence of target protein, the aptamer hybridizes with cDNA will inhibit the Exo III-assisted nucleotides cleavage. The signal DNA then hybridizes with capture DNA on the electrode. Subsequently, horse radish peroxidase is fixed on electrode by avidin-biotin reaction and then catalyzes hydrogen peroxide and hydroquinone to produce electrochemical response. Therefore, a bridge can be established between the concentration of target protein and the degree of the attenuation of the obtained signal, providing a quantitative measure of target protein with a broad detection range of 0.0001-1 nM and a detection limit of 20 fM.

A layered tungsten disulfide/acetylene black composite based DNA biosensing platform coupled with hybridization chain reaction for signal amplification.

A 2-dimensional tungsten disulfide-acetylene black (WS2-AB) composite is synthesized by a simple hydrothermal method to achieve excellent electrochemical properties for applications as a DNA biosensor. The biosensor is fabricated based on the Au nanoparticles (AuNPs) and WS2-AB composite modified electrode, which subsequently is used to couple with a capture probe by an Au-S bond, then modified with target DNA, auxiliary DNA and bio-H1-bio-H2 (H1-H2) to perform hybridization chain reaction for signal amplification. Herein, two DNA hairpins H1 and H2 are opened by the recognition probe. The nicked double helices from hybridization chain reaction are used to immobilize horseradish peroxidase enzymes via biotin-avidin reaction, which produces signal-amplification detection of target DNA through the catalytic reaction of the hydrogenperoxide + hydroquinone system. Under optimum conditions, the as-prepared biosensor shows a good linear relationship between the current value and logarithm of the target DNA concentration ranging from 0.001 pM to 100 pM and a detection limit as low as 0.12 fM. Moreover, the fabricated biosensor exhibits good selectivity to differentiate the one-base mismatched DNA sequence. This work will open a pathway for ultrasensitive detection of other biorecognition events and gene-related diseases based on layered WS2-AB and hybridization chain reaction.

Ultrasensitive electrochemical sensing platform for microRNA based on tungsten oxide-graphene composites coupling with catalyzed hairpin assembly target recycling and enzyme signal amplification.

An ultrasensitive electrochemical biosensor for microRNA (miRNA) is developed based on tungsten oxide-graphene composites coupling with catalyzed hairpin assembly target recycling and enzyme signal amplification. WO3-Gr is prepared by a simple hydrothermal method and then coupled with gold nanoparticles to act as a sensing platform. The thiol-terminated capture probe H1 is immobilized on electrode through Au-S interaction. In the presence of target miRNA, H1 opens its hairpin structure by hybridization with target miRNA. This hybridization can be displaced from the structure by another stable biotinylated hairpin DNA (H2), and target miRNA is released back to the sample solution for next cycle. Thus, a large amount of H1-H2 duplex is produced after the cyclic process. At this point, a lot of signal indicators streptavidin-conjugated alkaline phosphatase (SA-ALP) are immobilized on the electrode by the specific binding of avidin-biotin. Then, thousands of ascorbic acid, which is the enzymatic product of ALP, induces the electrochemical-chemical-chemical redox cycling to produce a strongly electrochemical response in the presence of ferrocene methanol and tris (2-carboxyethyl) phosphine. Under the optimal experimental conditions, the established biosensor can detect target miRNA down to 0.05fM (S/N=3) with a linear range from 0.1fM to 100pM, and discriminate target miRNA from mismatched miRNA with a high selectivity.