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PURPOSE: We aimed to explore the prevalence and within-host evolution of resistance in polymyxin-heteroresistant carbapenem-resistant Klebsiella pneumoniae (PHR-CRKP) in critically ill patients. METHODS: We performed an epidemiological analysis of consecutive patients with PHR-CRKP from clinical cases. Our study investigated the within-host resistance evolution and its clinical significance during polymyxin exposure. Furthermore, we explored the mechanisms underlying the dynamic evolution of polymyxin resistance at both subpopulation and genetic levels, involved population analysis profile test, time-killing assays, competition experiments, and sanger sequencing. Additionally, comparative genomic analysis was performed on 713 carbapenemase-producing K. pneumoniae strains. RESULTS: We enrolled 109 consecutive patients, and PHR-CRKP was found in 69.7% of patients without previous polymyxin exposure. 38.1% of PHR-CRKP isolates exhibited polymyxin resistance and led to therapeutic failure in critically ill scenarios. An increased frequency of resistant subpopulations was detected during PHR-CRKP evolution, with rapid regrowth of resistant subpopulations under high polymyxin concentrations, and a fitness cost in an antibiotic-free environment. Mechanistic analysis revealed that diverse mgrB insertions and pmrB hypermutations contributed to the dynamic changes in polymyxin susceptibility in dominant resistant subpopulations during PHR evolution, which were validated by comparative genomic analysis. Several deleterious mutations (e.g. pmrBLeu82Arg, pmrBSer85Arg) were firstly detected during PHR-CRKP evolution. Indeed, specific sequence types of K. pneumoniae demonstrated unique deletions and deleterious mutations. CONCLUSIONS: Our study emphasizes the high prevalence of pre-existing heteroresistance in CRKP, which can lead to polymyxin resistance and fatal outcomes. Hence, it is essential to continuously monitor and observe the treatment response to polymyxins in appropriate critically ill scenarios.
ABSTRACT
Tumor recurrence commonly results from tumor-positive resection margins and metastatic lesions. The complete removal of tumor-positive margins is particularly essential in clinics. Thus, we designed a strategy based on Escherichia coli Nissle 1917 (EcN) nitroreductase (NTR) with a polyethylene glycol (PEG) polymer coating (PC-EcN-NTR) to specifically target and colonize in tumors for high-contrast tumor imaging by providing a large amount of NTR as biomarkers in situ. NTR is a favorable biomarker for tumor detection and imaging. The nfsB-encoding plasmid with a 16S promoter was transfected into EcN for the continuous and stable expression of NTR (E. coli. NfsB). PC-EcN-NTR can accumulate and proliferate for a long time in tumors to substantially express NTR. When the NTR-activated fluorescence (FL) probe was sprayed on the tumor, the tumor region showed fluorescence signals within 5 min. Compared to the tumor without colonization with bacteria, the PC-EcN-NTR-colonized tumors displayed 3.15× enhanced fluorescence signals. Furthermore, the fluorescence signals of the whole tumor can last at least 3 h, which is suitable for a long and meticulous surgical operation. More importantly, in the PC-EcN-NTR-harboring tumor, obvious FL appeared even at the very edge (approximately 200 µm away from the edge) of the tumor tissue. A TCF-Based near-infrared-II fluorescent probe (probe 2) was designed and synthesized. Results similar to those of probe 1 were observed when probe 2 was used for in vivo tumor imaging, which further proved the generality of the enhancing ability of the tumor-targeting probiotic. This strategy will hopefully guide the surgical resection of tumors via monitoring intense NTR activity. It may spur the use of tumor-targeting probiotic and enzyme-activated fluorescent probes for the processes of tumor diagnosis and image-guided surgery.
Subject(s)
Neoplasms , Probiotics , Surgery, Computer-Assisted , Biomarkers , Escherichia coli/metabolism , Fluorescent Dyes/metabolism , Humans , Neoplasms/diagnostic imaging , Neoplasms/surgery , Nitroreductases/metabolismABSTRACT
OBJECTIVE: To test the effects of Tanshinone IIA (Tan IIA) on cell viability, cycle, apoptosis, and autophagy of human glioma cell U251 by regulating phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signal pathway. METHODS: Tan IIA and PI3K agonist (740 Y-P) were used to treat glioma cells U251. MTT assay was used to assess cell viability and flow cytometry was used to detect cell apoptosis and cell cycle. The expressions of apoptosis-related proteins (Bcl-2 and Bax), autophagy-related proteins (LC3B and Beclin 1) and PI3K/Akt/mTOR signal pathway-associated proteins (p-PI3K, p-Akt and p-mTOR) were evaluated by Western blotting. RESULTS: Tan IIA decreased the expression of p-PI3K and p-Akt proteins, inhibited cell viability and promoted apoptosis. Meanwhile, the expression of Bax increased, while the expression of Bcl-2 decreased. In addition, Tan IIA promoted autophagy in U251 glioma cells and raised the expression of LC3B and Beclin 1. However, 740 Y-P played a reversed role of Tan IIA in cell viability, cycle, apoptosis, and autophagy of U251 cells. CONCLUSION: Tan IIA could suppress the viability of U251 cells and induce cell apoptosis and autophagy, which might be related to the inhibition of the PI3K/Akt/mTOR signal pathway.
Subject(s)
Abietanes/pharmacology , Apoptosis/drug effects , Glioma , Phosphoinositide-3 Kinase Inhibitors , Proto-Oncogene Proteins c-akt/antagonists & inhibitors , TOR Serine-Threonine Kinases/antagonists & inhibitors , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Apoptosis/physiology , Autophagy/drug effects , Autophagy/physiology , Cell Line, Tumor , Dose-Response Relationship, Drug , Glioma/metabolism , Glioma/pathology , Humans , Phosphatidylinositol 3-Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction/drug effects , Signal Transduction/physiology , TOR Serine-Threonine Kinases/metabolismABSTRACT
Background: The effects of heart failure (HF) on cortical brain structure remain unclear. Therefore, the present study aimed to investigate the causal effects of heart failure on cortical structures in the brain using Mendelian randomization (MR) analysis. Methods: We conducted a two-sample MR analysis utilizing genetically-predicted HF trait, left ventricular ejection fraction (LVEF), and N-terminal prohormone brain natriuretic peptide (NT-proBNP) levels to examine their effects on the cortical surface area (SA) and thickness (TH) across 34 cortical brain regions. Genome-wide association study summary data were extracted from studies by Rasooly (1,266,315 participants) for HF trait, Schmidt (36,548 participants) for LVEF, the SCALLOP consortium (21,758 participants) for NT-proBNP, and the ENIGMA Consortium (51,665 participants) for cortical SA and TH. A series of MR analyses were employed to exclude heterogeneity and pleiotropy, ensuring the stability of the results. Given the exploratory nature of the study, p-values between 1.22E-04 and 0.05 were considered suggestive of association, and p-values below 1.22E-04 were defined as statistically significant. Results: In this study, we found no significant association between HF and cortical TH or SA (all p > 1.22E-04). We found that the HF trait and elevated NT-proBNP levels were not associated with cortical SA, but were suggested to decrease cortical TH in the pars orbitalis, lateral orbitofrontal cortex, temporal pole, lingual gyrus, precuneus, and supramarginal gyrus. Reduced LVEF was primarily suggested to decrease cortical SA in the isthmus cingulate gyrus, frontal pole, postcentral gyrus, cuneus, and rostral middle frontal gyrus, as well as TH in the postcentral gyrus. However, it was suggested to causally increase in the SA of the posterior cingulate gyrus and medial orbitofrontal cortex and the TH of the entorhinal cortex and superior temporal gyrus. Conclusion: We found 15 brain regions potentially affected by HF, which may lead to impairments in cognition, emotion, perception, memory, language, sensory processing, vision, and executive control in HF patients.
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Background: Depression is a primary cause of illness and disability among teenagers, and the incidence of depression and the number of untreated young people have increased in recent years. Effective intervention for those youths could decrease the disease burden and suicide or self-harm risk during preadolescence and adolescence. Objective: To verify the short efficacy of the systemic couple group therapy (SCGT) on youths' depression changes and families with depressed adolescents. Methods: The study was a self-control trial; only within-group changes were evaluated. Participants were couples with a depressed child who was resistant to psychotherapy; they were recruited non-randomly through convenient sampling. The paired-sample t-test and Wilcoxon signed-rank test were used to compare differences before and after interventions. The effect sizes were also estimated using Cohen's d. Spearman's correlation analysis was used to examine associations between changes. Results: A downward trend was seen in depressive symptoms after treatment, and Cohen's d was 0.33 (p = 0.258). The adolescents perceived fewer interparental conflicts, and the effect sizes were medium for perceived conflict frequency (0.66, p = 0.043), conflict intensity (0.73, p = 0.028), conflict solutions (0.75, p = 0.025), coping efficacy (0.68, p = 0.038), and perceived threat (0.57, p = 0.072). For parents, global communication quality, constructive communication patterns, and subjective marital satisfaction significantly improved after interventions, with large effect sizes (1.11, 0.85, and 1.03, respectively; all p < 0.001). Other destructive communication patterns such as demand/withdraw (p = 0.003) and mutual avoidance (p = 0.018) and communication strategies like verbal aggression (p = 0.012), stonewalling (p = 0.002), avoidance-capitulation (p = 0.036), and child involvement (p = 0.001) also reduced, with medium effect sizes (0.69, 0.52, 0.55, 0.71, 0.46, and 0.79, respectively). Meanwhile, the associations between depression changes and changes in interparental conflicts (p < 0.001) and marital satisfaction (p = 0.001) were significant. Conclusions and clinical relevance: The SCGT offers the possibility for the treatment of families with depressed children who are unwilling to seek treatment. Helping parents improve communication and marital quality may have benefits on children's depressive symptoms.
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BACKGROUND: With the widespread spread of carbapenem-resistant gram-negative bacteria (CR-GNB) in medical facilities, the carriage of CR-GNB among critically ill patients has become a significant concern in intensive care units (ICU). This study aimed to develop a scoring system to identify CR-GNB carriers upon ICU admission. METHODS: Consecutive critically ill patients admitted to the ICU of Shanghai Ruijin Hospital between January 2017 and December 2020 were included. The patients were then divided into training and testing datasets at a 7:3 ratio. Parameters associated with CR-GNB carriage were identified using least absolute shrinkage and selection operator regression analysis. Each parameter was assigned a numerical score ranging from 0 to 100 using logistic regression analysis. Subsequently, a four-tier risk-level system was developed based on the cumulative scores, and assessed using the area under the receiver operating characteristic curve (AUC). RESULTS: Of the 1736 patients included in this study, the prevalence of CR-GNB carriage was 10.60%. The clinical scoring system including seven variables (neurological disease, high-risk department history, length of stay ≥ 14 days, ICU history, invasive mechanical ventilation, gastrointestinal tube placement, and carbapenem usage) exhibited promising predictive capabilities. Patients were then stratified using the scoring system, resulting in CR-GNB carriage rates of 2.4%, 12.0%, 36.1%, and 57.9% at the respective risk levels (P < 0.001). Furthermore, the AUC of the developed model in the training set was calculated to be 0.82 (95% CI, 0.78-0.86), while internal validation yielded an AUC of 0.83 (95% CI, 0.77-0.89). CONCLUSIONS: The ICU-CARB Score serves as a straightforward and precise tool that enables prompt evaluation of the risk of CR-GNB carriage at the time of ICU admission, thereby facilitating the timely implementation of targeted pre-emptive isolation.
Subject(s)
Anti-Bacterial Agents , Carbapenems , Humans , Carbapenems/pharmacology , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/therapeutic use , Critical Illness , China/epidemiology , Gram-Negative Bacteria , Intensive Care UnitsABSTRACT
Acute respiratory distress syndrome (ARDS) is associated with high mortality rates in patients admitted to the intensive care unit (ICU) patients with overwhelming inflammation considered to be an internal cause. The authors' previous study indicated a potential correlation between phenylalanine levels and lung injury. Phenylalanine induces inflammation by enhancing the innate immune response and the release of pro-inflammatory cytokines. Alveolar macrophages (AMs) can respond to stimuli via synthesis and release of inflammatory mediators through pyroptosis, one form of programmed cell death acting through the nucleotide-binging oligomerization domain-like receptors protein 3 (NLRP3) signaling pathway, resulting in the cleavage of caspase-1 and gasdermin D (GSDMD) and the release of interleukin (IL) -1ß and IL-18, aggravating lung inflammation and injury in ARDS. In this study, phenylalanine promoted pyroptosis of AMs, which exacerbated lung inflammation and ARDS lethality in mice. Furthermore, phenylalanine initiated the NLRP3 pathway by activating the calcium-sensing receptor (CaSR). These findings uncovered a critical mechanism of action of phenylalanine in the context of ARDS and may be a new treatment target for ARDS.
Subject(s)
Pneumonia , Respiratory Distress Syndrome , Animals , Mice , Macrophages, Alveolar/metabolism , Pyroptosis , NLR Family, Pyrin Domain-Containing 3 Protein/metabolism , Receptors, Calcium-Sensing , Phenylalanine , InflammationSubject(s)
Dementia, Vascular/pathology , Endoplasmic Reticulum Stress , Homocysteine/physiology , Animals , HumansABSTRACT
Coordination polymers are highly desirable for various applications due to their functionality control of crystal structures. In this work, an unique class of amorphous Co coordination polymer spheres anchored onto 3D macroporous carbon (MPC) support (denoted as Co CPSs/MPC) was prepared via a facile hydrothermal method. The formation of Co CPSs/MPC was systematically verified by a series of characterizations, like scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction, etc. The synergic effects between the superior electrical conductivity of 3D MPC supports and the excellent electrocatalytic activity of Co CPSs result in the increase of electron transfer from electrocatalyst, and then form significant number available reactive sites on the surface of electrode, which exhibit an exceptional catalytic activity and oxidation ability towards glucose. Under optimized conditions, amperometry results also indicated that the Co CPSs/MPC exhibit excellent electroanalysis towards glucose. The current work can shed light on the promising Co CPSs/MPC for further exploited as a sensitive and simple non-enzymatic glucose analytical platform.
ABSTRACT
Objective: To verify the effects of comprehensive infection prevention and control (IPC) interventions for the prevention of the cross-transmission of carbapenem-resistant Klebsiella pneumoniae (CRKP) within intensive care units (ICUs) in an epidemic region. Methods: A historical control, quasi-experimental design was performed. The study was conducted between January 2017 and December 2019, following the implementation of a multimodal IPC bundle. The baseline period was established from January 2013 to June 2013, when only basic IPC measures were applied. Results: A total of 748 patients were enrolled during the entire study. The incidence of ICU-acquired CRKP colonization/infection was 1.16 per 1,000 patient-days during the intervention period, compared with 10.19 per 1,000 patient-days during the baseline period (p = 0.002). The slope of the monthly incidence of CRKP at admission showed an increasing trend (p = 0.03). The incidence of ICU-acquired catheter-related bloodstream infections caused by CRKP decreased from 2.54 to 0.96 per 1,000 central-line-days (p = 0.08). Compliance with contact precautions and terminal room disinfection improved during the intervention period. All environmental surface culture samples acquired after terminal room disinfection were negative for CRKP. Conclusion: Our findings suggest that in epidemic settings, multimodal IPC intervention strategies and consistent monitoring of compliance, may limit the spread of CRKP in ICUs.
ABSTRACT
Exploring a cheap catalyst with effective activity for oxygen reduction reaction (ORR) to replace precious metal electrocatalysts has gained tremendous attention for several decades. In this study, we designed and synthesized cobalt and nitrogen supported on mesoporous hollow carbon hemisphere (Co/N/HCHs) nanocomposites by a facile and economical approach. Semisphere-shaped mesoporous hollow carbon is self-generated using silica particles as template, followed by a pyrolysis-etching process; and exhibits high electrical conductivity and high specific surface. The unique porous structure of carbon provides significant number of the abundant defective sites and shortens the mass transfer pathway, leading to a greatly enhanced electrocatalytic activity with mainly 4e- reduction. Moreover, the synergistic effects of large electrochemically active areas and good electrical conductivity, resulting from the introduction of Co and N heteroatom, are the main reason for displaying outstanding ORR activity with a high half-wave potential of 0.8 V and the electron transfer numbers of 3.89. Furthermore, an excellent long-term stability (the current density retention of 87.0%) and superb methanol tolerance in alkaline medium are achieved. Undoubtedly, this demonstrates a potential way to strategically design the non-precious metal doped carbon catalysts for wider practical applications.
ABSTRACT
A hybridization chain reaction (HCR) amplification-based electrochemical impedimetric biosensor is fabricated for the quick, sensitive, and specific detection of miRNA-21 (miR-21) via monitoring of electrode interfacial property changes in real-time. Two sequences of H1 and H2 are adopted to trigger HCR amplification. A large amount of linear DNA concatemer are formed which could change the interfacial properties of the electrode. Interfacial charge transfer resistance difference (Rct) is probed via electrochemical impedance spectroscopy (EIS) and Randles equivalent circuit. After amplifying via HCR, oligonucleotides with negatively charged repelling [Fe(CN)6]3-/4- ions can form a spatial blockage. HCR amplification strategy markedly enhanced the electrochemical signal with a limit of detection (LOD) down to 4.63 fM (S/N = 3). This strategy exhibited excellent selectivity for three different miRNAs: miR-199a, miR-141, and miR-155. Moreover, results show that the proposed method can be applied to miR-21 detection in the total RNA extracted from five cells. This work presents an enzyme-free and label-free EIS nucleic acid sensor for sensitively and selectively detecting miR-21, offering a promising approach in early diseases diagnosis.
Subject(s)
Biosensing Techniques , MicroRNAs , Dielectric Spectroscopy , Electrochemical Techniques , Limit of Detection , MicroRNAs/genetics , Nucleic Acid HybridizationABSTRACT
The development of highly efficient, stable, and low-cost non-noble-metal electrocatalysts for oxygen evolution reactions (OER) is a major challenge for facilitate the efficiency of green energy storage. Bimetallic oxides are considered promising candidates as the electrocatalysts for OER because of their remarkable electrocatalytic activity, good stability, and low cost. In this work, ZIF-67 precursors were prepared via microwave irradiation and used as a self-sacrificing template. We proposed a rapid and scalable strategy to prepare Fe, Co bimetal embedded nanoporous carbon (Fe-Co/NPC) polyhedron composites by thermal decomposition of Fe species incorporated ZIF-67 precursor. Benefiting from the distinctive 3D polyhedron structural and compositional advantages, Fe-Co/NPC with hierarchical porous structure showed excellent electrochemical performance as ideal electrode material for OER. The resulting Fe-Co/NPC displayed outstanding electrocatalytic activity for OER with appreciable onset potential (1.59 V (vs. RHE)), small Tafel slope (53.55 mV dec-1), low over-potential (396 mV) to reach 10 mA cm-2, and excellent durability with negligible loss in current density after 1000 cycles. The current work demonstrated new insight into the design and construction of 3D structured Fe-Co/NPC polyhedron catalysts with highly electrocatalytic activity and good stability for electrocatalysis applications.
ABSTRACT
Glucose is a popular biosensor target due to its closely with diabetes or hypoglycemia in blood. Designing efficiency electrocatalysts for the determination of glucose is vital to develop glucose detection devices. CoMoO4, as a kind of bimetallic oxide material, exhibits unique electrochemical properties. 3D macroporous carbon (MPC) has large specific surface area and excellent electrical conductivity, providing an effective support for loading other nano-entities to form novel composite with good synergetic effects. Herein, nanorod-like CoMoO4 anchored onto MPC support was synthesized for the development of a promising electrochemical sensing platform for glucose. Attributing to the synergic effects between the good electrocatalytic performance of CoMoO4 nanorods and the extraordinary electrical conductivity of 3D layered MPC, the novel CoMoO4/MPC composites non-enzymatic sensor shows excellent electrocatalytic performance for oxidation of glucose. Under the optimum conditions, the proposed CoMoO4/MPC hybrids provided a reliable linear range of 5â¯×â¯10-7 to 1.08â¯×â¯10-4â¯M with a low limit of detection (0.13⯵M) for the detection of glucose. Meanwhile, the CoMoO4/MPC sensing platform shows fast response time of 1.76â¯s, good stability and selectivity for detecting glucose. Moreover, this non-enzymatic sensor also has been successfully applied to measure glucose level in human blood samples. Therefore, the developed sensor holds a new promise for the construction of facile and sensitive non-enzymatic glucose analytical platform.
Subject(s)
Carbon/chemistry , Cobalt/chemistry , Electrodes , Glucose/analysis , Molybdenum/chemistry , Nanotubes/chemistry , Biosensing Techniques , Catalysis , Electrochemical Techniques , Humans , Limit of Detection , Oxidation-ReductionABSTRACT
MicroRNA-21 (miR-21) has been widely investigated as important biomarkers for cancer diagnosis and treatment. Herein, a highly sensitive nonenzymatic electrochemical biosensor based on Pd@metal-organic frameworks (Pd@UiO-66) and target-catalytic hairpin assembly (CHA) with target recycling approach has been proposed for the detection of miR-21. The proposed biosensor integrates the efficient CHA strategy and excellent electrocatalytic performance of Pd@UiO-66 nanocomposites. The concentration of miRNA-21 is related to the amount of the adsorbed electrocatalyst, leading to the different electrochemical signals for readout towards paracetamol (AP). This biosensor shows a low limit of detection of 0.713 fM with the dynamic range of 20 fM -600 pM under the optimal experimental conditions, providing a powerful platform for detecting miR-21. Furthermore, the designed biochemical self-assembly strategy of this electrochemical biosensor is promising candidate for potential applications in the analysis of other important genetic biomarkers for early diagnosis of cancers.
Subject(s)
Biosensing Techniques , Metal-Organic Frameworks , MicroRNAs , Catalysis , Electrochemical Techniques , Humans , Limit of Detection , MicroRNAs/analysisABSTRACT
The preparation of Pt/cerium oxide and highly ordered mesoporous carbon (Pt/CeO2/OMC) nanohybrids is reported. CeO2 can be used as an active material that enhances the electrocatalytic properties of Pt nanoparticles. OMC exhibits excellent electrical conductivity and large specific surface area, which makes it a highly promising electrocatalyst support. Benefiting from the synergistic effects of the catalytic performance of Pt/CeO2 and excellent conductivity of OMC supports, the new nanocomposite of Pt/CeO2/OMC are able to create novel features of electrocatalytic activities. Pt/CeO2/OMC tri-component composite was used as an excellent sensing platform for the determination of adrenaline. The developed sensor exhibited excellent activity and convincing analytical performance towards adrenaline, such as wide linear range, high sensitivity, low limit of detection, and low limit of quantification. In addition, the recoveries ranging from 93.4 to 103.6% were obtained in human serum samples. The successful preparation of Pt/CeO2/OMC tri-component composite may promote the development of novel electrocatalyst and facilitate the design of new electrochemical sensors.
Subject(s)
Carbon/chemistry , Cerium/chemistry , Electrochemical Techniques , Epinephrine/chemistry , Platinum/chemistry , Catalysis , Oxidation-Reduction , PorosityABSTRACT
Efficient platforms for detecting telomerase activity are essential for early tumor monitoring and diagnosis. Herein, an enzyme-free electroanalytical strategy was developed for reliable and highly sensitive telomerase activity assay based on the increased electrochemical signals of methylene blue (MB) catalyzed by well monodisperse Au nanorods (AuNRs). In the presence of dNTPs and telomerase extracts, the assistant DNA 1 in the double stranded DNA can be extended to telomere repeat units (TTAGGG)n, which could form a hairpin structure by telomerase-triggered extension. The assistant DNA 2 was ingeniously dissociated from the double stranded DNA to combine with capture DNA. As a result, a large amount of AuNRs could be anchored on the surface of these sequences and used for electrocatalytic oxidation of MB. The developed biosensor showed a low limit of detection of 8.20 HeLa cells mL-1 and a wide dynamic range from 30 to 1.04â¯×â¯107 HeLa cells mL-1 for the determination of telomerase activity, which can provide a new way for telomerase activity assays in early diagnosis for cancers.
Subject(s)
Biosensing Techniques/methods , Gold/chemistry , Nanotubes/chemistry , Telomerase/analysis , DNA/chemistry , Electrochemical Techniques/methods , Enzyme Assays/methods , HeLa Cells , Humans , Nanotubes/ultrastructureABSTRACT
Hydrazine is a possible human carcinogen because of its hyper toxicity. Therefore, the determination of hydrazine is particularly important for environmental protection and public security. Electrochemical method for the detection of hydrazine has drawn great interests because of its high sensitivity, fast response time, simple operation, and low cost. In this work, a leaf-like copper oxide (CuO) anchored onto wormlike ordered mesoporous carbon (OMC) composite was prepared for the construction of an electrochemical sensing platform for hydrazine. Because of the synergetic catalytic effect and unique structural properties, the obtained nanosized CuO incorporated in OMC exhibited good electrocatalytic performance for the oxidation of hydrazine with a catalytic rate constant (kcat) of 1.28â¯×â¯105 M-1s-1. Moreover, the content ratio of CuO: OMC was optimized to improve the electrocatalytic performance. The CuO/OMC hybrids can act as a sensitive and effective sensing platform for the determination of hydrazine, exhibiting wide linear range, high sensitivity, low limit of detection, and good stability. This comprehensive and systematic study may provide great opportunities for the design and construction of electrochemical sensors for environmental monitoring.
ABSTRACT
The preparation of palladium nanoparticles (Pd NPs) attached on nitrogen-doping hollow carbon spheres (NHCSs) surface using polyoxometalates (POMs) as both the reductant and bridging molecules by a green strategy was described in this paper. The samples have been thoroughly comprehensive characterized using scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, energy-dispersive X-ray spectra, and X-ray photoelectron spectroscopy. The as-prepared Pd/POMs/NHCSs tri-component nanohybrids provide enhanced electro-catalytic activities for oxidation of acetaminophen (AP) with the catalytic rate constant (kcat) of 2.34â¯×â¯103â¯M-1s-1 and diffusion coefficient (D) of 6.18â¯×â¯10-5 cm2s-1, because of the synergetic effects of Pd NPs and NHCSs. We assessed the use of Pd/POMs/NHCSs as an effective sensing template for electrochemical detection of AP, which showed high analytical performance, such as a linear range of 0.02⯵M-0.63⯵M with a sensitivity of 508.46⯵AmM-1; a linear range of 0.63⯵M to 0.083â¯mM with a sensitivity of 154.27⯵AmM-1, and a low limit of detection of 3â¯nM. This strategy provides a new direction opportunity to promote the electrochemical performance of AP.
Subject(s)
Acetaminophen/analysis , Carbon/chemistry , Metal Nanoparticles/chemistry , Nanocomposites/chemistry , Palladium/chemistry , Tungsten Compounds/chemistry , Acetaminophen/chemistry , Electrochemical Techniques/methods , Limit of Detection , Oxidation-ReductionABSTRACT
Here we report an Au nanoparticles supported on nanostructured porous carbon (NPCs) hybrid through a coordination-assisted strategy. Metal-organic frameworks (MOFs) have been demonstrated as suitable precursors for preparing NPCs through the impregnation of a secondary carbon source within pores of MOFs. The thermal transformation of Au/UiO-66-NH2 composites in an inert atmosphere has yielded ultrafine Au-embedded NPCs (Au/NPCs). The formation of these composite materials was verified by a comprehensive characterization using X-ray diffraction, N2 adsorption, scanning electron microscopy, and transmission electron microscopy. Because of the unique structural properties and synergetic catalytic effect, Au/NPCs can be developed as an effective sensing platform for the detection of acetaminophen (AP), which showed high activity and excellent analytical performance towards AP, such as a wide linear range of 0.12-95.10⯵M, a high sensitivity of 357.62⯵Aâ¯mM-1, and a low limit of detection of 49.4â¯nM. Importantly, the successfully fabricated Au/NPCs device accurately measured the amount of AP in pharmaceutical samples.