The human immunodeficiency virus (HIV) remains a major worldwide health problem. Nowadays, many methods have been developed for quantitative detecting human immunodeficiency virus DNA (HIV-DNA), such ...as fluorescence and colorimetry. However, these methods still have the disadvantages of being expensive and requiring professional technicians. Early diagnosis of pathogens is increasingly dependent on portable instruments and simple point-of-care testing (POCT). Therefore, it is meaningful and necessary to develop portable and cheap methods for detecting disease markers.
In this work, a label-free chemiluminescence (CL) method was developed for detecting HIV-DNA via a handheld luminometer. To achieve label-free target detection, the CL catalyst, G-triplex-hemin DNAzyme (G3-hemin DNAzyme), was in-situ assembled in the presence of HIV-DNA. For improving sensitivity, HIV-DNA induced the cyclic strand displacement reaction (SDR), which can form three G3-hemin DNAzymes in one cycle. So, the chemiluminescence reaction between luminol and H2O2 was highly effectively catalyzed, and the CL intensity was linearly related with the concentration of HIV-DNA in the range of 0.05–10 nM with a detection limit of 29.0 pM. Due to the high specificity of hairpin DNA, single-base mismatch can be discriminated, which ensured the specific detection of HIV-DNA.
In-situ formation of G3-hemin DNAzyme led to label-free and selective detection without complex synthesis and functionalization. Therefore, it offers a cheap, selective, sensitive and portable method for detecting disease-related genes, which is promising for POCT of clinical diagnosis in resource-limited settings.
A label-free, cheap and portable CL method for detecting HIV-DNA via a handheld luminometer. Display omitted
•A label-free, cheap and portable CL method was developed for detecting HIV-DNA via a handheld luminometer.•G-triplex-hemin DNAzyme as CL catalyst was in-situ assembled in the presence of HIV-DNA.•HIV-DNA was detected with a detection limit of 29.0 pM due to the SDR.•The activity of HIV-DNA in serum was detected.
By tuning the applied potential of the UNCNs-900 electrode, we could easily tune the H2/CO ratios in clean syngas within a wide range with extra high FE: ∼100 %. And the maximum FECO could reach 91 % ...which represented the highest values among the reported non-metallic carbon-based electrocatalysts for CO2 reduction to syngas. Based on both experiments and DFT calculations, we have proved the pyridinic-N of UNCNs-900 is the active site of CO2RR, and graphitic-N may be the active site for HER.
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•We have successfully prepared a highly active UNCN electrocatalyst using ug-C3N4.•We were able to tailor the H2/CO ratio in the clean syngas products in a large range.•The maximum FECO of the UNCNs-900 reached 91%.
Developing nonmetallic carbon-based electrocatalysts that are affordable and have high activity and stability for carbon dioxide (CO2) reduction to syngas is a new and challenging strategy for solving the energy crisis. Here, we prepared a highly active ultrathin nitrogen (N)-doped carbon nanosheet (UNCN) electrocatalyst. By tuning the applied potential of the UNCN-900 (900 represents the carbonization temperature) electrode, we could tune the H2/CO ratio in clean syngas within a wide range with extra-high Faradic efficiency (FE). The maximum FECO reached 91%, which represented the highest value among the reported nonmetallic carbon-based electrocatalysts for CO2 reduction to syngas. According to the results of experiments and density functional theory calculations, we proved that pyridinic-N in UNCNs-900 is the active site of the CO2 reduction reaction (CO2RR) and that graphitic-N may be the active site for the hydrogen evolution reaction. These results provide a useful case for electrochemical CO2 reduction to syngas with a tunable H2/CO ratio using nonmetallic carbon-based electrocatalysts.
Automated and sensitive detection of nucleic acid is crucial for reliable and safe disease diagnostics because the minimum manual operation can effectively avoid sample contamination and infection ...risk. Herein, a sensitive, label-free and automated method was developed for detecting trace DNA by integrating digital microfluidics (DMF) with chemiluminescence (CL) detection. DMF can automatically manipulate discrete droplets. Taking advantage of sensitive and simple CL detection, DMF-CL integration can automatically and sensitively detect HIV DNA via the preset pathway. To further improve the sensitivity, on-chip exponential amplification reaction (EXPAR) was explored to produce large quantities of double-stranded DNA (dsDNA) in the presence of HIV DNA. Then, SYBR Green I (SG) intercalated into dsDNA to generate singlet oxygen upon light irradiation, which in situ oxidized potassium ferrocyanide into potassium ferricyanide. Finally, the CL reaction of potassium ferricyanide and luminol ensured the label-free, reliable and specific detection of HIV DNA in the range of 10 pM to 2 nM. Saving time-consuming and laborious manual operations, the DMF-CL integration greatly reduced the reagent consumption and avoided the contamination of DNA sample as well. Therefore, DMF-CL offers a promising and useful technology for developing automated and reliable biosensing and bioanalysis.
•Digital microfluidic (DMF) was successfully integrated with chemiluminescence (CL) to achieve automatic and on line analysis.•The exponential amplification reaction (EXPAR) was employed for on-chip isothermal DNA amplification for the first time.•An automated, label-free and sensitive method was developed for detecting HIV DNA via DMF-CL integration.
Alzheimer's disease (AD) is a degenerative disease of the brain worldwide. Currently, there is no effective cure. But accurate and early diagnosis of AD is critical to the development of patient care ...and future treatments. MiRNA-16 has been considered as an effective diagnostic biomarker for AD because of its regulatory effect on key proteins of AD. Herein, a colorimetric lateral flow assay (LFA) was developed for sensitive detection of miRNA-16 based on entropy-driven catalysis (EDC) amplification strategy. MiRNA-16 triggered EDC and released more linker DNAs (LDNA) of sandwich structure. Thus, AuNPs were enriched at the T-line to enhance the colorimetric signal and improve the sensitivity of visual assay. It showed good specificity and sensitivity for detecting miRNA-16 with a detection limit of 1.01 pM. The practical detection of miRNA-16 in human serum obtained satisfactory result. Significantly, EDC achieved signal amplification in homogeneous solution without enzyme and DNA labeling, leading to a cheap and easy detection of miRNA-16. Therefore, it provided a portable and rapid assay for AD-related nucleic acid, which holds a potential for point-of-care testing (POCT) of AD.
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•Enzyme-free and label-free amplification method was developed for sensitive detection of AD-related miRNA.•The colorimetric lateral flow assay made it possible to easily screen AD.•It offered a cheap and facile method for screening of AD.
The fundamental understanding of the surface reconstruction induced by the applied potential is of great significance for enhancing the oxygen evolution reaction (OER). Here, we show that a ...previously overlooked discharge current in the low applied potential region also leads to in situ electrochemical activation of a nitrogen‐doped nickel oxyhydroxide surface. We exploit the fact that doping of heteroatoms weakens the surface structure, and hence, a weak discharge current originating from the capacitive nature of nickel oxyhydroxide has a strong structure‐reforming ability to promote the formation of nitrogen and oxygen vacancies. The current density at 1.4 V (vs. Hg/HgO) can dramatically increase by as much as 31.3 % after discharge in the low applied potential region. This work provides insight into in situ enhancement of the OER and suggests that the low applied potential region must be a primary consideration in evaluating the origin of the activity of electrocatalysts.
Current mechanism studies mainly concern surface reconstruction at high potential with respect to formation of high‐valence metal sites and metal oxyhydroxides. The understanding of correlation between low potential scanning, surface structure, and electrochemical activity is lacking. This work suggests that the low applied potential region must be a primary consideration in evaluating the origin of the activity of electrocatalysts.
Objective
Microvascular invasion (MVI) is a significant adverse prognostic indicator of intrahepatic cholangiocarcinoma (ICC) and affects the selection of individualized treatment regimens. This ...study sought to establish a radiomics nomogram based on the optimal VOI of multi-sequence MRI for predicting MVI in ICC tumors.
Methods
160 single ICC lesions with MRI scanning confirmed by postoperative pathology were randomly separated into training and validation cohorts (TC and VC). Multivariate analysis identified independent clinical and imaging MVI predictors. Radiomics features were obtained from images of 6 MRI sequences at 4 different VOIs. The least absolute shrinkage and selection operator algorithm was performed to enable the derivation of robust and effective radiomics features. Then, the best three sequences and the optimal VOI were obtained through comparison. The MVI prediction nomogram combined the independent predictors and optimal radiomics features, and its performance was evaluated via the receiver operating characteristics, calibration, and decision curves.
Results
Tumor size and intrahepatic ductal dilatation are independent MVI predictors. Radiomics features extracted from the best three sequences (T1WI-D, T1WI, DWI) with VOI
10mm
(including tumor and 10 mm peritumoral region) showed the best predictive performance, with AUC
TC
= 0.987 and AUC
VC
= 0.859. The MVI prediction nomogram obtained excellent prediction efficacy in both TC (AUC = 0.995, 95%CI 0.987–1.000) and VC (AUC = 0.867, 95%CI 0.798–0.921) and its clinical significance was further confirmed by the decision curves.
Conclusion
A nomogram combining tumor size, intrahepatic ductal dilatation, and the radiomics model of MRI multi-sequence fusion at VOI
10mm
may be a predictor of preoperative MVI status in ICC patients.
As an important and universal tumor marker, the reliable and in situ detection of intracellular telomerase activity is crucial for cancer diagnosis. Herein, a ratiometric fluorescence resonance ...energy transfer (FRET) method was developed for detecting intracellular telomerase activity. It takes full advantage of manganese dioxide nanosheets (MnO2NS) that can carry DNA probes with different conformations into cells and then completely release the DNA probes via decomposition of MnO2NS by intracellular reduced glutathione (GSH). In the presence of telomerase, a telomere substrate (TS) could be extended to form long telomerase extension products (TEPs), which trigger the cycling strand displacement reaction (SDR) between two fluorophore-labeled hairpin DNA probes to form lots of DNA duplexes. The close contact of two fluorophores led to an effective ratiometric FRET for reliable detection of telomerase activity. Fluorescence confocal imaging demonstrated that the activity of telomerase in tumor cells was reliably detected. The inhibition of telomerase activity by an inhibitor resulted in a decrease in FRET signal. For extracellular detection, the FRET ratio (FA/FD) shows a good linear relationship with the number of HeLa cells in the range of 20-1000 cells. Therefore, it offers a more facile method for reliable and sensitive detection of intracellular telomerase activity.
This paper aims to study the electrical parameters (electrical resistivity and alternating current (AC) impedance spectroscopy) of cement paste with rice husk ash (RHA). The water to cement (Mass ...ratio of water to cement (w/c)) ratios of the paste in this study varied from 0.4 to 0.5. The mass ratio of rice husk ash in each w/c ratio of specimens ranged from 0% to 15% by t mass of cement. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to determine the microstructures of specimens. Moreover, the slump flow and plastic viscosity of fresh paste were determined. The results indicated that with the increasing dosage of RHA, the fluidity decreased, while the plastic viscosity increased. Meanwhile, a high w/c ratio led to a low plastic viscosity and high slump flow. The electrical resistivity of RHA cement paste gradually ascended with the increasing curing period. The conduction of specimens intricately changed by mixing RHA, a reasonable equivalent circuit was selected to describe the conduction mechanism by AC impedance spectroscopy. Additionally, the results of XRD and SEM showed that RHA could effectively promote the hydration process as well as decrease the size and number of cracks in hardened cement paste.
The Sn and W ions are implanted into the outer surface of TiO2 by the ex-situ flame doping and synergistically boost the photoelectrochemical water oxidation reaction.
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•An efficient, ...low-cost and versatile ex-situ flame doping method is developed.•Co-doped TiO2 exhibits enhanced photoelectrochemical performance.•The synergistic enhancement is derived from enhanced electron localization.
Ex-situ doping has an obvious advantage in tailoring the intrinsic properties of semiconductor due to the crucial dopant depth-control. However, the developed ex-situ doping technologies encounter dilemmas of high cost and low yield. Herein, we report an efficient, facile and depth-controllable ex-situ flame doping and the TiO2 nanorod arrays, dopants of Sn and W ions are prototypical system for photoelectrochemical water splitting, in which the dopants are diffused quickly into the outer surface region of the TiO2 in less than 30 s. The characterizations and theoretical calculations reveal that the enhanced electron localization on coordinatively unsaturated W atoms is induced by adjacent Sn atoms, which not only facilitate to absorb H2O molecules but also diminish activation energy barrier through stabilizing the *OH intermediates during oxygen evolution reaction. The desirable ex-situ flame doping strategy exhibits great versatility in the configuration of efficient photoelectrochemical systems over prevalent metal-oxide semiconductors.
•MoS2@GA-Fe enhanced the Fe(III)-based Fenton reaction in the tumor microenvironment.•The degradation of MoS2 had a “snowball effect” for the Fenton reaction.•Hydrogen sulfide was also produced for ...cancer treatment.•The MoS2@GA-Fe nanoreactor showed excellent antitumor efficiency and biosafety.
We report the preparation of gallic acid (GA)-modified MoS2 nanosheets (MoS2@GA) with high Fe(III) loading. The MoS2@GA-Fe can function as a “Fenton Nanoreactor” in the tumor microenvironment (TME), in which GA-Fe(III) can be reduced to GA-Fe(II) by glutathione (GSH) and amounts of reactive hydroxyl radicals (•OH) are generated during the Fenton reaction. Notably, the MoS2 degrades into small fragments during the process, and more Mo(IV) reaction sites are exposed on the surface, resulting in a “snowball effect” and enhanced •OH production. Furthermore, unsaturated S atoms can capture protons in the TME and form hydrogen sulfide (H2S). We combined the photoacoustic imaging and magnetic resonance imaging contrast properties of MoS2@GA-Fe and constructed an imaging-guided chemodynamic treatment, featuring excellent antitumor efficiency and biosafety. The TME-responsive “Fenton Nanoreactor” provides a promising strategy with enhanced translational potency for tumor therapy.
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