Latest ArticlesDevelopment of sensitive and accurate methods for sialic acid (SA) determination is of great significance in early cancer diagnosis. Here, a colorimetric-assisted Photoelectrochemical (PEC) sensor was constructed for SA detection based on the two pairs of cis-diol groups in SA molecule. With the specific recognition of SA via the two pairs of cis-diol groups, the prepared gold-modified Bi2S3 (Au NPs@Bi2S3) and metal organic framework (Au@PCN-224) were introduced to the electrode and formed a sandwich structure. Based on the properties of inert electroconductivity and nanozyme of the PCN-224, dual-readout of photocurrent and visualization was achieved with the presence of 3, 3′, 5, 5′-tetramethylbenzidine (TMB). Moreover, to intensify the visualization signal, Ce3+ was employed as the mediator to boost the catalysis capability by transferring energy from PCN-224 surface to the whole system. With the unique SA recognition and the mediation of Ce3+, both the photocurrent and the visualization signals sensitively responded with the SA concentration linearly. The present method showed greatly high sensitivity, selectivity and accuracy for SA detection with a limit of detection of 1.44 µmol/L and a wide linear range of 5–1000 µmol/L. This method provided a new promising platform for SA detection and a potential strategy for design of novel biosensors with dual-model readout.
The Z-scheme heterostructure for photocatalyst can effectively prolong the lifetime of photogenerated carriers and retain a higher conduction/valence band position, promoting the synergistic coupling of photocatalysis and peroxymonosulfate (PMS) activation. In order to fully utilize the luminous energy and realize the efficient activation of PMS, this work achieved successful construction of NiCo2O4/BiOCl/Bi24O31Br10 ternary Z-scheme heterojunction by simultaneously synthesizing BiOCl and NiCo2O4 with NiCl2 and CoCl2 as the precursors. The intercalated BiOCl could serve as a carrier migration ladder to further achieve the spatial separation of electron-hole pairs, so that the oxidation and reduction processes separately occurred in different regions. Compared with the reported catalysts, the as-prepared composites exhibited the enhanced removal efficiency for tetracycline hydrochloride (TCH) in the visible light/PMS system, with a degradation efficiency of 85.30% in 2 min, and possessed good stability. Z-scheme heterojunction was shown to be beneficial for maximizing the superiority of photo-assisted Fenton-like reaction system. The experimental and characterization results confirmed that both non-radicals (1O2) and radicals (SO5•− and SO4•−) were involved in the reaction process and the SO5•− generated by the oxidation of PMS played a crucial role in the TCH degradation. The possible reaction mechanism was finally proposed. This study provided new insight into the Z-scheme heterostructure to promote the photo-assisted Fenton-like reaction.
Accurate detection and imaging of adenosine triphosphate (ATP) expression levels in living cells is of great value for understanding cell metabolism, physiological activities, and pathologic mechanisms. Here, we developed a DNA tetrahedron-based split aptamer probe (TD probe) for ratiometric fluorescence imaging of ATP in living cells. The TD probe is constructed by hybridizing two split ATP aptamer probes (Apt-a and Apt-b) to a DNA tetrahedron assembled by four DNA oligonucleotides (T1, T2, T3 and T4). In the presence of ATP, the TD probe will alter its structure from the open to closed state, thus bringing the separated donor and acceptor fluorophores into close proximity for high fluorescence resonance energy transfer (FRET) signals. The TD probe exhibits low cytotoxicity, efficient cell internalization and good biological stability. Moreover, based on the FRET "off" to "on" signal output mode, the TD probe can effectively avoid false-positive signals from complex biological matrices, which is significant for long-term reliable imaging in living cells. In addition, by changing the split aptamers attached to DNA tetrahedron, the proposed strategy may be extended for detecting various intracellular targets. Collectively, this strategy provides a valuable sensing platform for biomarkers analysis in living cells, thus having great potential for early clinical diagnosis and therapeutic evaluation.
Angiotensin-converting enzyme 2 (ACE2) is not only an enzyme but also a functional receptor on cell membrane for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, the activity of ACE2 in single living cell is firstly determined using a nanokit coupled electrospray ionization mass spectrometry (nanokit-ESI-MS). Upon the insertion of a micro-capillary into the living hACE2-CHO cell and the electrochemical sorting of the cytosol, the target ACE2 enzyme hydrolyses angiotensin II inside the capillary to generate angiotensin 1–7. After the electrospray of the mixture at the tip of the capillary, the product is differentiated from the substrate in molecular weight to achieve the detection of ACE2 activity in single cells. The further measurement illustrates that the inflammatory state of cells does not lead to the significant change of ACE2 catalytic activity, which elucidates the relationship between intracellular ACE2 activity and inflammation at single cell level. The established strategy will provide a specific analytical method for further studying the role of ACE2 in the process of virus infection, and extend the application of nanokit based single cell analysis.
The increasing pollution and human demand for a cleaner environment have made achieving the environmental sustainability a current research focus. As a "green" technology, semiconductor photocatalysis is of great significance to the environmental purification. Benefiting from the unique anisotropic crystal structure and electronic properties, layered photocatalytic nanomaterials show great potential for efficient photocatalytic environmental treatment. This review comprehensively summarizes the recent progress on layered photocatalytic nanomaterials for oxidation or reduction of pollutants in water and air along with the basic understanding of related mechanisms and developments in this field. First, the existing diversified layered photocatalysts are classified, and their different synthesis and modification strategies are discussed in detail to provide a comprehensive view of the material design that affects their photocatalytic performance. Subsequently, the extensive applications of the above-mentioned layered photocatalytic nanomaterials in environmental fields are systematically summarized, including photooxidation of water and air pollutants, and photoreduction of heavy metal pollutants, NO3-, BrO3- and CO2. Finally, based on the current research achievements in layered photocatalysts for environmental remediation, the future development direction and challenges are proposed.
The development of efficient and cost-effective electrocatalysts for oxygen evolution reaction (OER) is crucial for the overall water splitting. Herein, we prepared a highly exposed NiFeOx ultra-small nanoclusters supported on boron-doped carbon nonotubes catalyst, which achieves a 10 mA/cm2 anodic current density at a low overpotential of 213 mV and the Tafel slope of 52 mV/dec in 1.0 mol/L KOH, superior to the pristine NiFeOx-CNTs and other state-of-the-art OER catalysts in alkaline media. A combination study (XPS, sXAS and XAFS) verifies that the local atomic structure of Ni and Fe atoms in the nanoclusters are similar to NiO and Fe2O3, respectively, and the B atoms which are doped into the crystal lattice of CNTs leads to the optimization of Ni 3d eg orbitals. Furthermore, in-situ X-ray absorption spectroscopies reveal that the high valence state of Ni atoms are served as the real active sites. This work highlights that the precise control of highly exposed multicomponent nanocluster catalysts paves a new way for designing highly efficient catalysts at the atomic scale.
Achieving efficient degradation of organic pollutants via activation of sulfite is meaningful but challenging. Herein, we have constructed a heterogeneous catalyst system involving Co3O4 and TiO2 nanoparticles to form the p-n heterojunction (Co3O4/TiO2) to degrade acetaminophen (ACE) through photocatalytic activation of sulfite. Specifically, X-ray photoelectron spectroscopy analysis and theoretical calculations provide compelling evidence of electron transfer from Co3O4 to TiO2 at the heterointerface. The interfacial electron redistribution of Co3O4/TiO2 tunes the adsorption energy of HSO3‒/SO32‒ in sulfite activation process for enhanced the catalytic activity. Owing to its unique heterointerface, the degradation efficiency of ACE reached 96.78% within 10 min. The predominant active radicals were identified as •OH, h+, and SOx•− through radical quenching experiments and electron spin resonance capture. Besides, the possible degradation pathway was deduced by monitoring the generated intermediate products. Thereafter, the enhanced roles of well-engineered compositing interface in photocatalytic activation of sulfite for complete degradation of ACE were unveiled that it can improve light absorption ability, facilitate the generation of active species, and optimize reactive pathways. Considering that sulfite is a waste from flue gas desulfurization process, the photocatalytic activation of sulfite system will open up new avenues of beneficial use of air pollutants for the removal of pharmaceutical wastewater.
Ribosomal RNAs (rRNAs) provide the structural framework of ribosomes and play critical roles in protein translation. In ribosome biogenesis, rRNAs acquire various modifications that can influence the structure and catalytic activity of ribosomes. However, rRNA modifications in plants have yet to be fully defined. Herein, we proposed a method to purify rRNAs by a successive isolation with different strategies, including polyA-based mRNA depletion and agarose gel electrophoresis-based purification, with which highly pure rRNAs could be obtained. In addition, we developed a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method to systematically profile and characterize modifications from the isolated highly pure plant 18S rRNA and 25S rRNA. LC-ESI-MS/MS analysis showed that 10 and 12 kinds of modifications were present in plant 18S rRNA and 25S rRNA, respectively. Notably, among these identified modifications, 2 kinds of modifications of N2,N2-dimethylguanosine (m2,2G) and N6,N6-dimethyladenosine (m6,6A) in 18S rRNA, and 4 kinds of modifications of m2,2G, m6,6A, N7-methylguanosine (m7G) and 3-methyluridin (m3U) in 25S rRNA, were first reported to be present in plants. Moreover, exposure of Arabidopsis thaliana to cadmium (Cd) led to significant changes of modifications in both 18S rRNA and 25S rRNA of plants, indicating that rRNA modifications play important roles in response to environmental stress. The discovery of new modifications in plant rRNAs improves the spectra of plant rRNA modifications and may promote the investigation of the functional roles of plant ribosomes in regulating gene expression.
Developing a high-quality photoelectrode for photoelectrochemical applications is still an ongoing challenge. In this study, we prepared the g-C3N4 film on the indium tin oxide (ITO) glass through conventional coating, liquid-based growth, in-situ calcination, and vapor deposition methods, respectively. These electrodes were characterized and used as photoanodes to degrade methylene blue (MB) in water. Among these methods, the in-situ calcination method was most appropriate for preparing the continuous and organized g-C3N4 film electrodes with uniform g-C3N4 coverage and strong adhesion to the ITO substrate. It also had the highest activity in the photocatalytic (PC), electrochemical (EC), and photoelectrocatalytic (PEC) degradation processes of MB. In the PEC reaction, at an applied potential of 1.0 V and a light intensity of 0.96 W/cm2, the removal rate of MB was 62.5%, which was much higher than those in the PC and EC reactions. The high degradation rate was due to the synergistic effect of PEC degradation, wherein the PC and EC reactions promote and optimize each other. In the PC reaction, MB was degraded by −CH3 elimination, while the EC degradation pathway mainly included the conversion of sulfhydryl into sulfoxide and the opening of the central aromatic ring. Both methyl loss and aromatic ring opening occurred in the PEC reaction. Moreover, some monocyclic compounds were formed, and MB showed more complete degradation in the PEC reaction.
5-Formylcytosine (5fC), as an important epigenetic modification, plays a vital role in diverse biological processes and multiple diseases by regulating gene expression. Owing to the extremely low abundance of 5fC in all mammalian tissues and high structural similarity with other cytosine derivatives, the precise and sensitive detection of 5fC is challenging. Herein, a photo-elutable and template-free isothermal amplification strategy has been proposed for the sensitive detection of 5fC in genomic DNA based on 5fC-specific biotinylation, enrichment, photocleavage, and terminal deoxynucleotidyl transferase (TdT)-assisted fluorescence signal amplification, which is termed 5fC-PTIAS. By introducing the highly specific chemolabeling and the one-step photoelution processes, this strategy possesses a minimal nonspecific background as well as a much higher amplification efficiency. With the high signal-to-noise ratio, this strategy can achieve the accurate quantification of 5fC in various biological samples including mouse brain, kidney, and liver, with a limit of detection (LOD) of 0.025‰ in DNA (S/N = 3). These results not only confirm the widespread distribution of 5fC but also indicate its significant variation in different tissues and ages. The bisulfite- and mass spectrometry-free strategy is highly sensitive, selective, and easily mastered, holding great promise in detecting other epigenetic modifications with much lower levels.
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