Latest ArticlesWhile enol-keto tautomerism has attracted great interest in Schiff bases and related compounds in solution and crystal states, the self-assembly of energy-unfavored keto form were scarcely investigated. Here, we report a keto-form directed self-assembly of a naphthalene-attached enantiomeric N-salicylideneanil analog L/DGG-Nap accompanied with a significantly amplified circularly polarized luminescence (CPL). It was found that LGG-Nap exists as a mixture of enol and keto form in monomer at a diluted toluene solution. The increment of the concentrations leads to the formation of predominated keto form, which subsequently triggers the self-assembly. Cryo-transmission electron microscopy (Cryo-TEM) revealed that a hierarchical assembly process happened upon increasing the concentration of LGG-Nap in toluene. Individual nanofibers formed at 1 × 10−4 mol/L and transferred into helical nanofiber bundles in 5 × 10−3 mol/L. Interestingly, while these is nearly no circular dichroism (CD) or CPL in the monomeric solution, the assembly showed strong CD and CPL. Remarkably, the dissymmetry factor (glum) was significantly amplified from zero in solution through the 0.005 in individual nanofiber to 0.1 in nanofiber bundles. This work demonstrates that the enol-keto tautomerism can be broken and trigger the self-assembly upon increasing the concentration, which can subsequently direct the chiral self-assembly and significantly amplify the dissymmetry factor of assembled CPL materials.
In the process of electrocatalytic water splitting, the management of gaseous products is an important task. Timely detachment of gaseous products from the electrode surface and the electrolyte is beneficial to the reduction of energy consumption of the electrolytic cell. In the existing industrial electrolytic cells, the circulating pump drives the electrolyte flowing to discharge the gaseous products. Up to now, several much more advanced strategies have been explored to deal with the negative effects of bubbles. In this review, we summarized various strategies for bubble detachment, including electrode design, external field imposing and system upgrading. We also elaborated the principle, functional features, practicability, advantages and limitations of each method. Finally, challenges and perspectives are also provided for the further development of advanced bubbles detachment strategies for efficient hydrogen evolution.
The irregular defects and residual tumor tissue after surgery are challenges for effective breast cancer treatment. Herein, a smart hydrogel with self-adaptable size and dual responsive cargos release was fabricated to treat breast cancer via accurate tumor elimination, on-demand adipose tissue regeneration and effective infection inhibition. The hydrogel consisted of thiol groups ended polyethylene glycol (SH-PEG-SH) and doxorubicin encapsulated mesoporous silica nanocarriers (DOX@MSNs) double crosslinked hyaluronic acid (HA) after loading of antibacterial peptides (AP) and adipose-derived stem cells (ADSCs). A pH-cleavable unsaturated amide bond was pre-introduced between MSNs and HA frame to perform the tumor-specific acidic environment dependent DOX@MSNs release, meanwhile an esterase degradable glyceryl dimethacrylate cap was grafted on MSNs, which contributed to the selective chemotherapy in tumor cells with over-expressed esterase. The bond cleavage between MSNs and HA would also cause the swelling of the hydrogel, which not only provide sufficient space for the growth of ADSCs, but allows the hydrogel to fully fill the irregular defects generated by surgery and residual tumor atrophy, resulting in the on-demand regeneration of adipose tissue. Moreover, the sustained release of AP could be simultaneously triggered along with the size change of hydrogel, which further avoided bacterial infection to promote tissue regeneration.
Paper-based biosensors are widely employed in point-of-care testing (POCT) due to their convenience, portability, low cost, and ease of use. This study reports an integrated distance-based paper biosensor fabricated with a mesoporous membrane coated with stimuli-responsive polymer. The detection of α-amylase (AMY) using amylopectin-coated mesoporous membrane is demonstrated as an example. After introducing the AMY solution, it is observed that the aqueous solution flows along the paper strip due to AMY-catalyzed hydrolysis of amylopectin. The flow distance is proportional to the concentration of AMY with a detection limit as low as 4 mU/mL. In addition, the detection of AMY is demonstrated in human serum. Furthermore, the inhibitory effect of acarbose on AMY is evaluated. This reagent-free and disposable biosensor allows single-step rapid detection of the analyte. This approach is very promising for the development of user-friendly, equipment-free, and cost-effective biosensors with remarkable sensitivity and excellent selectivity for disease diagnosis and hypoglycemic drug screening.
Talaroclauxins A and B (1 and 2), two novel duclauxin hybrids, were obtained from Talaromyces stipitatus, along with three new (3−5) and one known analogue (6). Their structures were determined by NMR spectroscopy, HRESIMS, single-crystal X-ray diffraction, and quantum chemical calculations. Compound 1 is the first example of duclauxin-ergosterol hybrid featuring an unprecedented dodecacyclic ring system formed via a [4 + 2] cycloaddition, while compound 2, bearing an unusual 6/6/6/5/6/6/6/6 ring system, is a new member of the rare duclauxin-polyketide hybrid class of natural products. Plausible biosynthetic pathways for 1−6 are proposed. Compound 5 displayed moderate neuroprotective effects in glutamate sodium-induced SH-SY5Y cells.
As an emerging star in the family of two-dimensional (2D) materials, 2D transition metal carbides, carbonitrides and nitrides, collectively referred to as MXenes, have large specific surface area, rich active sites, metallic conductivity and adjustable surface chemical properties. These features make MXenes promising candidates for gas-sensing materials. For the past few years, MXene-based sensors have drawn increasing attention due to their enhanced sensor performance. Based on this, this review systematically represents the structure, synthesis methods and properties of MXenes, and summarizes their applications in gas sensors. Firstly, the types, structure, main synthesis methods and properties of MXenes are introduced in a comprehensive way. Next, the corresponding design principle and working mechanism of MXene-based gas sensor are clarified. Subsequently, the sensing performances of pristine MXenes and the MXene-based nanocomposite are discussed. Finally, some future opportunities and challenges of MXene-based sensors are pointed out.
The scope of stereochemistry recognition usually occurs near the chiral scaffold of a ligand or catalyst. Remote stereocontrol, which can surpass the limits of stereorecognition of remote prochiral centers, has long been a challenging object of great interest in asymmetric catalysis. The current work realized the remote stereocontrol of 1,7-zwitterion intermediates formed from Huang's o-amino aryl MBH carbonates. With simple and easily accessible β-ICD as the bifunctional catalyst, multifunctionalized tetrahydroquinoline derivatives could be synthesized via (4 + 2) cycloadditions with excellent enantioselectivity and diastereoselectivity under mild conditions. The strategy possesses broad substrate scope, and three types of electron-deficient enones are successfully applied. Mechanistic studies disclosed the Lewis base-catalyzed reaction pathway, and H-bonding between the catalyst and enones is crucial for long-range stereocontrol. Scale-up reaction and transformations of the tetrahydroquinoline products demonstrated the potential of this strategy.
The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in late 2019 has negatively affected people's lives and productivity. Because the mode of transmission of SARS-CoV-2 is of great concern, this review discusses the sources of virus aerosols and possible transmission routes. First, we discuss virus aerosol collection methods, including natural sedimentation, solid impact, liquid impact, centrifugal, cyclone and electrostatic adsorption methods. Then, we review common virus aerosol detection methods, including virus culture, metabolic detection, nucleic acid-based detection and immunology-based detection methods. Finally, possible solutions for the detection of SARS-CoV-2 aerosols are introduced. Point-of-care testing has long been a focus of attention. In the near future, the development of an instrument that integrates sampling and output results will enable the real-time, automatic monitoring of patients.
Photodynamic therapy (PDT) is a clinically approved cancer treatment that uses energy of light to generate active substances that cause damage to the cancer. Photosensitizers are employed to absorb light and generate toxic reactive oxygen species (ROS) to damage biomolecules like DNA. At the same time, some chemotherapy drugs like nucleotide analogues can provide mechanism-guided promotion in the treatment efficacy of PDT. However, the photosensitizer and chemotherapy drugs used in PDT is usually organic molecules, which suffers from bad solubility, fast clearance, and acute toxicity. To achieve targeted treatment, a reasonable delivery system is necessary. Therefore, we reported a metal-phenolic network where IR780 and gemcitabine were coupled chemically to overcome these shortcomings. The enhanced PDT effects can be realized by the promoted cell death both in vitro and in vivo. Moreover, the synergistic therapy also induced T-cell mediated anti-tumor immune response, which was significant for the inhibition of distant tumor growth. This work expanded the biomedical application of metal-phenolic materials and contribute to the wider application of photodynamic cancer therapy.
Exciton behavior is crucial to the exploitation of light-emitting conjugated polymer (LCPs) for optoelectronic devices. Singlet excitons are easily trapped by the intrinsically defect structures. Herein, we set a polyfluorenol (PPFOH) as an example to systematically investigate its photophysical behavior to check the role of defect structures in LCPs. According to time-resolved photoluminescence analysis, the feature emission peaks from individual chain of PPFOH in diluted DMF solution is effectively avoided the influence of fluorenone formation, but the residual green-band emission at 550 nm is easily observed in the PL spectra of PPFOH dilute toluene solution obtained delay 1.5 ns, confirmed the formation of "guest" physical aggregation-induced defect structure. Remarkably, efficient and ultrafast energy transfer from individual chain to defect structure is observed in PPFOH films. Interestingly, the efficient energy transfer happened for the film obtained from DMF solution (200 ps) than those of toluene ones (600 ps). Meanwhile, compared to relatively stable green-band emission in PPFOH film from toluene solution, red-shifted emission peak (11 nm) of PPFOH film from DMF solutions exposed to saturated DNT vapor also confirmed their different aggregation-induced green-band emission. Therefore, this aggregation defect structures are influenced on the photophysical property of LCPs in solid states.
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