Latest ArticlesBacteria producing β-lactamases have become a major issue in the global public health field. To restrain the development of drug resistance and reduce the abuse of antibiotics, it is very important to rapidly identify bacteria producing β-lactamases and put forward a reasonable treatment plan. Here, an integrated microfluidic chip-mass spectrometry system was proposed for rapid screening of β-lactamase-producing bacteria and optimization of β-lactamase inhibitor dosing concentration. The concentration gradient generator followed by an array of bacterial culture chambers, as well as micro-solid-phase extraction columns was designed for sample pretreatment before mass analysis. By using the combination system, the process of the hydrolysis of antibiotics by β-lactamase-producing bacteria could be analyzed. To validate the feasibility, four antibiotics and two antibiotic inhibitors were investigated using three strains including negative control, SHV-1 and TEM-1 strains. SHV-1 and TEM-1 strains were successfully distinguished as the β-lactamase producing strains. And the acquired optimal concentrations of β-lactamase inhibitors were in accordance with the results by that obtained from the traditional microdilution broth method. The total analysis time only needed around 2 h, which was faster than conventional methods that require a few days. The technique presented herein provides an easy and rapid protocol for β-lactamase resistance related studies, which is important for the inhibition of antimicrobial resistance development and the reduction of antibiotics abuse.
In recent twenty years, aggregation-induced emission (AIE), due to its excellent application prospect, has aroused widespread interests. The development of novel and easy to make AIE luminogens (AIEgens) is an attractive subject. For this purpose, it is very important to study the structure-property relationship of AIEgens. Because azine derivatives are easy to synthesis and some of them have nice AIE properties, herein, a series of azine derivatives (ADs) were employed as models to study the influence of different functional groups, electronic effects and structures on the AIE properties of azine derivatives. The AIE mechanism were studied by single crystal analysis, density functional theory (DFT) calculations and so on. The results indicated that the o-hydroxyl aryl substituted azine compounds could show good AIE properties. Meanwhile, the AIE properties of o-hydroxyl aryl substituted azine compounds were also influenced by the electronic effects of the aryl groups in the azine compounds. The o-hydroxyl groups could form intramolecular hydrogen bond with imine group, which play key role to restrict the intramolecular rotation of the aryl groups and act as base stone for the AIE process of this kind compounds. The HOMO-LUMO energy gaps of o-hydroxyl substituted azine are smaller than other homologous compounds, which is agree with the proposed AIE mechanism. Finally, thanks to the AIE properties, the o-hydroxy-substituted azines could be used as efficient Al3+ and Cu2+ fluorescent chemosensors in different conditions. In addition, test strips based on AD10 has been prepared, which can conveniently detect Cu2+ in industrial wastewater. This research supplied a way for the design of novel easy to make AIEgens through simple azine derivatives.
Benefiting from the large Stokes shift between fluorescence and phosphorescence, fluorescence/phosphorescence dual-emitting carbon dots (CDs) have gradually entered at the stage of single-phase white light-emitting diodes (WLEDs) as 'green material'. However, most of the developed dual-emitting CDs have weak phosphorescence, short emission wavelength and narrow emission band, resulting in relatively bluish white light emission and low color rendering index (CRI). Herein, an ultrabroad-band fluorescence/phosphorescence dual-emitting CD-based material (UB-CD@BA) is prepared by thermal treatment of boric acid (BA) and CDs with large conjugated structure. The stable covalent bonding between CDs and BA, as well as three-dimensional spatial restriction effect of self-polymerization BA molecules around CDs during long-term heating efficiently rigidified the single/triplet excited states of CDs from non-radiative deactivation, thus producing strong dual emissive materials with the high phosphorescence quantum yield of 21%. Remarkable, the prepared UB-CD@BA powders exhibit bright pure white light emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.33) and the highest reported full width at half maximum of 250 nm. Based on the unique characteristics of UB-CD@BA, it was used as a color conversion layer to prepare a WLED with CIE coordinates of (0.35, 0.33) and the CRI value of 87.
Point-of-care testing (POCT) technology is highly desirable for clinical diagnosis, healthcare monitoring, food safety inspection, and environment surveillance, because it enables rapid detection anywhere, anytime, and by anyone. Electrochemiluminescence (ECL) has been widely used in chemo-/bio analysis due to its advantages such as high sensitivity, simplicity, rapidity and easy to control, and is now attracting increasing attention for POCT applications. However, to realize the accurate on-site quantitation, it is still challenging to develop portable devices which can precisely collect, analyze, transmit and display the ECL signals. This review will focus on how to develop a portable ECL device by summarizing recent examples and analyzing their key components part by part. Then the possible solutions to the existing challenges in the development and applications of portable ECL devices are summarized and discussed in detail, followed by offering future perspectives. We attempted to provide an appealing viewpoint to inspire interested researchers to comprehend and explore portable ECL sensing systems for practical applications and even commercialization.
Plant-parasitic nematodes are major threat for crop protection. The lack of nematicides with new mode of action and increasing resistance raises the need for novel nematicides. In order to seek new nematicidal lead, originating from the structure of chalcone, a series of fused ring compounds was obtained by ring closure design strategy. These compounds were modified further. The nematicidal activity against M. incognita of synthesized compounds was evaluated. The bioassay showed that compound 3 and some of its derivatives such as compounds 18, 19, 21, 22, 23, 24 and 26 exhibited excellent nematicidal activity. Among them, compound 23 exhibited significant bioactivity. The LC50/72 h value reached 3.20 mg/L in vitro and the inhibition rate was 100.00% at 40 mg/L in the matrix. The structure-activity relationship of synthesized compounds was discussed in details. The influence of compound 23 on egg hatching, motility, and feeding behavior of C. elegans was also evaluated.
Intramedullary spinal cord tumor (IMSCT) is comparatively rare malignant tumor in the central nervous system and is very difficult accessible by conventional chemotherapy regimen. Currently, there are very limited researches for IMSCT treatment using nanomedicine. To fill this gap, we originally reported a targeted strategy by leveraging nano-engineered mesenchymal stem cells (MSCs) for synergistic anti-IMSCT treatment. In this study, two mode drugs paclitaxel (PTX) and metformin (MET) were co-loaded in maleimide-modified poly(lactic-co-glycolicacid) (PLGA-MAL) nanoparticles, which were further conjugated onto MSCs surface via the thioether bond formed between PLGA-MAL and MSCs without affecting the migration ability of MSCs. Owing to the excellent tumor tropism and penetrability of MSCs and good biodegradability of PLGA, the designed drug delivery platform could accurately target IMSCT sites to exert long-term synergistic antitumor efficacy, exhibiting promising research value for alternative IMSCT management beyond surgery.
Heme proteins play various important roles in a variety of physiological and pathological processes. Surfactant assemblies have drawn great attention in fabricating fluorescent sensors to detect and identify proteins. In this study, an acetylpyrene fluorophore containing imidazole HP-1 was synthesized, and it could be well modulated by an anionic surfactant sodium dodecyl sulfate (SDS). The selected ensemble based on HP-1/SDS assemblies exhibited selective fluorescence sensing performance towards the heme proteins, including neuroglobin (Ngb), myoglobin (Mb) and cytochrome c (Cyt c). Besides, phospholipid DMPC vesicles as membrane models were particularly explored the association process between the heme protein Mb and membrane. The present work showed that Mb induced the lysis of DMPC liposomes visualized by transmission electron microscopy and optical microscope.
The dioxygen activation catalyzed by 4-hydorxylphenyl pyruvate dioxygenase (HPPD) were reinvestigated by using hybrid quantum mechanics/molecular mechanics (QM/MM) approaches at the B3LYP/6-311++G(d, p): AMBER level. These studies showed that this reaction consisted of two steps including the dioxygen addition/decarboxylation and hetero OO bond cleavage, where the first step was found to be rate-determining. The former step initially runs on a septet potential energy surface (PES), then switches to a quintet PES after crossing a septet/quintet minimum energy crossing point (MECP) 5-7M2, whereas the rest step runs on the quintet PES. The reliability of our theoretical predictions is supported by the excellent agreement of the calculated free-energy barrier value of 16.9 kcal/mol with available experimental value of 16–17 kcal/mol. The present study challenges the widely accepted view which holds that the O2 activation catalyzed by α-keto glutamate (α-KG) dioxygenase mainly runs on the quintet PES and provides new insight into the catalytic mechanism of α-KG dioxygenase and/or other related Fe(Ⅱ)-dependent oxygenase.
The first assembly of a conjugation-ready hexasaccharide from the capsular glycan of C. jejuni. strain BH0142 has been accomplished. The synthesis features the efficient preparation of 6-deoxy-d-ido-heptopyranosyl fluoride donors proceeding from allyl α-d-C-glucopyranoside by a C1-to-C5 switch strategy with radical dehydroxymethylative fluorination as a key step, stereocontrolled construction of 1,2-trans-α-d-ido-heptopyranosidic bonds and of 1,2-cis-α-d-galactopyranosidic linkages. The obtained target oligosaccharide sets a solid foundation for making structurally-defined multivalent glycoconjugate vaccine candidates against C. jejuni. infections.
Photodynamic therapy (PDT) agents may accumulate in skin and cause severe skin cytotoxicity. We report a pro-guest-based supramolecular strategy to selectively activate PDT in the reactive oxygen specie (ROS) overexpressed microenvironment, which is often existing in tumor and inflammatory tissues. PDT agents methylene blue (MB) and basic blue 17 (BB17) are used as model drugs. When encapsulated by acyclic cucurbit[n]uril (CB[n]), the efficacy of PDT agents is significantly inhibited. By contrast, in the presence of ROS (H2O2) and pro-guest, PDT agents are displaced and reactivated to show a dramatically enhanced PDT efficacy in cells.
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