Latest ArticlesA new continuous-flow process for the enzymatic synthesis of optically pure γ-lactones, which are used as flavors and fragrances in the food and cosmetic industries, was developed in a three-dimensional microfluidic reactor. The microchannels (175 mm in length, 0.9 mm in depth, and 1.72 mL in volume) were carved precisely inside a single borosilicate glass (90 mm × 75 mm × 12 mm) with ultrafast femtosecond laser micromachining. The flow field analysis and reaction simulation showed that the mixing of substrates and enzymes was enhanced, allowing the adjustment of residence time in a wide window. SmCRV4, a carbonyl reductase with excellent catalytic activity and enantioselectivity toward γ/δ-keto acids, was employed for the asymmetric synthesis of various chiral lactones. 30 mmol/L (R)-γ-decalactone (3g) can be obtained in 26 s with a space-time yield (STY) up to 16,877 g L−1 d−1, which is 14.4 times higher than the highest STY of batch reaction reported previously. This continuous-flow process was applied to the synthesis of 6 chiral lactones. In addition, the scaled-up synthesis of 3g was carried out in 6 cascade microreactors continuously for 6 h, demonstrating the feasibility and stability of the 3D continuous-flow process in enzymatic synthesis of optically pure compounds.
The innovation in polymer design to rival conventional polyethylene glycol (PEG) is an important approach to achieving a more sustainable society. Here, cyclic PEG-like polycarbonates having high molecular weight (4.4–49.5 kg/mol) were enabled through zwitterionic ring-opening polymerization (ZROP) of macrocyclic carbonates (MCs) mediated by N-heterocyclic carbene (NHC). The thermodynamic behavior of polymerization depends on the ring size of monomers. During this process, the ZROP of 11-membered MC was driven by the change of enthalpy (ΔHp) which differed from the ZROP of 14-membered MC driven by the entropic change (ΔSp). Cyclic polycarbonates depicted improved thermostability (Td5% ≥ 204 ℃) and higher glass transition temperatures (Tg > ‒40 ℃) in comparison to their linear analogues (Td5% ≤ 185 ℃, Tg ~‒50 ℃). In addition, the mechanism of ZROP of MC was addressed through computational study. A distinct mechanism of polymerization distinguishable from the well-known NHC-mediated ZROP of cyclic esters was revealed, where the zwitterion from nucleophilic addition to MC, i.e. tetrahedral intermediate, cannot be ring-opened probably due to the delocalization of negative charge on the carbonate group, but serves as an active center for the polymerization. In comparison to PEG, the attained polymer demonstrated comparable hydrophilic and biocompatible properties, as revealed by the results of contact angle and in vitro cytotoxicity studies, suggesting that cyclic polycarbonate hold the promise as the alternative of PEG.
Silyl cobalt species are putative intermediates in cobalt-catalyzed transformations of hydrosilanes. However, their reactivity has remained poorly understood. Reported here is the investigation on four-coordinate disilyl Co(Ⅱ) complexes with N-hetereocyclic carbene ligation. The reactions of [(ICy)2Co(vtms)] (ICy = 1, 3-dicyclohexylimidazol-2-ylidene, vtms = vinyltrimethylsilane) with primary and secondary hydrosilanes (3 equiv.) furnish the four-coordinate disilyl complexes [trans-(ICy)2Co(SiHRRʹ)2] (SiHRRʹ = SiH2Mes, 1; SiH2Ph, 2; SiH2Cy, 3; SiHPh2, 4; SiHEt2, 5) in moderate to good yields. The structures of 1, 2 and 4 were established by single-crystal X-ray diffraction. Solution magnetic susceptibility measurement and EPR spectroscopy indicate their low-spin nature (S = 1/2). Reactivity studies on 4 led to the establishment of the conversions of 4 to the disilyl dihydride Co(Ⅲ) complex [K(THF)][(ICy)2Co(H)2(SiHPh2)2]n (6) and the fluorosilyl Co(Ⅱ) complex [(ICy)2Co(THF)(SiFPh2)][BF4] (7) when 4 was treated with excess amount of K and AgBF4, respectively, in THF. These conversions hint at the high activity of low-valent and high-valent disilyl cobalt species [trans-(ICy)2Co(SiHPh2)2]1− and [trans-(ICy)2Co(SiHPh2)2]2+. Complex 4 is reactive toward terminal alkynes, but inert toward alkenes and internal alkynes. The reactions of 4 with terminal alkynes CyCCH and Me3SiCCH (3 equiv.) yield the Co(Ⅱ) complexes [(ICy)2Co(CCCy)2] (8) and [(ICy)2Co(CCSiMe3)((SiMe3)CCH2)] (9), respectively, along with H2SiPh2 and alkynylsilanes RCCSiHPh2 (R = Cy, SiMe3), whereas the reaction with 4-CF3C6H4CCH (3 equiv.) produce [(ICy)2Co(CCAr)((Ar)CCH(SiHPh2)CCHAr)] (Ar = 4-CF3C6H4) (10) and H2SiPh2. These reactions are proposed to involve σ-bond metathesis reactions between alkyne C(sp)-H bonds and Co-Si bonds in 4. Complexes 6–10 have been characterized by NMR spectroscopy, X-ray diffraction study, and elemental analysis.
The Wnt signaling pathway plays a critical role in bone homeostasis, and the related protein therapy strategies have been reported to have great potential in osseointegration; however, they face formidable challenges such as complex external environments and unavoidable protein denaturation. In this work, we report a novel approach combining the synthesis of metal–organic frameworks (MOFs) and protein encapsulation in a one-pot process based on zeolitic imidazolate framework-8 (ZIF-8) and Wnt3a protein, with improved biomechanical behavior and enhanced protein biological response. This combination was designed to enhance the Wnt3a protein function through the improved chemical stability provided by the ZIF-8 crystals. Additionally, the zinc ions contained in the ZIF-8 crystals induced bone homeostasis, further favoring the osteogenesis. The results showed that the Wnt3a protein-loaded ZIF-8 crystals served as efficient drug delivery vehicles to promote osteogenesis, preventing protein denaturation. In particular, Wnt3a-loaded ZIF-8 nanoparticles (Wnt3a@ZIF-8 NPs) had higher efficacy on bone marrow mesenchymal stem cells (BMSCs) than ZIF-8 NPs or Wnt3a proteins, contributing to the osteogenesis through ZIF-8 crystals and intracellular Wnt3a proteins released from Wnt3a@ZIF-8 NPs. Furthermore, polymerase chain reaction (PCR) analysis showed that the osteogenic pathways were upregulated. Overall, the present one-pot process can open up new avenues to develop signaling protein-delivery systems for applications in protein therapy strategies.
Thrombosis remains a major global health concern mainly characterized by high rates of morbidity and mortality. Animal models serve as an indispensable tool to understand the underlying pathogenesis of thrombosis and assess the efficacy of novel antithrombotic drugs. Currently, zebrafish has emerged as a valuable model organism for thrombosis research. However, the traditional method of studying zebrafish thrombosis requires a laborious and time-consuming procedure, including anesthesia and manual immobilization of zebrafish. In this study, based on hydrodynamic force, a lateral-immobilization zebrafish microfluidic chip (LIZMC) was designed to evaluate the cardiovascular system of multiple larvae within a single microscope field of view. Specifically, coupling with microscope imaging, real-time monitoring of the peripheral blood circulation in the tail of phenylhydrazine (PHZ)-induced zebrafish thrombosis was enabled. Furthermore, the reliability of LIZMC for in vivo evaluation of antithrombotic agents in zebrafish was verified using aspirin. Collectively, this novel LIZMC-based system can be used for in vivo zebrafish thrombosis studies and rapid screening of antithrombotic agents.
A facile chemical method for the development of photocatalytic coating products was proposed based on practical application perspective for the Hong Kong roadside nitrogen oxides (NOx) mitigation. TiO2-based photocatalytic coating PC-C film with crystallized size of around 5–6 nm was synthesized with the peptization of H2O2. The PC-C coating possesses a super-hydrophilicity surface and is proven to have a NOx degradation rate of 46.8% with an optimum pH level of 7. In addition, the PC-C coating presents a promising photocatalytic NOx degradation compared with other commercially available coating products and P25 when applied on two building materials of poly-methyl methacrylate (PMMA) and concrete surface. A weather resistance simulation and a 180-day on-site field trial were carried out the attenuation effects of photocatalytic coating applied in outdoor exposure. Based on epidemiological estimation and field investigation, hospital admissions for respiratory diseases (HARD) and mortality cases (MC) could be reduced with the application of PC-C coating along the street canyon. This work demonstrates the feasibility of air pollution control measures for the local roadside NOx using photocatalytic technology, offering promising health benefits with environmental remediation.
Manganese oxides (MnOx), as low-toxicity and high-abundance catalysts, have been demonstrated to hold great promise for application in advanced oxidation processes (AOPs). However, further application of this material is restricted due to its unsatisfactory oxidant activation efficiency. Fortunately, recently remarkable research on deep activation mechanisms and modification of MnOx have been undertaken to improve its reactivity. Herein, modification enhancement mechanisms of MnOx to efficiently degrade various organic contaminants were discussed and highlighted, including metal doping, coupling with other metal oxides, composite with carbonaceous material, and compounding with other support. The activation mechanisms of different MnOx and derivative-modified material (such as doped MnOx, metal oxide-MnOx hybrids, and MnOx-carbonaceous material hybrids) were summarized in great details, which was specifically categorized into both radical and non-radical pathways. The effects of pH, inorganic ions, and natural organic matter on degradation reactions are also discussed. Finally, future research directions and perspectives are presented to provide a clear interpretation on the MnOx initiated AOPs.
It is well-established that high carbonization temperature will trigger the enzyme-like activity of carbon-based materials. However, the catalytic mechanism is still ambiguous, which hinders the further rational design of nanomaterials as enzyme mimics. Hereby, N, S-rich carbonized wool nanosheets (CWs) were synthesized at different pyrolysis temperatures. As expected, only CWs treated with high-temperature possess intrinsic oxidase- and peroxidase-like activities. Meanwhile, density functional theory (DFT) calculations demonstrate that graphitic nitrogen and the co-existence of nitrogen and sulfur in the carbon matrix serve as the active sites for the enzyme-like process. More importantly, combining theoretical calculations and experimental observations, the high-temperature triggered catalytic mechanism can be ascribed to the fact that an appropriate high-temperature maximizes the graphitization degree to a certain extent, at which most of the catalytic active sites are well retained rather than evaporating. Moreover, coupling with excellent photothermal conversion efficiency and catalytic performance, CWs can be applied to photothermal-catalytic cancer therapy under near-infrared region (NIR) light irradiation. We believe this work will contribute to understanding the catalytic mechanism of carbon-based nanozymes and promote the development of new biomedical and pharmaceutical applications.
The high specific capacity and low negative electrochemical potential of lithium metal anodes (LMAs), may allow the energy density threshold of Li metal batteries (LMBs) to be pushed higher. However, the existing detrimental issues, such as dendritic growth and volume expansion, have hindered the practical implementation of LMBs. Introducing three-dimensional frameworks (e.g., copper and nickel foam), have been regarded as one of the fundamental strategies to reduce the local current density, aiming to extend the Sand' time. Nevertheless, the local environment far from the skeleton is almost the same as the typical plane Li, due to macroporous space of metal foam. Herein, we built a double-layered 3D current collector of Li alloy anchored on the metal foam, with micropores interconnected macropores, via a viable thermal infiltration and cooling strategy. Due to the excellent electronic and ionic conductivity coupled with favorable lithiophilicity, the Li alloy can effectively reduce the nucleation barrier and enhance the Li+ transportation rate, while the metal foam can role as the primary promotor to enlarge the surface area and buffer the dimensional variation. Synergistically, the Li composite anode with hierarchical structure of primary and secondary scaffolds realized the even deposition behavior and minimum volume expansion, outputting preeminent prolonged cycling performances under high rate.
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