Highly Recyclable and Tough Elastic Vitrimers from a Defined Polydimethylsiloxane Network

Despite intensive research on sustainable elastomers, achieving elastic vitrimers with significantly improved mechanical properties and recyclability remains a scientific challenge. Herein, inspired by the classical elasticity theory, we present a design principle for ultra-tough and highly recyclable elastic vitrimers with a defined network constructed by chemically crosslinking the pre-synthesized disulfide-containing polydimethylsiloxane (PDMS) chains with tetra-arm polyethylene glycol (PEG). The defined network is achieved by the reduced dangling short chains and the relatively uniform molecular weight of network strands. Such elastic vitrimers with the defined network, i.e., PDMS-disulfide-D, exhibit significantly improved mechanical performance than random analogous, previously reported PDMS vitrimers, and even commercial silicone-based thermosets. Moreover, unlike the vitrimers with random network that show obvious loss in mechanical properties after recycling, those with the defined network enable excellent thermal recyclability. The PDMS-disulfide-D also deliver comparable electrochemical signals if utilized as substrates for electromyography sensors after the recycling. The multiple relaxation processes are revealed via a unique physical approach. Multiple techniques are also applied to unravel the microscopic mechanism of the excellent mechanical performance and recyclability of such defined network.     

Visible-Light-Driven Three-Component Reaction of Unactivated Alkenes Enables Access to Monofluoro γ-Amino Acids

A strategy for the synthesis of diverse protected α-monofluoro-γ-amino acid derivatives has been developed. This reaction assembles a simple enamide, quinoxalin-2(1H)-one, and diethyl 2-bromo-2-fluoromalonate through a three-component reaction driven by visible light. The advantages of this protocol include the simplicity of its operation, mild conditions, high functional group tolerance, and applicability to a wide variety of substrates. The synthesis of this fluorine-containing amino acid derivative has significant value for potential applications in medicinal chemistry and chemical biology.     

Fe-Doped CoS2 Nanoarrays: Efficient Electrocatalytic Nitrate Reduction to Ammonia under Ambient Conditions

The electrocatalytic nitrate reduction reaction (NO₃⁻RR) enables the reduction of nitrate to ammonium ions under ambient conditions. It was considered as an alternative reaction for the production of ammonia (NH₃) in recent years. In this paper, we report that the Fe doping CoS₂ nanoarrays can effectively catalyze the formation of NH₃ from nitrate (NO₃⁻) under ambient conditions. This is mainly due to the increase of the NO₃⁻ reaction active site by Fe doping and the porous nanostructure of the catalyst, which greatly improves the catalytic activity. Specifically, at −0.9 V vs. RHE, the NH₃ yield rate (R_NH3) of Fe−CoS₂/CC is 17.8×10⁻² mmol h⁻¹ cm⁻² with Faraday Efficiency (FE) of 88.93 %. Besides, such catalyst shows good durability and catalytic stability, which provides the possibility for the future application of electrocatalytic NH₃ production.     

Cellulose nanofibrils derived from pulp as a high performance separator for lithium-ion batteries

Cellulose nanofibrils (CNFs) from hardwood bleached kraft pulp (HwBKP) are produced via enzymatic, chemical, and mechanical treatment. A nanoporous structured CNF-based separator is produced, and the electrochemical performance, morphology, and thermal stability analyses are performed in comparison to the commercial polyethylene separator. The results obtained show that the electrolyte-philic CNF separator has capacity retention of 88.6% over 200 cycles and very good ionic conductivity and wettability results due to its high hydrophilic nature. At 140°C, the CNF separator was resilient to heat and remained intact. The CNF separator reflects high thermal resistance and good electrolyte uptake properties that are among the mandatory requirements of a separator hence, a promising contender for use in lithium-ion batteries.     

Positively charged liposomes consisting of the KTTKS pentapeptide conjugated with rhodamine increase rhodamine toxicity in E. coli and zebrafish embryo

Liposomes composed of cell‐penetrating peptide derivatives increased transport across the cell membrane. Conjugating rhodamine to a cell‐penetrating peptide increased the toxicity of rhodamine in E. coli and zebrafish embryos. A similar total protein inhibition pattern with different intensities, indicating that the interaction pathways of the rho‐KTTKS‐CONH₂ monomer and liposomes were the same. It suggests that the rho‐KTTKS‐CONH₂ liposomes showed higher toxicity because better transport across the cell membrane increased the effective concentration inside cells. The staining of zebrafish embryos using rho‐KTTKS‐CONH₂ liposomes showed a longer retention time, suggesting that it can penetrate deeper tissues or organs in zebrafish.     

DNA G-四链体的结构完整性对催化性质的影响

DNA酶中的G-四链体-血红素(G4-hemin)DNA酶结构具有较高的设计性和化学稳定性,因此格外受研究者关注.G-平面作为辅酶因子hemin的结合位点,不仅提供大π平面与hemin结合,而且其平面上的G碱基还可以充当近端配位基团与hemin进行配位.因此,研究G-平面完整性在G4-DNA酶体系中的作用具有重要意义.本文设计了一系列含有空位的G4(G-vacancy,GV)及G-三链体,通过“鸟嘌呤类似物插入”策略实现G-平面完整性以及DNA酶催化活性的恢复.结果表明,末端G-平面完整性是G4-DNA酶具有催化活性的必要条件,且其能够充当近端配位基团与末端碱基协同激活G4-DNA酶.考虑到hemin会选择性地结合于G4的3’-端平面,本文以含有3’-端空位的G4以及G-三链体为模型进行DNA酶的构建.结果表明,相较于末端完整的G4-hemin DNA酶,末端不完整的G4结构所形成的DNA酶催化活性很低.为了进一步验证该平面完整性的重要性,本文提出了“鸟嘌呤衍生物插入”策略,即将鸟嘌呤衍生物(无环鸟苷和鸟苷)插入G-空位以恢复G-平面的完整性.通过圆二色光谱和紫外熔解实验,发现末端平面完整性的缺失会使圆二色特征峰信号和G4结构热稳定性下降,而鸟嘌呤碱基类似物的加入则可以使特征峰信号以及热稳定性得到一定程度的恢复,表明鸟嘌呤碱基类似物的加入确实使G-平面完整性得到恢复.与此同时,随着鸟嘌呤碱基类似物浓度的增加,G4-hemin DNA酶活性逐渐增强,最终恢复至与完整G4一样的活性.在以G-三链体为模型的实验中,本文通过另一条富G序列与G-三链体进行结合,形成复合的(3+1)型G4结构,最终实现了DNA酶活性的恢复.同时,在3’-G-平面末端增加了激活碱基(dA或dTC),结果表明,即使G-平面不完整,末端碱基依旧能够激活DNA酶,但酶活性整体弱于完整G4时的活性.同样,“鸟嘌呤衍生物插入”策略可以使酶活性得到恢复.本文系列实验充分说明了末端碱基可与G-平面形成协同作用,与hemin的铁中心共同形成六配位关系,加速催化中间体生成,进而增强催化活性.有趣的是,通过设计Holliday junction结构研究发现,“鸟嘌呤衍生物插入”策略仅适用于平行G4结构.G-空位的存在不仅降低了G4结构的稳定性,而且降低了其与hemin间的亲和力,二者均是造成G4-DNA酶催化能力下降的主要因素.总之,本文证明了3’-端G-平面的完整性是G4-DNA酶实现其催化能力必不可少的因素,对理解末端G-平面在G4-DNA酶中的作用具有重要的参考意义.     

Combinatorial Therapeutic Effect of Inhibitors of Aldehyde Dehydrogenase and Mitochondrial Complex I,and the Chemotherapeutic Drug,Temozolomide against Glioblastoma Tumorspheres

Resident cancer cells with stem cell-like features induce drug tolerance, facilitating survival of glioblastoma (GBM). We previously showed that strategies targeting tumor bioenergetics present a novel emerging avenue for treatment of GBM. The objective of this study was to enhance the therapeutic effects of dual inhibition of tumor bioenergetics by combination of gossypol, an aldehyde dehydrogenase inhibitor, and phenformin, a biguanide compound that depletes oxidative phosphorylation, with the chemotherapeutic drug, temozolomide (TMZ), to block proliferation, stemness, and invasiveness of GBM tumorspheres (TSs). Combination therapy with gossypol, phenformin, and TMZ induced a significant reduction in ATP levels, cell viability, stemness, and invasiveness compared to TMZ monotherapy and dual therapy with gossypol and phenformin. Analysis of differentially expressed genes revealed up-regulation of genes involved in programmed cell death, autophagy, and protein metabolism and down-regulation of those associated with cell metabolism, cycle, and adhesion. Combination of TMZ with dual inhibitors of tumor bioenergetics may, therefore, present an effective strategy against GBM by enhancing therapeutic effects through multiple mechanisms of action.     

Upgrading Solid Digestate from Anaerobic Digestion of Agricultural Waste as Performance Enhancer for Starch-Based Mulching Biofilm

Developing a green and sustainable method to upgrade biogas wastes into high value-added products is attracting more and more public attention. The application of solid residues as a performance enhancer in the manufacture of biofilms is a prospective way to replace conventional plastic based on fossil fuel. In this work, solid digestates from the anaerobic digestion of agricultural wastes, such as straw, cattle and chicken manures, were pretreated by an ultrasonic thermo-alkaline treatment to remove the nonfunctional compositions and then incorporated in plasticized starch paste to prepare mulching biofilms by the solution casting method. The results indicated that solid digestate particles dispersed homogenously in the starch matrix and gradually aggregated under the action of a hydrogen bond, leading to a transformation of the composites to a high crystalline structure. Consequently, the composite biofilm showed a higher tensile strength, elastic modulus, glass transition temperature and degradation temperature compared to the pure starch-based film. The light, water and GHG (greenhouse gas) barrier properties of the biofilm were also reinforced by the addition of solid digestates, performing well in sustaining the soil quality and minimizing N₂O or CH₄ emissions. As such, recycling solid digestates into a biodegradable plastic substitute not only creates a new business opportunity by producing high-performance biofilms but also reduces the environmental risk caused by biogas waste and plastics pollution.     

KIT-6负载CeO2催化CO2和甲醇合成碳酸二甲酯

采用不同老化温度(80、100、120和150℃)合成了一系列KIT-6载体,并通过浸渍法制备了相应的CeO_2/KIT-6催化剂。结合X射线衍射、N_2物理吸附、NH_3程序升温脱附、CO_2程序升温脱附、透射电子显微镜、傅里叶变换红外光谱和X射线光电子能谱等表征结果,详细考察了老化温度对KIT-6结构以及CeO_2/KIT-6催化剂直接催化CO_2和甲醇合成碳酸二甲酯(DMC)反应活性的影响。结果表明,不同老化温度下制备的KIT-6均保持其独特的三维孔道结构。随着老化温度升高,KIT-6比表面积先增大后减小,当老化温度为100℃时,KIT-6比表面积达到最大(683 m~2·g~(-1))。KIT-6较高的比表面积有利于提高CeO_2分散度,进而提高暴露的活性位点数量,催化活性随催化剂表面中等碱/酸性吸附位数量和Ce~(3+)含量的增加而逐渐提高。其中,CeO_2/100-KIT-6催化剂中CeO_2颗粒尺寸最小(5.9 nm),暴露的活性位数量最高,催化活性最佳。随后,考察了反应温度和压力对CeO_2/100-KIT-6催化活性的影响。随着反应温度提高,催化活性先升高后降低,当反应温度为140℃时,催化活性最高;且催化活性随反应压力的提高而逐渐增加。在反应温度为140℃、压力为6.8 MPa条件下,催化剂经6次循环后,DMC收率由15 mmol·g_(CeO_2)~(-1)逐渐降低至2.8 mmol·g_(CeO_2)~(-1),原因归结为反应过程中CeO_2纳米颗粒发生团聚,使暴露出的活性位数量减少。     

Mixing of Racemic Poly(L-lactide)/Poly(D-lactide) Blend with Miscible Poly(D,L-lactide):Toward All Stereocomplex-type Polylactide with Strikingly Enhanced SC Crystallizability

Stereocomplex-type polylactide (SC-PLA) consisting of alternatively arranged poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) chains has gained a good reputation as a sustainable engineering plastic with outstanding heat resistance and durability,however its practical applications have been considerably hindered by the weak SC crystallizability.Current methods used to enhance the SC crystallizability are generally achieved at the expense of the precious bio-renewability and/or bio-degradability of PLAs.Herein,we demonstrate a feasible method to address these challenges by incorporating small amounts of poly(D,L-lactide) (PDLLA) into linear high-molecular-weight PLLA/PDLA blends.The results show that the incorporation of the atactic PDLLA leads to a significant enhancement in the SC crystallizability because its good miscibility with the isotactic PLAs makes it possible to greatly improve the chain mixing between PLLA and PDLA as an effective compatibilizer.Meanwhile,the melt stability (i.e.,the stability of PLLA/PDLA chain assemblies upon melting) could also be improved substantially.Very intriguingly,SC crystallites are predominantly formed with increasing content and molecular weight of PDLLA.More notably,exclusive SC crystallization can be obtained in the racemic blends with 20 wt％ PDLLA having weight-average molecular weight of above 1 ×10s g/mol,where the chain mixing level and intermolecular interactions between the PLA enantiomers could be strikingly enhanced.Overall,our work could not only open a promising horizon for the development of all SC-PLA-based engineering plastic with exceptional SC crystallizability but also give a fundamental insight into the crucial role of PDLLA in improving the SC crystallizability of PLLA/PDLA blends.