Molecular‐Level Insights into Intrinsic Peroxidase‐Like Activity of Nanocarbon Oxides

Nanocarbon oxides have been proved to possess great peroxidase‐like activity, catalyzing the oxidation of many peroxidase substrates, such as 3,3′,5,5′‐tetramethylbenzidine (TMB) and o‐phenylenediamine dihydrochloride (OPD), accompanied by a significant color change. This chromogenic reaction is widely used to detect glucose and occult blood. The chromogenic reaction was intensively investigated with density functional theory and molecular‐level insights into the nature of peroxidase‐like activity were gained. A radical mechanism was unraveled and the carboxyl groups of nanocarbon oxides were identified as the reactive sites. Aromatic domains connected with the carboxyl groups were critical to the peroxidase‐like activity.     

Enhanced Peroxidase‐Like Properties of Graphene–Hemin‐Composite Decorated with Au Nanoflowers as Electrochemical Aptamer Biosensor for the Detection of K562 Leukemia Cancer Cells

Graphene composites with hemin and gold nanoparticles show a better performance for hydrogen peroxide decomposition compared to that of the three components alone or duplex/hybrid complexes. Our previous studies showed that the morphology of the Au nanoparticles may greatly influence the catalytic activity of graphene‐family peroxidase mimics. Recently, we found that Au nanoflowers could grow in situ and form on the surface of hemin/RGO (reduced graphene oxide). The prickly morphology of this Au nanoflower brought a higher catalytic ability with enhanced kinetic parameters than traditional Au nanoparticles that showed a smooth surface. Therefore, based on this discovery, a smart electrochemical aptamer biosensor for K562 leukemia cancer cells was further presented with good performance in selectivity and sensitivity attributed to the excellent mimetic peroxidase catalytic activity of this newly synthesized Au nanoflower decorated graphene–hemin composite (H‐RGO‐Au NFs).     

Liposome-Boosted Peroxidase-Mimicking Nanozymes Breaking the pH Limit

Peroxidase-mimicking nanozymes such as Fe₃O₄ nanoparticles are promising substitutes for natural enzymes like horseradish peroxidase. However, most such nanozymes work efficiently only in acidic conditions. In this work, the influence of various liposomes on nanozyme activity was studied. By introducing negatively charged liposomes, peroxidase-mimicking nanozymes achieved oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in neutral and even alkaline conditions, although the activity towards anionic 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) was inhibited. The Fe₃O₄ nanoparticles adsorbed on the liposomes without disrupting membrane integrity as confirmed by fluorescence quenching, dye leakage assays, and cryo-electron microscopy. Stabilization of the blue-colored oxidized products of TMB by electrostatic interactions was believed to be the reason for the enhanced activity. This work has introduced lipids to nanozyme research, and it also has practically important applications for using nanozymes at neutral pH, such as the detection of hydrogen peroxide and glucose.     

基于捕集柱阵列的制备型二维液相色谱纯化烟草中的4个组分

二维液相色谱(2D-LC)因具有较高的峰容量,在复杂样品的分离分析中获得了广泛的关注。然而,制备型2D-LC以纯化高纯单体为目标,在方法开发和设备构成等方面与分析型2D-LC有较大的不同,目前尚未得到充分的开发,在大规模的制备纯化中应用较少。本文以一套制备液相色谱模块为分离系统,以稀释泵、切换阀和捕集柱阵列为接口,构建了新型的制备型2D-LC系统,旨在规模化纯化多个活性成分。以烟叶中可以用作医药原料的烟碱、绿原酸、芦丁和茄尼醇等组分为目标物,考察了不同类型填料对样品的捕集效率、过载条件下的色谱保留行为等,优化了制备色谱条件。进而利用在线2D-LC系统实现了烟叶提取物的纯化,通过一次运行获得了4个高纯化合物。该系统具有中压色谱纯化成本低、系统在线运行自动化程度高、稳定性好及容易放大等优点。烟叶中活性化学成分的回收利用对促进烟草行业的发展及带动地方农业经济开发具有重大的意义。     

基于羧基化聚吡咯-氯化血红素和点触发链置换反应信号放大的电化学生物传感器检测转基因作物中CaMV35S序列

为适应快速增长的转基因生物(GMOs)安全评价与管理的需求,高效、可靠的转基因检测技术研究与应用的重要性日益凸显。该文采用一步法合成了羧基化聚吡咯(cPPy)与氯化血红素(Hemin)的纳米复合物(cPPy-hemin),并以其为信号标签合成了一种DNA双链结构功能化的纳米信标(DNA-cPPy-hemin)。利用cPPy-hemin增强的模拟酶催化活性,结合点触发链置换反应(TSDR)信号放大策略,制备了一种新型电化学基因传感器用于转基因成分的灵敏检测。通过信号探针(Ps)与模板链(Ts)、辅助链(As)结合形成DNA双链体结构中的-NH2功能化cPPy-hemin,制备Ts/As/Ps-cPPy-hemin双链DNA结构的纳米信标。在目标花椰菜花叶病毒35S启动子(CaMV35S)序列和燃料链(Fs)存在下,TSDR过程释放出的Ps-cPPy-hemin与固定在电化学沉积金纳米粒子修饰GCE表面上巯基化的DNA捕获探针(Cs)相结合,利用cPPy-hemin对H₂O₂的模拟酶催化产生的电信号,可实现对CaMV35S的定量检测。在最优条件下...     

Immunoassay based on peroxidase silver conjugate for the determination of human immunoglobulins against tick-borne borreliosis (lyme disease) by voltammetry and spectrophotometry

In this work two strategies for the synthesis of peroxidase silver conjugates for the qualitative and quantitative determination of immunoglobulins (IgG) to ixodid tick-borne borreliosis (ITBB) (Lyme disease) in human serum were proposed. The first approach for Ab-HRP@AgNP conjugate synthesis involved silver nanoparticles (Ag NPs) capped with a commercial peroxidase conjugate (Ab-HRP) by passive adsorption. The second strategy was based on the initial coupling of Ag NPs with human anti-species antibodies (Ab) by passive adsorption followed by the introduction of horseradish peroxidase (HRP) enzyme into the reaction mixture as a blocking reagent for Ab@AgNP@HRP conjugate synthesis. The formation of peroxidase silver conjugates was proved by UV/Vis spectroscopy and Transmission Electron Microscopy (TEM). The catalytic activity of Ab-HRP@AgNP and Ab@AgNP@HRP conjugates was evaluated by Michaelis-Menten kinetics. A commercially available 96-well microtiter plate with recombinant antigens to ITBB was used as a platform for immobilization of analyzed IgG. The HRP in Ab-HRP@AgNP conjugate was found to retain a sufficient level of activity for interaction with the H₂O₂ substrate to form an intensely colored reaction product. Therefore Ab-HRP@AgNP conjugate can be used in enzyme-linked immunosorbent assay (ELISA) with spectrophotometric detection of 3,3’,5,5’-Tetramethylbenzidine (TMB Ox) for quantitative determination of IgG to ITBB in human serum in the concentration range 12.5–800 ng ml⁻¹ with LOD 2 ng ml⁻¹. Ab@AgNP@HRP conjugate is recommended for the electrochemical determination of IgG to ITBB in human serum at LOD 3 ng ml⁻¹ with registration of silver oxidation by linear sweep anodic stripping voltammetry (LSASV). Ag NPs in Ab-HRP@AgNP and Ab@AgNP@HRP conjugates do not change electrochemical activity during storage and can be used as an electrochemical label in LSASV method in case of HRP inactivation. The immunoassay based on peroxidase silver conjugates expands the analytical potential for the determination of IgG to ITBB especially during the period of increasing incidence.     

Separation,identification, and structural characterization of sucrose ester isomers from tobacco

Sucrose esters (SEs) are crucial tobacco smoke flavor precursors and play a significant role in tobacco's functionality. Due to their structural complexity, the separation and analysis of SEs in tobacco remain a major challenge, and massive structures of SEs have not yet been fully identified. In this study, the fractions enriched in SEs were obtained from oriental and flue-cured tobacco through a series of pretreatments, and two types of SEs (Types I and II) were distinguished by liquid chromatography-tandem mass spectrometry (LC-MSⁿ) analysis, with Type II SEs newly characterized in tobacco. Five groups of main SEs were further purified using preparative high-performance LC (HPLC) coupled to an evaporative light scattering detector, and their structures were characterized by nuclear magnetic resonance spectrometry techniques including ¹H, ¹³C, correlation spectroscopy, heteronuclear single quantum correlation, and heteronuclear multiple bond correlation. By combining LC-MSⁿ and nuclear magnetic resonance spectrometry, the structures of eight SE isomers were finally proposed, of which four were newly identified. These findings further enhance the understanding of the structural diversity of SEs in tobacco, serving as a valuable reference for future research on the elucidation, synthesis, and metabolism of SEs.     

离子色谱法测定电子烟烟液中氨的含量

建立了测定电子烟烟液中的氨含量离子色谱法。样品经10 mol·L-1盐酸溶液萃取10 min后,采用Dionex Ion Pac CS16A阳离子交换柱分离,以MSA为淋洗液进梯度洗脱,用电化学检测器检测。氨的质量浓度在0.05~1.0 mg·L-1范围内与峰面积呈线性关系,检出限(3S/N)为0.035μg·g-1,测定下限(10S/N)为0.12μg·g-1。方法用于12种市售品牌电子烟烟液中氨的测定,加标回收率在93.2%~106%之间,测定值的相对标准偏差(n=5)小于4%。     

不同微波膨胀烟梗的化学感官特性研究

研究不同来源包括产地、部位、年份、品种的烟梗原料经相同的微波膨胀工艺处理后的常规化学成分、致香成分、主流烟气(主要包括抽吸口数、焦油、烟碱及一氧化碳释放量)及感官特性差异,指导微波膨胀梗丝在产品中的配伍应用,为建立不同来源微波膨胀梗原料的品质特征评价体系及微波膨胀梗丝的工业应用提供依据。结果表明:不同产地来源的微波膨胀梗丝常规化学成分、致香成分、主流烟气存在差异。不同年份的微波膨胀梗丝间感官质量无明显差异,不同产地、品种、部位来源的微波膨胀梗丝总体感官质量存在差异。