Trigoxyphins O–T,six new heterodimers from Trigonostemon xyphophylloides

Phytochemical study of the twigs of Trigonostemon xyphophylloides led to the isolation of six new heterodimers, trigoxyphins O (1) and R–T (4–6) comprising of two different degraded diterpenoids, and trigoxyphins P (2) and Q (3) comprising a degraded diterpenoid and a phenylpropanoid, together with a known homodimer, neoboutomannin (7). The structures and relative configurations were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D NMR experiments. Compounds 1–6 were evaluated for their cytotoxicity against four human tumour cell lines by MTT assay.     

Ultrasensitive electrochemical immunosensor for zeranol detection based on signal amplification strategy of nanoporous gold films and nano-montmorillonite as labels

Nano-montmorillonites belong to aluminosilicate clay minerals with innocuity, high specific surface area, ion exchange, and favorable adsorption property. Due to the excellent properties, montmorillonites can be used as labels for the electrochemical immunosensors. In this study, nano-montmorillonites were converted to sodium montmorillonites (Na-Mont) and further utilized for the immobilization of thionine (TH), horseradish peroxidase (HRP) and the secondary anti-zeranol antibody (Ab₂). The modified particles, Na-Mont-TH-HRP-Ab₂ were used as labels for immunosensors to detect zeranol. This protocol was used to prepare the immunosensor with the primary antibody (Ab₁) immobilized onto the nanoporous gold films (NPG) modified glassy carbon electrode (GCE) surface. Within zeranol concentration range (0.01–12 ng mL⁻¹), a linear calibration plot (Y = 0.4326 + 8.713 X, r = 0.9996) was obtained with a detection limit of 3 pg mL⁻¹ under optimal conditions. The proposed immunosensor showed good reproducibility, selectivity, and stability. This new type of immunosensors with montmorillonites and NPG as labels may provide potential applications for the detection of zeranol.     

Morphology-controlled electrochemical sensing amaranth at nanomolar levels using alumina

Different-shaped aluminas were readily prepared via hydrothermal reaction. It was found that the morphology and the electrochemical sensing properties of alumina were heavily dependent on the reaction time. When extending the reaction time from 6 h to 24 h, the obtained alumina samples changed from amorphous bumps to regular microfibers in diameter of 200 nm, as confirmed by scanning electron microscopy. Transmission electron microscopy observation revealed that longer reaction time was beneficial for the formation of porous and uniform fiber-like structures. Electrochemical tests proved that alumina microfibers were more active for the oxidation of amaranth and exhibited much higher enhancement effect, compared with alumina bumps. On the surface of alumina microfibers, the oxidation peak currents of amaranth increased remarkably. The influences of pH value, amount of alumina microfibers, and accumulation time on the signal enhancement of amaranth were discussed. As a result, a novel electrochemical method was developed for the detection of amaranth. The linear range was from 1 to 150 nM, and the detection limit was 0.75 nM after 1-min accumulation. The analytical application in drink samples was investigated, and the results consisted with the values that obtained by high-performance liquid chromatography.     

Droplet-based microfluidics for dose–response assay of enzyme inhibitors by electrochemical method

A simple but robust droplet-based microfluidic system was developed for dose–response enzyme inhibition assay by combining concentration gradient generation method with electrochemical detection method. A slotted-vials array and a tapered tip capillary were used for reagents introduction and concentration gradient generation, and a polydimethylsiloxane (PDMS) microfluidic chip integrated with microelectrodes was used for droplet generation and electrochemical detection. Effects of oil flow rate and surfactant on electrochemical sensing were investigated. This system was validated by measuring dose–response curves of three types of acetylcholinesterase (AChE) inhibitors, including carbamate pesticide, organophosphorus pesticide, and therapeutic drugs regulating Alzheimer's disease. Carbaryl, chlorpyrifos, and tacrine were used as model analytes, respectively, and their IC₅₀ (half maximal inhibitory concentration) values were determined. A whole enzyme inhibition assay was completed in 6 min, and the total consumption of reagents was less than 5 μL. This microfluidic system is applicable to many biochemical reactions, such as drug screening and kinetic studies, as long as one of the reactants or products is electrochemically active.     

双核烷基咪唑过氧磷钨酸盐相转移催化剂合成及催化烯烃环氧化性能

合成并表征了一类双核长链烷基咪唑阳离子修饰的过氧磷钨杂多酸盐催化剂[Dnmin]1.5PW4O24,考察了催化剂在过氧化氢为氧源的烯烃环氧化反应中的催化活性.研究表明,这类催化剂在反应过程中表现出相转移催化现象,并具有较高的催化活性和选择性.其中,双核十二烷基咪唑杂多酸盐催化剂[D12min]1.5PW4O24的活性最佳,其环己烯转化率和环氧环己烷选择性分别达到97.7%和96.3%.催化剂在经过简单离心分离后可重复使用,重复使用4次后环己烯转化率和环氧环己烷选择性仍可分别达到72.4%和97.2%.催化剂[D12min]1.5PW4O24在其它几种烯烃的环氧化反应中均表现出相转移催化特性,且具有较高的催化活性.     

新型磺酸盐型Gemini表面活性剂的合成及其与聚合物相互作用

以溴代正烷烃、乙二胺、1,3-丙磺内酯合成了一系列新型磺酸盐型Gemini表面活性剂(SGS-8、SGS-10、SGS-12、SGS-14);采用IR、1H NMR及元素分析等手段对合成产物进行结构表征,并研究了其表面活性,采用等温滴定微量热技术、表面张力法和稳态荧光光谱法研究了SGS-12与聚丙烯酰胺(PAM)的相互作用规律及热力学参数。结果表明,合成的产物纯度较高,具有较低的cmc值和较好的表面活性;SGS-12/PAM混合体系的表面张力曲线和芘探针在体系中微极性的变化表明,二者发生相互作用且形成混合胶束;SGS-12与PAM结合是一个由焓驱动的自发过程,△H和△S均小于0,表明相互作用力以氢键和范德华力为主,合成产物在聚丙烯酰胺分子上的平均结合数为287。     

聚苯胺/醋酸纤维素复合膜的制备及其超级电容特性

通过电化学原位聚合法制备多孔网状结构的聚苯胺(PANI)/醋酸纤维素(CA)复合膜电极,该复合膜的内层(与电极接触的一面)呈墨绿色,外层呈白色。采用原子力显微镜(AFM)、扫描电镜(SEM)、红外光谱(FTIR)对其形貌和化学组成进行表征。通过循环伏安、恒电流充放电和电化学阻抗研究了复合膜电极的超级电容特性。结果表明,多孔网状结构的PANI/CA复合材料具有良好的电容性能,其比电容可达到410F/g,并且该超级电容器具有较小的内阻和较好的循环稳定性,300次循环后,容量仍维持在342F/g,比电容的保持率为83.4%。     

Facile Fabrication of Nanorod‐Assembled Fluorine‐Substituted Hydroxyapatite (FHA) Microspheres

Nanorod‐assembled FHA microspheres with different F contents were for the first time prepared through a facile one‐step hydrothermal method. The effect of the reaction time and pH value of reaction solutions on the FHA morphology was investigated to elucidate the self‐assembly process of FHA microspheres. The results showed pH values had significant effect on the morphology of the formed FHA crystals, which were self‐assembled into sphere‐like sturctures at high pH conditions and rod‐like structures at low pH values. The results suggested that formation of FHA crystals with varied morphology may be directly related to Ca²⁺ release kinetics from EDTA‐Ca‐Na₂ at different pH conditions. Furthermore, it was found that the chemical stability of FHA microspheres was dependent on the F content in the materials, and high F contents in FHA microspheres lead to improved chemical stability. These results suggest that the prepared self‐assembled FHA microspheres may be used for teeth substitution materials due to their unique hierarchical structures and controllable chemical stability.