层层自组装纳米金与乙酰胆碱酯酶电化学生物传感器检测有机磷农药

采用层层自组装技术制备了快速检测有机磷农药的生物传感器,利用带正电荷的高分子聚电解质聚二烯丙基二甲基氯化铵(PDDA)将乙酰胆碱酯酶(AChE)和金纳米粒子(AuNPs)通过静电力逐层固定到玻碳电极(GCE)表面,并采用交流阻抗和微分脉冲伏安法研究了此生物传感器的电化学行为。由于金纳米粒子优异的电催化性能和良好的生物相容性,使固定化的乙酰胆碱酯酶对其底物具有更高的亲和力和更快的响应速度。实验结果表明:修饰金纳米粒子后,传感器的氧化电流明显增大,在4.6×10-5～5.3×10-3mol/L范围内,固定化酶的抑制率与甲基对硫磷浓度的对数成正比,检出限为7.6×10-6mol/L。该生物传感器具有制备方法简便、成本低、灵敏度高等优点,已成功用于蔬菜样品中甲基对硫磷含量的测定。     

Acetylcholinesterase Sensor Based on Polyelectrolyte Complexes with DNA Inclusion for the Determination of Reversible Inhibitors

The acetylcholinesterase (AChE) biosensor has been developed for the determination of reversible inhibitors applied in the Alzheimer's disease therapy, i. e., Huperzine A (HupA) and galantamine (Gal). For this purpose, glassy carbon electrode (GCE) was first modified with carbon black (CB) and Co phthalocyanine and then polyelectrolyte complex was self‐assembled on its surface by drop casting of reactants and washing. To extend the stability and improve biosensor performance, it was proposed for the first time to use DNA as polyanion in the complex assembly. The DNA showed higher charge density than conventional polyelectrolytes and stabilized the surface coating by adsorption of higher enzyme amount and prevention of its leaching during the biosensor operation. Complex formation and the influence of structural factors were monitored with surface plasmon resonance. Kinetic study showed mixed inhibition of the enzyme within micro‐ and nanomolar range of inhibitor concentrations. The AChE biosensor showed limit of detection of HupA equal to 0.9 and that of Gal to 70 nM. The sensitivity of drug determination was found to be close or better than that of the AChE biosensors previously reported in the literature. The biosensor was tested on the sample of artificial urine and showed 102 % recovery of the drugs determination.     

Virtual Screening and Hit Selection of Natural Compounds as Acetylcholinesterase Inhibitors

Acetylcholinesterase (AChE) is one of the classical targets in the treatment of Alzheimer’s disease (AD). Inhibition of AChE slows down the hydrolysis of acetycholine and increases choline levels, improving the cognitive function. The achieved success of plant-based natural drugs acting as AChE inhibitors, such as galantamine (GAL) from Galanthus genus and huperzine A from Huperzia serrate (approved drug in China), in the treatment of AD, and the fact that natural compounds (NCs) are considered as safer and less toxic compared to synthetic drugs, led us to screen the available NCs (almost 150,000) in the ZINC12 database for AChE inhibitory activity. The compounds were screened virtually by molecular docking, filtered for suitable ADME properties, and 32 ligands from 23 structural groups were selected. The stability of the complexes was estimated via 1 μs molecular dynamics simulation. Ten compounds formed stable complexes with the enzyme and had a vendor and a reasonable price per mg. They were tested for AChE inhibitory and antioxidant activity. Five compounds showed weak AChE inhibition and three of them exhibited high antioxidant activity.     

Calix[4]arene‐Functionalised Silver Nanoparticles as Hosts for Pyridinium‐Loaded Gold Nanoparticles as Guests

A series of lipophilic gold nanoparticles (AuNPs) circa 5 nm in diameter and having a mixed organic layer consisting of 1‐dodecanethiol and 1‐(11‐mercaptoundecyl) pyridinium bromide was synthesised by reacting tetraoctylammonium bromide stabilised AuNPs in toluene with different mixtures of the two thiolate ligands. A bidentate ω‐alkylthiolate calix[4]arene derivative was instead used as a functional protecting layer on AgNPs of approximately 3 nm. The functionalised nanoparticles were characterised by transmission electron microscopy (TEM), and by UV/Vis and X‐ray photoelectron spectroscopy (XPS). Recognition of the pyridinium moieties loaded on the AuNPs by the calix[4]arene units immobilised on the AgNPs was demonstrated in solution of weakly polar solvents by UV/Vis titrations and DLS measurements. The extent of Au‐AgNPs aggregation, shown through the low‐energy shift of their surface plasmon bands (SPB), was strongly dependent on the loading of the pyridinium moieties present in the organic layer of the AuNPs. Extensive aggregation between dodecanethiol‐capped AuNPs and the Ag calix[4]arene‐functionalised NPs was also promoted by the action of a simple N‐octyl pyridinium difunctional supramolecular linker. This linker can interdigitate through its long fatty tail in the organic layer of the dodecanethiol‐capped AuNPs, and simultaneously interact through its pyridinium moiety with the calix[4]arene units at the surface of the modified AgNPs.     

基于聚多巴胺纳米粒子的荧光增强型探针检测乙酰胆碱酶

以多巴胺盐酸盐为原料,在碱性条件下通过氧化反应制备聚多巴胺荧光纳米粒子(F-PDA),再与二氧化锰(MnO_2)纳米片进行复合,构建了用于检测乙酰胆碱酶(AChE)的F-PDA@MnO_2复合物荧光探针。MnO_2纳米片和F-PDA复合,体系的荧光被猝灭。在底物乙酰硫代胆碱(ATCh)存在下,加入AChE后,体系荧光恢复,恢复程度与AChE浓度在5.0～100 mU/mL范围内呈良好的线性关系,检出限为0.14 mU/mL(S/N=3)。该方法用于缓冲溶液中AChE的检测,加标回收率为89.5%～120%,相对标准偏差为1.6%～2.5%,且具有较高的选择性。可为基于F-PDA传感体系构建提供新的方法学模型。     

Mechanism of Producing Metallic Nanoparticles,with an Emphasis on Silver and Gold Nanoparticles,Using Bottom-Up Methods

Bottom-up nanoparticle (NP) formation is assumed to begin with the reduction of the precursor metallic ions to form zero-valent atoms. Studies in which this assumption was made are reviewed. The standard reduction potential for the formation of aqueous metallic atoms—E⁰(Mⁿ⁺_aq/M⁰_aq)—is significantly lower than the usual standard reduction potential for reducing metallic ions Mⁿ⁺ in aqueous solution to a metal in solid state. E⁰(Mⁿ⁺_aq/M⁰_solid). E⁰(Mⁿ⁺_aq/M⁰_aq) values are negative for many typical metals, including Ag and Au, for which E⁰(Mⁿ⁺_aq/M⁰_solid) is positive. Therefore, many common moderate reduction agents that do not have significantly high negative reduction standard potentials (e.g., hydrogen, carbon monoxide, citrate, hydroxylamine, formaldehyde, ascorbate, squartic acid, and BH₄⁻), and cannot reduce the metallic cations to zero-valent atoms, indicating that the mechanism of NP production should be reconsidered. Both AgNP and AuNP formations were found to be multi-step processes that begin with the formation of clusters constructed from a skeleton of M⁺-M⁺ (M = Ag or Au) bonds that is followed by the reduction of a cation M⁺ in the cluster to M⁰, to form M_n⁰ via the formation of NPs. The plausibility of M⁺-M⁺ formation is reviewed. Studies that suggest a revised mechanism for the formation of AgNPs and AuNPs are also reviewed.     

Salivary Excretion of Renal-Clearable Silver Nanoparticles

Salivary elimination is an important pathway for the body to excrete small molecules with digestive enzymes. However, very few engineered nanoparticles can be excreted through salivary glands, which often host bacteria or viruses during infection and involve in disease transmission. Herein, we report that renal clearable glutathione coated AgNPs (GS-AgNPs) can selectively accumulate in the submandibular salivary gland, followed by being excreted in its excretory duct. By conducting head-to-head comparison on in vivo transport and interactions of both GS-AgNPs and glutathione coated gold nanoparticles (GS-AuNPs) with the same sizes, we found that low-density GS-AgNPs showed much higher vascular permeability than GS-AuNPs and can rapidly penetrate into submandibular salivary glands, be efficiently taken up by striated and excretory duct cells, and eventually secreted into saliva.     

Free Energy of Bare and Capped Gold Nanoparticles Permeating through a Lipid Bilayer

Herein, we study the permeation free energy of bare and octane‐thiol‐capped gold nanoparticles (AuNPs) translocating through a lipid membrane. To investigate this, we have pulled the bare and capped AuNPs from bulk water to the membrane interior and estimated the free energy cost. The adsorption of the bare AuNP on the bilayer surface is energetically favorable but further loading inside it requires energy. However, the estimated free‐energy barrier for loading the capped AuNP into the lipid membrane is much higher compared to bare AuNP. We also demonstrate the details of the permeation process of bare and capped AuNPs. Bare AuNP induces the curvature in the lipid membrane whereas capped AuNP creates an opening in the interacting monolayer and get inserted into the membrane. The insertion of capped AuNP induces a partial unzipping of the lipid bilayer, which results in the ordering of the local lipids interacting with the nanoparticle. However, bare AuNP disrupts the lipid membrane by pushing the lipid molecules inside the membrane. We also analyze pore formation due to the insertion of capped AuNP into the membrane, which results in water molecules penetrating the hydrophobic region.     

金粒子包封介孔二氧化硅杂化载药控释体系

靶向给药控释体系既可以增强药物在病灶部位的疗效, 又可以降低药物对正常部位的毒副作用. 基于介孔二氧化硅为"容器"-金纳米粒子为"开关"(MSN-AuNPs)的杂化纳米阀门体系同时具备两种纳米粒子的优良特性, 在化学、生物材料以及临床医药等多学科受到广泛关注. 本文根据刺激手段和应用功能分类, 介绍了单一功能和多重功能的MSN-AuNPs杂化纳米阀门体系的重要研究进展, 以及目前面临的挑战和今后的发展方向.     

Highly Sensitive Fluorometric Assay Method for Acetylcholinesterase Inhibitor Based on Nile Red‐Adsorbed Gold Nanoparticles

A new sensitive fluorometric assay method for acetylcholinesterase (AChE) and its inhibitor was developed using a fluorescent dye, nile red (NR). Due to the fluorescence resonance energy transfer between the NR and the gold nanoparticle (AuNPs), the fluorescence was quenched. AChE can break down acetylthiocholine to produce a thiol‐bearing compound, thiocholine. In the presence of thiocholine, the nile red is replaced from the AuNPs surfaces and simultaneously transformed to a derivative of nile red. The fluorescence intensity of the derivative is much stronger than that of the native nile red with the same concentration and its maximum emission wavelength has a blue shift so that the sensor achieves a good signal‐to‐background ratio. In addition, when organophosphate pesticide (OPs) exists, the activity of AChE can be inhibited, the generation of thiocholine will be prevented and no fluorescence enhancement occurs. The results show that the method is sensitive to AChE and paraoxon with the detection limits of 0.2 mU/mL and 0.05 ng/mL, respectively.     

Ferromagnetism Exhibited by Nanoparticles of Noble Metals

Gold nanoparticles with average diameters in the range 2.5–15 nm, prepared at the organic/aqueous interface by using tetrakis(hydroxymethyl)phosphonium chloride (THPC) as reducing agent, exhibit ferromagnetism whereby the saturation magnetization M_S increases with decreasing diameter and varies linearly with the fraction of surface atoms. The value of M_S is higher when the particles are present as a film instead of as a sol. Capping with strongly interacting ligands such as alkane thiols results in a higher M_S value, which varies with the strength of the metal–sulfur bond. Ferromagnetism is also found in Pt and Ag nanoparticles prepared as sols, and the M_S values vary as Pt>Au>Ag. A careful study of the temperature variation of the magnetization of Au nanoparticles, along with certain other observations, suggests that small bare nanoparticles of noble metals could indeed possess ferromagnetism, albeit weak, which is accentuated in the presence of capping agents, specially alkane thiols which form strong metal–sulfur bonds.     

油酸修饰PbO纳米微粒的合成及结构表征

利用表面修饰法合成了表面为油酸所修饰的PbO纳米微粒 ,并用红外光谱、X -射线光电子能谱、透射电子显微镜和热分析仪对产物的结构、形貌及化学状态及热稳定性进行了研究 .结果表明 :所制备的PbO纳米微粒大小均匀 ,粒径约为 5nm ,在有机溶剂及石蜡油中的分散性良好 ;表面修饰剂与纳米微粒表面之间发生化学键合作用 ,这使得PbO纳米微粒在有机溶剂及基础油中的分散性得以改善 ,并使得表面修饰层的热稳定性得以明显提高     

Acetylcholinesterase‐capped Mesoporous Silica Nanoparticles Controlled by the Presence of Inhibitors

Two different acetylcholinesterase (AChE)‐capped mesoporous silica nanoparticles (MSNs), S1‐AChE and S2‐AChE , were prepared and characterized. MSNs were loaded with rhodamine B and the external surface was functionalized with either pyridostigmine derivative P1 (to yield solid S1 ) or neostigmine derivative P2 (to obtain S2 ). The final capped materials were obtained by coordinating grafted P1 or P2 with AChE′s active sites (to give S1‐AChE and S2‐AChE , respectively). Both materials were able to release rhodamine B in the presence of diisopropylfluorophosphate (DFP) or neostigmine in a concentration‐dependent manner via the competitive displacement of AChE through DFP and neostigmine coordination with the AChE‘s active sites. The responses of S1‐AChE and S2‐AChE were also tested with other enzyme inhibitors and substrates. These studies suggest that S1‐AChE nanoparticles can be used for the selective detection of nerve agent simulant DFP and paraoxon.     

Galvanic Replacement Reactions of Active‐Metal Nanoparticles

We present a systemic investigation of a galvanic replacement technique in which active‐metal nanoparticles are used as sacrificial seeds. We found that different nanostructures can be controllably synthesized by varying the type of more noble‐metal ions and liquid medium. Specifically, nano‐heterostructures of noble metal (Ag, Au) or Cu nanocrystals on active‐metal (Mg, Zn) cores were obtained by the reaction of active‐metal nanoparticles with more noble‐metal ions in ethanol; Ag nanocrystal arrays were produced by the reaction of active‐metal nanoparticles with Ag⁺ ions in water; spongy Au nanospheres were generated by the reaction of active‐metal nanoparticles with AuCl₄^? ions in water; and SnO₂ nanoparticles were prepared when Sn²⁺ were used as the oxidant ions. The key factors determining the product morphology are shown to be the reactivity of the liquid medium and the nature of the oxidant–reductant couple, whereas Mg and Zn nanoparticles played similar roles in achieving various nanostructures. When microsized Mg and Zn particles were used as seeds in similar reactions, the products were mainly noble‐metal dendrites. The new approach proposed in this study expands the capability of the conventional nanoscale galvanic replacement method and provides new avenues to various structures, which are expected to have many potential applications in catalysis, optoelectronics, and biomedicine.     

Polyvinylpyrrolidone as an Efficient Stabilizer for Silver Nanoparticles

Aggregation of nanoparticles is a serious problem in their applications. In this article, stability of biosynthesized silver nanoparticles (AgNPs) was initially studied with different concentrations of sodium chloride (NaCl). Surfactant screening showed that polyvinylpyrrolidone (PVP) was an ideal stabilizer, which not only was effective at a low concentration (0.1%, V/V), but also could protect silver colloids from aggregation for a long period at 1 mol·L^?1 NaCl, and 6 h even at 3 mol·L^?1 NaCl. However, some other surfactants, such as sodium dodecyl (SDS), Triton X‐100, Tween‐20, and Tween‐80, could not prevent AgNPs from aggregation even at a high concentration up to 0.5% (V/V). This AgNPs stabilizer is simple and convenient for a variety of applications compared with others.     

Novel Uracil-Based Inhibitors of Acetylcholinesterase with Potency for Treating Memory Impairment in an Animal Model of Alzheimer’s Disease

Novel derivatives based on 6-methyluracil and condensed uracil, 2,4-quinazoline-2,4-dione, were synthesized with terminal meta- and para-benzoate moieties in polymethylene chains at the N atoms of the pyrimidine ring. In the synthesized compounds, the polymethylene chains were varied from having tris- to hexamethylene chains and quaternary ammonium groups; varying substituents (ester, salt, acid) at benzene ring were introduced into the chains and benzoate moieties. In vivo biological experiments demonstrated the potency of these compounds in decreasing the number of β-amyloid plaques and their suitability for the treatment of memory impairment in a transgenic model of Alzheimer’s disease.     

Novel Multifunctional Graphene Sheets with Encased Au/Ag Nanoparticles for Advanced Electrochemical Analysis of Organic Compounds

This work is the first presentation of the synthesis of few‐layer graphene decorated with gold and silver nanoparticles (Gr–Au–Ag) by chemical vapor deposition over a catalytic system formed of bimetallic Au–Ag nanoclusters supported on MgO and with methane used as the source of carbon. The sheetlike morphology of the graphene nanostructures, with mean sizes in the range of hundreds of nanometers, was observed by high‐resolution electron microscopy. The distinctive feature found in all the samples was the regular rectangular or square shapes. This multi‐component organic–inorganic nanomaterial was used to modify a platinum substrate and subsequently employed for the detection of carbamazepine, an anti‐convulsion drug. UV/Vis spectroscopy revealed that a strong hypochromism occurred over time, after mixing solutions of graphene–Au–Ag with carbamazepine. This can be attributed to π–π stacking between the aromatic groups of the two compounds. Linear sweep voltammetry (LCV) provided evidence that the modified platinum substrate presented a significant electrocatalytic reaction toward the oxidation of carbamazepine. The intensity of the current was found to increase by up to 2.5 times, and the oxidation potential shifted from +1.5 to +1.35 V(Ag/AgCl) in comparison with the unmodified electrode. Electrochemical impedance spectroscopy (EIS) was further used to thoroughly assess the activity of the platinum electrode that was modified by the deposition of the Gr‐Au‐Ag composites in the presence of various concentrations of carbamazepine. The experimental EIS records were used for the generation of an equivalent electrical circuit, based on the charge‐transfer resistance (R_ct), Warburg impedance (Z_D), solution resistance (R_s), and a constant phase element (CPE) that characterizes the non‐ideal interface capacitive responses.     

Synthesis, Biological Activity Evaluation and Molecular Modeling Study on the New Isoconessimine Derivatives as Acetylcholinesterase Inhibitors

New isoconessimine derivatives were synthesized from conessine （1） and evaluated as acetylcholinesterase （ACHE） inhibitors. The derivatives were prepared via two reaction steps, N-demethylation and nuc]eophilic substi- tution. All of the synthesized derivatives exhibited more potential anti-acetylcholinesterase activities than conessine （1） （IC50=16μmol·L^-1） and isoconessimine （2） （IC50〉300 μmol·L ^-1）. Compound 7b （3fl-[methyl-[2-（4-nitro- phenoxy）ethyl]amino]con-5-enine） showed the most potent inhibitory activity with an IC50 of 110 μmol/L which is close to that of reference compound huperzine A （IC50= 70 μmol/L）. The mode of AChE inhibition by 7h was re- versible and non-competitive. In addition, molecular modeling was performed to explore the binding mode of in- hibitor 7b at the active site of AChE and the results showed that 7b could be docked into the acetylcholinesterase active site and compound 7h had hydrophobic interactions with Trp279 and Leu282.     

Plasmonic Spherical Nanoparticles Coupled with Titania Nanotube Arrays Prepared by Anodization as Substrates for Surface-Enhanced Raman Spectroscopy Applications: A Review

As surface-enhanced Raman spectroscopy (SERS) continues developing to be a powerful analytical tool for several probes, four important aspects to make it more accessible have to be addressed: low-cost, reproducibility, high sensibility, and recyclability. Titanium dioxide nanotubes (TiO₂ NTs) prepared by anodization have attracted interest in this field because they can be used as safe solid supports to deposit metal nanoparticles to build SERS substrate nanoplatforms that meet these four desired aspects. TiO₂ NTs can be easily prepared and, by varying different synthesis parameters, their dimensions and specific features of their morphology can be tuned allowing them to support metal nanoparticles of different sizes that can achieve a regular dispersion on their surface promoting high enhancement factors (EF) and reproducibility. Besides, the TiO₂ photocatalytic properties enable the substrate’s self-cleaning property for recyclability. In this review, we discuss the different methodological strategies that have been tested to achieve a high performance of the SERS substrates based on TiO₂ NTs as solid support for the three main noble metal nanoparticles mainly studied for this purpose: Ag, Au, and Pt.     

Natural Antioxidants,Tyrosinase and Acetylcholinesterase Inhibitors from Cercis glabra Leaves

Cercis glabra is a plant belonging to the legume family, whose flowers and barks are commonly used as food and traditional Chinese medicines. However, its leaves are usually disposed of as wastes. This research comprehensively investigated the bioactive constituents of C. glabra leaves, and two new phenolic, ceroffesters A-B (1–2) and thirteen known compounds (3–15) were isolated. Their structures were elucidated by spectroscopic methods such as nuclear magnetic resonance (1D NMR and 2D NMR), high-resolution electrospray ionization mass spectra (HR-ESI-MS), optical rotatory dispersion (ORD) and electronic circular dichroism (ECD). All of them were assessed for their antioxidant activities through ABTS, DPPH and PTIO methodologies, and evaluated for inhibitory activities against two enzymes (mushroom tyrosinase and acetylcholinesterase). As a result, compounds 3–6, 10 and 13 exhibited evident antioxidant activities. Meanwhile, compounds 5, 10 and 13 showed the most potent tyrosinase inhibitory activities, with IC₅₀ of 0.64, 0.65 and 0.59 mM, and compared with the positive control of 0.63 mM (kojic acid). In the initial concentration of 1 mg/mL, compounds 3, 5 and 6 demonstrated moderate inhibitory activities against acetylcholinesterase with 85.27 ± 0.06%, 83.65 ± 0.48% and 82.21 ± 0.09%, respectively, compared with the positive control of 91.17 ± 0.23% (donepezil). These bioactive components could be promising antioxidants, tyrosinase and acetylcholinesterase inhibitors.