Cytotoxic activity of two polyaspartamide‐ based monoamineplatinum(II) conjugates against the HeLa cancer cell line

In this screening study in vitro, two polymer‐conjugated, square‐planar platinum(II) complexes bound to the carrier via a single primary amine ligand were tested for antineoplastic activity against the HeLa human cervical epithelioid carcinoma cell line. In the first of these conjugates, 1‐Pt , the spacer connecting the metal complex with the carrier backbone is a short oligo(ethylene oxide) segment, whereas a long poly(ethylene oxide) chain represents the spacer unit in the second conjugate, 2‐Pt . IC₅₀ data, expressed as conjugate concentration at 50% cell growth inhibition, are 48 µg Pt ml⁻¹ for 1‐Pt and 120 µg Pt ml⁻¹ (estimated) for 2‐Pt , the long tether in the latter conjugate presumably causing retarded enzymic release and lysosomal membrane crossing of the monomeric complex. The IC₅₀ value of 1‐Pt is close to that (44 µg Pt ml⁻¹) of a similar conjugate of an earlier investigation, 3‐Pt , in which the metal is chelated by two carrier‐attached, cis‐oriented amino groups in conformance with the ligand arrangement in cisplatin. It thus appears that, in the carrier‐bound state, both monoamine‐ and cis‐diamine‐coordinated platinum(II) complexes of suitable structures may well show similar biological performance patterns. Copyright­© 1999 John Wiley & Sons, Ltd.     

Amplified Electrochemical Immunosensor for Calmodulin Detection Based on Gold‐Silver‐Graphene Hybrid Nanomaterials and Enhanced Gold Nanorods Labels

Calmodulin (CaM) is an important intracellular calcium‐binding protein. It plays a critical role in a variety of biological and biochemical processes. In this paper, a new electrochemical immunosensing protocol for sensitive detection of CaM was developed by using gold‐silver‐graphene (AuAgGP) hybrid nanomaterials as protein immobilization matrices and gold nanorods (GNRs) as enhanced electrochemical labels. Electrode was first modified with thionine‐chitosan film to provide an immobilization support for gold‐silver‐graphene hybrid nanomaterials. The hybrid materials formed an effective matrix for binding of CaM with high density and improved the electrochemical responses as well. Gold nanorods were prepared for the fabrication of enhanced labels (HRP‐Ab₂‐GNRs), which provided a large capacity for HRP‐Ab₂ immobilization and a facile pathway for electron transfer. With two‐step immunoassay format, the HRP‐Ab₂‐GNRs labels were introduced onto the electrode surface, and produced electrochemical responses by catalytic reaction of HRP toward enzyme substrate of hydrogen peroxide (H₂O₂) in the presence of thionine. The proposed immunosensor showed an excellent analytical performance for the detection of CaM ranging from 50 pg mL^?1 to 200 ng mL^?1 with a detection limit of 18 pg mL^?1. The immunosensor has also been successfully applied to the CaM analysis in two cancer cells (HepG2 and MCF‐7) with high sensitivity, which has shown great potency for improving clinic diagnosis and treatment for cancer study.     

Fabrication of Ag Nanoparticles Embedded in TiO2 Nanotubes: Using Electrospun Nanofibers for Controlling Plasmonic Effects

Composites of electrospun poly(ethylene oxide) (PEO) fibers and silver nanoparticles (Ag NPs) were used as a soft template for coating with TiO₂ by atomic layer deposition (ALD). Whereas the as‐deposited TiO₂ layers on PEO fibers and Ag NPs were completely amorphous, the TiO₂ layers were transformed into polycrystalline TiO₂ nanotubes (NTs) with embedded Ag NPs after calcination. Their plasmonic effect can be controlled by varying the thickness of the dielectric Al₂O₃ spacer between Ag NPs and dye molecules by means of the ALD process. Electronic and spectroscopic analyses demonstrated enhanced photocurrent generation and solar‐cell performance due to the intense electromagnetic field of the dye resulting from the surface plasmon effect of the Ag NPs.     

Micelle‐Directing Synthesis of Ag‐Doped WO3 and MoO3 Composites for Photocatalytic Water Oxidation and Organic‐Dye Adsorption

In this paper, an Ag‐doped WO₃ (and MoO₃) composite has been prepared by following a simple micelle‐directed method and high‐temperature sintering route. The as‐prepared samples were characterized by X‐ray diffraction, inductively coupled plasma, transmission electron microscopy, X‐ray photoelectron spectroscopy, UV/Vis diffuse reflectance spectroscopy, Brunauer–Emmett–Teller, photoluminescence spectroscopy, and electrochemical impedance spectroscopy techniques. The photocatalytic experiments reveal that their oxygen‐production rates are up to 95.43 μmol (75.45 μmol) for Ag‐doped WO₃ (MoO₃), which is 9.5 (7.3) times higher than that of pure WO₃: 9.012 μmol (MoO₃: 9.00 μmol) under visible‐light illumination (λ ≥420 nm), respectively. The improvement of their photocatalytic activity is attributed to the enhancement of their visible‐light absorption and the separation efficiency of photogenerated carriers by Ag doping. Moreover, Ag‐doped WO₃ (MoO₃) also shows excellent adsorption of rhodamine B (RhB) and methylene blue (MB) in aqueous solution, with maximum adsorption capacities towards RhB and MB of 822 and 820 mg g⁻¹ for Ag‐doped WO₃, and 642 and 805 mg g⁻¹ for Ag‐doped MoO₃, respectively.     

Green synthesis and characterization of monodispersed silver nanoparticles obtained using oak fruit bark extract and their antibacterial activity

Green synthesis of silver nanoparticles (Ag NPs) has been achieved using oak fruit bark extract as a reducing, capping and stabilizing agent. The biosynthesized Ag NPs were characterized using various techniques. UV–visible spectrum of prepared silver colloidal solution showed absorption maximum at 433 nm. X‐ray diffraction and transmission electron microscopy analysis revealed that Ag NPs have a face‐centred cubic structure being spherical in shape with an average particle size of 20–25 nm. The toxicity of the Ag NPs was tested on bacterial species such as Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli by comparison based on diameter of inhibition zone in disc diffusion tests and minimum inhibitory concentration and minimum bactericidal concentration of NPs dispersed in liquid cultures. The antimicrobial activity of Ag NPs was greater towards Gram‐positive bacteria (S. aureus and B. subtilis) compared to Gram‐negative bacteria as determined using standard Kirby–Bauer disc diffusion assay and serial dilution. Copyright © 2016 John Wiley & Sons, Ltd.     

Green synthesis of silver nanoparticles using Thymus kotschyanus extract and evaluation of their antioxidant,antibacterial and cytotoxic effects

Present study used ecofriendly, cost efficient and easy method for synthesis of silver nanoparticles (Ag NPs) at the room temperature by Thymus Kotschyanus extract as reducing and capping agent. Various analytical technique including UV–Vis absorption spectroscopy determined presence of Ag NPs in the solution, the functional groups of Thymus Kotschyanus extract in the reduction and capping process of Ag NPs are approved by FT‐IR, crystallinity with the fcc plane approved from the X‐ray diffraction (XRD) pattern, energy dispersive spectroscopy (EDS) determined existence of elements in the sample, surface morphology, diverse shapes and size of present Ag NPs were showed by using scanning electron microscopy (SEM), atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). Beginning and end destroy temperature of present silver nanoparticles were determined by thermal gravimetric spectroscopy (TGA). In addition, antibacterial, antioxidant and cytotoxicity properties of Ag NPs were studied. Agar disk and agar well diffusion are the methods to determined antibacterial properties of synthesized Ag NPs. Also MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) were recognized by macro broth dilution assay. DPPH free radical scavenging assay was used for antioxidant property and compare to butylated hydroxytoluene (BHT) as standard antioxidant that showed high antioxidant activity more than BHT. Synthesized Ag NPs have great cell viability in a dose depended manner and demonstrate that this method for synthesis silver nanoparticles provided nontoxic. The average diameter of synthesized Ag NPs was about 50–60 nm.     

Group 6 Hexacarbonyls as Ligands for the Silver Cation: Syntheses,Characterization, and Analysis of the Bonding Compared with the Isoelectronic Group 5 Hexacarbonylates

The syntheses of the two novel complexes [Ag{Mo/W(CO)₆}₂]⁺[F-{Al(OR^F)₃}₂]⁻ (R^F=C(CF₃)₃) are reported along with their structural and spectroscopic characterization. The X-ray structure shows that three carbonyl ligands from each M(CO)₆ fragment bend towards the silver atom within binding Ag−C distance range. DFT calculations of the free cations [Ag{M(CO)₆}₂]⁺ (M=Cr, Mo, W) in the electronic singlet state give equilibrium structures with C₂ symmetry with two bridging carbonyl groups from each hexacarbonyl ligand. Similar structures with C₂ symmetry (M=Nb) and D₂ symmetry (M=V, Ta) are calculated for the isoelectronic group 5 anions [Ag{M(CO)₆}₂]⁻ (M=V, Nb, Ta). The electronic structure of the cations is analyzed with the QTAIM and EDA-NOCV methods, which provide detailed information about the nature of the chemical bonds between Ag⁺ and the {M(CO)₆}₂^q (q = −2, M = V, Nb, Ta; q = 0, M = Cr, Mo, W) ligands.     

γ-Ray synthesis of starch-stabilized silver nanoparticles with antibacterial activities

Silver nanoparticles (Ag NPs) are fabricated through γ-irradiation reduction of silver ions in aqueous starch solutions. The UV–vis analyses show smaller sizes of Ag NPs produced, with higher yields, as the irradiation doses and/or Ag⁺ concentrations are increased. Higher concentrations of starch enhance the yields of Ag NPs, with no significant effects on their size. The most economical Ag NPs are produced at 5 kGy γ-irradiation of a 2×10⁻³ M solution of AgNO₃ containing 0.5% starch. They show a relatively narrow size distribution, indicated by TEM and its corresponding size distribution histogram. The XRD pattern confirms the face-centered cubic (fcc) Ag NPs embedded in starch molecules. Interactions between these nanoparticle surfaces and starch oxygen atoms are indicated by FT–IR. Antibacterial activities of Ag NPs against Escherichia coli appear dependent on the γ-ray doses applied.     

基于多层酶/纳米金固定甲胎蛋白免疫传感器的研究

>利用自组装技术和静电吸附作用, 将甲胎蛋白抗体(anti-AFP)固定在多层辣根过氧化物酶/纳米金及L-半胱胺酸修饰的金电极表面, 制备出用于检测甲胎蛋白抗原(AFP)的无试剂型免疫传感器. 通过交流阻抗技术、循环伏安法和计时电流法考察了电极的电化学特性, 并对该免疫传感器的作用机理及性能进行了详细的研究. 用计时电流法测得AFP的线性范围为1.0～10.0和10～200 ng•mL^－1, 检出限为0.5 ng•mL^－1. 实验结果表明, 该方法提高了抗体的固定量, 增强了传感器的灵敏度和稳定性, 且该传感器响应迅速、选择性好, 血清中常见抗原不干扰测定. 将其用于临床血清检验, 与放射免疫测定法(RIA)的符合率为86.7%.     

Pistacia atlantica leaf extract mediated synthesis of silver nanoparticles and their antioxidant,cytotoxicity, and antibacterial effects under in vitro condition

Recently, researchers have investigated the therapeutical properties of metal nanoparticles especially silver nanoparticles in vitro and in vivo conditions. The aim of the experiment was green synthesis and chemical characterization of silver nanoparticles from aqueous extract of Pistacia atlantica leaf (Ag NPs) and evaluation of their cytotoxicity, antioxidant, and antibacterial effects under in vitro condition. Ag NPs were spherical with a size range of 40-60 nm and characterized using various analysis techniques including UV–Vis absorption spectroscopy to determine the presence of Ag NP in the solution. We studied functional groups of Pistacia atlantica extract in the reduction and capping process of Ag NP by FT-IR, crystallinity and FCC planes by XRD pattern, elemental analysis of the sample by EDS, and surface morphology, shapes, and size of Ag NPs by SEM, AFM, and TEM. Destroy initiation and termination temperatures of the Ag NPs were determined by TGA. DPPH free radical scavenging test was done to evaluate the antioxidant potentials, which indicated similar antioxidant potentials for Ag NPs and butylated hydroxytoluene. The synthesized Ag NPs had great cell viability dose-dependently and indicated this method was nontoxic. Agar diffusion tests were done to determine the antibacterial characteristic. Ag NPs revealed similar antibacterial property to the standard antibiotic. Also, Ag NPs prevented the growth of all bacteria at 1-7 μg/ml concentrations and removed them at 3-15 μg/ml concentrations. Finally, synthesized Ag NPs revealed non-cytotoxicity, antioxidant and antibacterial activities in a dose-depended manner.     

Signal amplification for DNA detection based on the HRP-functionalized Fe3O4 nanoparticles

An electrochemical approach for the sensitive detection of sequence-specific DNA has been developed. Horseradish peroxidase (HRP) assembled on the Fe₃O₄ nanoparticles (NPs) were utilized as signal amplification sources. High-content HRP was adsorbed on the Fe₃O₄ NPs via layer-by-layer (LbL) technique to prepare HRP-functionalized Fe₃O₄ NPs. Signal probe and diluting probe were then immobilized on the HRP-functionalized Fe₃O₄ NPs through the bridge of Au NPs. Thereafter, the resulting DNA-Au-HRP-Fe₃O₄ (DAHF) bioconjugates were successfully anchored to the gold nanofilm (GNF) modified electrode surface for the construction of sandwich-type electrochemical DNA biosensor. The electrochemical behaviors of the prepared biosensor had been investigated by the cyclic voltammetry (CV), chronoamperometry (i-t), and electrochemical impedance spectroscopy (EIS). Under optimal conditions, the proposed strategy could detect the target DNA down to the level of 0.7 fmol with a dynamic range spanning 4 orders of magnitude and exhibited excellent discrimination to two-base mismatched DNA and non-complementary DNA sequences.     

Electrochemical stripping analysis of nanogold label-induced silver deposition for ultrasensitive multiplexed detection of tumor markers

A multiplexed electrochemical immunoassay method was developed for simultaneous ultrasensitive measurement of tumor markers based on electrochemical stripping analysis of silver nanoparticles (Ag NPs). The Ag NPs were deposited on a disposable immunosensor array with a reduction reaction catalyzed by nanogold labels. The immunosensor array was prepared by covalently immobilizing capture antibodies on chitosan modified screen-printed carbon electrodes. Through a sandwich-type immunoreaction, antibody-functionalized Au NPs were captured onto immunosensor surface to induce the silver deposition from a silver enhancer solution. The deposited Ag NPs could be directly measured by anodic stripping analysis in KCl solution. The catalytic deposition enhanced the analytical sensitivity for detection of protein markers. The interference of dissolved oxygen could be avoided as the detection was performed with positive stripping potential range. Using carcinoembryonic antigen and α-fetoprotein as model analytes, the proposed multiplexed immunoassay method showed wide linear ranges of three orders of magnitude with the detection limits down to 3.5 and 3.9 pg mL⁻¹, respectively. The localized silver deposition, as well as the stripping detection process, eliminated completely the electrochemical cross talk between adjacent immunosensors. The immunosensor array exhibited acceptable reproducibility, stability and accuracy, showing a promising potential in multianalyte determination for clinical application.     

Idiosyncratic Ag7Pt2O7: An Electron Imprecise yet Diamagnetic Small Band Gap Oxide

The seminal qualitative concepts of chemical bonding, as presented by Walter Kossel and Gilbert Newton Lewis back in 1916, have lasting general validity. These basic rules of chemical valence still serve as a touchstone for validating the plausibility of composition and constitution of a given chemical compound. We report on Ag₇Pt₂O₇, with a composition that violates the basic rules of chemical valence and an exotic crystal structure. The first coordination sphere of platinum is characteristic of tetravalent platinum. Thus, the electron count corresponds to Ag₇Pt₂O₇*e⁻, where excess electrons are associated with the silver substructure. Such conditions given, it is commonly assumed that the excess electrons are either itinerant or localized in Ag−Ag bonds. However, the material does not show metallic conductivity, nor does the structure feature Ag-Ag pairs. Instead, the excess electrons organize themselves in 2e−4c bonds within the silver substructure. This subvalent silver oxide reveals a new general facet pertinent to silver chemistry.     

Enzyme-catalyzed silver deposition on irregular-shaped gold nanoparticles for electrochemical immunoassay of alpha-fetoprotein

A new and disposable electrochemical immunosensor was designed for detection of alpha-fetoprotein (AFP), as a model analyte, with sensitivity enhancement based on enzyme-catalyzed silver deposition onto irregular-shaped gold nanoparticles (ISGNPs). The assay was carried out with a sandwich-type immunoassay protocol by using ISGNP-labeled anti-AFP antibodies conjugated with alkaline phosphatase (ALP–Ab₂) as detection antibodies. The enzymatically catalytic deposition of silver on the electrode could be measured by stripping analysis in KCl solution due to the Ag/AgCl solid-state voltammetric process. Several labeling protocols including spherical gold nanoparticle-labeled ALP–Ab₂ and ISGNP-labeled ALP–Ab₂ were investigated for determination of AFP, and improved analytical properties were achieved with the ISGNP labeling. With the ISGNP labeling method, the effects of incubation time and incubation temperature for antigen-antibody reaction, and deposition time of silver on the current responses of the electrochemical immunosensors were also monitored. Under optimal conditions, the electrochemical immunosensor exhibited a wide dynamic range from 0.01 ng mL⁻¹ to 200 ng mL⁻¹ with a detection limit of 5.0 pg mL⁻¹ AFP. The immunosensor displayed a good stability and acceptable reproducibility and accuracy. No significant differences at the 95% confidence level were encountered in the analysis of 10 clinical serum samples between the developed immunoassay and the commercially available electrochemiluminescent method for determination of AFP.     

Synthesis of aza-crown ether-modified silver nanoparticles as colorimetric sensors for Ba2+

In this paper, we have demonstrated a facile strategy of preparing aza-crown ether (ACE)-modified silver nanoparticles (Ag NPs) by an efficient nano-conjugate technology named dithiocarbamate. This is the first report of using ACE to modify Ag NPs. ACE-modified Ag NPs have a good recognition of Ba²⁺, with the detection limit of 10^? 8 mol/l. It is reasonable to believe that Ba²⁺ induced the self-assembly of Ag NPs by the formation of the sandwich structure with ACE.

     

Using a photochemical method and chitosan to prepare surface-enhanced Raman scattering–active silver nanoparticles

In this paper, we report a new strategy for the preparation of surface-enhanced Raman scattering (SERS)-active silver nanoparticles (Ag NPs), using a photochemical method and the presence of chitosan (Ch). First, Ag substrates were subjected to electrochemical oxidation/reduction cycles (ORCs) in deoxygenated aqueous solutions containing 0.1 M HNO₃ and 1 g L⁻¹ Ch (pH 6.9, adjusted by adding 1 M NaOH), resulting in Ag⁺–Ch complexes. These substrates were then irradiated with UV light at various wavelengths to yield the SERS-active Ag NPs. A stronger SERS effect was observed on the SERS-active Ag NPs prepared by using UV irradiation at 310 nm. The pH of the solution and the presence of Ch during the preparation process both affected the resulting SERS activities.     

Iron oxide nanoparticles coated with green tea extract as a novel magnetite reductant and stabilizer sorbent for silver ions: Synthetic application of Fe3O4@green tea/Ag nanoparticles as magnetically separable and reusable nanocatalyst for reduction of 4‐nitrophenol

Green tea extract having many phenolic hydroxyl and carbonyl functional groups in its molecular framework can be used in the modification of Fe₃O₄ nanoparticles. Moreover, the feasibility of complexation of polyphenols with silver ions in aqueous solution can improve the surface properties and capacity of the Fe₃O₄@green tea extract nanoparticles (Fe₃O₄@GTE NPs) for sorption and reduction of silver ions. Therefore, the novel Fe₃O₄@GTE NPs nano‐sorbent has potential ability as both reducing and stabilizing agent for immobilization of silver nanoparticles to make a novel magnetic silver nanocatalyst (Fe₃O₄@GTE/Ag NPs). Inductively coupled plasma analysis, transmission and scanning electron microscopies, energy‐dispersive X‐ray and Fourier transform infrared spectroscopies, and vibrating sample magnetometry were used to characterize the catalyst. Fe₃O₄@GTE/Ag NPs shows high catalytic activity as a recyclable nanocatalyst for the reduction of 4‐nitrophenol at room temperature.     

Performance of a Flow-Through Enzyme Reactor Prepared from a Silica Monolith and an α-Poly(D-Lysine)-Enzyme Conjugate

Horseradish peroxidase (HRP) is covalently bound in aqueous solution to polycationic α-poly(D-lysine) chains of ≈1000 repeating units length, PDL, via a bis-aryl hydrazone bond (BAH). Under the experimental conditions used, about 15 HRP molecules are bound along the PDL chain. The purified PDL-BAH-HRP conjugate is very stable when stored at micromolar HRP concentration in a pH 7.2 phosphate buffer solution at 4 °C. When a defined volume of such a conjugate solution of desired HRP concentration (i.e., HRP activity) is added to a macro- and mesoporous silica monolith with pore sizes of 20–30 µm as well as below 30 nm, quantitative and stable noncovalent conjugate immobilization is achieved. The HRP-containing monolith can be used as flow-through enzyme reactor for bioanalytical applications at neutral or slightly alkaline pH, as demonstrated for the determination of hydrogen peroxide in diluted honey. The conjugate can be detached from the monolith by simple enzyme reactor washing with an aqueous solution of pH 5.0, enabling reloading with fresh conjugate solution at pH 7.2. Compared to previously investigated polycationic dendronized polymer-enzyme conjugates with approximately the same average polymer chain length, the PDL-BAH-HRP conjugate appears to be equally suitable for HRP immobilization on silica surfaces.     

Silver(I) and Silver(II) Complexes with Some Tetraazamacrocyclic Ligands in Aqueous Solutions

The reactions of silver(I) with isocyclam, scorpiand,trans-Me₂[14]anN₄, cis-Me₆[14]anN₄,(N-Me)Me₂py[14]anN₄ and py[12]anN₄ were investigated.The stability constant of the Ag(I) complex with py[12]anN₄ was determined. The aqueous solutions of the silver(II) complexes with the 14-membered ligands were obtained, and characterized by means of UV-VIS and CVA measurements. The Ag²⁺ ion does not form a five-coordinate complex with scorpiand. The formal potentials of the Ag(II)/Ag(I) system in the presence of scorpiand, trans-Me₂[14]anN₄, cis-Me₆[14]anN₄ and(N-Me)Me₂py[14]anN₄ were determined. The mechanism is also proposedfor the electroreduction of the silver(II) complexes with these compounds on a platinum electrode in aqueous solution.     

Calcium Carbonate–Gold Nanocluster Hybrid Spheres: Synthesis and Versatile Application in Immunoassays

Fluorescent gold nanoclusters (AuNCs) were incorporated into porous calcium carbonate spheres through electrostatic interaction. The resulting CaCO₃/AuNCs hybrid material exhibited interesting properties, such as porous structure, excellent biocompatibility, good water solubility, and degradability. These properties make the CaCO₃/AuNCs hybrid material a promising template to assemble horseradish peroxidase/antibody conjugates (HRP‐Ab₂). By using CaCO₃/AuNCs/HRP‐Ab₂ bioconjugates as probes, a versatile immunosensor was developed for fluorescent and electrochemical detection of the cancer biomarker neuron‐specific enolase (NSE). The detection limits of the sensor were 2.0 and 0.1 pg mL^?1 for fluorescent and electrochemical detection, respectively. The immunosensor shows high sensitivity and offers an alternative strategy for the detection of other proteins and DNA.