Nanosensors having dipicolinic acid imprinted nanoshell for Bacillus cereus spores detection

Molecular imprinted polymers (MIPs) as a recognition element for sensors are increasingly of interest and MIP nanoclusters have started to appear in the literature. In this study, we have proposed a novel thiol ligand-capping method with polymerizable methacryloylamido-cysteine (MAC) attached to gold–silver nanoclusters, reminiscent of a self-assembled monolayer and have reconstructed surface shell by synthetic host polymers based on molecular imprinting method for recognition. In this method, methacryloylamidoantipyrine–terbium ((MAAP)₂–Tb(III)) has been used as a new metal-chelating monomer via metal coordination–chelation interactions and dipicolinic acid (DPA) which is main participant of Bacillus cereus spores used as a model. Nanoshell sensors with templates give a cavity that is selective for DPA. The DPA can simultaneously chelate to Tb(III) metal ion and fit into the shape-selective cavity. Thus, the interaction between Tb(III) ion and free coordination spheres has an effect on the binding ability of the gold–silver nanoclusters nanosensor. The binding affinity of the DPA imprinted nanoclusters has been investigated by using the Langmuir and Scatchard methods, and the respective affinity constants (K _affinity) determined were found to be 1.43 × 10⁴ and 9.1 × 10⁶ mol L^?1.     

Steady-State and Frequency-Domain Lifetime Measurements of an Activated Molecular Imprinted Polymer Imprinted to Dipicolinic Acid

We recently demonstrated the synthesis and fluorescence activity associated with an optical detector incorporating a molecular imprinted polymer (MIP). Steady-state and time-resolved (lifetime) fluorescence measurements were used to characterize the binding activity associated with MIP microparticles imprinted to dipicolinic acid (DPA). DPA is a unique biomarker associated with the sporulation phase of endospore-forming bacteria. Vinylic monomers were polymerized in a dimethylformamide solution containing DPA as a template. The resulting MIP was then pulverized and sorted into small microscale particles. Tests were conducted on replicate samples of biologically active cultures representing both vegetative stationary phase and sporulation phase of Bacillus subtilis in standard media. Samplers were adapted incorporating the MIP particles within a dialyzer cartridge (500 MW). The permeability of the dialyzer membrane permitted diffusion of lighter molecular weight constituents from microbial media effluents to enter the dialyzer chamber and come in contact with the MIP. Results showed dramatic (10-fold over background) steady-state fluorescence changes (as a function of excitation, emission and intensity) for samples associated with high endospore biomass (DPA), and a frequency-domain lifetime of 5.3 ns for the MIP-DPA complex.     

Fluorescence of Metal–Ligand Complexes of Mono- and Di-Substituted Naphthalene Derivatives

In this work, metal ion complexes for several naphthalene derivatives have been investigated. Different working pH values were chosen: 2.5 for complexes with Zr(IV), 4.0 for complexes with Fe(III), 5.0 for complexes with Al(III), and 7.5 for complexes with Cu(II). A stoichiometry of 1:1 for all complexes except two has been established by use of the Benesi–Hildebrand method and the stability constants have been calculated. All complexes between naphthalene derivatives and Cu(II) and Fe(III) show fluorescence quenching. In the case of Al(III), all complexes provided enhanced fluorescence. For Zr(IV), only the complex with 3-hydroxy-2-naphthoic acid provided enhanced fluorescence. The value of the stability constants as a function of the substituents of naphthalene derivatives has been analyzed. One can conclude that Cu(II) showed the largest binding affinity for the mono-substituted derivatives. However, Al(III) and Zr(IV) produced greater selectivity for the di-substituted derivatives. Iron(III) showed no specific binding with any of the naphthalene derivatives.     

A Novel Ultraviolet Irradiation Technique for Fabrication of Polyacrylamide–metal (M = Au,Pd) Nanocomposites at Room Temperature

Polyacrylamide (PAM)–metal (M = gold, palladium) nanocomposites with metal nanoparticles homogeneously dispersed in the polymer matrix have been prepared via a novel ultraviolet irradiation technique at room temperature, which is based on the simultaneous occurrence of photo-reduction formation of the colloidal metal particles and photo-polymerization of the acrylamide (AM) monomer. The UV–vis absorption spectra and TEM were employed to characterize the M-PAM nanocomposites by different irradiation times. The average sizes of the colloidal gold and palladium particles dispersed in the nanocomposites were calculated by XRD patterns and TEM images. The present method may be extended to prepare other metal–polymer hybrid nanocomposite materials.     

Quenched Emission of Fluorescence by Ligand Functionalized Gold Nanoparticles

A fluorescence-based detection scheme that uses ligand functionalized gold nanoparticles is proposed. The transduction scheme is based on the strong quenching of the fluorescence emission exerted by metallic surfaces on fluorophores positioned in their immediate vicinity (< 5 nm). Binding of fluorophore-labeled anti-biotin to biotinylated gold nanoparticles resulted in decreased fluorescence emission intensity. Subsequent competitive dissociation of labeled anti-biotin with D-biotin resulted in increased fluorescence emission intensity. These interactions occurred by means of specific molecular recognition because when the binding sites of anti-biotin were saturated with D-biotin prior to interaction with the gold nanoparticles; changes in the fluorescence emission intensity were not observed.     

Cation-Responsive Fluorescence Of Dansyl-Labeled Polyanions Bearing Crown Ether Units

Anionic polymers bearing both crown ether units and Dansyl units were prepared by radical terpolymerization of the corresponding monomers, and the effect of cations on the fluorescence properties of the polymers was studied in aqueous media. The fluorescence peaks of the polymers are observed at 500–527 nm. The fluorescence quantum yields () of the polymers were found to be 6.3 × 10^–3–4.0 × 10^–1, depending on the polymer structure. On the addition of alkali metal cations, the fluorescence intensity increases in the order LiCl < NaCl < KCl < RbCl < CsCl. The polymer which has almost-equimolar amounts of crown ether groups and–COOH groups shows the highest responsiveness to the cations added. The structure of the anionic moieties in polymers strongly affects the cation-responsive fluorescence. The mechanism for the cation-induced changes in fluorescence is discussed.     

Gold Nanoparticles Obtained by Bio-precipitation from Gold(III) Solutions

The use of metal nanoparticles has shown to be very important in recent industrial applications. Currently gold nanoparticles are being produced by physical methods such as evaporation. Biological processes may be an alternative to physical methods for the production of gold nanoparticles. Alfalfa biomass has shown to be effective at passively binding and reducing gold from solutions containing gold(III) ions and resulting in the formation of gold(0) nanoparticles. High resolution microscopy has shown that five different types of gold particles are present after reaction with gold(III) ions with alfalfa biomass. These particles include: fcc tetrahedral, hexagonal platelet, icosahedral multiple twinned, decahedral multiple twinned, and irregular shaped particles. Further analysis on the frequency of distribution has shown that icosahedral and irregular particles are more frequently formed. In addition, the larger particles observed may be formed through the coalescence of smaller particles. Through modification of the chemical parameters, more uniform particle size distribution may be obtained by the alfalfa bio-reduction of gold(III) from solution.     

Influence of Fe(III) on the Fluorescence of Lysozyme: a Facile and Direct Method for Sensitive and Selective Sensing of Fe(III)

Lysozyme is widely used for the synthesis of nanomaterials (e.g., gold nanoparticle) to fluorescently sense metal ions. However, the effect of metal ions on the fluorescence of lysozyme is not studied yet. Herein, we have explored the interactions of lysozyme with different metal ions to develop a direct sensing platform for Fe(III). It has been observed that the fluorescence of lysozyme was slightly decreased in the presence of Cu(II), Hg(II), As(V), Co(II), Cd(II), Cr(II), Fe(II), Mn(II), Pb(II), and Zn(II), while a significant decrease in the lysozyme fluorescence was observed for Fe(III). The effect of thermal stability on the fluorescence quenching was also studied from 25 to 60 °C. In the present study, the lysozyme sensing probe was able to selectively and accurately detect 0.5–50 ppm of Fe(III) with a LOD of 0.1 ppm (1.8 µM) at 25 °C.

     

Preparation and Characterization of a Molecularly Imprinted Polymer for Selective Recognition of Trichlorfon and Monocrotophos

In this study, a molecularly imprinted polymer (MIP) that can selectively recognize both the trichlorfon and the structurally related compound of monocrotophos pesticides was prepared using mixtures of trichlorfon and monocrotophos as template molecules, methacrylic acid (MAA) as a functional monomer, and ethylene glycol dimethacrylate as a cross-linker. The polymerization conditions had an important influence on the adsorption ability of imprinted polymer. When the ratio of trichlorfon and monocrotophos was 1.5:1 (mol/mol), the MIP had high adsorption capacity. The prepared polymers were characterized by Fourier transform infrared spectroscopy and static and kinetic adsorption experiments. The results indicated that the P = O groups of trichlorfon and monocrotophos reacted with the -OH groups of MAA during the synthesis of MIP. The imprinted polymer exhibited good recognition ability and higher selectivity toward trichlorfon and monocrotophos than the structurally related pesticide compounds of acephate and methamidophos, and offered fast kinetics for solid phase by the MIP adsorption of trichlorfon and monocrotophos from liquid phase.     

Size-dependent interaction of gold nanoparticles with transport protein: A spectroscopic study

Gold nanoparticles of different sizes have been synthesized using sodium citrate as a reducing agent for tetrachloroauric (III) acid. The formed gold nanoparticles have been characterized by the UV-visible and transmission electron microscopy (TEM) measurements. The different sized gold nanoparticles have been used to study the interaction with model transport protein, bovine serum albumin (BSA). Experimental results reveal that BSA molecules adsorbed on the metallic surfaces, suffer strong quenching of their fluorescence and the rate of quenching efficiency is different for different particle size. The analysis of the quenching results has been performed in terms of the Stern-Volmer equation. The mechanism of quenching of fluorescence has been explained. The extent of adsorption of BSA on the gold nanoparticles has been estimated.     

Hybridization of surface-modified metal nanoparticles and a resin

Mercapto-terminated linear polymers, which were prepared by a reversible addition-fragmentation chain transfer (RAFT) technique, were used to modify metal nanoparticle surfaces. Au and Ag nanoparticles which are approximately 3–6 nm were used. This modification resulted in easy dispersion of the nanoparticles in polymer resins by simple mixing. The quality of the dispersion was confirmed by UV–Vis spectroscopy and transmission electron microscopy.     

Development of New Molecular Imprinted Solid Phase Extraction Material for Dimethoate

In this study, we have proposed a novel organophosphate mimic surface molecular imprinted polymer for selective binding of the nerve agent by chitosan–Cd(II) as a new metal-chelating monomer via metal coordination–chelation interactions and dimethoate templates. We have improved a method for the selective binding behavior of dimethoate compounds on the surface of molecular imprinted polymer, which was prepared using ligand-exchange (chitosan–Cd(II)) monomers. The influence of ligand exchange imprinting on the creation of recognition sites toward dimethoate has determined application of adsorption isotherms. The effect of initial concentration of dimethoate, adsorption time, and imprinting efficiency on the adsorption selectivity for molecular imprinted polymer-ligand exchange has been investigated. The number of accessible sites (Qmax), relative selectivity coefficients (k′), and binding abilities have also been evaluated. Then, molecular imprinted polymer-ligand exchange was treated with formaldehyde to remove dimethoate templates.     

地西泮分子印迹聚合物的光谱学特性及其在传感测试中的应用

制备地西泮的分子印迹聚合物,应用紫外光谱(ultraviolet spectra,UV spectra)和红外光谱(infra-red spectra,IRspectra)分析该聚合物的识别特性及模板分子和功能单体的结合作用。在丝网印刷电极上原位制备地西泮的分子印迹膜,并在此基础上建立了检测地西泮的电导型传感方法。实验结果表明模板分子与功能单体可形成1:2型氢键配合物,印迹聚合物中存在可与模板分子通过协同氢键相互作用的官能团,该聚合物对地西泮有高度特异的识别力,电导型传感方法对地西泮的检测限达0.008mg.L-1,线性范围为0.039～0.62mg.L-1,可实现现场快速检测。     

Recent advances on amphiphilic polymer-based fluorescence spectroscopic techniques for sensing and imaging

Abstract

Amphiphilic polymers (APs) characterized with excellent water solubility, biodegradability, biocompatibility, and low toxicity have become popular materials for biological sensing and imaging in the recent years. Among the several sensing and imaging techniques, fluorescence-based methods show distinct advantages and present unique opportunities to address challenges afforded by other techniques. This review covers five different types of APs (amphiphilic-conjugated polymers, amphiphilic polysaccharides, amphiphilic molecularly imprinted polymers, amphiphilic block copolymers, and amphiphilic polymeric nanoparticles) and their application for fluorescence spectroscopic sensing and imaging, in particular how techniques have been progressed over recent years. Afterwards, the applications of APs in the diagnosis and treatment of diseases, water safety and environmental monitoring has been discussed.     

Fabrication and electrical characterization of a MOS memory device containing self-assembled metallic nanoparticles

Floating gate devices with nanoparticles embedded in dielectrics have recently attracted much attention due to the fact that these devices operate as non-volatile memories with high speed, high density and low power consumption. In this paper, memory devices containing gold (Au) nanoparticles have been fabricated using e-gun evaporation. The Au nanoparticles are deposited on a very thin SiO₂ layer and are then fully covered by a HfO₂ layer. The HfO₂ is a high-k dielectric and gives good scalability to the fabricated devices. We studied the effect of the deposition parameters to the size and the shape of the Au nanoparticles using capacitance–voltage and conductance–voltage measurements, we demonstrated that the fabricated device can indeed operate as a low-voltage memory device.     

Evaluation of cerium doped tin oxide nanoparticles as a sensitive sensor for selective detection and extraction of cobalt

Chemo-sensor technology demands to design a single, preconcentrator based sensing system having higher sensitivity, sufficient selectivity and efficient removal of metal ions with simple operating and recognition methodology. Here we effectively deliberated Ce doped SnO₂ nanoparticles based sensing system which can be exploited for the recognition and extraction of Co(II) ions in a single step by strong interaction between Ce doped SnO₂ nanoparticles and Co(II). The sensing ability of Ce doped SnO₂ nanoparticles were deliberated for a selective removal of cobalt using inductively coupled plasma-optical emission spectrometry. The sensing ability of Ce doped SnO₂ is studied for various metal ions, such as Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Ni(II) and Zn(II) but the designed sensor was most selective toward Co(II) which was 5000 time more sensitive to Co(II) rather than different interfering metal ions. In addition, the desorption study for regeneration of Ce doped SnO₂ nanoparticles was carried out. This novel approach provides a new route for simultaneous detection and removal of Co(II) in a single step and can be a time and cost alternative tool for environmental safety.     

荧光光谱法研究瑞香黄烷类化合物与牛血清白蛋白的相互作用

在模拟人体生理条件下（pH 7.4）,采用荧光光谱法研究了瑞香黄烷A（DPA）和瑞香黄烷B（DPB）与牛血清白蛋白（BSA）的相互作用。DPA和DPB通过静态猝灭过程使得BSA荧光强度减弱;在25℃下,DPA和DPB与BSA结合常数分别为3.35×106L.mol-1和7.36×106L.mol-1,结合位点数分别为1.073和1.196;通过计算反应热力学参数值,可推断DPA和DPB与BSA作用力主要为氢键或范德华力;根据Foerster非辐射能量转移理论计算DPA和DPB与BSA的结合距离分别为3.11nm和3.04nm;同步荧光光谱法研究表明,DPA和DPB与BSA的结合对蛋白质的构象未产生影响,其结合位点更接近于色氨酸;同时还考察了部分共存金属离子对DPA和DPB与BSA结合作用的影响。     

Dynamic of the Fluorescence of the Complex Zn++/Bis-N-Carbazolyl-Distyrylbenzene

The discrimination between similar concentrations of the different metal ions is one of the important roles of fluorescent sensors. Here we present the study of the fluorescence dynamic of the chromophore bis-N-carbazolyl-distyrylbenzene (BCDSB) in acetonitrile/water (mmol/L), doped with metal ions such as K+; Ca++; Mg++; Zn++(10 micromol/L). BCDSB has the fluorescence with lambda(max) at 448 nm by excitation at lambda(exc) = 378 nm, lifetime 1.089 ns: quantum yield of the fluorescence is 0.68. With continuation of irradiation fluorescence quenching has been registered for all investigated metal ions. However, in the presence of Zn++ oscillation of the intensity was observed. The energy activation of the oscillation as much as 15 kcal/mol was estimated. We believe, that the specificity of the complex Zn++/BCDSB, is in an asymmetrical structure, formed via binding sites of Zn++ with the electron-enriched binding sites of the BCDSB, excited in n(pi)* state. This asymmetrical complex structure can cause the photoinduced structural fluctuation in the complex coordination.     

Photoinduced interaction of colloidal TiO2 nanoparticles with lysozyme: Evidences from spectroscopic studies

The interaction between colloidal TiO₂ nanoparticles and lysozyme (LYSO) was studied using absorption, steady state and time resolved fluorescence, FT-IR and synchronous fluorescence spectroscopic measurements. The apparent association constant has been deduced from the absorption spectral changes of LYSO-colloidal TiO₂ nanoparticles using Benesi-Hildebrand equation. The number of binding sites and the apparent binding constant were calculated from relevant fluorescence data. Based on Forster's non-radiation energy transfer theory, distance between the donor (LYSO) and the acceptor (TiO₂) has also been calculated. The conformational changes of LYSO have been analyzed by means of FT-IR and synchronous fluorescence spectroscopy. In addition, the effect of metal ions on the binding constants of LYSO-TiO₂ complex has also been discussed.     

The amplification effect of functionalized gold nanoparticles on the binding of anticancer drug dacarbazine to DNA and DNA bases

The promising application of functionalized gold nanoparticles to amplify the performance of biosensors and relevant biomolecular recognition processes has been explored in this paper. Our observations illustrate the apparent enhancement effect of the gold nanoparticles on the electrochemical response of the anticancer drug dacarbazine (DTIC) binding to DNA and DNA bases, indicating that these functionalized gold nanoparticles could readily facilitate the specific interactions between DTIC and DNA/DNA bases. This raises the potential valuable applications of these biocompatible nanoparticles in the promising biosensors and biomedical engineering.