Peptide-Guided Surface-Enhanced Raman Scattering Probes for Localized Cell Composition Analysis

The ability to control the localization of surface-enhanced Raman scattering (SERS) nanoparticle probes in bacterial cells is critical to the development of analytical techniques that can nondestructively determine cell composition and phenotype. Here, selective localization of SERS probes was achieved at the outer bacterial membrane by using silver nanoparticles functionalized with synthetic hydrophobic peptides.     

表面增强拉曼散射机理研究进展

简要回顾表面增强拉曼散射（Surface—enhanced Raman Scattering,SERS）的发展历史,主要综述近年来SERS物理增强机理及理论计算方面的研究进展,并对SERS机理理论研究发展作了展望。     

Interface-Induced Ag Monolayer Film for Surface-Enhanced Raman Scattering Detection of Water-Insoluble Enrofloxacin

Water-insoluble molecules usually show poor surface-enhanced Raman scattering (SERS) signals, because they are hardly adsorbed on the surface of most commonly used SERS substrates, such as aqueous Ag or Au colloids. In this work, a highly sensitive and reproducible Ag monolayer film (Ag MLF) SERS substrate prepared by self-assembly of Ag nanoparticles (Ag NPs) on water/oil interface can realize the trace SERS detection of water-insoluble enrofloxacin. The positively charged phase transfer catalyst can transfer the negatively charged Ag nanoparticles in aqueous solution to the water/oil interface. At the same time, the water-insoluble enrofloxacin can also be attracted to the interface because of its lipophilic group. The type/volume of the oil phase and phase transfer catalyst and the vortex mixing time were all optimized to maximize the SERS effect of Ag MLF. Results showed that trace water-insoluble enrofloxacin can be identified by Ag MLF and its detection sensitivity was significantly improved. The proposed novel Ag MLF can be further applied to detect other water-insoluble molecules in SERS.

     

One-Step Synthesis of Gold Nanoparticles Using Liquid Crystal Molecules for Surface-Enhanced Raman Scattering Detection

Plasmonics - Gold nanoparticles have received widespread attention as surface-enhanced Raman scattering (SERS) detection active substrates. In this work, we used the nematic liquid crystal molecule...     

Detection of Melamine in Feed Using Liquid-Liquid Extraction Treatment Combined with Surface-Enhanced Raman Scattering Spectroscopy

A rapid, selective, and sensitive method to determine the melamine content in animal feeds was developed using surface-enhanced Raman scattering spectroscopy on aggregated 55 nm Au nanoparticles with liquid–liquid extraction sample preparation. Butyl alcohol was used as the initial extraction solvent, and liquid–liquid extraction was performed twice using HCl (pH 3–4) and 6∶1 (v/v) n-butyl alcohol/ethyl acetate. The intensity of the matrix-based peak at 731 cm⁻¹ was set at 100 as a basis for the feeds, and the peak at 707 cm⁻¹ was the characteristic peak of melamine used in the calculations. Sufficient linearity was obtained in the range 2–10 µg·g⁻¹ (R² = 0.991). Limits of detection and quantification in the feeds were 0.5 and 2 µg·g⁻¹, respectively. The recovery rates were 82.5–90.2% with coefficients of variation below 4.02%. This new protocol could be easily developed for the routine monitoring of on-site feed quality and market surveillance.     

A Real-Time Clinical Endoscopic System for Intraluminal,Multiplexed Imaging of Surface-Enhanced Raman Scattering Nanoparticles

The detection of biomarker-targeting surface-enhanced Raman scattering (SERS) nanoparticles (NPs) in the human gastrointestinal tract has the potential to improve early cancer detection; however, a clinically relevant device with rapid Raman-imaging capability has not been described. Here we report the design and in vivo demonstration of a miniature, non-contact, opto-electro-mechanical Raman device as an accessory to clinical endoscopes that can provide multiplexed molecular data via a panel of SERS NPs. This device enables rapid circumferential scanning of topologically complex luminal surfaces of hollow organs (e.g., colon and esophagus) and produces quantitative images of the relative concentrations of SERS NPs that are present. Human and swine studies have demonstrated the speed and simplicity of this technique. This approach also offers unparalleled multiplexing capabilities by simultaneously detecting the unique spectral fingerprints of multiple SERS NPs. Therefore, this new screening strategy has the potential to improve diagnosis and to guide therapy by enabling sensitive quantitative molecular detection of small and otherwise hard-to-detect lesions in the context of white-light endoscopy.     

Effect of Interparticle Field Enhancement in Self-Assembled Silver Aggregates on Surface-Enhanced Raman Scattering

The presence of so-called hot spots, regions with strongly enhanced electromagnetic field, is a critical property of a substrate enabling detection of surface-enhanced Raman scattering (SERS) signals at high enhancement levels. In this work, the effect of interparticle field enhancement on SERS signals was investigated comparing SERS spectra of ethylenediaminetetraacetic-disodium salt in the chemically produced colloids with isolated and aggregated silver nanoparticles using 473 and 532-nm wavelength excitation. The presence of aggregates in the colloidal solution resulted in SERS spectra that were insensitive to wavelength excitation and much richer in structural information and of higher resolution than the corresponding SERS spectra for the colloid with isolated nanoparticles. The experimental SERS spectra were found to be consistent with the finite-difference time-domain simulation results that explored the electromagnetic response of the isolated and aggregated nanoparticles. These results provide more evidence to suggest that the aggregate formation offers favorable electromagnetic properties increasing sensitivity of Raman spectroscopy.     

基于纳米信号标签的表面增强拉曼散射在病原菌检测中的应用

表面增强拉曼散射(surface-enhanced Ranan scattering,SERS)技术由于其灵敏度高、检测速度快、高特异性和无损等优点,在病原菌检测领域受到了广泛的关注.主要总结了近年来基于纳米信号标签的SERS方法在检测病原菌领域中的研究进展,并介绍了多功能SERS检测平台的构建及在病原菌检测中的应用....     

Application of AAO Matrix in Aligned Gold Nanorod Array Substrates for Surface-Enhanced Fluorescence and Raman Scattering

In this paper, we probed surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) from probe molecule Rhodamine 6G (R6G) on self-standing Au nanorod array substrates made using a combination of anodization and potentiostatic electrodeposition. The initial substrates were embedded within a porous alumina template (AAO). By controlling the thickness of the AAO matrix, SEF and SERS were observed exhibiting an inverse relationship. SERS and SEF showed a non-linear response to the removal of AAO matrix due to an inhomogeneous plasmon activity across the nanorod which was supported by FDTD calculations. We showed that by optimizing the level of AAO thickness, we could obtain either maximized SERS, SEF or simultaneously observe both SERS and SEF together.     

A Label-Free Nanogold DNAzyme-Cleaved Surface-Enhanced Resonance Raman Scattering Method for Trace UO2 2+ Using Rhodamine 6G as Probe

In pH?5.5 2-(N-morpholino)-ethanosulfonic acid buffer solution containing 0.25 M NaCl at 80 °C, the single-stranded substrate DNA hybridizes with the enzyme DNA to form double-stranded DNA (dsDNA). The substrate chain of dsDNA could be cracked catalytically by UO₂ ²⁺ to produce a short single-stranded DNA (ssDNA) that adsorbed on the nanogold (NG) surface to form a stable nanogold–ssDNA conjugate and then further combine with rhodamine 6G (RhG) to form a NG–ssDNA–RhG conjugate that can be monitored by the surface-enhanced resonance Raman scattering (SERRS) spectral technique at 1,360 cm^?1. Under the selected conditions, the increased SERRS intensity ΔI ₁₃₆₀ was linear to UO₂ ²⁺ concentration in the range of 5–125 nmol/L, with a detection limit of 1.6 nmol/L. Using a 0.5-μmol/L Hg²⁺ as enhancer, a 2.5–100-nmol/L UO₂ ²⁺ can be determined.     

A Rapid Surface-Enhanced Raman Scattering Method for the Determination of Trace Hg2+ Using Rhodamine 6G-Aggregated Nanosilver as Probe

In pH 6.0 Na₂HPO₄-NaH₂PO₄ buffer solution and in the presence of cetyltrimethyl ammonium bromide, nanosilver particles were aggregated to a stable suspension. Therein, rhodamine 6G (Rh6G) exhibited three strong surface-enhanced Raman scattering (SERS) peaks at 613, 1,363, and 1,510 cm^?1, and their SERS intensities were enhanced when the concentration of Rh6G increased. In the presence of Hg²⁺, the SERS intensity decreased greatly owing to formation of stable Rh6G-HgBr ₄ ^2? ternary association complex molecules as well as its particles. In the optimal condition, the decreased SERS intensity at 613 cm^?1 responds linearly with the concentration of Hg²⁺ over 25–2,000 nmol/L. Thus, a new sensitive SERS method has been proposed for the determination of trace Hg²⁺ in the water sample, with satisfactory results.     

Myxospore Formation in Myxococcus xanthus: Chemical Changes in the Cell Wall During Cellular Morphogenesis

Vegetative cells of Myxococcus xanthus (strain FB) were induced to form myxospores by the glycerol induction technique. Several structural changes took place in the peptidoglycan during myxospore formation. The percent of the peptidoglycan comprised of monomer (disaccharide peptide) decreased from about 20% to approximately 7%. The proportion of the total diaminopimelic acid possessing a free amino group decreased about 11%. A carbohydrate containing only glucose was found to be bound, possibly covalently, to the vegetative cell and myxospore peptidoglycan. The amount of carbohydrate relative to peptidoglycan decreased by two-thirds during myxospore formation. None of the above changes in the peptidoglycan were observed in a mutant (strain GNI) of M. xanthus which was unable to convert to myxospores when incubated in the glycerol induction medium, or in the parental wild type (FB) when it was incubated in induction medium lacking the myxospore inducer, glycerol.     

A Filter-based Surface Enhanced Raman Spectroscopic Assay for Rapid Detection of Chemical Contaminants

We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be applied to the detection of various chemical contaminants. Silver nanoparticles (Ag NPs) are synthesized via reduction of silver nitrate by sodium citrate. Then the NPs are aggregated by sodium chloride to form nanoclusters that could be trapped in the pores of the filter membrane. A syringe is connected to the filter holder, with a filter membrane inside. By loading the nanoclusters into the syringe and passing through the membrane, the liquid goes through the membrane but not the nanoclusters, forming a SERS-active membrane. When testing the analyte, the liquid sample is loaded into the syringe and flowed through the Ag NPs coated membrane. The analyte binds and concentrates on the Ag NPs coated membrane. Then the membrane is detached from the filter holder, air dried and measured by a Raman instrument. Here we present the study of the volume effect of Ag NPs and sample on the detection sensitivity as well as the detection of 10 ppb ferbam and 1 ppm ampicillin using the developed assay.     

Studies on the Cell Wall of Chlorella V. Comparison of the Cell Wall Chemical Compositions in Strains of Chlorella ellipsoidea

Cell walls of four strains of Chlorella ellipsoidea (IAM C-27,C-87, C-102 and C-183) were compared as to their chemical compositions.Many differences were found: (1) The sugar composition of alkali-soluble cell walls differedin quantity as well as quality with glucuronic acid being foundonly in C-27 and C-87. (2) In alkali-insoluble cell walls glucosamine was found onlyin C-27. The other three strains contained mainly glucose. (3) The amino acid compositions of the alkali-insoluble cellwalls markedly differed among the four strains. The cell wallof C-102 contained more amino acids than carbohydrates, butC-27 and C-87 contained extremely little amino acid. In addition to the variation in cell wall composition, the opticalanisotropy findings also differed for these cell walls of Chlorellastrains which had been grouped as the same species. (Received August 16, 1983; Accepted December 27, 1983)     

Changes of Cell Wall Composition and Polymer Size in Primary Roots of Cotton Seedlings Under High Salinity

The aim of this study was to investigate changes in cell wallchemical composition and polymer size in the root tip of intactcotton seedlings (Gossypium hirsutum L. cv. Acala SJ-2) grownin saline environments, in order to relate the interaction betweenhigh salinity and root growth to possible changes in cell wallmetabolism. Cotton seedlings were grown in modified Hoagland nutrient solutionwith various combinations of NaCl and CaCl₂. Cell walls werefractionated into four fractions (pectin, hemicellulose 1 and2, cellulose), and analysed for their total sugar content, neutralsugar composition and size of polysaccharides. At 1 mol m^–3Ca, 150 mol m^–3 NaCl resulted in a significant increasein the cell wall uronic acid content, but a reduction in cellulosecontent on a per unit dry weight basis. Supplemental Ca overcamethe inhibitory effect of high Na on cellulose content. The neutralsugar composition of the cell wall fractions showed no majorchanges caused by varied Na/Ca ratios. Determinations of polysaccharidepolymer size showed that high Na at 1 mol m^–3 Ca led toan increase in the amount of polysaccharides of intermediatemolecular size and a decrease in that of small size in the hemicellulose1 fraction, indicating a possible inhibition of polysaccharidedegradation by high Na. This change was not observed in the10 mol m^–3 Ca treatments. The results reveal a relationshipbetween the effects of high salinity on root growth and cellwall metabolism, particularly in regard to cellulose biosynthesis Key words: Gossypium hirsutum, salinity, root, cell wall     

Cell Wall Metabolism in Ripening Fruit (VI. Effect of the Antisense Polygalacturonase Gene on Cell Wall Changes Accompanying Ripening in Transgenic Tomatoes)

Cell walls of tomato (Lycopersicon esculentum Mill.) fruit, prepared so as to minimize residual hydrolytic activity and autolysis, exhibit increasing solubilization of pectins as ripening proceeds, and this process is not evident in fruit from transgenic plants with the antisense gene for polygalacturonase (PG). A comparison of activities of a number of possible cell wall hydrolases indicated that antisense fruit differ from control fruit specifically in their low PG activity. The composition of cell wall fractions of mature green fruit from transgenic and control (wild-type) plants were indistinguishable except for trans-1,2-diaminocyclohexane-N,N,N[prime],N[prime]-tetraacetic acid (CDTA)-soluble pectins of transgenic fruit, which had elevated levels of arabinose and galactose. Neutral polysaccharides and polyuronides increased in the water-soluble fraction of wild-type fruit during ripening, and this was matched by a decline in Na2CO3-soluble pectins, equal in magnitude and timing. This, together with compositional analysis showing increasing galactose, arabinose, and rhamnose in the water-soluble fraction, mirrored by a decline of these same residues in the Na2CO3-soluble pectins, suggests that the polyuronides and neutral polysaccharides solubilized by PG come from the Na2CO3-soluble fraction of the tomato cell wall. In addition to the loss of galactose from the cell wall as a result of PG activity, both antisense and control fruit exhibit an independent decline in galactose in both the CDTA-soluble and Na2CO3-soluble fractions, which may play a role in fruit softening.     

Characterization of Non-Starter Lactic Acid Bacteria from Italian Ewe Cheeses Based on Phenotypic, Genotypic, and Cell Wall Protein Analyses

Non-starter lactic acid bacteria (NSLAB) were isolated from 12 Italian ewe cheeses representing six different types of cheese, which in several cases were produced by different manufacturers. A total of 400 presumptive Lactobacillus isolates were obtained, and 123 isolates and 10 type strains were subjected to phenotypic, genetic, and cell wall protein characterization analyses. Phenotypically, the cheese isolates included 32% Lactobacillus plantarum isolates, 15% L. brevis isolates, 12% L. paracasei subsp. paracasei isolates, 9% L. curvatus isolates, 6% L. fermentum isolates, 6% L. casei subsp. casei isolates, 5% L. pentosus isolates, 3% L. casei subsp. pseudoplantarum isolates, and 1% L. rhamnosus isolates. Eleven percent of the isolates were not phenotypically identified. Although a randomly amplified polymorphic DNA (RAPD) analysis based on three primers and clustering by the unweighted pair group method with arithmetic average (UPGMA) was useful for partially differentiating the 10 type strains, it did not provide a species-specific DNA band or a combination of bands which permitted complete separation of all the species considered. In contrast, sodium dodecyl sulfate-polyacrylamide gel electrophoresis cell wall protein profiles clustered by UPGMA were species specific and resolved the NSLAB. The only exceptions were isolates phenotypically identified as L. plantarum and L. pentosus or as L. casei subsp. casei and L. paracasei subsp. paracasei, which were grouped together. Based on protein profiles, Italian ewe cheeses frequently contained four different species and 3 to 16 strains. In general, the cheeses produced from raw ewe milk contained a larger number of more diverse strains than the cheeses produced from pasteurized milk. The same cheese produced in different factories contained different species, as well as strains that belonged to the same species but grouped in different RAPD clusters.     

Lymphocyte Display: A Novel Antibody Selection Platform Based on T Cell Activation

Since their onset, display technologies have proven useful for the selection of antibodies against a variety of targets; however, most of the antibodies selected with the currently available platforms need to be further modified for their use in humans, and are restricted to accessible antigens. Furthermore, these platforms are not well suited for in vivo selections. We present here a novel cell based antibody display platform, which takes advantage of the functional capabilities of T lymphocytes. The display of antibodies on the surface of T lymphocytes, as a part of a chimeric-immune receptor (CIR) mediating signaling, may ideally link the antigen-antibody interaction to a demonstrable change in T cell phenotype, due to subsequent expression of the early T cell activation marker CD69. In this proof-of-concept, an in vitro selection was carried out using a human T cell line lentiviral-transduced to express a tumor-specific CIR on the surface, against a human tumor cell line expressing the carcinoembryonic antigen. Based on an effective interaction between the CIR and the tumor antigen, we demonstrated that combining CIR-mediated activation with FACS sorting of CD69⁺ T cells, it is possible to isolate binders to tumor specific cell surface antigen, with an enrichment factor of at least 10³-fold after two rounds, resulting in a homogeneous population of T cells expressing tumor-specific CIRs.     

Auxin-Induced Changes in the Cell Wall Xyloglucans: Effects of Auxin on the Two Different Subtractions of Xyloglucans in the Epicotyl Cell Wall of Vigna angularis

In order to study the IAA-induced modifications of the cellwall of azuki bean (Vigna angularis Ohwi et Ohashi cv. Takara)epicotyl segments, the xyloglucans were subfractionated intotwo components, i.e., 4K-U and 24K xyloglucans, which were obtainedby extraction with 4% KOH solution containing 8 M urea and 24%KOH solution, respectively. The weight-average molecular weightsof 4K-U and 24K xyloglucans were estimated to be 40 x 10⁴ and106 x 10⁴, respectively. Complete acid hydrolysis of 4K-U and24K xyloglucans gave glucose, xylose, galactose and fucose inmole % 48.3 : 33.5 : 13.8 : 4.4 and 45.3 : 30.9 : 19.6 : 4.3,respectively. Treatment of epicotyl segments with IAA (0.1 mM) caused a decreasein the amount of 24K xyloglucans and an increase in 4K-U xyloglucans,whereas the total amount of the two xyloglucans remained constant.Furthermore, IAA treatment caused a decrease in the molecularweight of 24K xyloglucans from 106 x 10⁴ to 78 x 10⁴ withoutcausing changes in their sugar compositions. With 4K-U xyloglucans,IAA caused an increase in the mole % of xylose and a decreasein the mole % of galactose and fucose. ¹ This paper is dedicated to the late Professor Joji Ashida. (Received November 26, 1982; Accepted February 7, 1983)