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...     

Surface-Enhanced Raman Spectroscopy of the Endothelial Cell Membrane

We applied surface-enhanced Raman spectroscopy (SERS) to cationic gold-labeled endothelial cells to derive SERS-enhanced spectra of the bimolecular makeup of the plasma membrane. A two-step protocol with cationic charged gold nanoparticles followed by silver-intensification to generate silver nanoparticles on the cell surface was employed. This protocol of post-labelling silver-intensification facilitates the collection of SERS-enhanced spectra from the cell membrane without contribution from conjugated antibodies or other molecules. This approach generated a 100-fold SERS-enhancement of the spectral signal. The SERS spectra exhibited many vibrational peaks that can be assigned to components of the cell membrane. We were able to carry out spectral mapping using some of the enhanced wavenumbers. Significantly, the spectral maps suggest the distribution of some membrane components are was not evenly distributed over the cells plasma membrane. These results provide some possible evidence for the existence of lipid rafts in the plasma membrane and show that SERS has great potential for the study and characterization of cell surfaces.     

Theoretical Simulation and Focused Ion Beam Fabrication of Gold Nanostructures for Surface-Enhanced Raman Scattering (SERS)

This paper describes the fabrication of gold nanopillar and nanorod arrays and theoretical calculations of electromagnetic fields (EMFs) around ordered arrangements of these nanostructures. The EMFs of both single nanopillars and dimers of nanopillars—having nanoscale gaps between the two adjacent nanopillars forming the dimers—are simulated in this work by employing the finite-difference time-domain method. In the case of simulations for dimers of nanopillars, the nanoscale gaps between the nanopillars are varied between 5 and 20 nm, and calculations of the electromagnetic fields in the vicinity of the nanopillars and in the gaps between the nanopillars were carried out. Fabrication of gold nanopillars in a controlled manner for forming SERS substrates involves focused ion beam (FIB) milling. The nanostructures were fabricated on gold-coated silica, mica, and quartz planar substrates as well as on gold-coated tips of four mode and multimode silica optical fibers.     

Single-molecule detection of yeast cytochrome c by Surface-Enhanced Raman Spectroscopy

The giant enhancement of Raman signal near silver colloidal nanoparticles is exploited to study the Raman spectrum of Cytochrome c from Saccharomyces cerevisiae (Yeast Cytochrome c--YCc) in the limit of single-molecule. The investigation is performed on proteins both in solution and immobilised onto a glass slide using a quasi resonant laser line as exciting source with low excitation intensity. In both cases, spectra acquired at different times exhibit dramatic temporal fluctuations in both the total spectrum and in the specific line intensity, even though averaging of several individual spectra reproduces the main Raman features of bulk YCc. Analysis of the spectral intensity fluctuations from solutions reveals a multimodal distribution of some specific Raman lines, consistent with the approaching of single molecule regime. Among other results, the statistical analysis of the spectra from immobilised samples seems to indicate dynamical processes involving the reorientational of the heme with respect to the metal surface.     

Single-Molecule Imaging and Spectroscopy Using Fluorescence and Surface-Enhanced Raman Scattering

We extended single molecule fluorescence imaging and time-resolved fluorometry from the green to the violet-excitation regime to find feasibility of detecting and identifying fluorescent analogs of nucleic-acid bases at the single-molecule level. Using violet excitation, we observed fluorescent spotsfrom single complexes composed of a nucleotide analogue and the Klenow fragmentof DNA polymerase I. Also, we implemented Raman imaging and spectroscopy of adenine molecules adsorbed on Ag colloidal nanoparticles to find feasibility of identifying nucleic-acid bases at the single-molecule level. Surface enhanced Raman scattering (SERS) of adenine molecules showed an intermittent on-and-off behavior called blinking. The observation of blinking provides substantial evidence for detecting single adenine molecules.     

Application of Surface-Enhanced Raman Spectroscopy for Detection of Beta Amyloid Using Nanoshells

Currently, no methods exist for the definitive diagnosis of AD premortem. β-amyloid, the primary component of the senile plaques found in patients with this disease, is believed to play a role in its neurotoxicity. We are developing a nanoshell substrate, functionalized with sialic acid residues to mimic neuron cell surfaces, for the surface-enhanced Raman detection of β-amyloid. It is our hope that this sensing mechanism will be able to detect the toxic form of β-amyloid, with structural and concentration information, to aid in the diagnosis of AD and provide insight into the relationship between β-amyloid and disease progression. We have been successfully able to functionalize the nanoshells with the sialic acid residues to allow for the specific binding of β-amyloid to the substrate. We have also shown that a surface-enhanced Raman spectroscopy response using nanoshells is stable and concentration-dependent with detection into the picomolar range.     

Morphology Dependence on Surface-Enhanced Raman Scattering Using Gold Nanorod Arrays Consisting of Agglomerated Nanoparticles

Plasmonics - Highly ordered arrays of vertically aligned Au nanorod arrays consisting of agglomerated nanoparticles are fabricated by porous anodic aluminum oxide (AAO) template-assisted...     

NIR-SERS技术结合统计分析结直肠癌氧合血红蛋白

基于一种新型、高效近红外表面增强拉曼散射(NIR-SERS)基底,检测了20例健康人和16例结直肠癌患者氧合血红蛋白NIR-SERS光谱。对比发现,结直肠癌患者和健康人氧合血红蛋白NIR-SERS光谱之间存在明显差异。通过谱峰归属分析,发现结直肠癌患者氧合血红蛋白中吡咯环和乙烯基团的振动模式、数量和构象发生了一定的变化,尤其是吡咯环的对称呼吸振动和乙烯集团的反对称伸缩振动模式的数量比健康人要少很多,这些变化很可能是结直肠癌患者组织出现变异以及体内杂乱的新陈代谢引起。利用统计分析方法诊断结直肠癌的特异性与灵敏度分别为85.0%和93.8%,为验证利用统计方法的可靠性,使用受试样品的工作特征曲线方法进行评价。研究表明NIR-SERS光谱技术结合统计分析方法有望发展成为一种新型的结直肠癌临床诊断工具。     

Tunable Surface-Enhanced Raman Spectroscopy via Plasmonic Coupling Between Nanodot-Arrayed Ag Film and Ag Nanocube

Herein, a flexible surface-enhanced Raman spectroscopy (SERS) substrate composed of nanodot-arrayed Ag film and Ag nanocubes was fabricated through a simple method. The large-area nanodot-arrayed Ag film was produced at low cost and high reproducibility. The experimental results show that the coupled structure produces a much stronger SERS signal than the Ag nanocube alone and the isolated nanodot-arrayed Ag film. Furthermore, the coupling effect is sensitive to geometrical parameter of the period of the dot-array. Numerical simulations are performed to verify the electric field enhancement of the composite SERS substrate and support the experimental results.     

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.     

Gold Nanoparticle (AuNP)-Based Surface-Enhanced Raman Scattering (SERS) Probe of Leukemic Lymphocytes

Plasmonics - Identification of cellular surface marker is an effective approach in the early diagnosis of tumor. In this study, based on the finite difference time domain (FDTD) simulation, combing...     

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.     

Fabrication of Sub-10-nm Plasmonic Gaps for Ultra-Sensitive Raman Spectroscopy

Plasmonics - The past two decades have witnessed the explosion of activities in the field of surface enhanced Raman spectroscopy (SERS). SERS platforms employ nano-structures that excite plasmonic...     

On the Choice of a Blocking Protein Agent when Creating an Immunochemical Assay with Surface-Enhanced Raman Spectroscopy

Biophysics - Abstract—The choice of a blocking protein agent for a rapid and sensitive immunochemical assay with surface-enhanced Raman spectroscopy (SERS) was the aim of this study. An...     

Study of Surface-Enhanced Raman Scattering of Plasmonic Coupled Biomolecule: Role of Multi-Layered Nanosphere

Plasmonics - In this communication, we study the surface enhanced Raman scattering (SERS) by a molecule which is adsorbed on a trilayer (Ag@SiO2@Ag) spherical shaped metallic nanostructure. We have...     

MXS-Chaining: A Highly Efficient Cloning Platform for Imaging and Flow Cytometry Approaches in Mammalian Systems

The continuous improvement of imaging technologies has driven the development of sophisticated reporters to monitor biological processes. Such constructs should ideally be assembled in a flexible enough way to allow for their optimization. Here we describe a highly reliable cloning method to efficiently assemble constructs for imaging or flow cytometry applications in mammalian cell culture systems. We bioinformatically identified a list of restriction enzymes whose sites are rarely found in human and mouse cDNA libraries. From the best candidates, we chose an enzyme combination (MluI, XhoI and SalI: MXS) that enables iterative chaining of individual building blocks. The ligation scar resulting from the compatible XhoI- and SalI-sticky ends can be translated and hence enables easy in-frame cloning of coding sequences. The robustness of the MXS-chaining approach was validated by assembling constructs up to 20 kb long and comprising up to 34 individual building blocks. By assessing the success rate of 400 ligation reactions, we determined cloning efficiency to be 90% on average. Large polycistronic constructs for single-cell imaging or flow cytometry applications were generated to demonstrate the versatility of the MXS-chaining approach. We devised several constructs that fluorescently label subcellular structures, an adapted version of FUCCI (fluorescent, ubiquitination-based cell cycle indicator) optimized to visualize cell cycle progression in mouse embryonic stem cells and an array of artificial promoters enabling dosage of doxycyline-inducible transgene expression. We made publicly available through the Addgene repository a comprehensive set of MXS-building blocks comprising custom vectors, a set of fluorescent proteins, constitutive promoters, polyadenylation signals, selection cassettes and tools for inducible gene expression. Finally, detailed guidelines describe how to chain together prebuilt MXS-building blocks and how to generate new customized MXS-building blocks.     

The Synergism of DMSO and Diethyl Ether for Highly Reproducible and Efficient MA0.5FA0.5PbI3 Perovskite Solar Cells

Composition and film quality of perovskite are crucial for the further improvement of perovskite solar cells (PSCs), including efficiency, reproducibility, and stability. Here, it is demonstrated that by simply mixing 50% of formamidinium (FA⁺) into methylammonium lead iodide (MAPbI₃), a highly crystalline, stable phase, and compact, polycrystalline grain morphology perovskite is formed by using a solvent‐mediated phase transformation process via the synergism of dimethyl sulfoxide and diethyl ether, which shows long carrier lifetime, low trap state density, and a record certified 21.8% power conversion efficiency (PCE) in pure‐iodide, alkaline‐metal‐free MA_0.5FA_0.5PbI₃ perovskite‐based PSCs. These PSCs show very high operational stability, with 85% PCE retention upon 1000 h 1 Sun intensity illumination. A 17.33% PCE module (6.5 × 7 cm²) is also demonstrated, attesting to the scalability of such devices.     

Inexpensive and Highly Reproducible Cloud-Based Variant Calling of 2,535 Human Genomes

Population scale sequencing of whole human genomes is becoming economically feasible; however, data management and analysis remains a formidable challenge for many research groups. Large sequencing studies, like the 1000 Genomes Project, have improved our understanding of human demography and the effect of rare genetic variation in disease. Variant calling on datasets of hundreds or thousands of genomes is time-consuming, expensive, and not easily reproducible given the myriad components of a variant calling pipeline. Here, we describe a cloud-based pipeline for joint variant calling in large samples using the Real Time Genomics population caller. We deployed the population caller on the Amazon cloud with the DNAnexus platform in order to achieve low-cost variant calling. Using our pipeline, we were able to identify 68.3 million variants in 2,535 samples from Phase 3 of the 1000 Genomes Project. By performing the variant calling in a parallel manner, the data was processed within 5 days at a compute cost of $7.33 per sample (a total cost of $18,590 for completed jobs and $21,805 for all jobs). Analysis of cost dependence and running time on the data size suggests that, given near linear scalability, cloud computing can be a cheap and efficient platform for analyzing even larger sequencing studies in the future.     

Raman Spectroscopy: A Conformational Probe in Biochemistr

RNA localization, the enrichment of RNA in a specific subcellular region, is a mechanism for the establishment and maintenance of cellular polarity in a variety of systems. Ultimately, this results in a universal method for spatially restricting gene expression. Although the consequences of RNA localization are well-appreciated, many of the mechanisms that are responsible for carrying out polarized transport remain elusive. Several recent studies have illuminated the roles that molecular motor proteins play in the process of RNA localization. These studies have revealed complex mechanisms in which the coordinated action of one or more motor proteins can act at different points in the localization process to direct RNAs to their final destination. In this review, we discuss recent findings from several different systems in an effort to clarify pathways and mechanisms that control the directed movement of RNA.     

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.