Fabrication of a Au Nanoporous Film by Self-Organization of Networked Ultrathin Nanowires and Its Application as a Surface-Enhanced Raman Scattering Substrate for Single-Molecule Detection

Surfactant-Free Method to Prevent Gold Nanoparticle Aggregation and Its Surface-Enhanced Raman Scattering Applications

The introduction of surfactants to stabilize colloidal citrate-reduced gold nanoparticles (prevent aggregation) is usually used in surface-enhanced Raman scattering (SERS) applications. However, the surfactants have many drawbacks for SERS applications, such as increasing the SERS background and blocking surface active sites. Here, we develop a surfactant-free method to stabilize colloidal cit-AuNPs based on alkali regulation, and this method can prevent gold nanoparticle aggregation under different harsh treatments, including ligand modification, centrifugation-based washing/enrichment, and salt addition. The SERS spectra, density functional theory simulation, and ζ potentials of cit-AuNPs indicate that the stability of enhanced cit-AuNPs under alkaline conditions is attributed to both the increased negative charge density (by ∼6 times from pH 7 to 12) and the molecular configuration on the metal surface. Compared with surfactant-based methods, this method can well maintain the inherent optical and interface properties of nanoparticles, avoid the SERS background, and avoid blocking of the surface active site due to the presence of surfactants. This method will enable AuNPs to have a wide range of applications in areas such as highly sensitive SERS sensors.

Lamellar nanoporous gold thin films with tunable porosity for ultrasensitive SERS detection in liquid and gas phase

Lamellar nanoporous gold thin films, constituted of a stack of very thin layers of porous gold, are synthesized by chemical etching from a stack of successively deposited nanolayers of copper and gold. The gold ligament size, the pore size and the distance between lamellas are tunable in the few tens nanometer range by controlling the initial thickness of the layers and the etching time. The SERS activity of these lamellar porous gold films is characterized by their SERS responses after adsorption of probe bipyridine and naphtalenethiol molecules. The SERS signal is investigated as a function of the bipyridine concentration from 10^-14 mol L^-1 to 10^-3 mol L^-1. The higher SERS response corresponds to an experimental detection limit down to 10^-12 mol L^-1. These performance is mainly attributed to the specific nanoporous gold architecture and the larger accessible surface to volume ratio. The lamellar nanoporous gold substrate is explored for sensitive SERS detection of dimethyl methylphosphonate (DMMP), a surrogate molecule of the highly toxic G-series nerve agents. The resultant nanostructure facilitates the diffusion of target molecules through the nanopores and their localization at the enhancing metallic surface leading to the unequivocal Raman signature of DMMP at a concentration of 5 parts per million.

TiO2 particles in seafood and surimi products: Attention should be paid to their exposure and uptake through foods

The sustainable development of nanotechnology requires a thorough understanding of the life cycle of synthesized nanomaterials, including environmental release, deposition, exposure, and potential health risks. Titanium dioxide (TiO₂) materials containing nanosized TiO₂ (nTiO₂) are commonly used as food additives. Thus, dietary intake through foods is the most important route for the exposure of TiO₂ materials. Given the toxic effects of nTiO₂ on the gastrointestinal tract and other tissues, it is imperative to investigate their sources and concentrations in popular foods. Therefore, we conducted a survey on TiO₂ particles in white-colored seafood and surimi products in Beijing. Our data indicated that the total Ti levels reached 6-12 μg/g (dry weight) in some white-colored seafood products, such as squid and cuttlefish, whereas relatively low concentrations were observed in jellyfish at approximately 1-3 μg/g (dry weight). For the locally favorite surimi-based food products in the market, the Ti concentrations ranged from 2 to 81 μg/g (dry weight). The exposure assessment showed that the average daily intake of TiO₂ particles through foods varied from 0.02 to 3.09 μg TiO₂/kg_bw/day, reflected by the Ti concentrations in this study, and that young people of age 20-30 showed the highest exposure level. Together, these results show relatively high concentrations of TiO₂ particles in some seafood and surimi products available in the market, and our findings therefore call for attention on TiO₂ particle exposure and uptake through daily foods.

Island-like Nanoporous Gold: Smaller Island Generates Stronger Surface-Enhanced Raman Scattering

The surface-enhanced Raman scattering properties of nanoporous gold prepared by the dealloying technique have been investigated for many years.The relatively low enhancement factor and the poor uniformity of existing conventional or advanced nanoporous gold structures are still the main factors that limit their wide application as Raman enhancement substrates. Here, we report island-like nanoporous gold (INPG) fabricated by simply controlling the composition of the dealloying precursor.This nanostructure can generate ∼10 times higher enhancement factor (above 10⁷) with ∼4 times lower gold consumption than conventional nanoporous gold. The dimensions of the gold islands can be controlled by the composition of the precursor. The enhancement factor can therefore be controlled by the gold island dimensions, which suggests an effective approach to fabricate better Raman enhancement substrates. Furthermore, INPG exhibits excellent Raman enhancement uniformity and reproducibility with the relative standard deviations of only 2.5% and 6.5%, which originate from the extremely homogeneous structure of INPG at both the microscale and macroscale. The excellent surface-enhanced Raman scattering properties make INPG a potential surface-enhanced Raman scattering substrate.

Rational Design of Branched Nanoporous Gold Nanoshells with Enhanced Physico-Optical Properties for Optical Imaging and Cancer Therapy

Reported procedures on the synthesis of gold nanoshells with smooth surfaces have merely demonstrated efficient control of shell thickness and particle size, yet no branch and nanoporous features on the nanoshell have been implemented to date. Herein, we demonstrate the ability to control the roughness and nanoscale porosity of gold nanoshells by using redox-active polymer poly(vinylphenol)-b-(styrene) nanoparticles as reducing agent and template. The porosity and size of the branches on this branched nanoporous gold nanoshell (BAuNSP) material can be facilely adjusted by control of the reaction speed or the reaction time between the redox-active polymer nanoparticles and gold ions (Au³⁺). Due to the strong reduction ability of the redox-active polymer, the yield of BAuNSP was virtually 100%. By taking advantage of the sharp branches and nanoporous features, BAuNSP exhibited greatly enhanced physico-optical properties, including photothermal effect, surface-enhanced Raman scattering (SERS), and photoacoustic (PA) signals. The photothermal conversion efficiency can reach as high as 75.5%, which is greater than most gold nanocrystals. Furthermore, the nanoporous nature of the shells allows for effective drug loading and controlled drug release. The thermoresponsive polymer coated on the BAuNSP surface serves as a gate keeper, governing the drug release behavior through photothermal heating. Positron emission tomography imaging demonstrated a high passive tumor accumulation of ⁶⁴Cu-labeled BAuNSP. The strong SERS signal generated by the SERS-active BAuNSP in vivo, accompanied by enhanced PA signals in the tumor region, provide significant tumor information, including size, morphology, position, and boundaries between tumor and healthy tissues. In vivo tumor therapy experiments demonstrated a highly synergistic chemo-photothermal therapy effect of drug-loaded BAuNSPs, guided by three modes of optical imaging.

Carbon Nanotubes Disrupt Iron Homeostasis and Induce Anemia of Inflammation through Inflammatory Pathway as a Secondary Effect Distant to Their Portal-of-Entry

Although numerous toxicological studies have been performed on carbon nanotubes (CNTs), a few studies have investigated their secondary and indirect effects beyond the primary target tissues/organs. Here, a cascade of events are investigated: the initiating event and the subsequent key events necessary for the development of phenotypes, namely CNT-induced pro-inflammatory effects on iron homeostasis and red blood cell formation, which are linked to anemia of inflammation (AI). A panel of CNTs are prepared including pristine multiwall CNTs (P-MWCNTs), aminated MWCNTs (MWCNTs-NH₂ ), polyethylene glycol MWCNTs (MWCNTs-PEG), polyethyleneimine MWCNTs (MWCNTs-PEI), and carboxylated MWCNTs (MWCNTs-COOH). It has been demonstrated that all CNT materials provoke inflammatory cytokine interleukin-6 (IL-6) production and stimulate hepcidin induction, associated with disordered iron homeostasis, irrespective of exposure routes including intratracheal, intravenous, and intraperitoneal administration. Meanwhile, PEG and COOH modifications can ameliorate the activation of IL-6-hepcidin signaling. Long-term exposure of MWCNTs results in AI and extramedullary erythropoiesis. Thus, an adverse outcome pathway is identified: MWCNT exposure leads to inflammation, hepatic hepcidin induction, and disordered iron metabolism. Together, the combined data depict the hazardous secondary toxicity of CNTs in incurring anemia through inflammatory pathway. This study will also open a new avenue for future investigations on CNT-induced indirect and secondary adverse effects.

Ultrasensitive SERS performance in 3D "sunflower-like" nanoarrays decorated with Ag nanoparticles

Low-cost, stabilized and ultrasensitive three-dimensional (3D) hierarchical surface-enhanced Raman scattering substrates ("sunflower-like" nanoarrays decorated with Ag nanoparticles, denoted as SLNAs-Ag) have been obtained by fabricating binary colloidal crystals and then decorating with Ag nanoparticles. In order to provide a larger density of hot spots within the laser-illumination area, the silica sphere arrays were chosen as the island-type platform for the polystyrene (PS) nanosphere deposition, and the distances between the PS nanospheres were tuned by etching for different durations. Compared with conventional 2D planar systems, the as-fabricated 3D SLNAs-Ag exhibited extremely high SERS sensitivity ascribed to the larger SERS active regions. Quantitative detection of molecules with an extremely low incident laser power was achieved on the "sunflower-like" nanoarrays in which the PS nanospheres were etched for 5 minutes and decorated with Ag nanoparticles, and the corresponding analytical enhancement factor is calculated to be 2 × 10¹⁴ with the concentration of rhodamine 6G down to 10^-15 M. Based on the achieved SERS substrates, we have further demonstrated the highly sensitive detection of molecules such as melamine for food safety inspection.

Use of Polycrystalline Ice for Assembly of Large Area Au Nanoparticle Superstructures as SERS Substrates

It is still a great challenge to develop simple and low-cost methods for preparation of surface-enhanced Raman scattering (SERS) substrates with high sensitivity and reproducibility. Taking advantage of the microstructure of polycrystalline ice, we developed a new method to assemble large area gold nanoparticle (AuNP) superstructures as SERS substrates without external templating and aggregating agent. The assembly was conducted by freezing AuNP colloid at -20 °C, which concentrated AuNPs in the ice veins and produced an AuNP superstructure upon thawing the ice. The AuNP superstructures exhibited high SERS activity with enhancement factors on the order of 7.63 × 10⁷ owing to the high-density hot spots throughout the superstructures. The SERS activity was found to increase with particle size and aggregate size of AuNP superstructures. Besides, the substrates showed good uniformity and reproducibility with relative standard deviations of 11.9% and 12.4%, respectively. The substrates showed long-term stability, maintaining SERS activity over a period of five months without noticeable change in morphology of the superstructures. The substrates was further used for label-free detection of trace Thiram on apple fruit with high sensitivity down to the concentration of 0.28 ng/cm², offering great potential to monitor Thiram levels in foodstuffs and environmental samples.

Green Synthesis of High-Purity Mesoporous Gold Sponges Using Self-Assembly of Gold Nanoparticles Induced by Thiolated Poly(ethylene glycol)

A facile and green synthesis method for mesoporous gold sponges has been developed, which involves a simple mixing of a very small amount of thiolated-poly(ethylene glycol) (SH-PEG) and citrate-covered gold nanoparticles (Au NPs) in aqueous solution at room temperature. While SH-PEG molecules have been widely used as biocompatible hydrophilic capping agents for Au NPs for stable dispersion in aqueous solution, here they are used as destabilizing agents. When SH-PEG molecules are mixed with citrate-covered Au NPs at the molar ratio ranging from 3 to 20 (SH-PEG/Au NP), mesoporous gold sponges with randomly interconnected 3D network structures are formed within 2 to 3 h. This is driven by the destabilization of negatively charged citrate molecules on Au NPs by a small number of SH-PEG molecules bonded on the particle surface, which results in the decrease in zeta potential and thus the assembly of Au NPs into porous sponges. The use of very low concentration of SH-PEG (ca. 20-200 nM) in aqueous solution at room temperature makes the method highly eco-friendly as well as results in high-purity as-synthesized gold sponges (98.7 wt %). The mesoporous gold sponges fabricated with the present method exhibit a high SERS activity, making them highly applicable for sensitive SERS detection of molecules.

Crucial Role of Lateral Size for Graphene Oxide in Activating Macrophages and Stimulating Pro-inflammatory Responses in Cells and Animals

Graphene oxide (GO) is increasingly used in biomedical applications because it possesses not only the unique properties of graphene including large surface area and flexibility but also hydrophilicity and dispersibility in aqueous solutions. However, there are conflicting results on its biocompatibility and biosafety partially due to large variations in physicochemical properties of GO, and the role of these properties including lateral size in the biological or toxicological effects of GO is still unclear. In this study, we focused on the role of lateral size by preparing a panel of GO samples with differential lateral sizes using the same starting material. We found that, in comparison to its smaller counterpart, larger GO showed a stronger adsorption onto the plasma membrane with less phagocytosis, which elicited more robust interaction with toll-like receptors and more potent activation of NF-κB pathways. By contrast, smaller GO sheets were more likely taken up by cells. As a result, larger GO promoted greater M1 polarization, associated with enhanced production of inflammatory cytokines and recruitment of immune cells. The in vitro results correlated well with local and systemic inflammatory responses after GO administration into the abdominal cavity, lung, or bloodstream through the tail vein. Together, our study delineated the size-dependent M1 induction of macrophages and pro-inflammatory responses of GO in vitro and in vivo. Our data also unearthed the detailed mechanism underlying these effects: a size-dependent interaction between GO and the plasma membrane.

Monolayer graphene on nanostructured Ag for enhancement of surface-enhanced Raman scattering stable platform

We have reported that the Ag nanostructure-based substrate is particularly suitable for surface-enhanced Raman scattering when it is coated with monolayer graphene, an optically transparent and chemistry-inertness material in the visible range. Ag bowtie nanoantenna arrays and Ag nanogrids were fabricated using plasma-assisted nanosphere lithography. Our measurements show that atmospheric sulfur containing compounds are powerless to break in the monolayer graphene to vulcanize the surfaces of the Ag bowtie nanoantenna arrays and Ag nanogrids by various means, including scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS). Furthermore, the Ag nanostructure substrate coated with the monolayer graphene film shows a larger enhancement of Raman activity and the electromagnetic field than the uncoated substrate. Compared with those of bare Ag nanostructures, the averaged EFs of graphene-film-coated Ag nanostructures were estimated to be about 21 and 5 for Ag bowtie nanoantenna arrays and nanogrids after one month later in air, respectively. These observations are further supported by theoretical calculations.

SERS quantitative analysis of trace HSA with a Coomassie brilliant blue G-250 molecular probe in nanogold sol substrate

A SERS quantitative analysis method was developed for the detection of trace HSA with a Coomassie brilliant blue G-250 probe in nanogold sol substrate.

Fabrication of highly-specific SERS substrates by co-precipitation of functional nanomaterials during the self-sedimentation of silver nanowires into a nanoporous film

In this report, we propose and demonstrate the fabrication of a highly-specific SERS substrate by co-precipitating of functional materials, such as nanosorbents and nanocatalysts, into Ag nanoporous films.

SERS quantitative detection of trace human chorionic gonadotropin using a label-free Victoria blue B as probe in the aggregated immunonanogold sol substrate

Nanogold particles (NG) were modified by anti-rabbit antibody (RAb) against human chorionic gonadotropin to obtain an immunonanogold probe (ING). In pH 7.0 Na2HPO4-citrate buffer solution containing KCl, ING probes formed large aggregates in which Victoria blue B (VBB) molecules were adsorbed on the surface and which exhibited strong surface-enhanced Raman scattering (SERS) at a peak of 1612 cm(-1). After addition of human chorionic gonadotropin (hCG) an immune reaction with the ING probe occurred to form dispersive ING-hCG complexes with non-SERS activity that led to a decreased SERS peak at 1612 cm(-1). The decreased SERS intensity was linear to the concentration of hCG over 2.4-73.2 ng/mL. The ING reaction was studied in detail by SERS, scanning electron microscope (SEM), resonance Rayleigh scattering (RRS), surface plasmon resonance (SPR) absorption and laser scattering techniques. SERS quenching was observed and discussed.

Coffee-ring effect-based simultaneous SERS substrate fabrication and analyte enrichment for trace analysis

Based on the "coffee-ring effect", we developed a highly efficient SERS platform which integrates the fabrication of SERS-active substrates and the preconcentration of analytes into one step. The high sensitivity, robustness, reproducibility and simplicity make this platform ideal for on-site analysis of small volume samples at low concentrations in complex matrices.

Quantitative analysis of trace Pb(II) by a DNAzyme cracking-rhodamine 6G SERRS probe on Au(core)Ag(shell) nanosol substrate

In pH 7.2 Tris-HCl buffer solution containing 0.09 mol/L NaCl at 80°C, the single-stranded substrate DNA hybrids with the enzyme DNA to form double-stranded DNA (dsDNA). The substrate chain of dsDNA could be cracked catalytically by Pb(2+) to produce a short single-stranded DNA (ssDNA) that adsorbed on the Au(core)Ag(shell) nanoparticle (Au/AgNP) surface to form stable Au/AgNP-ssDNA conjugate to prevent aggregation by NaCl, and it combined with rhodamine 6G (RhG) to form RhG-Au/AgNP-ssDNA probe that exhibited a strong surface-enhanced resonance Raman scattering (SERRS) peak at 1510 cm(-1). With the increase of Pb(2+) concentration, the SERRS peak increased linearly due to the more RhG-Au/AgNP-ssDNA probe forming. Under the selected conditions, the increased SERRS intensity ΔI was linear to Pb(2+) concentration in the range of 5.0×10(-8)-7.0×10(-7) mol/L, with a detection limit of 7×10(-9) mol/L Pb(2+).

Si/ZnO nanocomb arrays decorated with Ag nanoparticles for highly efficient surface-enhanced Raman scattering

High-density ZnO nanocombs were first grown on a nanoporous silicon pillar array, and pre-prepared 3D Si/ZnO/Ag nanocomb arrays were employed as substrates for surface-enhanced Raman scattering (SERS). The finite-difference time-domain simulation result shows that two kinds of inter-Ag-NP nanogaps in the geometry create a large number of SERS "hot spots," which contributes to the detection limits for rhodamine-6G as low as 10⁻¹² M and the Raman enhancement factor as large as 10⁹. The linear dependence between the Raman peak intensities and the concentrations of thiram provides a new calibration method for rapid and quantitative detection of trace organic molecules.

Flexible membranes of Ag-nanosheet-grafted polyamide-nanofibers as effective 3D SERS substrates

We report on a synthetic approach to produce self-supported flexible surface-enhanced Raman scattering (SERS) active membranes consisting of polyamide (PA) nanofibers grafted with vertical Ag-nanosheets, via a combinatorial process of electrospinning PA-nanofiber membranes, assembling Au-nanoparticles on the PA-nanofibers as seeds for subsequent growth of Ag-nanosheets, and electrodepositing Ag-nanosheets on the electrospun PA-nanofibers. As a high density of Ag-nanosheets are vertically grown around each PA-nanofiber in the three-dimensional (3D) networked PA-nanofiber membranes, homogeneous nano-scaled gaps between the neighboring Ag-nanosheets are formed, leading to a high density of 3D SERS "hot spots" within the Ag-nanosheet-grafted PA-nanofiber membranes. The Ag-nanosheet-grafted PA-nanofiber membranes demonstrate high SERS activity with excellent Raman signal reproducibility for rhodamine 6G over the whole membrane. For a SERS-based trial analysis of polychlorinated biphenyls (PCBs, a kind of global environmental hazard), the 3D SERS substrate membranes are modified with mono-6-β-cychlodextrin to effectively capture PCB molecules. As a result, not only a low concentration down to 10(-6) M is reached, but also two congeners of PCBs in their mixed solution are identified, showing promising potential in SERS-based rapid detection of trace organic pollutants such as PCBs in the environment.

Submonolayer-Pt-Coated Ultrathin Au Nanowires and Their Self-Organized Nanoporous Film: SERS and Catalysis Active Substrates for Operando SERS Monitoring of Catalytic Reactions

For their unique properties, core-shell bimetal nanostructures are currently of immense interest. However, their synthesis is not a trivial work, and most works have been conducted on nanoparticles. We report herein a new synthetic tactic for submonolyer-Pt coated ultrathin Au nanowires (NWs). Besides providing a strong electromagnetic field for Raman signal enhancing, the underlined Au NWs markedly enhanced the catalytic activity of Pt atoms through increasing their dispersity and altering their electronic state. The integration of excellent SERS and high catalytic activity within Au@Pt NWs enable it work as platform for catalyzed reaction study. As a proof of principle, the self-organized Au@Pt NWs thin film is employed in operando SERS monitoring of the p-nitrothiophenol reduction process. In addition to providing kinetic data for structure-activity relationship study, the azo-intermidate independent path is also directly witnessed. This synthetic tactic can be extended to other metals, thus offering a general approach to modulate the physical/chemical properties of both core and shell metals.

Investigation of halide-induced aggregation of Au nanoparticles into spongelike gold

We present a facile method for fabricating spongelike Au structures by halide-induced aggregation and fusion of gold nanoparticles (AuNPs). Halide ions (F(-), Cl(-), Br(-), and I(-)) showed distinctly different effects on the synthesized AuNPs, which were characterized by localized surface plasmon resonance (LSPR) and dynamic light scattering measurements. A noticeable red-shift in the LSPR peak was found after Br(-) and I(-) ion treatment, which indicates the adsorption of halide atoms or ions on the AuNPs. The surface potential of AuNPs varied by treatment with different types of halides; this finding indicates that different halide ions have different effects on the AuNPs. Br(-) and I(-) ions showed strong affinity toward the AuNPs. The different affinities of halide ions toward the AuNPs play an important role in controlling the formation process of spongelike gold. Citrate ions adsorbed on AuNPs were displaced by halide ions to different extents. Such displacement determined the aggregation and fusion behaviors of the AuNPs and eventually the formation of different spongelike structures.

Nanostructured materials for applications in surface-enhanced Raman scattering

This highlight summarizes current advances in the design and the employment of nanostructured materials in SERS substrates especially from the dimensional point of view. We then talk about synthesis methods and the novel properties of these nanostructured materials with their potential applications in SERS.

Facile synthesis of ultrathin worm-like Au nanowires for highly active SERS substrates

Ultrathin worm-like Au nanowires were facilely synthesized and used for the fabrication of porous Au films as highly active SERS substrates.

Ag@SiO2 core-shell nanoparticles on silicon nanowire arrays as ultrasensitive and ultrastable substrates for surface-enhanced Raman scattering

Ag nanoparticles (NPs) coated with silica nanolayers were decorated onto a large-scale and uniform silicon nanowire array (SiNWA) by simple chemical etching and metal reduction processes. The three-dimensional Ag/SiNWAs thus formed are employed as a substrate for surface-enhanced Raman scattering (SERS), and a detection limit for rhodamine 6G as low as 10(-16) M and a Raman enhancement factor as large as 10(14) were obtained. Simulation results show that two kinds of inter-Ag-NP nanogaps in three-dimensional geometry create a huge number of SERS 'hot spots' where electromagnetic fields are substantially amplified, contributing to the higher SERS sensitivity and lower detection limit. The excellent SERS stability of Ag/SiNWAs is attributed to the presence of the SiO2 nanolayer around Ag NPs that prevented the Ag NP surface from being oxidized. The calibration of the Raman peak intensities of rhodamine 6G and thiram allowed their quantitative detection. Our finding is a significant advance in developing SERS substrates for the fast and quantitative detection of trace organic molecules.

Graphene oxide induces toll-like receptor 4 (TLR4)-dependent necrosis in macrophages

Graphene and graphene-based nanomaterials display novel and beneficial chemical, electrical, mechanical, and optical characteristics, which endow these nanomaterials with promising applications in a wide spectrum of areas such as electronics and biomedicine. However, its toxicity on health remains unknown and is of great concern. In the present study, we demonstrated that graphene oxide (GO) induced necrotic cell death to macrophages. This toxicity is mediated by activation of toll-like receptor 4 (TLR4) signaling and subsequently in part via autocrine TNF-α production. Inhibition of TLR4 signaling with a selective inhibitor prevented cell death nearly completely. Furthermore, TLR4-deficient bone marrow-derived macrophages were resistant to GO-triggered necrosis. Similarly, GO did not induce necrosis of HEK293T/TLR4-null cells. Macrophagic cell death upon GO treatment was partially attributed to RIP1-RIP3 complex-mediated programmed necrosis downstream of TNF-α induction. Additionally, upon uptake into macrophages, GO accumulated primarily in cytoplasm causing dramatic morphologic alterations and a significant reduction of the macrophagic ability in phagocytosis. However, macrophagic uptake of GO may not be required for induction of necrosis. GO exposure also caused a large increase of intracellular reactive oxygen species (ROS), which contributed to the cause of cell death. The combined data reveal that interaction of GO with TLR4 is the predominant molecular mechanism underlying GO-induced macrophagic necrosis; also, cytoskeletal damage and oxidative stress contribute to decreased viability and function of macrophages upon GO treatment.

Highly efficient SERS test strips

We present a facile production approach to highly efficient SERS test strips by physical vapor deposition of silver on paper, which contains natural wrinkle and fibril structures. The SERS test strips open the door to highly sensitive (e.g., 10(-10) M) SERS detection in a convenient fashion.