Selective Flocculation and H2O2-Free Oxidative Etching-Based Synthesis of Highly Monodisperse Ag Nanospheres for Uniform Quantum Dot Photoluminescence-Enhancing Plasmonic Cavity Applications.

Ag nanoparticles have garnered significant attention for their excellent plasmonic properties and potential use as plasmonic cavities, primarily because of their intrinsically low ohmic losses and optical properties in the visible range. These are particularly crucial in systems involving quantum dots that absorb light at low wavelengths, where the need for a high threshold energy of interband transitions necessitates the incorporation of Ag nanostructures. However, the synthesis of Ag nanoparticles still encounters challenges in achieving structural uniformity and monodispersity, along with chemical stability, consequentially inducing inconsistent and poorly reliable optical responses. Here, we present a two-step approach for synthesizing highly uniform spherical Ag nanoparticles involving depletion-induced flocculation and Cu(II)-mediated oxidative etching. We found that the selective flocculation of multitwinned Ag nanocrystals significantly enhances the uniformity of the resulting Ag nanostructures, leaving behind only single-crystalline and single-twinned nanostructures. Subsequent oxidative etching, in which cupric ions are directly involved in the reaction, was designed based on Pourbaix diagrams to proceed following thermodynamically favorable states and circumvent the generation of reactive chemical species such as H2O2. This leads to perfectly spherical shapes of final Ag nanoparticles with a synthetic yield of 99.5% and additionally reduces the overall reaction time. Furthermore, we explore the potential applications of these monodisperse Ag nanospheres as uniform plasmonic cavities. The fabricated Ag nanosphere films uniformly enhanced the photoluminescence of InP/ZnSe/ZnS quantum dots, showcasing their capabilities in exhibiting consistent plasmonic responses across a large area.

Plasmonic Cyclic Au Nanosphere Hexamers.

Rational design of plasmonic colloidal assemblies via bottom-up synthesis is challenging but would show unprecedented optical properties that strongly relate to the assembly's shape and spatial arrangement. Herein, the synthesis of plasmonic cyclic Au nanosphere hexamers (PCHs) is reported, wherein six Au nanospheres (Au NSs) are connected via thin metal ligaments. By tuning Au reduction, six dangling Au NSs are interconnected with a core hexagon nanoplate (NPL). Then, Pt atoms are selectively deposited on the edges of the spheres. After etching of the core, necklace-like nanostructures of Pt framework are obtained. Deposition of Au is followed, leading to PCHs in high yield (≈90%). Notably, PCHs exhibit the combinatorial plasmonic characteristics of individual Au NSs and the in-plane coupling of the six linked Au NSs. They yield highly uniform, reproducible, and polarization-independent single-particle surface-enhanced Raman scattering signals, which are attributed to the 2-dimensional isotropic alignment of the Au NSs. Those are applied to a SERS-based immunoassay as quantitative and qualitative single particle SERS nanoprobes. This assay shows a low limit-of-detection, down to 100 pm, which is orders of magnitude lower than those based on Au NSs, and one order of magnitude lower than an assay using analogous particles of smooth Au nanorings.

Ring-in-a-Triangle Nanoframes: Integrating with Intra- and Interhotspots for Highly Amplified Near-Field Focusing.

The development of a stepwise synthetic strategy for Au ring-in-a-triangle nanoframes with a high degree of structural solidity is essential to the advancement of highly amplified near-field focusing. This strategy leads to the formation of an inscribed nanoring in a triangular metal frame with stability to withstand elevated temperatures and an oxidizing environment, which is critical for successful single-particle surface-enhanced Raman scattering (SERS). The existence of inscribed nanorings plays an important role in enhancing the so-called "lightning rod effect," whereby the electromagnetic near-field enhancement occurs on the highly curved curvature of a metallic interface. We evaluated the corresponding single-particle SERS as a function of the thickness of the rims and then constructed two-dimensional (2D) bulk SERS substrates, wherein an ensemble of hotspots exists. The synergic contribution from both inter- and intrahotspots allowed the outstanding linearity of the calibration curve and the lowest limit of detection, ∼10-18 M for the analyte concentration.

Toward Quantitative Surface-Enhanced Raman Scattering with Plasmonic Nanoparticles: Multiscale View on Heterogeneities in Particle Morphology, Surface Modification, Interface, and Analytical Protocols.

Surface-enhanced Raman scattering (SERS) provides significantly enhanced Raman scattering signals from molecules adsorbed on plasmonic nanostructures, as well as the molecules' vibrational fingerprints. Plasmonic nanoparticle systems are particularly powerful for SERS substrates as they provide a wide range of structural features and plasmonic couplings to boost the enhancement, often up to >108-1010. Nevertheless, nanoparticle-based SERS is not widely utilized as a means for reliable quantitative measurement of molecules largely due to limited controllability, uniformity, and scalability of plasmonic nanoparticles, poor molecular modification chemistry, and a lack of widely used analytical protocols for SERS. Furthermore, multiscale issues with plasmonic nanoparticle systems that range from atomic and molecular scales to assembled nanostructure scale are difficult to simultaneously control, analyze, and address. In this perspective, we introduce and discuss the design principles and key issues in preparing SERS nanoparticle substrates and the recent studies on the uniform and controllable synthesis and newly emerging machine learning-based analysis of plasmonic nanoparticle systems for quantitative SERS. Specifically, the multiscale point of view with plasmonic nanoparticle systems toward quantitative SERS is provided throughout this perspective. Furthermore, issues with correctly estimating and comparing SERS enhancement factors are discussed, and newly emerging statistical and artificial intelligence approaches for analyzing complex SERS systems are introduced and scrutinized to address challenges that cannot be fully resolved through synthetic improvements.

DNA-Engineerable Ultraflat-Faceted Core-Shell Nanocuboids with Strong, Quantitative Plasmon-Enhanced Fluorescence Signals for Sensitive, Reliable MicroRNA Detection.

There has been enormous interest in understanding and utilizing plasmon-enhanced fluorescence (PEF) with metal nanostructures, but maximizing the enhancement in a reproducible, quantitative manner while reliably controlling the distance between dyes and metal particle surface for practical applications is highly challenging. Here, we designed and synthesized fluorescence-amplified nanocuboids (FANCs) with highly enhanced and controlled PEF signals, and fluorescent silica shell-coated FANCs (FS-FANCs) were then formed to fixate the dye position and increase particle stability and fluorescence signal intensity for biosensing applications. By uniformly modifying fluorescently labeled DNA on Au nanorods and forming ultraflat Ag shells on them, we were able to reliably control the distance between fluorophores and Ag surface and obtained an ∼186 fluorescence enhancement factor with these FANCs. Importantly, FS-FANCs were utilized as fluorescent nanoparticle tags for microarray-based miRNA detection, and we achieved >103-fold higher sensitivity than commercially available chemical fluorophores with 100 aM to 1 pM dynamic range.

Nontrivial, Unconventional Electrochromic Behaviors of Plasmonic Nanocubes.

Plasmonic electrochromism, a change in the localized surface plasmon resonance (LSPR) with an applied electric potential, has been attracting increasing attention for the development of spectroscopic tools or optoelectronic systems. There is a consensus on the mechanism of plasmonic electrochromism based on the classical capacitor and the Drude model. However, the electrochromic behaviors of metallic nanoparticles in narrow optical windows have been demonstrated only with small monotonic LSPR shifts, which limits the use of the electrochromism. Here, we observed three distinct electrochromic behaviors of gold nanocubes with a wide potential range through in situ dark-field electrospectroscopy. Interestingly, the nanocubes show a faster frequency shift under the highly negative potential, and this opens the possibility of largely tunable electrochromic LSPR shifts. The reversibility of the electrochemical switching with these cubes are also shown. We attribute this unexpected change beyond classical understandings to the material-specific quantum mechanical electronic structures of the plasmonic materials.

Effects and Mechanism of Particulate Matter on Tendon Healing Based on Integrated Analysis of DNA Methylation and RNA Sequencing Data in a Rat Model.

Exposure to particulate matter (PM) has been linked with the severity of various diseases. To date, there is no study on the relationship between PM exposure and tendon healing. Open Achilles tenotomy of 20 rats was performed. The animals were divided into two groups according to exposure to PM: a PM group and a non-PM group. After 6 weeks of PM exposure, the harvest and investigations of lungs, blood samples, and Achilles tendons were performed. Compared to the non-PM group, the white blood cell count and tumor necrosis factor-alpha expression in the PM group were significantly higher. The Achilles tendons in PM group showed significantly increased inflammatory outcomes. A TEM analysis showed reduced collagen fibrils in the PM group. A biomechanical analysis demonstrated that the load to failure value was lower in the PM group. An upregulation of the gene encoding cyclic AMP response element-binding protein (CREB) was detected in the PM group by an integrated analysis of DNA methylation and RNA sequencing data, as confirmed via a Western blot analysis showing significantly elevated levels of phosphorylated CREB. In summary, PM exposure caused a deleterious effect on tendon healing. The molecular data indicate that the action mechanism of PM may be associated with upregulated CREB signaling.

Au Nanorings with Intertwined Triple Rings.

We designed complex Au nanorings with intertwined triple rings (ANITs) in a single entity to amplify the efficacy of near-field focusing. Such a complex and unprecedented morphology at the nanoscale was realized through on-demand multistepwise reactions. Triangular nanoprisms were first sculpted into circular nanorings, followed by a series of chemical etching and deposition reactions eventually leading to ANITs wherein thin metal bridges hold the structure together without any linker molecules. In the multistepwise reaction, the well-faceted growth pattern of Au, which induces the growth of two distinctive flat facets in a lateral direction, is important to evolve the morphology from single to multiple nanorings. Although our synthesis proceeds through multiple steps in one batch without purification steps, it shows a remarkably high yield (>∼90%) at the final stage. The obtained high degree of homogeneity (in both shape and size) of the resulting ANITs allowed us to systematically investigate the corresponding localized surface plasmon resonance (LSPR) coupling with varying nanoring arrangements and observe their single-particle surface enhanced Raman scattering (SERS). Surprisingly, individual ANITs exhibited an enormously large enhancement factor (∼109), which confirms their superior near-field focusing relative to other reported nanoparticles.

Web-above-a-Ring (WAR) and Web-above-a-Lens (WAL): Nanostructures for Highly Engineered Plasmonic-Field Tuning and SERS Enhancement.

Synthetic strategies of web-above-a-ring (WAR) and web-above-a-lens (WAL) nanostructures are reported. The WAR has a controllable gap between the nanoring core and a nanoweb with nanopores for the effective confinement of electromagnetic field in the nanogap and subsequent surface-enhanced Raman scattering (SERS) of Raman dyes inside the gap with high signal reproducibility, which are attributed to the generation of circular 3D hot zones along the rim of Pt@Au nanorings with wrapping nanoweb architecture. More specifically, Pt@Au nanorings are adopted as a plasmonic core for structural rigidity and built porous nanowebs above them through a controlled combination of galvanic exchange and the Kirkendall effect. Both nanoweb and nanolens structures are also formed on Pt@Au nanoring, which is WAL. structure. Remarkably, plasmonic hot zone, nanopores, and hot lens are formed inside a single WAL nanostructure, and these structural components are orchestrated to generate stronger SERS signals.

Synthesis and Surface Plasmonic Characterization of Asymmetric Au Split Nanorings.

In this Letter, a rational and stepwise method for the solution-phase synthesis of asymmetric Au split nanorings by adopting Au nanoprisms as a template has been demonstrated. The selective chemical etching of Au nanoprism tips activated the surface reactivity of edges and led to the selective deposition of Pt at the periphery of Au nanoplates. By controlling the total amount of Pt on the edges, different degrees of split Au@Pt nanorings were obtained; the subsequent Au coating around the Au@Pt scaffold eventually resulted in asymmetric Au hexagonal split nanorings. Their surface plasmonic features as a function of split degrees were investigated, including straight nanorods, bent nanorods, split nanorings, and full nanorings. The electrical field focusing using single-particle surface-enhanced Raman spectroscopy was evaluated under different polarization angles of the incident light for two different structures with the point gap and line gap between two arms.

Three-Dimensional Gold Nanosphere Hexamers Linked with Metal Bridges: Near-Field Focusing for Single Particle Surface Enhanced Raman Scattering.

Herein, we report the novel strategy for the synthesis of complex 3-dimensional (3D) nanostructures, mimicking the linker molecule-free 3D arrangement of six Au nanospheres at the vertices of octahedrons. We utilized 3D PtAu skeleton for the structural rigidity and deposited Au around the PtAu skeleton in a site-selective manner, allowing us to investigate their surface plasmonic coupling phenomenon and near-field enhancement as a function of sizes of nanospheres, which are directly related to the intrananogap distance and interior volume size. The resulting 3D Au hexamer structures with octahedral arrangement were realized through precise control of the Au growth pattern. The complex 3D Au hexamers were composed of six Au nanospheres connected by thin metal conductive bridges. The standard deviation of the metal conductive bridges and Au nanospheres was within ca. 10%, exhibiting a high degree of homogeneity and precise structural tunability. Interestingly, charge transfer among the six Au nanospheres occurred along the metal conductive bridges leading to surface plasmonic coupling between Au nanospheres. Accordingly, electric near fields were strongly and effectively focused at the vertices, intrananogap regions between Au nanospheres, and interior space, exhibiting well-resolved single-particle surface-enhanced Raman spectroscopy signals of absorbed analytes.

Correction to: M1 macrophage dependent-p53 regulates the intracellular survival of mycobacteria.

The original version of this article unfortunately contains an error in the acknowledgement section. The text "Brain Korea 21 PLUS Project for Medical Science, Chungnam National University" was omitted by mistake. The correct and complete acknowledgment is given below: Acknowledgments This work was supported by the research fund of Chungnam National University and the Brain Korea 21 PLUS Project for Medical Science, Chungnam National University. The funders had no role in study design, data collection and analysis decision to publish, or preparation of the manuscript.

M1 macrophage dependent-p53 regulates the intracellular survival of mycobacteria.

Tumor suppressor p53 is not only affects immune responses but also contributes to antibacterial activity. However, its bactericidal function during mycobacterial infection remains unclear. In this study, we found that the p53-deficient macrophages failed to control Mycobacterium tuberculosis (Mtb), manifested as a lower apoptotic cell death rate and enhanced intracellular survival. The expression levels of p53 during Mtb infection were stronger in M1 macrophages than in M2 macrophages. The TLR2/JNK signaling pathway plays an essential role in the modulation of M1 macrophage polarization upon Mtb infection. It facilitates p53-mediated apoptosis through the production of reactive oxygen species, nitric oxide and inflammatory cytokines in Mtb-infected M1 macrophages. In addition, nutlin-3 effectively abrogated the intracellular survival of mycobacteria in both TB patients and healthy controls after H37Ra infection for 24 h, indicating that the enhancement of p53 production effectively suppressed the intracellular survival of Mtb in hosts. These results suggest that p53 can be a new therapeutic target for TB therapy.

Hierarchic Interfacial Nanocube Assembly for Sensitive, Selective, and Quantitative DNA Detection with Surface-Enhanced Raman Scattering.

Surface-enhanced Raman scattering (SERS)-based sensing is promising in that it has potential to allow for highly sensitive, selective, and multiplexed detection and imaging. However, the controlled assembly and gap formation between plasmonic particles for generating strong SERS signals in a quantitative manner is highly challenging, especially on biodetection platforms, and particle-to-particle variation in the signal enhancement can vary by several orders of magnitude in a single batch, largely limiting the reliable use of SERS for practical sensing applications. Here, a hierarchic-nanocube-assembly based SERS (H-Cube-SERS) bioassay to controllably amplify the electromagnetic field between gold nanocubes (AuNCs) is developed. Based on this strategy, H-Cube-SERS assay allows for detecting target DNA with a wide dynamic range from 100 aM to 10 pM concentrations in a stable and reproducible manner. It is also found that the uniformly formed AuNCs with flat surfaces are much more suitable for highly sensitive, reliable, and quantitative biodetection assays due to faster DNA binding kinetics, sharper DNA melting transition, wider hot spot regions, and less dependence on light polarization direction than spherical Au nanoparticles with curved interfaces. This work paves the pathways to the quantitative and sensitive biodetection on a SERS platform and can be extended to other particle assembly systems.

Highly Controlled Synthesis and Super-Radiant Photoluminescence of Plasmonic Cube-in-Cube Nanoparticles.

The plasmonic properties of metal nanostructures have been heavily utilized for surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF), but the direct photoluminescence (PL) from plasmonic metal nanostructures, especially with plasmonic coupling, has not been widely used as much as SERS and MEF due to the lack of understanding of the PL mechanism, relatively weak signals, and the poor availability of the synthetic methods for the nanostructures with strong PL signals. The direct PL from metal nanostructures is beneficial if these issues can be addressed because it does not exhibit photoblinking or photobleaching, does not require dye-labeling, and can be employed as a highly reliable optical signal that directly depends on nanostructure morphology. Herein, we designed and synthesized plasmonic cube-in-cube (CiC) nanoparticles (NPs) with a controllable interior nanogap in a high yield from Au nanocubes (AuNCs). In synthesizing the CiC NPs, we developed a galvanic void formation (GVF) process, composed of replacement/reduction and void formation steps. We unraveled the super-radiant character of the plasmonic coupling-induced plasmon mode which can result in highly enhanced PL intensity and long-lasting PL, and the PL mechanisms of these structures were analyzed and matched with the plasmon hybridization model. Importantly, the PL intensity and quantum yield (QY) of CiC NPs are 31 times and 16 times higher than those of AuNCs, respectively, which have shown the highest PL intensity and QY reported for metallic nanostructures. Finally, we confirmed the long-term photostability of the PL signal, and the signal remained stable for at least 1 h under continuous illumination.

Associating and Dissociating Nanodimer Analysis for Quantifying Ultrasmall Amounts of DNA.

The amplification- and enzyme-free quantification of DNA at ultralow concentrations, on the order of 10-1000 targets, is highly beneficial but extremely challenging. To address this challenge, true detection signals must be reliably discriminated from false or noise signals. Herein, we describe the development of associating and dissociating nanodimer analysis (ADNA) as a method that enables a maximum number of detection signals to be collected from true target-binding events while keeping nonspecific signals at a minimum level. In the ADNA assay for ultralow target concentrations, Au nanoprobes on a lipid micropattern were monitored and analyzed in situ, and newly defined dissociating dimers, which are eventually decoupled into monomers again, were incorporated into the detection results. Tens to thousands of DNA copies can be reliably quantified with excellent single-base-mismatch differentiation capability by this non-enzymatic, amplification-free ADNA method.

Mycobacterium abscessus activates the NLRP3 inflammasome via Dectin-1-Syk and p62/SQSTM1.

Numerous atypical mycobacteria, including Mycobacterium abscessus (Mabc), cause nontuberculous mycobacterial infections, which present a serious public health threat. Inflammasome activation is involved in host defense and the pathogenesis of autoimmune diseases. However, inflammasome activation has not been widely characterized in human macrophages infected with atypical mycobacteria. Here, we demonstrate that Mabc robustly activates the nucleotide binding and oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome via dectin-1/Syk-dependent signaling and the cytoplasmic scaffold protein p62/SQSTM1 (p62) in human macrophages. Both dectin-1 and Toll-like receptor 2 (TLR2) were required for Mabc-induced mRNA expression of pro-interleukin (IL)-1ß, cathelicidin human cationic antimicrobial protein-18/LL-37 and ß-defensin 4 (DEFB4). Dectin-1-dependent Syk signaling, but not that of MyD88, led to the activation of caspase-1 and secretion of IL-1ß through the activation of an NLRP3/apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) inflammasome. Additionally, potassium efflux was required for Mabc-induced NLRP3/ASC inflammasome activation. Furthermore, Mabc-induced p62 expression was critically involved in NLRP3 inflammasome activation in human macrophages. Finally, NLRP3/ASC was critical for the inflammasome in antimicrobial responses to Mabc infection. Taken together, these data demonstrate the induction mechanism of the NLRP3/ASC inflammasome and its role in innate immunity to Mabc infection.

Heterogeneous Component Au (Outer)-Pt (Middle)-Au (Inner) Nanorings: Synthesis and Vibrational Characterization on Middle Pt Nanorings with Surface-Enhanced Raman Scattering.

We report a synthetic approach for heterometallic (Au-Pt-Au) nanorings with intertwined triple rings (NITs), wherein three differently sized metal circular nanorings concentrically overlap in a single entity. The synthetic method allows one to control the component of core nanorings (Au or Pt) with a tunable gap distance. The narrow circular nanogaps between inner and outer Au rings strongly enhance the electromagnetic near-field via intraparticle coupling of localized surface plasmon resonance, which realizes surface-enhanced Raman scattering (SERS) at the single-particle level. Importantly, when the component of the middle ring is Pt, in situ SERS measurement for electrochemical reactions on Pt domains could be monitored with electrochemical potential variations due to the near-field focusing that is assisted by plasmonically active inner and outer Au nanorings, which is not feasible with pure Pt nanoparticle systems. The resulting NIT systems are robust and may benefit the synthesis of complicated nanostructures, giving myriad applications.

Copy number variations of chromosome 17p13.1 might be linked to high risk of lung cancer in heavy smokers.

Lung cancer is the most common cause of cancer death worldwide. Smoking is known as the strongest single factor in the development of lung cancer. However, there are inherited genetic factors that cause different responses to cigarette smoking exposure among individuals. We tried to identify these differences in heavy smokers by examining copy number variations (CNVs) between lung cancer patients and healthy controls. Analysis by array comparative genomic hybridization which was tested with 20-person training set (10 lung cancer patients, 10 healthy controls) showed 26 significant (adjusted P < 0.05) clones with either copy number gains or losses. Three genes, KCTD11, FGF11, and PTPRH on chromosomal regions 17p13.1 (KCTD11 and FGF11) and 19q13.42 (PTPRH), were selected (adjusted P < 0.001) and tested by real-time quantitative PCR with 34 healthy controls and 54 lung cancer patients. KCTD11 on the chromosomal region 17p13.1 showed significant high odds ratio (OR = 16.0) in heavy smokers, implying that this is a susceptibility region for lung cancer in this group. Therefore, CNVs of 17p13.1 is a promising candidate to identify individuals with a high genetic risk for the development of lung cancer.

A rapid and sensitive fluorescence biosensor based on plasmonic PCR.

Plasmonic PCR utilizing metallic nanoparticles has shown great advantages compared to the commercial thermocycler equipment in terms of cost, size and processing time. However, due to the strong fluorescence quenching, plasmonic nanoparticle-based PCR requires additional post-processing steps such as centrifugation and gel electrophoresis. This process increases the overall diagnostic time, offsetting the benefits of fast thermocycling. Here, we report a rapid and sensitive plasmonic photothermal PCR (PPT-PCR) assay method based on in situ end-point fluorescence detection. By using plasmonic magnetic bi-functional nanoparticles, PPT-PCR involving 30 thermocycles and fluorescence detection following magnetic separation has successfully shown that DNA targets can be detected within 5.5 minutes. The limit of detection (3.3 copies per µL) is comparable with that of the conventional real-time quantitative PCR; however, the assay time is about 5.5 times shorter for the PPT-PCR. The strategy of combining the photothermal effect and magnetic separation into a single particle will open new horizons in the development of fast and sensitive PCR-based biosensors for point-of care testing.