Fiber-Optic Localized Surface Plasmon Resonance Sensors Based on Nanomaterials.

Applying fiber-optics on surface plasmon resonance (SPR) sensors is aimed at practical usability over conventional SPR sensors. Recently, field localization techniques using nanostructures or nanoparticles have been investigated on optical fibers for further sensitivity enhancement and significant target selectivity. In this review article, we explored varied recent research approaches of fiber-optics based localized surface plasmon resonance (LSPR) sensors. The article contains interesting experimental results using fiber-optic LSPR sensors for three different application categories: (1) chemical reactions measurements, (2) physical properties measurements, and (3) biological events monitoring. In addition, novel techniques which can create synergy combined with fiber-optic LSPR sensors were introduced. The review article suggests fiber-optic LSPR sensors have lots of potential for measurements of varied targets with high sensitivity. Moreover, the previous results show that the sensitivity enhancements which can be applied with creative varied plasmonic nanomaterials make it possible to detect minute changes including quick chemical reactions and tiny molecular activities.

Isoform-Specific Lysine Methylation of RORα2 by SETD7 Is Required for Association of the TIP60 Coactivator Complex in Prostate Cancer Progression.

The retinoid acid-related orphan receptor α (RORα), a member of the orphan nuclear receptor superfamily, functions as an unknown ligand-dependent transcription factor. RORα was shown to regulate a broad array of physiological processes such as Purkinje cell development in the cerebellum, circadian rhythm, lipid and bone metabolism, inhibition of inflammation, and anti-apoptosis. The human RORα gene encodes at least four distinct isoforms (RORα1, -2, -3, -4), which differ only in their N-terminal domain (NTD). Two isoforms, RORα2 and 3, are not expressed in mice, whereas RORα1 and 4 are expressed both in mice and humans. In the present study, we identified the specific NTD of RORα2 that enhances prostate tumor progression and proliferation via lysine methylation-mediated recruitment of coactivator complex pontin/Tip60. Upregulation of the RORα2 isoform in prostate cancers putatively promotes tumor formation and progression. Furthermore, binding between coactivator complex and RORα2 is increased by lysine methylation of RORα2 because methylation permits subsequent interaction with binding partners. This methylation-dependent activation is performed by SET domain containing 7 (SETD7) methyltransferase, inducing the oncogenic potential of RORα2. Thus, post-translational lysine methylation of RORα2 modulates oncogenic function of RORα2 in prostate cancer. Exploration of the post-translational modifications of RORα2 provides new avenues for the development of tumor-suppressive therapeutic agents through modulating the human isoform-specific tumorigenic role of RORα2.

Experimental confirmation of plasmonic field cancellation under specific conditions of trapezoidal nanopatterns.

In this study, we investigated plasmonic field localization with trapezoidal nanopatterns under normal incident light excitation to find optimum structures for sensing and imaging. A finite element method was used to calculate the fundamental characteristics of the localized surface plasmon with varied trapezoidal nanopatterns. First, we describe how to localize the plasmonic fields on the trapezoidal patterns and then report our results from the investigation of the optimum properties of the nanopatterns for maximized field intensity. Initially, we expected that maximized field localization would lead to enhancement of the sensing sensitivity or imaging resolution in plasmon-based sensing and imaging systems. However, more interestingly, we found a field cancellation effect under specific modality conditions through the simulation. Thus, we thoroughly investigated the principle of the effect and extracted the modality conditions that induced field cancellation. In addition, specific modality conditions of nanopatterns that could be fabricated with conventional lithographic methods were numerically determined. Then, the field cancellation effect was experimentally verified using scanning nearfield optical microscopy. The results indicate that trapezoidal nanopatterns bring about enhanced field localization at the shaper edge of nanopatterns than do conventional rectangular nanopatterns and that plasmonic field cancellation can be observed under specific modality conditions of nanopatterns, even for conventional rectangular nanopatterns. Thus, it is suggested that careful fabrication and maintenance are needed to obtain strong plasmonic localization. Finally, the feasibility of providing a novel sensing platform using the field cancellation effect is suggested.

A Localized Surface Plasmon Resonance Sensor Using Double-Metal-Complex Nanostructures and a Review of Recent Approaches.

From active developments and applications of various devices to acquire outside and inside information and to operate based on feedback from that information, the sensor market is growing rapidly. In accordance to this trend, the surface plasmon resonance (SPR) sensor, an optical sensor, has been actively developed for high-sensitivity real-time detection. In this study, the fundamentals of SPR sensors and recent approaches for enhancing sensing performance are reported. In the section on the fundamentals of SPR sensors, a brief description of surface plasmon phenomena, SPR, SPR-based sensing applications, and several configuration types of SPR sensors are introduced. In addition, advanced nanotechnology- and nanofabrication-based techniques for improving the sensing performance of SPR sensors are proposed: (1) localized SPR (LSPR) using nanostructures or nanoparticles; (2) long-range SPR (LRSPR); and (3) double-metal-layer SPR sensors for additional performance improvements. Consequently, a high-sensitivity, high-biocompatibility SPR sensor method is suggested. Moreover, we briefly describe issues (miniaturization and communication technology integration) for future SPR sensors.

Multi-target aptamer assay for endocrine-disrupting phthalic acid ester panel screening in plastic leachates.

A multi-target aptamer assay was developed as a phthalic acid ester (PAE) panel to screen selected PAEs in plastic leachate samples. The panel comprises 13 PAEs (PAE-13), namely dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, di-n-hexyl phthalate, diisobutyl phthalate, diisononyl phthalate, diisodecyl phthalate, mono-2-ethylhexyl phthalate, di-2-ethylhexyl phthalate, diphenyl phthalate, butyl benzyl phthalate, dicyclohexyl phthalate, and phthalic acid. Herein, we proposed an aptamer assay using a newly truncated aptamer (20-mer) and the 7-aminoactinomycin D fluorophore, which selectively binds to guanine in single-stranded DNA, resulting in increased fluorescence intensity. The assay is highly selective for PAE-13 clusters. The selectivity of the assay was evaluated using 13 different PAEs and mixtures depending on the side chain structure. The quantitative detection of PAEs was demonstrated by adopting mixed PAE-13 simulants and achieved a limit of detection of ∼1.4 pg/mL. The repeatability and reproducibility of the assay were also evaluated by presenting acceptable coefficients of variation (%CV less than 10% and 15%, respectively). The performance of the assay was demonstrated by analyzing the plastic leachate samples, and the positive correlation (correlation coefficient, r = 0.985) was confirmed by comparing them with the total sum of individual PAE peak areas obtained by gas chromatography mass spectrometry analysis.

Development of an aptasensor for dibutyl phthalate detection and the elucidation of assay inhibition factors.

We developed a fluorescence aptasensor (hereafter 'SG-aptasensor') using SYBR Green I, a newly truncated 20-mer aptamer, and probe DNA to detect dibutyl phthalate (DBP). The detection range of DBP was 0.1-100 ng L-1 with 0.08 ng L-1 as the limit of detection. To adapt the assay to environmental samples in the near future, possible inhibition factors (experimental and environmental) have been tested and reported. The experimental inhibitors included the incubation time, temperature, pH, and ionic strength. Consequently, temperature (2-25 °C) and pH (7.0-9.0) ranges did not significantly inhibit the assay. The incubation time required for sufficient reaction was at least 4 h, and a relative humidity <20% may have induced fluorescence quenching. Tris-HCl-based incubation buffer with excess ionic strength (more than 0.2 M NaCl) demonstrated an abnormal increase in fluorescence. Environmental inhibitors including cations (Mg2+, Ca2+, and Cu2+) and humic acids were tested. The fluorescence signal was significantly reduced (∼99%) by 100 mM Cu2+ compared to that by 0 mM Cu2+. In contrast, the reduction in fluorescence signal was marginal (<15%) when Mg2+ or Ca2+ ions were present. Inhibition of the assay was observed (∼28%) in the presence of 100 mg L-1 humic acids.

A Review of Advanced Impedance Biosensors with Microfluidic Chips for Single-Cell Analysis.

Electrical impedance biosensors combined with microfluidic devices can be used to analyze fundamental biological processes for high-throughput analysis at the single-cell scale. These specialized analytical tools can determine the effectiveness and toxicity of drugs with high sensitivity and demonstrate biological functions on a single-cell scale. Because the various parameters of the cells can be measured depending on methods of single-cell trapping, technological development ultimately determine the efficiency and performance of the sensors. Identifying the latest trends in single-cell trapping technologies afford opportunities such as new structural design and combination with other technologies. This will lead to more advanced applications towards improving measurement sensitivity to the desired target. In this review, we examined the basic principles of impedance sensors and their applications in various biological fields. In the next step, we introduced the latest trend of microfluidic chip technology for trapping single cells and summarized the important findings on the characteristics of single cells in impedance biosensor systems that successfully trapped single cells. This is expected to be used as a leading technology in cell biology, pathology, and pharmacological fields, promoting the further understanding of complex functions and mechanisms within individual cells with numerous data sampling and accurate analysis capabilities.

RORα Regulates Cholesterol Metabolism of CD8+ T Cells for Anticancer Immunity.

Retinoic acid-related orphan receptor α (RORα) functions as a transcription factor for various biological processes, including circadian rhythm, inflammation, cancer, and lipid metabolism. Here, we demonstrate that RORα is crucial for maintaining cholesterol homeostasis in CD8+ T cells by attenuating NF-kB transcriptional activity. Cholesterol sulfate, the established natural agonist of RORα, exhibits cellular cytotoxicity on, and increased effector responses in, CD8+ T cells. Transcript analysis reveals that the suppression of RORα leads to the upregulation of NF-kB target genes in T cells. Chromatin immunoprecipitation analysis was used to determine the corecruitment of RORα and histone deacetylase (HDAC) on NF-kB target promoters and the subsequent dismissal of coactivators for transcriptional repression. We demonstrate that RORα/HDAC-mediated attenuation of NF-kB signaling controls the balance of cholesterol metabolism in CD8+ T cells, and that therapeutic strategies targeting this epigenetic regulation could be beneficial to the treatment of solid tumors including colon cancers.

Intermolecular distance measurement with TNT suppressor on the M13 bacteriophage-based Förster resonance energy transfer system.

An M13 bacteriophage-based Förster resonance energy transfer (FRET) system is developed to estimate intermolecular distance at the nanoscale using a complex of CdSSe/ZnS nanocrystal quantum dots, genetically engineered M13 bacteriophages labeled with fluorescein isothiocyanate and trinitrotoluene (TNT) as an inhibitor. In the absence of trinitrotoluene, it is observed that a significant spectral shift from blue to green occur, which represents efficient energy transfer through dipole-dipole coupling between donor and acceptor, or FRET-on mode. On the other hand, in the presence of trinitrotoluene, the energy transfer is suppressed, since the donor-to-acceptor intermolecular distance is detuned by the specific capturing of TNT by the M13 bacteriophage, denoted as FRET-off mode. These noble features are confirmed by changes in the fluorescence intensity and the fluorescence decay curve. TNT addition to our system results in reducing the total energy transfer efficiency considerably from 16.1% to 7.6% compared to that in the non-TNT condition, while the exciton decay rate is significantly enhanced. In particular, we confirm that the energy transfer efficiency satisfies the original intermolecular distance dependence of FRET. The relative donor-to-acceptor distance is changed from 70.03 Å to 80.61 Å by inclusion of TNT.

Optical measurements of paintings and the creation of an artwork database for authenticity.

Paintings have high cultural and commercial value, so that needs to be preserved. Many techniques have been attempted to analyze properties of paintings, including X-ray analysis and optical coherence tomography (OCT) methods, and enable conservation of paintings from forgeries. In this paper, we suggest a simple and accurate optical analysis system to protect them from counterfeit which is comprised of fiber optics reflectance spectroscopy (FORS) and line laser-based topographic analysis. The system is designed to fully cover the whole area of paintings regardless of its size for the accurate analysis. For additional assessments, a line laser-based high resolved OCT was utilized. Some forgeries were created by the experts from the three different styles of genuine paintings for the experiments. After measuring surface properties of paintings, we could observe the results from the genuine works and the forgeries have the distinctive characteristics. The forgeries could be distinguished maximally 76.5% with obtained RGB spectra by FORS and 100% by topographic analysis. Through the several executions, the reliability of the system was confirmed. We could verify that the measurement system is worthwhile for the conservation of the valuable paintings. To store the surface information of the paintings in micron scale, we created a numerical database. Consequently, we secured the databases of three different famous Korean paintings for accurate authenticity.

Current achievements of nanoparticle applications in developing optical sensing and imaging techniques.

Metallic nanostructures have recently been demonstrated to improve the performance of optical sensing and imaging techniques due to their remarkable localization capability of electromagnetic fields. Particularly, the zero-dimensional nanostructure, commonly called a nanoparticle, is a promising component for optical measurement systems due to its attractive features, e.g., ease of fabrication, capability of surface modification and relatively high biocompatibility. This review summarizes the work to date on metallic nanoparticles for optical sensing and imaging applications, starting with the theoretical backgrounds of plasmonic effects in nanoparticles and moving through the applications in Raman spectroscopy and fluorescence biosensors. Various efforts for enhancing the sensitivity, selectivity and biocompatibility are summarized, and the future outlooks for this field are discussed. Convergent studies in optical sensing and imaging have been emerging field for the development of medical applications, including clinical diagnosis and therapeutic applications.

Microfluidic assay-based optical measurement techniques for cell analysis: A review of recent progress.

Since the early 2000s, microfluidic cell culture systems have attracted significant attention as a promising alternative to conventional cell culture methods and the importance of designing an efficient detection system to analyze cell behavior on a chip in real time is raised. For this reason, various measurement techniques for microfluidic devices have been developed with the development of microfluidic assays for high-throughput screening and mimicking of in vivo conditions. In this review, we discuss optical measurement techniques for microfluidic assays. First of all, the recent development of fluorescence- and absorbance-based optical measurement systems is described. Next, advanced optical detection systems are introduced with respect to three emphases: 1) optimization for long-term, real-time, and in situ measurements; 2) performance improvements; and 3) multimodal analysis conjugations. Moreover, we explore presents future prospects for the establishment of optical detection systems following the development of complex, multi-dimensional microfluidic cell culture assays to mimic in vivo tissue, organ, and human systems.

Biomimetic self-templating optical structures fabricated by genetically engineered M13 bacteriophage.

Here, we describe a highly sensitive and selective surface plasmon resonance sensor system by utilizing self-assembly of genetically engineered M13 bacteriophage. About 2700 copies of genetically expressed peptide copies give superior selectivity and sensitivity to M13 phage-based SPR sensor. Furthermore, the sensitivity of the M13 phage-based SPR sensor was enhanced due to the aligning of receptor matrix in specific direction. Incorporation of specific binding peptide (His Pro Gln: HPQ) gives M13 bacteriophage high selectivity for the streptavidin. Our M13 phage-based SPR sensor takes advantage of simplicity of self-assembly compared with relatively complex photolithography techniques or chemical conjugations. Additionally, designed structure which is composed of functionalized M13 bacteriophage can simultaneously improve the sensitivity and selectivity of SPR sensor evidently. By taking advantages of the genetic engineering and self-assembly, we propose the simple method for fabricating novel M13 phage-based SPR sensor system which has a high sensitivity and high selectivity.

Identification of Endocrine Disrupting Chemicals using a Virus-Based Colorimetric Sensor.

A simple and portable colorimetric sensor based on M13 bacteriophage (phage) was devised to identify a class of endocrine disrupting chemicals, including benzene, phthalate, and chlorobenzene derivatives. Arrays of structurally and genetically modified M13 bacteriophage were fabricated so as to produce a biomimetic colorimetric sensor, and color changes in the phage arrays in response to several benzene derivatives were characterized. The sensor was also used to classify phthalate and chlorobenzene derivatives as representatives of endocrine disrupting chemicals. The characteristic color patterns obtained on exposure to various benzene derivatives enabled similar chemical structures in the vapor phase to be classified. Our sensing approach based on the use of a genetically surface modified M13 bacteriophage offers a promising platform for portable, simple environmental monitors that could be extended for use in numerous application areas, including food monitoring, security monitoring, explosive risk assessment, and point of care testing.

Virus based Full Colour Pixels using a Microheater.

Mimicking natural structures has been received considerable attentions, and there have been a few practical advances. Tremendous efforts based on a self-assembly technique have been contributed to the development of the novel photonic structures which are mimicking nature's inventions. We emulate the photonic structures from an origin of colour generation of mammalian skins and avian skin/feathers using M13 phage. The structures can be generated a full range of RGB colours that can be sensitively switched by temperature and substrate materials. Consequently, we developed an M13 phage-based temperature-dependent actively controllable colour pixels platform on a microheater chip. Given the simplicity of the fabrication process, the low voltage requirements and cycling stability, the virus colour pixels enable us to substitute for conventional colour pixels for the development of various implantable, wearable and flexible devices in future.