To replace molecular biological and immunological methods, biosensors have recently been developed for the rapid and sensitive detection of bacteria. Among a wide variety of biological materials, ...bacteriophages have received increasing attention as promising alternatives to antibodies in biosensor applications. Thus, we herein present a rapid and highly selective detection method for pathogenic bacteria, which combines dark-field light scattering imaging with a plasmonic biosensor system. The plasmonic biosensor system employs bacteriophages as the biorecognition element and the aggregation-induced light scattering signal of gold nanoparticle-assembled silica nanospheres as a signal transducer. Using Staphylococcus aureus strain SA27 as a model analyte, we demonstrated that the plasmonic biosensor system detects S. aureus in the presence of excess Escherichia coli in a highly selective manner. After the sample and the S. aureus phage S13′-conjugated plasmon scattering probe were mixed, S. aureus detection was completed within 15–20 min with a detection limit of 8 × 104 colony forming units per milliliter.
High‐speed two‐photon microscopy can be used to analyze vascular dynamics in living animals and is essential for the understanding of brain diseases. Recent advances in fluorescent probes/optical ...systems have allowed successful imaging of the hippocampal vasculature in the deep brain of mice (1 mm from the brain surface) under low‐speed conditions (1–2 fps); however, using high‐speed techniques (>30 fps), observation of the deep‐brain vasculature is still challenging. Here, a new nanoemulsion that encapsulates thousands of red‐emissive pyrene dye molecules while maintaining their high two‐photon brightness 1.5 × 102 GM (GM = 10−50 cm4·s·photon−1·molecule−1) at 960 nm excitation and delivers a large amount of such pyrene dyes (65 nmol) into the blood vessels of mice is developed. Remarkably, the nanoprobe is found to exploit the inherent performance of a commonly used Ti:sapphire excitation laser and a sensitive gallium arsenide phosphide nondescanned fluorescence detector to the limit, enabling visualization of the brain vasculature under the cortex region of mice (up to 1.5 mm) under very low‐speed conditions. As a highlight, such a nanoprobe is successfully used to directly observe the blood flow in the hippocampal CA1 region (1.1 mm) through high‐speed resonant scanning (120 fps).
A novel dye‐loaded nanoemulsion is developed for high‐speed two‐photon microscopic imaging of the deep‐brain vasculature in mice. The nanoprobe delivers numerous bright pyrene dyes into the blood vessels of mice, fully exploiting the performance of a Ti:sapphire laser and a gallium arsenide phosphide detector. This approach allows the visualization of hippocampal blood flow in mice at above the video rate.
For in vivo two-photon fluorescence microscopy (2PM) imaging, the development of techniques that can improve the observable depth and temporal resolution is an important challenge to address ...biological and biomedical concerns such as vascular dynamics in the deep brain (typically the hippocampal region) of living animals. Improvements have been achieved through two approaches: an optical approach using a highly tissue-penetrating excitation laser oscillating in the second near-infrared wavelength region (NIR-II, 1100–1350 nm) and a chemical approach employing fluorescent probes with high two-photon brightness (characterized by the product of the two-photon absorption cross section, σ2, and the fluorescence quantum yield, Φ). To integrate these two approaches, we developed a fluorescent dye exhibiting a sufficiently high σ2Φ value of 68 Goeppert-Mayer units at 1100 nm. When a nanoemulsion encapsulating >1000 dye molecules per particle and a 1100 nm laser were employed for 2PM imaging, capillary blood vessels in almost the entire hippocampal CA1 region of the mouse brain (approximately 1.1–1.5 mm below the surface) were clearly visualized at a frame rate of 30 frames s–1 (averaged over eight frames, practically 3.75 frames s–1). This observable depth and frame rate are much higher than those in previous reports on 2PM imaging. Furthermore, this nanoemulsion allowed for the visualization of blood vessels at a depth of 1.8 mm, corresponding to the hippocampal dentate gyrus. These results highlight the advantage of combining bright probes with NIR-II lasers. Our probe is a promising tool for studying the vascular dynamics of living animals and related diseases.
One of the authors discovered helix-sense-selective polymerization (HSSP) of an achiral substituted phenylacetylene which has two hydroxymethyl groups and a relatively hydrophobic substituent by ...using a chiral catalytic system in 2003. The one-handed helicity is stable and static in nonpolar solvents because it is maintained by intramolecular hydrogen bonds. Since the resulting polymer has extremely tight helicity in its main chain, it shows many interesting and unusual properties including highly selective photocyclic aromatization (SCAT). In this review, the discovery and development of the HSSP and SCAT reactions, and the properties and application of the resulting polymers prepared by HSSP and the resulting supramolecular polymers prepared by SCAT will be examined.
To develop new phenylacetylene monomers more suitable for helix-sense-selective polymerization (HSSP) we reported previously and to improve the efficiency of the HSSP and membrane performance of the ...resulting polymers, novel phenylacetylenes having a flexible oligosiloxanyl group (SnBDHPA) together with the other related three series of monomers were synthesized and polymerized by using a chiral catalytic system and enantioselectivity in permeation of the membranes from the resulting chiral polymers were examined. SnBDHPA was the most suitable for the HSSP and the CD absorptions (G values) of poly(SnBDHPA) were stronger and more stable than those of the corresponding polymers having rigid alkyl groups. The polymers could be fabricated to flexible self-supporting membranes by using solvent-casting method. In addition, enantioselectivity in permeation of one of poly(SnBDHPA) membranes was much higher than that of a poly(phenylacetylene) membrane having alkyl groups. This was because the polymers having oligosiloxane groups had high regularity of structures, i.e., chemical structures of the macromolecules such as one handedness and high order structures such as columnar contents in the membranes, and the membranes were flexible and had almost no defects. These good properties as optical resolution membrane materials were caused by flexibility, hydrophobicity, and bulkiness of the oligosiloxane chains. S3BDHPA having a trisiloxanyl group was found to be the best monomer for the HSSP and for obtaining good optical resolution membrane materials.
Three novel chiral phenylacetylenes having an octyloxyethanolamine residue derived from a l-aminoalcohol and two hydroxymethyl groups were synthesized and polymerized by two achiral catalysts ...((nbd)Rh+η6-(C6H5)B−(C6H5)3 and Rh(nbd)Cl2/triethylamine (TEA)) and a chiral catalytic system (Rh(nbd)Cl2/(S)- or (R)-phenylethylamine ((S)- or (R)-PEA)). All of the resulting polymers showed Cotton effects at wavelengths around 430 nm. This observation indicated that they had an excess of one-handed helical backbones. Positive and negative Cotton effects were observed for the polymers having an l-valinol residue produced by using (S)- and (R)-PEA as a cocatalyst, respectively, although the monomers had the same chirality. The two polymers having an l-alaninol or l-phenylalaninol residues obtained by using (S)- and (R)-PEA as a cocatalyst showed CD absorptions with identical signs. Therefore, we found that the chiral monomer having an l-valinol residue was suitable for both modes of asymmetric polymerization, that is, helix-sense-selective polymerization (HSSP) with the chiral catalytic system and asymmetric-induced polymerization ( AIP ) with the achiral catalysts. However, the other two monomers having an l-alaninol or l-phenylalaninol residue were not suitable for HSSP because the helix sense could not be controlled by the chirality of PEA. To explain the unexpected behaviors in the asymmetric polymerizations of the two chiral monomers having a chiral bidentate ligand, a novel third mechanism of asymmetric polymerization, that is, self-helix-sense-selective polymerization (SHSSP), is proposed in this Article. This Article discusses the contribution of the three mechanisms (AIP, HSSP, and SHSSP) in asymmetric polymerizations of the three monomers.
4‐Alkyloxy‐3,5‐bis(hydroxymethyl)phenylacetylenes with eight types of alkyl groups were synthesized and polymerized with a chiral catalytic system. We found that the length of the alkyl groups played ...a very important role in achieving helix‐sense‐selective polymerization. Five helix‐sense‐selective polymerizations were achieved resulting in polymers with alkyl groups whose chain length was longer than six. We think that the longer‐chain alkyl groups prevented the polymers from becoming insoluble by forming intermolecular hydrogen bonds between the hydroxyl groups, and stabilized their one‐handed helical structure by promoting the formation of intramolecular hydrogen bonds.
Full Paper: Helix‐sense‐selective polymerization was achieved using four new 4‐alkyloxy‐3,5‐bis(hydroxymethyl)‐phenylacetylene monomers with more than six carbon atoms in the alkyl groups. $\overline M_{\rm w}$ of the soluble polymers were above 106 g · mol−1. One polymer displayed enantioselective membrane permeability. This is the first example to confirm directly the effect of a one‐handed helical main chain on chiral recognition ability.
Helix-sense-selective polymerization of {4-(3,5-di-tert-butyl-4-hydroxyphenyl)(3,5-di-tert-butyl-4-oxo-cyclohexa-2,5-dienylidene)methylphenyl}acetylene (abbreviated as ...(4-ethynylphenyl)hydrogalvinoxyl) was promoted by Rh(cod)Cl2 and Rh(nbd)Cl2 catalyst in the presence of (R)-(+)-1-phenylethylamine or (S)-(−)-1-phenylethylamine (PEA). The Rh(cod)Cl2 catalyst system gave red polymers whose CD spectra showed the stronger Cotton effect though the yield (2−3%) and molecular weight (M n = (1.1−1.4) × 104) were lower than those of polymers obtained by Rh(nbd)Cl2. Moreover, we investigated the effect of bulkiness of the catalyst, cocatalyst, and monomer on helix-sense-selective polymerization of (4-ethynylphenyl)hydrogalvinoxyl in the presence of (R)-PEA. The CD patterns of polymers obtained by Rh(nbd)Cl2 and Rh(cod)Cl2 were nearly mirror image of each other, except for the magnitudes of the signals in spite of the same chiral condition, i.e., in the presence of (R)-PEA. That is, Rh(nbd)Cl2 and Rh(cod)Cl2 catalysts generated P-helix and M-helix, respectively. This is a novel result, since the control of helix sense is usually achieved by enantiomeric moieties of catalysts or initiators for the helix-sense-selective polymerization.
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