Synthesis of new, pyrene-containing, metal-chelating lipids and sensing of cupric ions

Design of Pyrene-Fatty Acid Conjugates for Real-Time Monitoring of Drug Delivery and Controllability of Drug Release

Fluorescence probes are usually employed to analyze pharmacokinetics of drug carriers; however, this method using usual probes is not suitable to monitor drug carriers in detail because fluorescence spectra do not change by the disruption of drug carriers. In this study, pyrene-fatty acid conjugates were investigated as probes to monitor the state of drug carriers in real time. 1-Pyrenemethanol was conjugated with fatty acids, such as lauric acid, stearic acid, and behenic acid, and the conjugates were stirred in ethanol, resulting in the formation of submicron particles; these particles exhibited excimer emission. When J774.1 and Colon 26 cells were treated with these particles, the associated fluorescence spectra shifted from excimer emission to monomer emission. Moreover, the degree of change was controlled by the type of fatty acid. These results support the design of drug carriers that can be used to monitor pharmacokinetics in real time and to control the disruption time.

A colorimetric and fluorometric investigation of Cu(ii) ion in aqueous medium with a fluorescein-based chemosensor

A colorimetric and fluorometric chemosensor, 1,4-bis(1-fluorescein)-2,3-diaza-1,3-butadiene (L, 3) as Schiff base is developed for naked-eye detection of Cu²⁺ ion in aqueous medium due to the formation of a 1 : 1 copper–ligand complex.

A fluorescent sensor for Cu2+and Fe3+based on multiple mechanisms

A new fluorescent sensor for the selective and sensitive sensing of Cu²⁺and Fe³⁺based on the rational control of multiple mechanisms has been developed.

Highly Fluorescent Pyrene-Functional Polystyrene Copolymer Nanofibers for Enhanced Sensing Performance of TNT

A pyrene-functional polystyrene copolymer was prepared via 1,3-dipolar cycloaddition reaction (Sharpless-type click recation) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the maximum allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concentrations of toxic metal pollutants such as Cd(2+), Co(2+), Cu(2+), and Hg(2+). The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphology. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.

DNA as sensors and imaging agents for metal ions

Increasing interest in detecting metal ions in many chemical and biomedical fields has created demands for developing sensors and imaging agents for metal ions with high sensitivity and selectivity. This review covers recent progress in DNA-based sensors and imaging agents for metal ions. Through both combinatorial selection and rational design, a number of metal-ion-dependent DNAzymes and metal-ion-binding DNA structures that can selectively recognize specific metal ions have been obtained. By attachment of these DNA molecules with signal reporters such as fluorophores, chromophores, electrochemical tags, and Raman tags, a number of DNA-based sensors for both diamagnetic and paramagnetic metal ions have been developed for fluorescent, colorimetric, electrochemical, and surface Raman detection. These sensors are highly sensitive (with a detection limit down to 11 ppt) and selective (with selectivity up to millions-fold) toward specific metal ions. In addition, through further development to simplify the operation, such as the use of "dipstick tests", portable fluorometers, computer-readable disks, and widely available glucose meters, these sensors have been applied for on-site and real-time environmental monitoring and point-of-care medical diagnostics. The use of these sensors for in situ cellular imaging has also been reported. The generality of the combinatorial selection to obtain DNAzymes for almost any metal ion in any oxidation state and the ease of modification of the DNA with different signal reporters make DNA an emerging and promising class of molecules for metal-ion sensing and imaging in many fields of applications.

A “Light-up” 1D supramolecular nanoprobe for silver ions based on assembly of pyrene-labeled peptide amphiphiles: cell-imaging and antimicrobial activity

The histidine-coated fibrils response to Ag⁺ with fluorescence enhancement was developed through a rational design based on the aqueous self-assembly of peptides for potential use as cell-imaging and antimicrobial agents.

A new chemosensor based on rhodamine 101 hydrazone for Cu (II) in the red region

A new chemosensor based on the spirolactam form of rhodamine 101 hydrazone (III) is found to exhibit a reversible colorimetric response toward Cu2+ in aqueous solutions in a selective, sensitive and rapid manner because of a formation of a Cu(II)-III complex. The dominating absorption maximum at 584 nm is uniquely red-shifted among rhodamine chemosensors toward Cu2+. The fluorescence of III can be detected in a low concentration of Cu2+. The results revealed that III is a good colorimetric sensor to Cu2+ in the red region.

Aqueous solutions of transition metal containing micelles

Incorporation of d- or f-block metals into ligand systems that renders a metal complex surface-active or drives its partitioning into surfactant phases enables the localisation of chemical functionality at interfaces. This article discusses a number of fundamental aspects of these interesting materials and examines potential applications.

Formation of ternary poly(acrylic acid)-surfactant-Cu2+ complexes in aqueous solution: quenching of pyrene fluorescence and pH-controlled "on-off" emitting properties

The formation of binary and ternary complexes of poly(acrylic acid) (PAA) with N, N, N, N-dodecyltrimethylammonium chloride (DTAC) and/or Cu (2+) ions is investigated in dilute aqueous solution through turbidimetry, viscometry, and pyrene fluorescence probing. It is shown that the PAA-DTAC and PAA-Cu (2+) complexation as well as the formation of ternary PAA-DTAC-Cu (2+) complexes are controlled from the pH of the aqueous solution. A pronounced quenching of the emission of pyrene is observed when ternary PAA-DTAC-Cu (2+) complexes are formed, as a result of the close proximity of Cu (2+) ions (complexed along the polymer chain) and the probe (solubilized in the hydrophobic mixed polymer-surfactant aggregates), as indicated from the corresponding Stern-Volmer plots. A significant quenching is also observed when poly(sodium styrene sulfonate) is used instead of PAA, indicating that electrostatically bound Cu (2+) ions are still effective quenchers of the emission of the probes under similar conditions. Finally, it is demonstrated that the formation-deformation of the ternary PAA-DTAC-Cu (2+) complexes upon changing pH may act as a pH-controlled "on-off" switch of the emission of pyrene in aqueous solution.

Self-Assembled Fluorescent Chemosensors

Self-assembling and self-organizing methodologies are powerful tools for the "bottom-up" approach for the realization of complex structure with functional properties. Recently, this concept has been extended to the design of fluorescent chemosensors providing new exciting potentialities for the development of innovative sensing systems. This Concept Article deals mainly with this new approach and discusses its evolution, applications, and limitations.

Recent advances in lipid molecular design

The area of lipid molecular design is attracting widespread interest among numerous research groups worldwide. Diverse lipid assemblies in aqueous media, such as vesicles, bilayers and nanorods, offer new applications in chemical biology. Lipids with specifically tailored molecular architecture have been successfully employed as gene delivery vehicles, for controlled drug release and the preparation of supramolecular gels. Such molecular design of lipids, as well as their characterization upon membrane formation, offers an insight into the possible molecular basis of their properties. This in turn helps in the design of further generations of lipid systems with more predictable characteristics. Here, we present an overview of the current trends in lipid design and their utilization in various biochemical, physical and chemical applications.

Design and synthesis of artificial phospholipid for selective cleavage of integral membrane protein

An artificial phospholipid, possessing saturated alkyl chains as a membrane anchor and protein recognition site as well as an Fe(III)-EDTA moiety as a protein cleavable polar head group, was designed and synthesized based on the amidite method for the purpose of examination of cleavage of integral membrane proteins.

Arginine magic with new counterions up the sleeve

The elusive questions how arginine-rich sequences allow peptides and proteins to penetrate cells or to form voltage-gated ion channels are controversial topics of current scientific concern. The possible contributions of exchangeable counterions to these puzzling processes remain underexplored. The objective of this report is to clarify scope and limitations of certain counteranions to modulate cellular uptake and anion carrier activity of oligo/polyarginines. The key finding is that the efficiency of counteranion activators depends significantly on many parameters such as activator-membrane and activator-carrier interactions. This finding is important because it suggests that counteranions can be used to modulate not only efficiency but also selectivity. Specifically, activator efficiencies are found to increase with increasing aromatic surface of the activator, decreasing size of the transported anion, increasing carrier concentration as well as increasing membrane fluidity. Efficiency sequences depend on membrane composition with coronene > pyrene >>fullerene > calix[4]arene carboxylates in fluid and crystalline DPPC contrasting to fullerene > calix[4]arene approximately coronene > pyrene carboxylates in EYPC with or without cholesterol or ergosterol. In HeLa cells, the efficiency of planar activators (pyrene) exceeds that of spherical activators (fullerenes, calixarenes). Polyarginine complexes with pyrene and coronene activators exhibit exceptional excimer emission. Decreasing excimer emission with increasing ionic strength reveals dominant hydrophobic interactions with the most efficient carboxylate activators. Dominance of ion pairing with the inefficient high-affinity sulfate activators is corroborated by the reversed dependence on ionic strength. These findings on activator-carrier and activator-membrane interactions are discussed as supportive of arene-templated guanidinium-carboxylate pairing and interface-directed translocation as possible origins of the superb performance of higher arene carboxylates as activators.

Diametrically Disubstituted Cyclam Derivative Having Hg2+-Selective Fluoroionophoric Behaviors

[reaction: see text] A new fluoroionophore has been synthesized by appending two signaling pyrenylacetamide subunits on the binding motif of 1,8-dimethylcyclam. The designed compound exhibited highly selective and sensitive fluoroionophoric behavior toward Hg(2+) ions of excimer emission in aqueous dioxane (dioxane/H(2)O = 1:9, v/v) solution with a detection limit of 1.3 x 10(-)(6) M. The "ON-OFF" type signaling behavior of the fluoroionophore is due to the metal ion induced conformational changes from folded to open-winged conformations by exploiting the two nearby appended pyrenyl fluorophores.