Pyrene Molecules Research Articles

Redox-sensitive micelles assembled from amphiphilic mPEG-PCL-SS-DTX conjugates for the delivery of docetaxel

Docetaxel (DTX) can produce anti-tumor effects by inhibiting cell growth and inducing apoptosis. However, the poor solubility of DTX restricts its application and its clinical formulation has caused serious adverse reaction due to the use of Tween-80. In the present study, DTX was conjugated to an amphiphilic di-block polymer to solve these problems. Methoxy poly(ethylene glycol)-poly(ε-caprolactone) (mPEG-PCL) was selected as the polymer skeleton and a redox sensitive disulfide bond was used as the linker between DTX and mPEG-PCL. The synthesized mPEG-PCL-SS-DTX conjugates were characterized by 1H-nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR). Interestingly, the mPEG-PCL-SS-DTX conjugates could self-assemble into micelles in aqueous solution. The critical micelle concentration (CMC) of mPEG-PCL-SS-DTX micelles was about 2.3mgL−1 determined using pyrene molecule fluorescent probe method while the size of mPEG-PCL-SS-DTX micelles was determined to be ca. 17.6nm and 116.0nm with a bimodal distribution by dynamic light scattering (DLS). The in vitro release results indicated that the as-prepared micelles exhibited a sustained release profile with good redox sensitive properties. In particular, the hemolytic toxicity test indicated the as-prepared mPEG-PCL-SS-DTX micelles had negligible hemolytic activity, demonstrating their safety in drug delivery system. Cytotoxicity assay of the mPEG-PCL-SS-DTX micelles verified their highly enhanced cytotoxicity to MCF-7/A and A549 cells. These results thus demonstrated that the present redox-sensitive mPEG-PCL-SS-DTX micelle was an efficient and safe sustained drug delivery system in the biomedical area.

Red-emitting Ͽ-conjugated oligomers infused single-wall carbon nanotube sheets

We demonstrate the one-step thermal fusion and infusion of pyrene molecules inside single-wall carbon nanotubes (SWCNTs). Despite the presence of metallic-SWCNTs, which behave as a quencher due to gapless electronic states, the nanohybrids consisting of pyrene and/or azupyrene oligomers infused SWCNT sheets exhibit red fluorescence by the ultraviolet, blue, and green light excitations. The wavelength-independent light-emitting behavior is explained by (1) infused PAH oligomers inside semiconducting-SWCNTs and (2) the peculiar Ͽ⿿Ͽ interaction through mixed Ͽ-conjugated state between the Ͽ-conjugated oligomers and non-armchair metallic-SWCNTs.

Effects of simultaneous hydrogen enrichment and carbon dioxide dilution of fuel on soot formation in an axisymmetric coflow laminar ethylene/air diffusion flame

Effects of simultaneous hydrogen enrichment and carbon dioxide dilution to hydrocarbon fuels on soot formation are of fundamental and practical interest. Previous studies found that addition of either hydrogen or carbon dioxide to fuel reduces soot chemically in addition to the dilution effect in laminar coflow ethylene/air diffusion flames. A numerical study was carried out in this work to investigate the effects of adding hydrogen and carbon dioxide simultaneously to fuel on soot formation in an axisymmetric laminar coflow ethylene/air diffusion flame at atmospheric pressure. Numerical calculations were conducted using detailed gas-phase chemistry and thermal and transport properties. Soot inception is assumed to be the result of collision of two pyrene molecules. The subsequent particle surface growth, soot oxidation, and particle interactions are modeled by the hydrogen abstraction C2H2 addition (HACA) mechanism and a sectional model. Soot surface growth through condensation of pyrene was also taken into account. The flame model is able to reproduce fairly well the chemical effects of adding either hydrogen or carbon dioxide to ethylene observed experimentally in the literature. Addition of hydrogen is more effective on soot inception suppression and addition of carbon dioxide is more effective on soot surface growth suppression. The simultaneous hydrogen enrichment and carbon dioxide dilution to ethylene retains the individual soot suppression benefits of hydrogen enrichment and carbon dioxide dilution. These results suggest that the chemical interactions between hydrogen and carbon dioxide on soot formation are weak.

ChemInform Abstract: Chirality Transfer from Graphene Quantum Dots

AbstractReview: 113 refs.

Ratiometric Fluorescent Pattern for Sensing Proteins Using Aqueous Polymer-Pyrene/γ-Cyclodextrin Inclusion Complexes.

A ratiometric, versatile, and selective fluorescent pattern to sense and distinguish proteins on the basis of dissociation of aqueous polymer-pyrene/γ-cyclodextrin (γ-CD) inclusion complexes was developed. First, two kinds of aqueous polymer-pyrene were prepared via atom transfer radical polymerization using pyrene functionalized initiator. Then, the pyrene molecules could be accumulated into γ-CD cavity and form polymer-pyrene/γ-CD complexes, resulting in appearance of excimer emissions. The resultant complexes responded to proteins in two ways: nonmetalloproteins binding to polymer component triggered dissociation of the inclusion complexes, accompanied by alteration of pyrene excimer/monomer emission and ratiometric fluorescent intensity changes; the presence of metalloproteins could quench pyrene excimer/monomer emission because of energy transfer. Moreover, the fluorescent responses of the inclusion complexes to different proteins could be modulated by changing polymer type and chain length, resulting in a tunable selectivity and sensitivity. The proposed fluorescent inclusion complexes could provide a promising platform for sensing proteins.

Cyclic up-regulation fluorescence of pyrene excimer for studying polynucleotide kinase activity based on dual amplification

Due to its important biological and clinical roles of polynucleotide kinase (PNK), accurate monitoring of PNK activity and inhibition is highly desirable. Herein, a homogeneous and sensitive fluorescence assay has been proposed for the detection of PNK activity by integrating target recycling signal amplification of DNA toehold strand displacement reaction (TSDR) with gamma-cyclodextrin (γ-CD) enhancement of pyrene excimer. A label-free hairpin DNA1 (H1) and two singly pyrene-labelled DNA, H2 and H3, are designed. Accompanying the occurrence of the efficient enzyme reactions, namely phosphorylation-actuated λ exonuclease reaction, a single-stranded DNA as a trigger DNA (tDNA) of TSDR can be released from H1. Then, tDNA drives circulatory interactions between H2 and H3 to continuously form H2/H3 duplex, resulting in formation of pyrene excimer and a “turn on” fluorescence signal of pyrene excimer. Furthermore, the fluorescence of pyrene excimer is further amplified by introducing gamma-cyclodextrin (γ-CD), which can regulate the space proximity of two pyrene molecules. Thus, TSDR-induced cyclic formation of pyrene excimer and γ-CD enhancement can specifically up-regulate the fluorescence of pyrene excimer for detection of PNK activity, the detection limit is 9.3×10−5UmL−1, which is superior to those of most existing approaches. Moreover, the proposed strategy can also be successfully utilized to study inhibition efficiency of different PNK inhibitors as well. Therefore, a dual amplification approach is provided for nucleic acid phosphorylation related researches.

Chirality transfer from graphene quantum dots

Chiral graphene quantum dots were prepared by acidic exfoliation and oxidation of graphite, dialysis, and esterification with enantiomerically pure (R) or (S)-2-phenyl-1-propanol. Circular dichroism studies support the formation of supramolecular aggregates with pyrene molecules, where a transfer of chirality occurs from the chiral graphene quantum dots to the pyrene.

ПРОСТРАНСТВЕННАЯ И ЭЛЕКТРОННАЯ СТРУКТУРА МОЛЕКУЛЫ ПИРЕНА, КАТИОНА ТРИПАФЛАВИНА И АНИОНОВ ЭОЗИНА КАК ПРЕДПОСЫЛКА ИНТЕРПРЕТАЦИИ ИХ ТВЁРДОФАЗНОЙ ФЛУОРЕСЦЕНЦИИ

ПРОСТРАНСТВЕННАЯ И ЭЛЕКТРОННАЯ СТРУКТУРА МОЛЕКУЛЫ ПИРЕНА, КАТИОНА ТРИПАФЛАВИНА И АНИОНОВ ЭОЗИНА КАК ПРЕДПОСЫЛКА ИНТЕРПРЕТАЦИИ ИХ ТВЁРДОФАЗНОЙ ФЛУОРЕСЦЕНЦИИ

Failure of hydrogenation in protecting polycyclic aromatic hydrocarbons from fragmentation

A recent study of soft X-ray absorption in native and hydrogenated coronene cations, C$_{24}$H$_{12+m}^+$ $m=0-7$, led to the conclusion that additional hydrogen atoms protect (interstellar) Polycyclic Aromatic Hydrocarbon (PAH) molecules from fragmentation [Reitsma et al., Phys. Rev. Lett. 113, 053002 (2014)]. The present experiment with collisions between fast (30-200 eV) He atoms and pyrene (C$_{16}$H$_{10+m}^+$, $m=0$, 6, and 16) and simulations without reference to the excitation method suggests the opposite. We find that the absolute carbon-backbone fragmentation cross section does not decrease but increases with the degree of hydrogenation for pyrene molecules.

Short communication: Changes in fluorescence intensity induced by soybean soluble polysaccharide–milk protein interactions during acidification

Interactions between stabilizer and milk protein are believed to influence the stabilizing behavior of the milk system. We investigated changes in fluorescence intensity induced by interactions of soybean soluble polysaccharide (SSPS) and milk protein (Mp) during acidification. The fluorescence intensity (If) of Mp increased as pH decreased from 6.8 to 5.2. Compared with Mp alone, If of SSPS-Mp mixtures increased as the pH decreased from 6.8 to 5.2. We found that the If of the SSPS-Mp mixture decreased in a pH range from 5.2 to 3.6, which indicated a change in the polarity microenvironment around the Trp residues. We also found that the maximum emission wavelength (λmax) shifted from 337 to 330nm as pH decreased from 6.8 to 3.6, in further support of SSPS interacting with the polar portion of Mp during acidification. Furthermore, an excited monomeric molecule (pyrene exciplex) was found as a ground-state pyrene formed and a broad band was shown at about 450nm. The intensity ratio of the first peak to the third peak (I1:I3) of Mp increased slightly, and the ratio of intensity of pyrene exciplex to monomer (Ie:Im) decreased because pyrene molecules were located in a less hydrophobic microenvironment during acidification. However, the ratio of I1:I3 decreased clearly at pH below 5.6 and the ratio of Ie:Im showed the opposite trend in the SSPS-Mp mixture. Changes in intrinsic and exogenous fluorescence intensity confirmed that interactions of SSPS and Mp could change the polarity of the microenvironment and that SSPS probably interacted with the polar portion of Mp. These results could give insight into the behavior of stabilizers in acid milk products.

Reaction pathways and transition states of the C-C and C-H bond cleavage in the aromatic pyrenemolecule - A Density Functional study

The activation and reaction energies of the C-C and C-H bonds cleavage in pyrene molecule are calculated applying the Density Functional Theory and 6-311G Gaussian basis. Different values for the energies result for the different bonds, depending on the location of the bond and the structure of the corresponding transition states. The C-C bond cleavage reactions include H atom migration, in many cases, leading to the formation of CH 2 groups and H-C≡C- acetylenic fragments. The activation energy values of the C-C reactions are greater than 190.00 kcal/mol for all bonds, those for the C-H bonds are greater than 160.00 kcal/mol. The reaction energy values for the C-C bonds range between 56.497 to 191.503 kcal/mol. As for the C-H cleavage reactions the activation energies range from 163.535 to 165.116 kcal/mol, the reaction energies are nearly constant, 117.500kcal/mol. The geometries of the transition states and reaction products are discussed too.

Phosphorescent π-Hole···π Bonding Cocrystals of Pyrene with Halo-perfluorobenzenes (F, Cl, Br, I)

Seven novel cocrystals of pyrene with halo-perfluorobenzenes (F, Cl, Br, I) were successfully prepared and well characterized by X-ray single-crystal diffraction. The stoichiometries of pyrene to halo-perfluorobenzene were all 1:1. The similar sandwich structures comprise pyrene and halo-perfluorobenzene alternatively stacked via π-interactions by which pyrene molecules are isolated from each other as expected instead of the dimer in the pure pyrene crystal. The phosphorescence or delayed fluorescence was, therefore, lightened under heavy atom perturbation from halo-perfluorobenzene. Moreover, based on the consideration of surface electrostatic potential (SEP) of interacting molecules, the π-interaction between halo-perfluorobenzenes with positive SEP and pyrene with negative SEP is more appropriately named the π-hole···π bond, which should be significant as a new strategy in assembling organic phosphors.

Theoretical calculation of the pyrene emission properties in different solvents

Due to its high quantum yield and long fluorescence lifetime, pyrene molecule is a widely used fluorescence probe. From a theoretical–computational viewpoint, the modeling of its emission properties in different environments still represents a challenge, mainly because the coupling with the environment severely affects its emission behavior. We employed our computational–theoretical approach to quantitatively model the pyrene emission, which combines quantum chemical calculations with all-atom molecular dynamics simulations. Our calculated fluorescence properties, well matching the experimental data, highlight that even slight geometrical fluctuations of pyrene at room temperature can provide relevant effects on its radiative lifetime.

Direct Visualization of Walking Motions of Photocontrolled Nanomachine on the DNA Nanostructure.

A light-driven artificial molecular nanomachine was constructed based on DNA scaffolding. Pyrene-modified walking strands and disulfide bond-connected stator strands, employed as anchorage sites to support walker movement, were assembled into a 2D DNA tile. Pyrene molecules excited by photoirradiation at 350 nm induced cleavage of disulfide bond-connected stator strands, enabling the DNA walker to migrate from one cleaved stator to the next on the DNA tile. The time-dependent movement of the walker was observed and the entire walking process of the walker was characterized by distribution of the walker-stator duplex at four anchorage sites on the tile under different irradiation times. Importantly, the light-fuelled mechanical movements on DNA tile were first visualized in real time during UV irradiation using high-speed atomic force microscopy (HS-AFM).

Mono- and Dinuclear Heteroleptic Cobalt Complexes with α-Diimine and Polyarene Ligands.

Reactions of the dimeric cobalt complex [(L(-) Co)2 ] (1, L=[(2,6-iPr2 C6 H3 )NC(Me)]2 ) with polyarenes afforded a series of mononuclear and dinuclear complexes: [LCo(η(4) -anthracene)] (2), [LCo(μ-η(4) :η(4) -naphthalene)CoL] (3), and [LCo(μ-η(4) :η(4) -phenanthrene)CoL] (4). The pyrene complexes [{Na2 (Et2 O)2 }{LCo(μ-η(3) :η(3) -pyrene)CoL}] (5) and [{Na2 (Et2 O)3 }{LCo(η(3) -pyrene)}] (6) were obtained by treating precursor 1 with pyrene followed by reduction with Na metal. These complexes contain three potential redox active centers: the cobalt metal and both α-diimine and polyarene ligands. Through a combination of X-ray crystallography, EPR spectroscopy, magnetic susceptibility measurement, and DFT computations, the electronic configurations of these complexes were studied. It was determined that complexes 2-4 have a high-spin Co(I) center coupled with a radical α-diimine ligand and a neutral polyarene ligand. Whereas, the ligand L in complexes 5 and 6 has been further reduced to the dianion, the cobalt remains in a formal (I) oxidation state, and the pyrene molecule is either neutral or monoanionic.

Theoretical Study on Molecules of Interstellar Interest. II. Radical Cation of Compact Polycyclic Aromatic Hydrocarbons.

Radical cations of polycyclic aromatic hydrocarbons have been postulated to be molecular carriers of diffuse spectroscopic features observed in the interstellar medium. Several important observations made by stellar and laboratory spectroscopists motivated us to undertake a detailed theoretical study attempting to validate the recorded data. In continuation of our work on this subject, we here focus on a detailed theoretical study of the doublet ground (X̃) and low-lying excited (Ã, B̃, and C̃) electronic states of the radical cation of phenanthrene, pyrene, and acenaphthene molecule. A multistate and multimode theoretical model in a diabatic electronic basis is developed here through extensive ab initio quantum chemistry calculations. Employing this model, first-principles nuclear dynamics calculations are carried out to unravel the spectral assignment, time-dependent dynamics, and photostability of the mentioned electronic states of the radical cations. The theoretical results compare well with the observed experimental data.

Selective Complexation in Three Component Cocrystals Composed of Pyrogallol[4]arene and Fluorescent Probes Pyrene and 1-(2-Pyridylazo)-2-naphthol

Cocrystals composed of a pyrogallol[4]arene molecule (one of C-propylpyrogallol[4]arene in ethanol and one of C-hexylpyrogallol[4]arene in isopropanol) and a pyrene molecule were crystallized and investigated with the aim to develop trends based on solvent and aliphatic tail length of the pyrogallol[4]arene. These new trends along with previously determined trends for the fluorescent probe 1-(2-pyridylazo)-2-naphthol (PAN), were then used to crystallize a cocrystal composed of C-hexylpyrogallol[4]arene and two fluorescent probes, pyrene and PAN. Within a two-component cocrystal of pyrene or PAN, the probe molecules are complexed in both the endo (inside the pyrogallol[4]arene bowl) and exo (outside the pyrogallol[4]arene bowl) positions. However, in the three component system, selective complexation of the probes is demonstrated whereby the PAN molecules prefer to be endo and the pyrene molecules occupy exo positions.

Synthesis of Stable Magnetic Polyaniline Nanohybrids with Pyrene as a Cross‐Linker for Simultaneous Diagnosis by Magnetic Resonance Imaging and Photothermal Therapy

AbstractWe have developed pyrene‐modified magnetic polyaniline nanoparticles (MPANs), a hybridization of MnFe2O4 magnetic nanoparticles (MNPs) and polyaniline (PANI) with pyrene as a cross‐linker, for diagnosis by simultaneous magnetic resonance (MR) imaging and photothermal therapy. In general, the strong affinity between PANI molecules, owing to interchain hydrogen bonding and the π–π interactions mediated by their aromatic composition, hinders the successful synthesis of complexes of PANI with inorganic materials. To overcome this obstacle, we used pyrene as a cross‐linker to synthesize a stable complex of PANI with MNPs. We first modified the hydrophobic MNPs with pyrene through a hydrophobic interaction and then formed a complex with PANI. The pyrene‐induced π–π interactions between the pyrene molecules on the MNPs and PANI reduced the affinity between the PANI molecules, and the strong affinity between the PANI molecules and MNPs rendered stable nanocomplexes of MPANs. Finally, Cetuximab‐conjugated MPANs were fully tested for simultaneous diagnosis by magnetic resonance imaging (MRI) from superparamagnetic MnFe2O4 and photothermal ablation therapy from the near‐infrared absorbing characteristics of PANI in epidermal growth factor receptor (EGFR) overexpressed cancer cells (A‐431 cells) in vitro.

Pyrene functionalized molecular beacon with pH-sensitive i-motif in a loop

In this work, we present a spectral characterization of pH-sensitive system, which combines the i-motif properties with the spatially sensitive fluorescence signal of pyrene molecules attached to hairpin ends. The excimer production (fluorescence max. ∼480nm) by pyrene labels at the ends of the molecular beacon is driven by pH-dependent i-motif formation in the loop. To illustrate the performance and reversible work of our systems, we performed the experiments with repeatedly pH cycling between pH values of 7.5±0.3 and 6.5±0.3. The sensor gives analytical response in excimer–monomer switching mode in narrow pH range (1.5 pH units) and exhibits high pH resolution (0.1 pH unit).

Usage of cellulose acetate membranes for the sorption-luminescence determination of pyrene in aqueous media

The applicability of cellulose acetate membranes (CAMs) as a solid matrix for the luminescence determination of pyrene in aqueous micellar solutions is shown. The effect of the concentrations of various surfactants, namely, anionic sodium dodecyl sulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB), and nonionic polyoxyethylene (10) mono-4-isooctyl phenyl ether (TX-100), on the fluorescence of pyrene in aqueous micellar solutions before and after sorption preconcentration and in an adsorbed state on a CAM has been studied. It has been found that the fluorescence intensity of pyrene on the solid-phase matrix increases as a result of pyrene solubilization in surfactant hemimiceles formed on the sorbent surface. The highest degree of pyrene extraction on CAMs has been achieved in the presence of cationic CTAB micelles. The CAM has a negative surface potential (−31.5 ± 2.5 mV), which affects the hydrocarbon recovery. The degree of extractlion and the polarity index of a microenvironment of pyrene molecules in solutions decrease in the order CTAB → SDS → TX-100.