Engineering thiophene-based nanoparticles to induce phototransduction in live cells under illumination.

We report that nanoparticles prepared from appropriately functionalized polythiophenes once administered to live cells can acquire phototransduction properties under illumination, becoming photoactive sites able to absorb visible light and convert it to an electrical signal through cell membrane polarization. Amine-reactive fluorescent nanoparticles with pendant N-succinimidyl-ester groups (NPs-NHS) are prepared from polythiophenes alternating unsubstituted and 3-(2,5-dioxopyrrolidin-1-yl-8-octanoate)-substituted thiophenes by a nanoprecipitation method. By 1H NMR of nanoparticles prepared using THF-d8/D2O (solvent/non-solvent) we demonstrate that the hydrolysis of the N-succinimidyl-ester group to free N-hydroxysuccinimide takes place slowly over several hours. NPs-NHS reactivity towards primary amine groups is tested towards the NH2 of d- and l-enantiomers of tryptophan. We show that the formation of a tryptophan-nanoparticle amidic bond creates a chiral shell displaying opposite CD signals for the nanoparticles bound to d or l enantiomers. The interaction of NPs-NHS with live HEK-293 cells is monitored via LSCM. We show that the NPs-NHS are not internalized but remain docked on the cell membrane. We assume that this is mainly the result of the reaction of the NHS groups in the external layer with NH2 groups present in cell membrane proteins, although the contribution of alternative mechanisms cannot be excluded. To support this assumption LSCM experiments show that nanoparticles of comparable size obtained from poly(3-hexylthiophene), NPs-P3HT, are rapidly internalized by live HEK-293 cells. Finally, using the whole-cell current clamp technique under light illumination we demonstrate that NPs-NHS can polarize the cell membrane upon light irradiation while NPs-P3HT cannot.

Experimental evidence of replica symmetry breaking in random lasers.

Spin-glass theory is one of the leading paradigms of complex physics and describes condensed matter, neural networks and biological systems, ultracold atoms, random photonics and many other research fields. According to this theory, identical systems under identical conditions may reach different states. This effect is known as replica symmetry breaking and is revealed by the shape of the probability distribution function of an order parameter named the Parisi overlap. However, a direct experimental evidence in any field of research is still missing. Here we investigate pulse-to-pulse fluctuations in random lasers, we introduce and measure the analogue of the Parisi overlap in independent experimental realizations of the same disordered sample, and we find that the distribution function yields evidence of a transition to a glassy light phase compatible with a replica symmetry breaking.

Live cell cytoplasm staining and selective labeling of intracellular proteins by non-toxic cell-permeant thiophene fluorophores.

A structurally correlated series of cell-permeant thiophene fluorophores, characterized by intense green or red fluorescence inside live mouse embryonic fibroblasts, was developed. The fluorophores displayed rapid internalization, excellent retention inside the cells, and high optical stability in the cytosolic environment and did not alter cell viability and reproducibility. Depending on the molecular structure, they experienced distinct fate inside the cells: from bright and lasting staining of the cytoplasm to selective tagging of a small set of globular proteins.

Uptake and distribution of labeled antibodies into pH-sensitive microgels.

We investigated the uptake and release of labeled antibodies from pH-sensitive hydrogel microparticles (i.e. microgels) by means of fluorescence analysis of labeled biological samples. The poly(methacrylic acid) (PMAA) hydrogel is a carbon-based network having carboxylic groups on the surface that dissociate according to their acid-base equilibrium. The ability of the PMAA microgel to encapsulate and release anti-CD4 and anti-CD8 monoclonal antibodies (MAbs), differing for the isotype and labeled with highly photostable fluorophore, was studied in solution by photoluminescence spectroscopy. The experimental results indicated that the uptake and release of the tested antibodies were controlled by pH. Furthermore, confocal microscopy analysis in the solid state revealed that the distribution of the labeled antibodies either on the surface or in the core of the microgel matrix was related to the specific properties of these MAbs.

Efficient second harmonic generation from thin films of V-shaped benzo[b]thiophene based molecules.

We have designed an original approach for efficient Second Harmonic Generation of tailored V-shape benzo[b]thiophene molecular systems enabling versatile and flexible one-step, dry and technologically friendly thin film processing. The designed moieties show chi((2)) values at least as high as the reference LiNbO(3) single crystal, without poling processing and matching the constrains of integrated optical configuration for nonlinear optical devices. This may open the way to a new class of organic materials exploitable for photonic applications.

Theoretical study on oligothiophene N-succinimidyl esters: size and push-pull effects.

We report a theoretical study on the optical properties of bithiophene and terthiophene N-succinimidyl esters, which have been functionalized with a methylsulfanyl group in the alpha or the beta positions. Time-dependent density functional theory (TD-DFT) and approximate coupled-cluster singles and doubles with the resolution of identity technique (RI-CC2) calculations have been performed in the ground and excited states. The RI-CC2 results for absorption and fluorescence energies are in better qualitative agreement with experiments, whereas TD-DFT does not correctly describe the higher energy part of the absorption spectra of beta-substituted bithiophenes, due to the presence of charge-transfer states. Systems functionalized at the alpha position show a large red-shift of the main absorption and fluorescence band and a larger Stokes-shift compared to the unsubstituted species. These effects are in most cases less pronounced for the beta-substituted structures. In particular, we found that the Stokes-shift of the alpha-substituted structures is larger than the one of the beta-substituted species due to a more planar orientation of the methylsulfanyl group with respect to the neighbouring thiophene in the excited state.

Optical properties of N-succinimidyl bithiophene and the effects of the binding to biomolecules: comparison between coupled-cluster and time-dependent density functional theory calculations and experiments.

We report a joint theoretical-experimental study on the optical properties of 5-N-succinimidyl-2,2'-bithiophene (NS-2T), a prototype system for a new class of biomarkers. Time-dependent density functional theory (TD-DFT) and approximate coupled-cluster single and doubles (CC2) calculations are performed in the ground and excited states. Theoretical results are compared with absorption, photoluminescence (PL), time-resolved PL, and PL quantum efficiency measurements. The excited state of NS-2T has a larger dipole moment as compared to that of the ground state, explaining the experimental shift of the PL peak in solvents of different polarity, and a smaller intersystem crossing (ISC) rate as compared to that of isolated bithiophene (2T), explaining the increased PL quantum efficiency. We also studied two model systems to describe the effects of the covalent binding of NS-2T to biomolecules and proteins with the epsilon-NH(2) lysine groups. These model systems show optical properties closer to 2T, as the PL quantum efficiency is reduced due to the increased ISC rate. Theoretical calculations and experimental results show that covalent binding of NS-2T to a biomolecule will blue-shift the absorption but not the photoluminescence. CC2 and TD-DFT can very well describe the absorption and photoluminescence energies of all three systems, but the presence of several charge-transfer transitions in the TD-DFT spectrum of NS-2T required the use of a correlated method to validate the TD-DFT results.

Nonradiative relaxation in thiophene-S,S-dioxide derivatives: the role of the environment.

The intramolecular radiative and nonradiative relaxation processes of three thiophene-S,S-dioxide derivatives with different molecular rigidity are investigated in different solutions and in inert matrix. We show that the fluorescence quantum efficiency and the relaxation dynamics are strongly dependent on the environment viscosity, whereas they are almost independent of the environment polarity. We demonstrate that this strong dependence is due to an environment dependent nonradiative decay rate, whereas no relevant variations of the radiative decay rate are observed. We demonstrate that the dipole coupling with the solvent does not provide an efficient nonradiative decay channel and that the S(n) - S(1) vibrational relaxation is very efficient in all of the molecules and for all of the investigated environments. Moreover first-principles time-dependent density-functional theory calculations in the correct, i.e., excited-state, molecular conformation, suggest that significant contributions of intersystem crossing to the triplet manifold can be excluded. We then conclude that the main nonradiative process determining the fluorescence quantum efficiency of this class of molecules is S(1) - S(0) internal conversion (IC). An explanation for the IC rate dependence in terms of the environment viscosity, molecular rigidity, S(1) - S(0) energy-gap, and molecular volume is presented.

The effects of oxygenation on the optical properties of dimethyl-dithienothiophenes: comparison between experiments and first-principles calculations.

Modifications of the optical properties of dimethyl-dithienothiophenes due to the oxygen functionalization of the central sulfur atom are investigated. We have measured the absorption, photoluminescence (PL) and PL excitation spectra, the PL quantum efficiencies, and the PL decay times. These experimental results are interpreted and compared with first-principles time-dependent density-functional theory calculations, which predict, for the considered systems, excitation and emission energies with an accuracy of 0.1 eV. It is found that the oxygenation strongly changes optical and photophysical properties. These effects are related to the modifications of the energetically lowest-unoccupied molecular orbital and the energetically second highest occupied one, which change the relative position of the two lowest singlet and triplet excited states.

Solution-phase microwave-assisted synthesis of unsubstituted and modified alpha-quinque- and sexithiophenes.

The facile synthesis of poorly soluble unsubstituted and modified alpha-quinque- and sexithiophenes under microwave irradiation in the liquid phase is described. The use of microwave irradiation allowed these compounds to be prepared in a few minutes and at high yields by means of the Suzuki cross-coupling reaction. Unsubstituted sexithiophene was obtained in 10 min via the one-pot borylation/Suzuki reaction, purified according to a very simple procedure, and isolated in 84% yield. The efficient synthesis of two new methylated quinque- and sexithiophenes displaying liquid crystalline properties is reported. A new microwave-assisted methodology for the conversion of aldehyde-terminated quinque- and sexithiophenes into the corresponding cyano derivatives is also described. The use of microwaves was extended to the Sonogashira coupling reaction and found to be very effective in the preparation of a quinquethiophene containing acetylenic spacers. The electronic and optical characterization of this compound is reported and discussed in relation to that of unsubstituted quinquethiophene.

Oligothiophene isothiocyanates as a new class of fluorescent markers for biopolymers.

The regioselective synthesis of fluorescent oligothiophene isothiocyanates is described. The isothiocyanates were reacted with bovine serum albumin (BSA) following standard procedures and the optical properties of the oligothiophene-BSA conjugates were analyzed as a function of oligomer concentration, time, and irradiation power. The oligothiophene-BSA conjugates were chemically very stable and their photoluminescence characteristics persisted unaltered for several months. Photoluminescence data relative to the conjugate of an oligothiophene-S,S-dioxide isothiocyanate with monoclonal anti-CD8 antibody are reported. No fluorescence quenching was observed following the binding of the isothiocyanate to the antibody and the conjugate displayed high chemical stability and photostability.

Photoluminescence Efficiency of Substituted Quaterthiophene Crystals.

The photoluminescence (PL) efficiency of substituted alpha-conjugated quaterthiophene crystals shows marked differences depending on crystal packing and molecular geometry. This effect is studied by evaluating the role of the intermolecular interactions and the effects of the single molecule conformation on the intersystem crossing (ISC) rate. The comparison of these calculations with absolute quantum efficiency measurements and with the experimental temperature dependence of the PL decay time, indicates that the differences in PL efficiency are not inherent to crystal packing effects but they are determined by the ISC rate.

Magnetic resonance spectroscopy study of low grade extra and intracerebral human neoplasms.

In this study we report an in vitro 1H magnetic resonance spectroscopy (MRS) characterization of water soluble metabolites obtained from 17 low grade extra and intracerebral human tumors (8 meningiomas, 5 oligodendrogliomas, 2 subependimomas and 2 ependimomas). In addition, the in vivo localized 1H MRS results for 4 of the meningiomas are reported. The main metabolic features characterizing low grade tumors were investigated. Meningiomas are characterized by high Cho/Cr and Ala/Cr ratios; in many cases both in the in vitro and the in vivo spectra these ratios cannot be evaluated, due to the absence of the Cr metabolite. Low grade oligodendrogliomas are characterized by low Cho/Cr ratios. High amounts of myo-inositol are found in the spectra of ependimomas and subependimomas which are distinguished by different Cho/Cr ratio values and by a different Ala content.

In vivo single voxel 1H MRS of glial brain tumors: correlation with tissue histology and in vitro MRS.

Eighteen patients affected by glial brain tumors were examined by localized single voxel magnetic resonance spectroscopy (1H MRS). For all patients histological diagnosis was obtained after stereotactic biopsy or surgical removal of the tumor. Histological nuclear atypia, tumor cellularity, necrosis, vascular proliferation and percentage of Ki-67 positive cells in the total cell populations were evaluated. It was found that some of the in vivo 1H MRS parameters were related to the histological features of the tumor. In particular, the Choi/Cri metabolite ratio obtained from the neoplastic tissues paralleled the Ki-67 cell proliferation index. For some of the patients 1H and 13C in vitro high resolution magnetic spectroscopy of surgical specimens was also carried out. 1H MRS of aqueous extracts from different biopsy specimens of the same tumor furnished fine biochemical information on intratumor heterogeneity. The degree of histological vascular proliferation of the tumor was correlated to the presence of cholesteryl esters in the 13C spectrum of the lipid fraction of surgical specimens.

Localised proton MR spectroscopy of brain metabolism changes in vegetative patients.

We examined 14 vegetative brain-injured patients with proton magnetic resonance single-volume spectroscopy (1H MRS) at 1.5 T to establish whether there were changes in relative concentrations of N-acetyl aspartate (NAA), choline (Cho) and creatine (CR) metabolites from those found in healthy brains. Spectra were obtained from two different (2 x 2 x 2 cm) volumes of interest in the left and in the right frontal cortex, normal on MRI. All spectra revealed abnormalities compared with normal spectra obtained from age-matched control subjects. Values outside the normal range for at least one of the metabolite ratios were observed in all patients. Cho/Cr was markedly higher and NAA/Cho and NAA/Cr were markedly lower than in the control subjects. At different times six patients regained awareness and the ability to obey commands, and four were re-examined; changes in metabolite ratios were observed, which were different in individual patients. The NAA/Cho ratio reaches statistical significance in discriminating between the patients with a poor outcome (death or prolonged vegetative state) and those who regained awareness; the dividing line appears to be at a value of about 1.6.

Brain perfusion SPET and proton magnetic resonance spectroscopy in the evaluation of two systemic lupus erythematosus patients with mild neuropsychiatric manifestations.

The diagnosis of central nervous system (CNS) involvement appears to be a major problem in systemic lupus erythematosus (SLE), especially when the clinical signs are non-specific or neuroimaging is unremarkable. Two SLE patients with mild neuropsychiatric manifestations were studied with magnetic resonance imaging (MRI), single photon emission tomography (SPET) and localized proton magnetic resonance spectroscopy (H-1 MRS). MRI was normal in both patients. SPET revealed areas of hypoperfusion in both patients. H-1 MRS demonstrated metabolic abnormalities in the regions corresponding to the hypoperfused areas. A correlation between H-1 MRS and SPET was noted: patients with mild neuropsychiatric SLE may have disturbances evident on SPET and H-1 MRS in the presence of normal anatomy on MRI, suggesting that CNS involvement in SLE has very strong physiological and neurometabolic components in individual patients.

In vitro and in vivo MRS study of human glioma metabolites.

In this study an in vitro multinuclear magnetic resonance spectroscopy (MRS) characterization of water soluble metabolites and of the lipid fraction obtained from 19 human gliomas (12 glioblastomas, 3 anaplastic astrocytomas, 2 anaplastic oligodendrogliomas and 2 oligodendrogliomas) with a total of 27 surgical specimens, is reported. Moreover, some in vivo H-1 MRS results are shown. The regional metabolic heterogeneity of glioblastomas, according to their morphological heterogeneity, is documented. For glioblastomas a specific in vitro H-1 MRS metabolite profile cannot be defined. Low and high grade oligodendrogliomas showed characteristic choline/creatine and alanine/creatine metabolite ratios. The spectroscopical characterization of histopathological factors concerning malignant gliomas is shown.

In vivo 1H MRS and in vitro multinuclear MR study of human brain tumors.

Localized in vivo 1H MR spectra of four patients with brain tumors and in vitro multinuclear (1H, 13C and 31P) MR characterization of water soluble and lipid components of the same tumors after surgical removal are reported herein. The in vivo spectra of the neoplastic regions of all patients showed N-Acetyl-Aspartate/Choline (NAA/Cho), Choline/Creatine (Cho/Cr) and N-Acetyl-Aspartate/Creatine (NAA/Cr) metabolite ratios markedly different from those of the controlateral healthy tissue. In vitro 1H MR measurements allowed for the identification of a much larger number of metabolites than those measured in vivo. Indeed, well resolved 1H, 13C and 31P MR spectra were obtained for water soluble and lipid components in all cases. Our data confirm that some metabolites observed in vitro could be specific markers of brain tumors.

Polyhydroxyoligothiophenes. 2. Hydrogen-Bonding-Oriented Solid State Conformation of 3,3'-Bis(2-hydroxyethyl)-2,2'-bithiophene and Regioselective Synthesis of the Corresponding Head-to-Head/Tail-to-Tail Quater- and Sexithiophene.

This paper reports the X-ray structure of 3,3'-bis(2-hydroxyethyl)-2,2'-bithiophene (1), which is the building block for the synthesis of head-to-head/tail-to-tail 2-hydroxyethyl-substituted oligothiophenes. Contrary to all the bithiophenes reported so far, 1 exhibits a noncoplanar anti conformation and an inter-ring twist angle (67.5 degrees ) which is the largest ever measured for adjacent rings of alpha-conjugated oligothiophenes. This unusual conformation appears to be dictated by intermolecular hydrogen-bonding interactions involving the OH groups, which bind the molecule in close packed layers. The paper also describes the regioselective synthesis of the dimer and the trimer of 1, namely of 3,3',4",3"'-tetrakis(2-hydroxyethyl)-2,2':5',2":5",2"'-quaterthiophene (3c) and of 3,3',4",3"',4"",3""'-hexakis(2-hydroxyethyl)-2,2':5',2":5",2"':5"',2"":5"",2""'-sexithiophene (4b). 3c And 4b were obtained through palladium(0)-catalyzed coupling of the mono- and distannanes of the tetrahydropyranyl derivative of 1 with the appropriate monobromo compound (Stille's reaction). Finally, the paper reports force-field calculations which suggest that the low lambda(max) values measured for 1, 3c, and 4b are also the result of intramolecular hydrogen-bonding interactions which favor highly twisted conformations in solution.