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Gold nanostructures focus light to a molecular length scale at their surface, creating the possibility to visualize molecular structure. The high optical intensity leads to surface enhanced Raman scattering (SERS) from nearby molecules. SERS spectra contain information on molecular position and orientation relative to the surface but are difficult to interpret quantitatively. Here we describe a ratiometric analysis method that combines SERS and unenhanced Raman spectra with theoretical calculations of the optical field and molecular polarizability. When applied to the surfactant layer on gold nanorods, the alkane chain is found to be tilted 25° to the surface normal, which matches previous reports of the layer thickness. The analysis was also applied to fluid phase phospholipid bilayers that contain tryptophan on the surface of gold nanorods. The lipid double bond was found to be oriented normal to the bilayer and 13 Å from the nitrogen atom. Tryptophan was found to sit near the glycerol headgroup region with its indole ring 43° from the bilayer normal. This new method can determine specific interfacial structure under ambient conditions, with microscopic quantities of material, and without molecular labels.
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Surface-enhanced Raman scattering (SERS) and localized surface plasmon resonance sensing (LSPR) have been applied for a detailed analysis of lipid bilayers at the surface of gold nanorods. The spatial dependence of surface enhancement and the optical effects of the lipid phase transition confirm the presence of a bilayer membrane structure. Deuterated lipids exchanged rapidly between the nanorod surface and lipid vesicles in solution, suggesting a loosely bound, natural membrane structure. However, at a low solution concentration of lipid vesicles, the lipids on the gold nanorod surface convert to a nonbilayer structure, which could impact biological applications of these nanomaterials.
Assuntos
Ouro/química , Bicamadas Lipídicas/análise , Nanotubos/química , Fosfolipídeos/química , Análise Espectral Raman/métodos , Ressonância de Plasmônio de SuperfícieRESUMO
Blending conjugated polymers with insulating matrices is often utilized for engineering extrinsic properties in organic electronics. Semiconductor/insulator blends are typically processed to form a uniformly distributed network of conductive domains within the insulating matrix, marrying electronic and physical properties from individual components. Understanding of polymer-polymer interactions in such systems is thus crucial for property co-optimization. One of the commonly overlooked parameters is the structural configuration of the insulator on the resulting properties, especially the electronic properties. This study investigated how the tacticity of the matrix polymer, among other relevant parameters in play, impacts solid state crystallization in semiconductor/matrix blends and hence the resulting charge transport properties. We found an intricate dependence of the film morphology, aggregation behavior, electronic charge transport, and mixed ionic-electronic coupling properties on the insulator's tacticity. Our experimentally iterative approach shows that for a given application, when selecting semiconductor/insulator combinations, the tacticity of the matrix can be leveraged to optimize performance and vary solid-state structure.
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Stretchable polymer semiconductors (PSCs) have seen great advancements alongside the development of soft electronics. But it remains a challenge to simultaneously achieve high charge carrier mobility and stretchability. Herein, we report the finding that stretchable PSC thin films (<100-nm-thick) with high stretchability tend to exhibit multi-modal energy dissipation mechanisms and have a large relative stretchability (rS) defined by the ratio of the entropic energy dissipation to the enthalpic energy dissipation under strain. They effectively recovered the original molecular ordering, as well as electrical performance, after strain was released. The highest rS value with a model polymer (P4) exhibited an average charge carrier mobility of 0.2 cm2V-1s-1 under 100% biaxial strain, while PSCs with low rS values showed irreversible morphology changes and rapid degradation of electrical performance under strain. These results suggest rS can be used as a parameter to compare the reliability and reversibility of stretchable PSC thin films.
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Semiconducting conjugated polymers possess attractive optoelectronic properties and low-cost solution processability and are inherently mechanically flexible. However, the device performance is susceptible to the fabrication methods because of the relatively weak intermolecular interaction of the polymers and their inherent conformational and energetic disorder. An efficient fabrication technique for large-scale integration of high-quality polymer architectures is essential for realizing high-performance optoelectronic devices. Here, we report an efficient method for fabrication of polymer nanowire arrays with a precise position, a smooth surface, a homogeneous size, high crystallinity, and ordered molecular packing. The controllable dewetting dynamics on a template with asymmetric wettability permits the formation of discrete capillary bridges, resulting in the ordered molecular packing arising from unidirectional recession of the three-phase contact line. The high quality of nanowire architectures is evidenced by the morphological characteristics and hybrid edge-on and face-on molecular packing with high crystallinity. On the basis of these high-quality nanowire arrays, photodetectors with a responsivity of 84.7 A W-1 and detectivity of >1012 Jones are realized. Our results provide a platform for integration of high-quality polymer architectures for use in high-performance optoelectronic devices.
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Deformable electronic devices that are impervious to mechanical influence when mounted on surfaces of dynamically changing soft matters have great potential for next-generation implantable bioelectronic devices. Here, deformable field-effect transistors (FETs) composed of single organic nanowires (NWs) as the semiconductor are presented. The NWs are composed of fused thiophene diketopyrrolopyrrole based polymer semiconductor and high-molecular-weight polyethylene oxide as both the molecular binder and deformability enhancer. The obtained transistors show high field-effect mobility >8 cm2 V-1 s-1 with poly(vinylidenefluoride-co-trifluoroethylene) polymer dielectric and can easily be deformed by applied strains (both 100% tensile and compressive strains). The electrical reliability and mechanical durability of the NWs can be significantly enhanced by forming serpentine-like structures of the NWs. Remarkably, the fully deformable NW FETs withstand 3D volume changes (>1700% and reverting back to original state) of a rubber balloon with constant current output, on the surface of which it is attached. The deformable transistors can robustly operate without noticeable degradation on a mechanically dynamic soft matter surface, e.g., a pulsating balloon (pulse rate: 40 min-1 (0.67 Hz) and 40% volume expansion) that mimics a beating heart, which underscores its potential for future biomedical applications.
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BACKGROUND: The STAT (Signal Transducers and Activators of Transcription) transcription factor family mediates cellular responses to a wide range of cytokines. Activated STATs (particularly STAT3) are found in a range of cancers. Further, STAT3 has anti-apoptotic functions in a range of tumour cell lines. After observing a proteolytic cleavage in STAT3alpha close to a potential apoptotic caspase protease cleavage site we investigated whether STAT3alpha might be a caspase substrate. METHODS: STAT3alpha status was investigated in vitro in several cell systems:- HM-1 murine embryonic stem (ES) cells following various interventions; IOUD2 murine ES cells following induction to differentiate along neural or adipocyte lineages; and in a number of breast cancer cell lines. STAT3alpha status was also analysed in vivo in wild type murine mammary glands undergoing controlled, forced involution. RESULTS: Immunoblotting for STAT3alpha in HM-1 ES cell extracts detected amino and carboxy terminal species of approximately 48 kDa and 43 kDa respectively--which could be diminished dose-dependently by cell treatment with the nitric oxide (NO) donor drug sodium nitroprusside (SNP). UV irradiation of HM-1 ES cells triggered the STAT3alpha cleavage (close to a potential caspase protease cleavage site). Interestingly, the pan-caspase inhibitor z-Val-Ala-DL-Asp-fluoromethylketone (z-VAD-FMK) and the JAK2 tyrosine kinase inhibitor AG490 both inhibited cleavage dose-dependently, and cleavage was significantly lower in a heterozygous JAK2 knockout ES cell clone. STAT3alpha cleavage also occurred in vivo in normal murine mammary glands undergoing forced involution, coinciding with a pulse of phosphorylation of residue Y705 on full-length STAT3alpha. Cleavage also occurred during IOUD2 ES cell differentiation (most strikingly along the neural lineage) and in several human breast cancer cell lines, correlating strongly with Y705 phosphorylation. CONCLUSION: This study documents a proteolytic cleavage of STAT3alpha into 48 kDa amino and 43 kDa carboxyl terminal fragments in a range of cell types. STAT3alpha cleavage occurs close to a potential caspase site, and can be inhibited dose-dependently by SNP, AG490 and z-VAD-FMK. The cleavage seems to be caspase-dependent and requires the phosphorylation of STAT3alpha at the Y705 residue. This highly regulated STAT3alpha cleavage may play an important role in modulating STAT3 transcriptional activity.
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Neoplasias da Mama/metabolismo , Caspases/fisiologia , Células-Tronco Embrionárias/metabolismo , Glândulas Mamárias Animais/metabolismo , Fator de Transcrição STAT3/metabolismo , Animais , Diferenciação Celular , Linhagem Celular Tumoral , Feminino , Humanos , Janus Quinase 2/metabolismo , Camundongos , Peso Molecular , Nitroprussiato/farmacologia , FosforilaçãoRESUMO
Previous studies have demonstrated a proapoptotic role for the transcription factor STAT3 in involuting murine mammary epithelium, resulting in delayed involution and lower levels of apoptosis in the STAT3 null gland relative to wild-type controls. As p53 was implicated in the eventual involution of the STAT3 null gland, we examined the effect of STAT3 loss in the mammary gland in a p53 null background. Combined loss of STAT3 and p53 severely perturbed involution, with hyperdelayed loss of epithelium and reappearance of adipocytes. The early apoptotic response was almost completely abrogated, although elevated levels of delayed apoptosis persisted at days 6, 17 and 4 weeks of involution in STAT3-p53 doubly null mammary glands. A 5.7-fold upregulation of the cyclin-dependent kinase inhibitor p21Waf1 at 3 days of involution in STAT3 null glands was abolished in STAT3-p53 doubly null glands -- suggesting that the critical factor triggering delayed involution in the STAT3 null gland is a p53-dependent rise in p21Waf1 levels around day 3 of involution. Further, STAT3-p53 doubly null glands showed significantly higher levels of proliferation compared to STAT3 or p53 singly null (or wild-type) glands at days 6, 17 and 4 weeks of involution. Combined loss of STAT3 and p53 therefore results in hyperdelayed involution, demonstrating their synergistic physiological roles in normal involution. This inappropriate retention of p53-deficient cells may represent a novel mechanism of tumour predisposition.
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Proteínas de Ligação a DNA/metabolismo , Glândulas Mamárias Animais/metabolismo , Neoplasias Mamárias Experimentais/metabolismo , Transativadores/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Adipócitos/metabolismo , Animais , Apoptose , Proteínas de Ciclo Celular/metabolismo , Proliferação de Células , Inibidor de Quinase Dependente de Ciclina p21 , Epitélio/metabolismo , Feminino , Genótipo , Immunoblotting , Imuno-Histoquímica , Antígeno Ki-67/biossíntese , Neoplasias Mamárias Animais , Camundongos , Mutação , Neoplasias/metabolismo , Fosforilação , Fator de Transcrição STAT3 , Fatores de Tempo , Tirosina/metabolismoRESUMO
The non-aggregating nature of a water-soluble pi-conjugated polythiophene has been characterised by concentration independent thermal denaturing.
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Polímeros/química , Tiofenos/química , Água/química , Íons/química , Estrutura Molecular , Análise Espectral , TemperaturaRESUMO
Both high gain and transconductance at low operating voltages are essential for practical applications of organic field-effect transistors (OFETs). Here, we describe the significance of the double-layer capacitance effect in polar rubbery dielectrics, even when present in a very low ion concentration and conductivity. We observed that this effect can greatly enhance the OFET transconductance when driven at low voltages. Specifically, when the polar elastomer poly(vinylidene fluoride-co-hexafluoropropylene) (e-PVDF-HFP) was used as the dielectric layer, despite a thickness of several micrometers, we obtained a transconductance per channel width 30 times higher than that measured for the same organic semiconductors fabricated on a semicrystalline PVDF-HFP with a similar thickness. After a series of detailed experimental investigations, we attribute the above observation to the double-layer capacitance effect, even though the ionic conductivity is as low as 10(-10) S/cm. Different from previously reported OFETs with double-layer capacitance effects, our devices showed unprecedented high bias-stress stability in air and even in water.
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Germ-line heterozygosity of the BRCA2 gene in women predisposes to breast and ovarian cancers. Successful therapies targeted specifically at these neoplasms have thus far remained elusive. Recent studies in mice have shown that inhibition of poly(ADP-ribose) polymerase-1 (PARP-1) targets cells lacking Brca2 and xenografts derived from BRCA2-deficient ES cells or Chinese hamster ovary cells. We set out to develop a more relevant preclinical model that will inform and accelerate translation into the clinic. As such, we conditionally deleted Brca2 and p53 within murine mammary epithelium and treated the resulting tumors in situ with a highly potent PARP-1 inhibitor (AZD2281) alone or in combination with carboplatin. Daily exposure to AZD2281 for 28 days caused significant regression or growth inhibition in 46 of 52 tumors. This response was shown to be specific to tumors lacking both Brca2and p53. AZD2281/carboplatin combination therapy for 28 days showed no advantage over carboplatin monotherapy. However, if PARP inhibitor treatment was continued, this significantly increased the time to tumor relapse and death in these mice. This preclinical study is the first to show in vivo hypersensitivity of spontaneously arising Brca2-deficient mammary tumors to PARP-1 inhibition monotherapy or combination therapy. As such, our data add substantial weight to the argument for the use of PARP inhibitors as therapeutic agents against human breast cancers in which BRCA2 is mutated. Moreover, the specificity that we have shown further suggests that PARP inhibitors will be generally effective against tumors caused by dysregulation of components of the homologous recombination pathway.
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Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Genes BRCA2 , Genes p53 , Neoplasias Mamárias Experimentais/tratamento farmacológico , Neoplasias Mamárias Experimentais/genética , Inibidores de Poli(ADP-Ribose) Polimerases , Animais , Proteína BRCA2/deficiência , Proteína BRCA2/genética , Carboplatina/administração & dosagem , Modelos Animais de Doenças , Feminino , Neoplasias Mamárias Experimentais/enzimologia , Camundongos , Camundongos Transgênicos , Mutação , Ftalazinas/administração & dosagem , Piperazinas/administração & dosagem , Poli(ADP-Ribose) Polimerase-1 , Proteína Supressora de Tumor p53/deficiência , Proteína Supressora de Tumor p53/genéticaRESUMO
Injection of photoexcited electrons from colloidal PbS quantum dots into TiO(2) nanoparticles is investigated. The electron affinity and ionization potential of PbS quantum dots, inferred from cyclic voltammetry measurements, show strong size dependence due to quantum confinement. On the basis of the measured energy levels, photoexcited electrons should transfer efficiently from the quantum dots into TiO(2) only for quantum-dot diameter below approximately 4.3 nm. Continuous-wave fluorescence spectra and fluorescence transients of PbS quantum dots coupled to titanium dioxide nanoparticles are consistent with electron transfer for small quantum dots. The measured electron transfer time is surprisingly slow ( approximately 100 ns), and implications of this for future photovoltaics will be discussed. Initial results obtained from solar cells sensitized with PbS quantum dots are presented.
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Coloides/química , Nanopartículas/química , Nanotecnologia/métodos , Pontos Quânticos , Titânio/química , Elétrons , Luz , Nanotecnologia/instrumentação , Oscilometria , Fotoquímica , Semicondutores , Espectrometria de Fluorescência/métodosRESUMO
We have created surfaces which switch from cationic at pH < 3 to anionic at pH > 5, by attaching aminodicarboxylic acid units to silica and gold substrates. Charge reversal was demonstrated by monitoring the adsorption of cationic dyes (methylene blue and a tetracationic porphyrin) and an anionic sulfonated porphyrin, at a range of pH using UV-vis absorption and reflection spectroscopy. The cationic dyes bind under neutral conditions (pH 5-7) and are released at pH 1-4, whereas the anionic dye binds under acidic conditions (pH 1-4) and is released at pH 5-7. Gold surfaces were functionalized with two different amphoteric disulfides with short (CH(2))(2) and long (CH(2))(10)CONH(CH(2))(6) linkers; the longer disulfide gave surfaces exhibiting charge reversal in a narrower pH range. Adsorption is much faster on the functionalized gold (t(1/2) = 62 s) than on functionalized silica (t(1/2) = 6900 s), but the final extents of coverage on both surface are similar, for a given dye at a given pH, with maximal coverages of around 2 molecules nm(-)(2). These charge-reversal processes are reversible and can be repeatedly cycled by changing the pH. We have also created surfaces which undergo irreversible proton-triggered charge switching, using a carbamate-linked thiol carboxylic acid which cleaves in acid. These surfaces are versatile new tools for controlling electrostatic self-assembly at surfaces.