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Silica nanoparticles decorated with aminocarboxylate ligands are novel vehicles to deliver antibiotics which are otherwise not able to penetrate the bacteria membrane and can also include agents for tracking and imaging.

Made available in DSpace on 2021-06-25T11:00:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-07-31 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Microencapsulation is a potential biotechnological tool, which can overcome antimicrobial peptides (AMP) instabilities and reduce toxic side effects. Thus, this study evaluates the antibacterial activities of the Ctx(Ile21)-Ha AMP against multidrug-resistant (MDR) and non-resistant bacteria and develop and characterize peptide-loaded microparticles coated with the enteric polymers hydroxypropylmethylcellulose acetate succinate (HPMCAS) and hydroxypropylmethylcellulose phthalate (HPMCP). Ctx(Ile21)-Ha was obtained by solid phase peptide synthesis (SPPS) method, purified and characterized by HPLC and Mass Spectrometry. The peptide exhibited potent antibiotic activities against Salmonella enteritidis, Salmonella typhimurium, Pseudomonas aeruginosa (MDR), Acinetobacter baumannii (MDR), and Staphylococcus aureus (MDR). Ctx(Ile21)-Ha microencapsulation was performed by ionic gelation with high efficiency, maintaining the physical-chemical stability. Ctx(Ile21)-Ha coated-microparticles were characterized by DSC, TGA, FTIR-Raman, XRD and SEM. Hemolytic activity assay demonstrated that hemolysis was decreased up to 95% compared to single molecule. In addition, in vitro release control profile simulating different portions of gastrointestinal tract was performed and showed the microcapsules' ability to protect the peptide and release it in the intestine, aiming pathogen's location, mainly by Salmonella sp. Therefore, use of microencapsulated Ctx(Ile21)-Ha can be allowed as an antimicrobial controller in monogastric animal production as an oral feed additive (antimicrobial controller), being a valuable option for molecules with low therapeutic indexes or high hemolytic rates. São Paulo State University (Unesp) School of Agricultural and Veterinarian Sciences, Jaboticabal São Paulo State University (Unesp) Institute of Chemistry, Araraquara São Paulo State University (Unesp) School of Sciences and Engineering, Tupã São Paulo State University (Unesp) School of Pharmaceutical Sciences, Araraquara São Paulo State University (Unesp) School of Technology and Sciences, Presidente Prudente Poultry Health Specialized Laboratory Biological Institute, Bastos Institute of Microbiology and Infection University of Birmingham School of Chemistry University of Birmingham São Paulo State University (Unesp) School of Agricultural and Veterinarian Sciences, Jaboticabal São Paulo State University (Unesp) Institute of Chemistry, Araraquara São Paulo State University (Unesp) School of Sciences and Engineering, Tupã São Paulo State University (Unesp) School of Pharmaceutical Sciences, Araraquara São Paulo State University (Unesp) School of Technology and Sciences, Presidente Prudente FAPESP: 2016/00446-7

Introducing both tetrazine radical and azido bridges afforded two air-stable square complexes [MII4(bpztz•-)4(N3)4] (MII = Zn2+, 1; Co2+, 2; bpztz = 3,6-bis(3,5-dimethylpyrazolyl)-1,2,4,5-tetrazine), where the metal ions are cobridged by μ1,1-azido bridges and tetrazine radicals. Magnetic studies revealed strong antiferromagnetic metal-radical interaction with a coupling constant of -64.7 cm-1 in the 2J formalism in 2. Remarkably, 2 exhibits slow relaxation of magnetization with an effective barrier for spin reverse of 96 K at zero applied field.

Optical microscopy techniques are ideal for live cell imaging for real-time nanoparticle tracking of nanoparticle localization. However, the quantification of nanoparticle uptake is usually evaluated by analytical methods that require cell isolation. Luminescent labeling of gold nanoparticles with transition metal probes yields particles with attractive photophysical properties, enabling cellular tracking using confocal and time-resolved microscopies. In the current study, gold nanoparticles coated with a red-luminescent ruthenium transition metal complex are used to quantify and track particle uptake and localization. Analysis of the red-luminescence signal from particles is used as a metric of cellular uptake, which correlates to total cellular gold and ruthenium content, independently measured and correlated by inductively coupled plasma mass spectrometry. Tracking of the luminescence signal provides evidence of direct diffusion of the nanoparticles across the cytoplasmic membrane with particles observed in the cytoplasm and mitochondria as nonclustered "free" nanoparticles. Electron microscopy and inhibition studies identified macropinocytosis of clusters of particles into endosomes as the major mechanism of uptake. Nanoparticles were tracked inside GFP-tagged cells by following the red-luminescence signal of the ruthenium complex. Tracking of the particles demonstrates their initial location in early endosomes and, later, in lysosomes and autophagosomes. Colocalization was quantified by calculating the Pearson's correlation coefficient between red and green luminescence signals and confirmed by electron microscopy. Accumulation of particles in autophagosomes correlated with biochemical evidence of active autophagy, but there was no evidence of detachment of the luminescent label or breakup of the gold core. Instead, accumulation of particles in autophagosomes caused organelle swelling, breakdown of the surrounding membranes, and endosomal release of the nanoparticles into the cytoplasm. The phenomenon of endosomal release has important consequences for the toxicity, cellular targeting, and therapeutic future applications of gold nanoparticles.

Sensing strategies for dual detection systems are of interest for rapid, accurate data collection in in vitro testing. We introduce an Ir(III) complex with a boronic acid binding receptor site on the 2-phenylpyridine ligand as an ideal probe with photo- and electro- chemical signals, sensitive to changes of monosaccharide binding. The complex displays orange luminescence at 618 nm which is reduced in intensity upon binding of the monosaccharides, 70 % and 40% for fructose and glucose, respectively. The electrochemiluminescent signal of the complex shows a direct response to monosaccharide binding. The complex's luminescence is also responsive to monosaccharide presence in cancer cells. The Ir(III) complex shows the same response upon incorporation into hydrogel matrices, demonstrating the potential of its integration into a device, as a non-toxic, simple to use tool to observe sugar binding in physiologically relevant pH ranges and saccharide concentrations.

The supramolecular self-assembly synthetic strategy provides a valid tool to obtain polynuclear Fe(II) complexes having effective communication between the metal centres and distinct spin crossover behaviour. Despite the great success in constructing various magnetic molecules, progress has not been made in SCO complexes based on azido bridges. In this article, the coordination-driven supramolecular assembly based on 3,6-substituted pyridazine and azide is presented to afford two Fe(II) grid-like complexes: [(L)4FeII4(N3)4][BPh4]4·sol (1, L = 3,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)pyridazine and 2, L = 3,6-di(pyridin-2-yl)pyridazine). The substitution of pyridinyl groups in 2 instead of pyrazolyl ones in 1 led to the only example exhibiting spin-crossover behaviour (T1/2 = 230 K) among the azido-bridged complexes. In addition, a temperature-dependent photoluminescence study of 2 demonstrates a visible synergetic effect between the SCO event and the luminescence.

Near infrared to visible up-conversion devices have every growing demand in a myriad of industrial sectors including photovoltaics, energy harvesting, medicine and imaging. Here we have demonstrated an up-conversion device which utilizes quantum dots for both infrared absorption and visible emission. The band structure of the device is designed and optimized with well-constructed carrier transport and blocking layers. The achieved up-conversion device exhibits an impressive conversion efficiency of over 6 %, with a high near infrared on-off ratio of over 10 4 . The device demonstrates a potential new approach for an up-conversion device designed solely on quantum dots with high efficiency.

Introducing both tetrazine radical and azido bridges afforded two air-stable square complexes [M

Microencapsulation is a potential biotechnological tool, which can overcome antimicrobial peptides (AMP) instabilities and reduce toxic side effects. Thus, this study evaluates the antibacterial activities of the Ctx(Ile

The self-assembly of Co(ii) salts, pyridazine derivatives and azides afforded two azido-bridged [2×2] grid-type complexes {[(L)4CoII4(N3)4][BPh4]4}·sol (1, L = 3,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)pyridazine (pzdz) and sol = 4CH3CN·3CHCl3·2CH3OH and 2, L = 3,6-di(pyridin-2-yl)pyridazine (pydz) and sol = 4CH3CN). Upon comparison with other related grid-like complexes, the incorporation of end-on azido-bridges resulted in overall intramolecular ferromagnetic couplings, and thus endowed complexes 1 and 2 single molecule magnet behaviour with field-induced slow magnetic relaxation.

A general concept of converting capsules into sensors is reported. Such simple conversion enables instantaneous nondestructive analysis for applications such as controlled release and energy storage among others. Converted capsule sensors are responsive in emission colors to varying core cargos via the incorporation of a solvatochromic fluorophore under excitation. Such cargo-responsive self-sensing abilities facilitate their application in capsule-level analysis such as cargo retention-leakage detection and release implications, as well as defect identification. The versatile concept is shown as an auxiliary tool in thermal energy storage to visualize phase transition, exhibiting promising potentials in application-level characterization.

Nanocarriers with unusual DNA binding properties provide enhanced cytotoxic activity beyond that conferred by the platinum agents they release., New gold and lipoic based nanocarriers for the delivery of platinum(ii) and platinum(iv) drugs are developed, which allow enhanced loading of the drug on the surface of the nanocarriers and release in a pH-dependent fashion, with superior release at lower pHs which are associated with many tumours. The conjugate nanoparticles and their conjugates enter cells rapidly (within 3 hours). They tend to cluster in vesicles and are also observed by light and electron microscopies in the cytoplasm, endoplasmic reticulum and nucleus. We further incorporate aminoanthraquinone units that are both fluorophores and DNA intercalators. This results in nanocarriers that after drug release will remain surface decorated with DNA-binders challenging the conventional design of the nanocarrier as an inert component. The outcome is nanocarriers that themselves have distinctive, remarkable and unusual DNA binding properties being able to bind and wrap DNA (despite their anionic charge) and provide enhanced cytotoxic activity beyond that conferred by the platinum agents they release. DNA coiling is usually associated with polycations which can disrupt cell membranes; anionic nanoparticles that can cause novel and dramatic effects on DNA may have fascinating potential for new approaches to in-cell nucleic acid recognition. Our findings have implications for the understanding and interpretation of the biological activities of nanoparticles used to deliver other DNA-binding drugs including clinical drug doxorubicin and its formulations.

Luminescence monitoring of DNA intercalator complexes is important for assessing their localisation and targeting: We report herein a luminescent hetero-trimetallic complex with europium as a luminescent reporter and two attached platinum acetylide terpyridyl units as the DNA recognition units. The ligand, based on a bisamide derivative of diethylenetriaminepentaacetic acid functionalized with two ethynyl groups, provides a backbone to anchor two platinum terpyridyl units, Pt-tpy, leading to the hairpin-shaped heterometallic complex 1. We also prepared a related mono-nuclear platinum complex 2 to compare its intercalation properties with 1. Linear dichroism, UV-visible and melting experiments show the ability of both complexes to interact with calf thymus DNA, with linear dichroism confirming intercalation and demonstrating the expected greater DNA stiffening by the bis-intercalator 1. Importantly, the tri-metallic complex 1 shows a three-fold enhancement in europium luminescence upon addition of calf thymus DNA; other mono-intercalator lanthanide designs have commonly shown a decrease in emission on binding. The ability of the complex to monitor DNA interactions gives the potential use as a luminescence switch in sensing experiments and highlights the design of heterometallic bis-intercalator complexes as an effective approach for DNA-responsive sensitisation of a lanthanide luminescence signal.

Smart contact lenses have been put forward for years, but there is still no commercial product in the market; the high cost due to expensive fabrication techniques could be one of the reasons. In this paper, first, a cost-efficient and reliable route to fabricate graphene grating on contact lens was designed and demonstrated based on the direct laser interference patterning graphene film on commercial contact lenses using an Nd:YAG laser. The thickness of the film and the interference angle have been taken into consideration. Optical characterization and simulation have been applied to evaluate the quality of our final achieved grating patterns with a grating size from 0.92 to 3.04 μm. Two-dimensional (2D) patterns could also be obtained through double-time laser interference. Contact angles for samples with different interference angles were presented considering the service environment of smart contact lenses. Of course, the conductivity of the samples was evaluated using a four-probe method. The most conductive sample had the sheet resistance lower than 30 Ω/sq. This research study highlighted the possibility of patterning graphene with the laser ablation method and provided a candidate solution for the fabrication of smart contact lenses under controlled cost.

The design of coordination sites around lanthanide ions has a strong impact on the sensitization of their luminescent signal. An imidodiphosphonate anionic binding site is attractive as it can be functionalized with "remote" sensitizer units, such as phenoxy moieties, namely, HtpOp, accompanied by an increased distance of the lanthanide from the ligand high-energy stretching vibrations which quench the luminescence signal, hence providing flexible shielding of the lanthanide. We report the formation and isolation of Ln(tpOp)3 complexes where Ln = Er, Gd, Tb, Dy, Eu, and Yb and the Y(tpOp)3 diamagnetic analogue. The complexes are formed from reaction of KtpOp and the corresponding LnCl3·6H2O salt either by titration and in situ formation or by mixing and isolation. All complexes are seven-coordinated by three tpOp ligand plus one ethanol molecule, except for Yb(tpOp)3 which has no solvent coordinated. Phosphorus NMR shows characteristic shifts to support the coordination of the lanthanide complexes. The complexes display visible and near-infrared luminescence with long lifetimes even for the near-infrared complexes which range from 3.3 μs for Nd(tpOp)3 to 20 μs for Yb(tpOp)3. The ligand shows more efficient sensitization than the imidodiphosphinate analogues for all lanthanide complexes with a notable quantum yield of the Tb(tpOp)3 complex at 45%. We attribute this to the properties of the remote sensitizer unit and its positioning further away from the lanthanide, eliminating quenching of high energy C-H vibrations from the ligand shell. Calculations of the ligand shielding support the photophysical properties of the complexes. These results suggest that these binding sites are promising in the further development of the lanthanide complexes in optoelectronic devices for telecommunications and new light emitting materials.

Objectives Functionalised silica sub-micron particles are being investigated as a method of delivering antimicrobials and remineralisation agents into dentinal tubules. However, their methods of application are not optimised, resulting in shallow penetration and aggregation. The aim of this study is to investigate the impact of cavitation occurring around ultrasonic scalers for enhancing particle penetration into dentinal tubules. Methods Dentine slices were prepared from premolar teeth. Silica sub-micron particles were prepared in water or acetone. Cavitation from an ultrasonic scaler (Satelec P5 Newtron, Acteon, France) was applied to dentine slices immersed inside the sub-micron particle solutions. Samples were imaged with scanning electron microscopy (SEM) to assess tubule occlusion and particle penetration. Results Qualitative observations of SEM images showed some tubule occlusion. The particles could penetrate inside the tubules up to 60 μm when there was no cavitation and up to ∼180 μm when there was cavitation. Conclusions The cavitation bubbles produced from an ultrasonic scaler may be used to deliver sub-micron particles into dentine. This method has the potential to deliver such particles deeper into the dentinal tubules. Clinical significance Cavitation from a clinical ultrasonic scaler may enhance penetration of sub-micron particles into dentinal tubules. This can aid in the development of novel methods for delivering therapeutic clinical materials for hypersensitivity relief and treatment of dentinal caries.

Colloidal PbS quantum dots (QDs) are promising candidates for various optoelectronic applications based on solution-processed thin-film techniques. In this work, a versatile layer-by-layer (LBL) spray deposition of the QDs is introduced aiming for a future large-scale fabrication process of optoelectronic devices. As compared to spin-coated QD solids, a smaller inter-dot distance and a better-ordered superlattice stacking behavior of the QDs are found in the spray-deposited QD solids as confirmed by grazing-incidence small-angle X-ray scattering (GISAXS). The spectral mapping combined time-resolved photoluminescence analysis indicates a longer charge carrier lifetime and better order of the energy state distribution of the spray-deposited QD solid comparing with the spin-coated one. Thus, photodetectors based on spray deposition of QD solids demonstrate an excellent device performance, with the responsivity achieving 365.1 A/W and the detectivity reaching up to 1.4 × 1012 Jones under an illumination power of 63.5 μW/cm2 at a wavelength of 1250 nm. The spray-deposited device performances indicate a great potential of spray deposition of large sized QDs in large-scale fabrications for optoelectronics using longer wavelengths.

In this study, lanthanum oxide nanoparticles (La2O3 NPs) synthesised via the facile sol-gel method, using a solution of micro-sized lanthanum oxide powders containing 20% nitric acid and high molecular weight polyethylene glycol (PEG). The as synthesised La2O3 NPs were then characterized using X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), energy-dispersive X-ray (EDS) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and photoluminescence (PL) spectroscopy. Our findings indicated that the concentration of PEG strongly influences the particle size and the lattice strain of the La2O3 NPs. A single phase hexagonal crystal structure was confirmed via XRD studies with lattice constants, a = b = 0.3973 nm and c = 0.6129 nm. The average crystallite size and lattice strains estimated were in the range of approximately 25–28 nm and 0.0050–0.0055 respectively. The incremental nature of the crystallinity and lattice strains of the NPs was observed with the subsequent enhancement of PEG-contents, while the average particle size was reduced. The average particle size of La2O3 NPs estimated from ESEM imaging was consistent with that obtained from the XRD data. The photoluminescence spectra revealed a strong emission band located at a wavelength of 365 nm (typical green band) for all La2O3NPsamples. This is ascribed to the recombination of delocalized electrons around the conduction band with a single charged state of a surface oxygen vacancy.

The development of long-lived luminescent nanoparticles for lifetime imaging is of wide interest as luminescence lifetime is environmentally sensitive detection independent of probe concentration. We report novel iridium-coated gold nanoparticles as probes for multiphoton lifetime imaging with characteristic long luminescent lifetimes based on iridium luminescence in the range of hundreds of nanoseconds and a short signal on the scale of picoseconds based on gold allowing multichannel detection. The tailor-made IrC

Objectives Sub-micron particles may assist in the delivery of compounds into dentine tubules. The surface interactions of the particles with dentine may prevent them from entering the tubules. The aim of this study is to investigate whether silica particles, treated with surfactants improves dentine tubules occlusion using both artificial and human tooth models Methods Spherical silica particles (size 130–810 nm) bearing an encapsulated ruthenium luminescent complex were coated with the following surfactants: Zonyl ® FSA, Triton ® X-100 and Tween20 ® . The particles were prepared as 0.004% w/v and 0.04% w/v solutions with deionized water and were applied to the surface of; (1) in vitro model of PET ThinCert™ cell culture inserts; (2) 0.1 mm thick sections of human molar teeth. Results Scanning electron and confocal fluorescence microscopy images show that particles without any coating and with TritonX-100 coating had the highest aggregation. Particles with Tween-20 are less aggregated on the surface and show inclusion in the tubules. Particles coated with fluorosurfactant Zonyl show a preference for aggregation at the tubule. With the ThinCert™ membranes high aggregation within the artificial tubules was increased by particle concentration. Conclusions The use of silica sub-micron particles on hard dental tissues is dependent on the modification of the surface chemistry of both the particle and the dentine and the employment of the fluorοsurfactant may improve tubule occlusion. The use of ThinCerts™ membrane is useful in vitro model to mimic dentinal tubules and observe the ability of particles to occlude small channels. Clinical significance The use of silica sub-micron particles on hard dentine tissues is dependent on the modification of the surface coating of the particles. This may influence how particles are incorporated in potential delivery vehicles applied to the dentine surface with the employment of a fluorosurfactant showing promise.

Imaging of blood flow in narrow channels and close to vessel walls is important in cardiovascular research for understanding pathogenesis. Our aim was to provide novel nanoprobes with visible emission and long lifetimes as trackers of flow.Gold nanoparticles coated with an iridium complex were prepared. Luminescence imaging was used to monitor their flows in different hematocrit blood and in murine tissues.The velocities are independent of hematocrit level and the nanoparticles entering blood circulation can be clearly detected in vessels in lungs, mesentery and the skeletal muscle.The work introduces for the first time iridium-based yellow-green luminescence with nanoparticle size of 100 nm for visualizing and monitoring flows with much higher resolution than conventional alternatives.

The use of gold nanoparticles as a scaffold on which to assemble molecular architectures presents a versatile approach to produce nanoprobes with modalities defined by the properties of the capping architectures at the molecular level. Lanthanide ions, with their characteristic magnetic and luminescent properties, are ideal probes for imaging applications. Gold nanoparticles represent an inert, biocompatible and rigid scaffold on which to assemble molecular complexes using clean, facile chemistries. The size of the gold nanoparticles can be easily tuned using robust and established chemistry. The combination of the stable, long-lived luminescence signal or characteristic magnetic properties afforded by the trivalent lanthanide ions with the size-tuneable inert gold core allows the formation of tailored nanoprobes ideally suited to the investigation of biological systems and biomedical applications. In this review the different methods for attachment of lanthanide complexes onto gold nanoparticles are presented for the production of nanoprobes with luminescence and magnetic resonance signal outputs. A short introduction outlining the development of the preparation methods for water-soluble gold nanoparticles is presented, followed by the approaches to the functionalisation of gold nanoparticles with metal-complexes which set the scene for the lanthanide studies. Two approaches of introducing lanthanides onto gold nanoparticles are identified and the systems are grouped in the discussion under the attachment of pre-assembled lanthanide complexes and the employment of ligands on nanoparticles that bind lanthanides. The preparation and properties of lanthanide-coated nanoparticles are then discussed in detail as luminescent visible and near infrared probes. Finally, the development of gold nanoparticles as a platform on which to assemble Gd(III) complexes for magnetic resonance imaging applications is discussed.

Zoe Pikramenou, Catriona McCallion, Sara Carreira, Peter Dobson, Katherine Brown, Yuri Antonio Diaz Fernandez, Maha Abdollah, Dejian Zhou, Dan Sun, Sandhya Moise, Lucio Litti, Lanry L. Yung, Stefan Borsley, Nadiya Dragneva, Annette Barchanski, Mostafa El-Sayed, Amelie Heuer-Jungemann, Roger M. Pallares, Edman Tsang, Nicolas Barry, Scott Mitchell, Nguyen T. K. Thanh, Maya Thanou, Ivan Parkin, Paresh Ray and Richard Jones

Water soluble, luminescent gold nanoparticles are delivered into human platelets via a rapid, pH-controlled mechanism using a pH low insertion peptide, pHLIP . The approach introduces cocoating of gold nanoparticles with a europium luminescent complex, EuL and the pHLIP peptide to give pHLIP • EuL • Au . The 13-nm diameter gold nanoparticles act as a scaffold for the attachment of both the luminescent probe and the peptide to target delivery. Their size allows delivery of approximately 640 lanthanide probes per nanoparticle to be internalized in human platelets, which are not susceptible to transfection or microinjection. The internalization of pHLIP • EuL • Au in platelets, which takes just minutes, was studied with a variety of imaging modalities including luminescence, confocal reflection, and transmission electron microscopy. The results show that pHLIP • EuL • Au only enters the platelets in low pH conditions, pH 6.5, mediated by the pHLIP translocation across the membrane, and not at pH 7.4. Luminescence microscopy images of the treated platelets show clearly the red luminescence signal from the europium probe and confocal reflection microscopy confirms the presence of the gold particles. Furthermore, transmission electron microscopy gives a detailed insight of the internalization and spatial localization of the gold nanoparticles in the platelets. Thus, we demonstrate the potential of the design to translocate multimodal nanoparticle probes into cells in a pH dependent manner.

An elementary supramolecular conducting system was constructed using a novel (±)-thioctic acid-functionalized β-cyclodextrin host deposited on a gold (Au) surface and an iridium-bearing guest molecule with biphenyl tails to insert specifically into the cyclodextrin cavity. The resulting supramolecular system was used to investigate remote electron communication between the flat Au surface and the platinum (Pt)/iridium (Ir) tip of a scanning tunnelling microscope. The morphology of the surfaces after successive deposition of host molecules followed by guest molecules was investigated. Formation of features of 2 nm size was shown on the Au surface functionalised with the supramolecular system. I–V spectroscopic analysis of the tunnelling current through this supramolecular layer revealed the relation between the effective barrier height and tunnelling distance. Thus, in the supramolecular host–metallo-guest system, a small increase of conductance is observed, compared to the layer without the guest. This can be attributed to the presence of the Ir-guest, which eventually creates intermediate energy states between the Au substrate and the Pt/Ir tip. Copyright © 2011 John Wiley & Sons, Ltd.

Lanthanide complexes based on bis(amides) of diethylenetriaminepentaacetic acid with thiol functionalities are modified with 2,2'-dipyridyl disulfide to give activated complexes that can selectively react with thiol-functionalized complexes to form heterometallic lanthanide macrocycles. The preparation and full characterization of the polyaminocarboxylate ligands N,N''-bis[p-thiophenyl(aminocarbonyl)]diethylenetriamine-N,N',N''-triacetic acid (H(3)L(x)) and the activated N,N''-bis[p-(pyridyldithio)[phenyl(aminocarbonyl)]]diethylenetriamine-N,N',N''-triacetic acid (H(3)L(y)) and the complexes LaL(x), NdL(x), SmL(x), EuL(x), GdL(x), DyL(x), TbL(x), ErL(x), and YbL(x) are reported. The luminescence properties of the LnL(x) complexes emitting in the visible (where Ln = Dy(3+), Tb(3+), Eu(3+), and Sm(3+)) are examined by steady-state and time-resolved photoluminescence, and the triplet state energy level of GdL(x) was estimated to be 24 100 cm(-1) from the 0-0 band of the 77 K phosphorescence spectrum. Near-infrared emission was detected for the NdL(x), YbL(x), and ErL(x) complexes, demonstrating the versatility of the thiophenol chromophore. The assembly of purely heterometallic EuTbL(x)(2) macrocycles by reaction of EuL(x) with TbL(y) was followed by UV-vis absorption spectroscopy, monitoring the characteristic absorption peak of pyridyl-2-thione at 353 nm. Analysis of the solution by mass spectrometry reveals the formation of purely heterometallic macrocycle EuTbL(x)(2). This is in contrast with the results obtained by dynamic self-assembly under oxidative conditions, where we observe a statistical mixture of macrocyclic complexes of Eu(2)L(x)(2), Tb(2)L(x)(2), and EuTbL(x)(2). The EuTbL(x)(2) macrocycle displays dual color emission, incorporating the characteristic f-f transitions of Eu(3+) and Tb(3+). Investigation into the time-resolved photophysical properties of EuTbL(x)(2) reveals energy transfer from Tb(3+) to Eu(3+), facilitated by the different conformations of the macrocycle in solution.

Planar nanodevices, consisted of gold electrodes in the nanometer scale fabricated by a conventional e-beam lithography and lift-off process and functionalized by suitably synthesized cyclodextrin-based self-assembled monolayers were electrically characterized. The monolayers were supramolecularly connected to gold nanoparticles, so that the electrodes were bridged. Thus, conductive paths through the cyclodextrin molecules (ideally Au contact/molecule/Au bridge/molecule/Au contact) were formed. In order to study the electrical behaviour of the various samples, different arrangements were used, varying in the cyclodextrin derivative exploited, the way the CD molecules were connected the underlying gold surface and the association of the gold nanoparticles with the monolayer. Hysteresis effects that can be exploited in molecular memory devices were studied in terms of the type of the cyclodextrin complex. The transport properties as well as the topography of the cyclodextrin monolayers were also investigated by scanning tunnelling microscopy.

Block copolymer micelles have been prepared with a dithiomaleimide (DTM) fluorophore located in either the core or shell. Poly(triethylene glycol acrylate)-b-poly(tert-butyl acrylate) (P(TEGA)-b-P(tBA)) was synthesized by RAFT polymerization, with a DTM-functional acrylate monomer copolymerized into either the core forming P(tBA) block or the shell forming P(TEGA) block. Self-assembly by direct dissolution afforded spherical micelles with Rh of ca. 35 nm. Core-labeled micelles (CLMs) displayed bright emission (Φf = 17%) due to good protection of the fluorophore, whereas shell-labeled micelles (SLMs) had lower efficiency emission due to collisional quenching in the solvated corona. The transition from micelles to polymer unimers upon dilution could be detected by measuring the emission intensity of the solutions. For the core-labeled micelles, the fluorescence lifetime was also responsive to the supramolecular state, the lifetime being significantly longer for the micelles (τAv,I = 19 ns) than for the polymer unimers (τAv,I = 9 ns). The core-labeled micelles could also self-report on the presence of a fluorescent hydrophobic guest molecule (Nile Red) as a result of Förster resonance energy transfer (FRET) between the DTM fluorophore and the guest. The sensitivity of the DTM fluorophore to its environment therefore provides a simple handle to obtain detailed structural information for the labeled polymer micelles. A case will also be made for the application superiority of core-labeled micelles over shell-labeled micelles for the DTM fluorophore.

Spontaneously adsorbed monolayers of [Co(ttp-CH2-SH)2](PF6)2 have been formed on platinum microelectrodes by exposure to micromolar solutions of the complex in 0.1 M TBABF4 in acetonitrile, ttp-CH2-SH is 4′-(p-(thiolmethyl)-phenyl)-2,2′:6′,2″-terpyridine. Resonance Raman spectroscopy on roughened polycrystalline platinum macro electrodes show that the molecule undergoes adsorption through the sulphur atom onto the platinum surface. The monolayers show reversible and well defined cyclic voltammetry when switched between Co2+ and Co3+ forms, with a peak to peak splitting of 0.040 ± 0.005 V up to 200 V s−1 and an FWHM of 0.138 ± 0.010 V. Adsorption is irreversible leading to the maximum surface coverage, 6.3 ± 0.3 × 10−11 mol cm−2 for 2.5 ≤ [Co(ttp-CH2-SH)2] ≤ 10 μM. The rate of monolayer formation appears to be controlled not by mass transport or interfacial binding but by surface diffusion of the complex. The surface diffusion coefficient is 5.5 ± 1.1 × 10−7 cm2 s−1 indicating that prior to formation of an equilibrated monolayer, the adsorbates have significant mobility on the surface. The electron transfer process across the monolayer–electrode interface has been probed by high speed chronoamperometry and the standard heterogeneous electron transfer rate constant, k°, is approximately 3.06 ± 0.03 × 104 s−1. The reorganization energy is at least 18.5 kJ mol−1.

Monolayers of di-6A,6B-deoxy-6-(4-pyridylmethyl)amino-gamma-cyclodextrin (gamma-CD-(py)2) have been formed on polycrystalline platinum electrodes and investigated using electrochemical and surface-enhanced Raman spectroscopy (SERS). The behavior of self-assembled monolayers of (gamma-CD-(py)2) alone, (gamma-CD-(py)2) backfilled with 1-nonanethiol, and 1-nonanethiol are reported. The potential dependence of the capacitance indicates that the film capacitance is higher for the backfilled CD layers than for 1-nonanethiol layers, most likely due to ion flux through the CD cavity. SERS spectra of the backfilled layer exhibit features associated with both pyridine-functionalized CD and alkane moieties. Investigations using [Fe(CN)6]4- as a solution-phase probe indicate that the backfilled CD-alkane thiol layer exhibits enhanced blocking properties compared to gamma-CD-(py)2 films alone. Complete blocking was achieved by a combination of backfilling and insertion of a high-affinity guest 1-adamantylamine into the cavity. Significantly, an electroactive guest with high affinity for gamma-CD, [Co(biptpy)2]2+, does not exhibit a redox response at the gamma-CD-(py)2 layer but molecular recognition is turned on by backfilling the CD layer with 1-nonanethiol molecules. This switching on of the electrochemical activity suggests that the CD hosts are initially inaccessible but reorientate upon backfilling, exposing the CD opening to solution and permitting a supramolecular host-guest complex to form. The binding of [Co(biptpy)2]2+ to gamma-CD in the backfilled monolayer depends on the bulk concentration of guest and is modeled by the Langmuir isotherm, yielding an association constant for the Co2+ state of 1.45 +/- 0.46 x 105 M-1 and a limiting surface coverage 1.49 +/- 0.25 x 10-11 mol cm-2. The surface coverage of the divalent state is higher than the trivalent state, reflecting the dynamic nature of the inclusion.

A supramolecular complex [Ru(dcb)2(α-CD-5-bpy)]Cl2 (1-α-CD) (dcb = 4,4′-dicarboxyl-2,2′-bipyridine, α-CD-5-bpy = 6-mono[5-methyl(5′-methyl-2,2′-bipyridyl)]-permethylated α-CD) (CD: cyclodextrin) based on a ruthenium tris-bipyridyl core with an appended α-CD cavity is designed and synthesised, in order to facilitate dye/redox couple interaction and dye regeneration in nanocrystalline TiO2 solar cells. The luminescent complex is fully characterized and anchored on mesoporous titania electrodes showing increased power-conversion efficiency in solid-state dye-sensitized solar cells using a composite polymer electrolyte. Direct comparison of the properties of the CD complex with an analogous ruthenium complex [Ru(dcb)2(5,5′-dmbpy)]Cl2 (2) (5,5′-dmbpy = 5,5′-dimethylbipyridine) without the CD cavity reveals that the photovoltaic performance of 1-α-CD is enhanced by about 40 % compared to 2. Independent studies have shown complexation of the iodide redox couple to the CD in 1-α-CD. These results indicate that the CD moiety is able to act as a mediator and fine tune the photoelectrode/electrolyte interface.

The photophysical properties of gold nanoparticles, AuNPs, with sizes of 13, 50 and 100 nm in diameter, coated with surface-active ruthenium complexes have been studied to investigate the effect of the distance of the ruthenium luminescent centre from the gold surface. Luminescence lifetimes of the three ruthenium probes, RuS1, RuS6 and RuS12, with different length spacer units between the surface active groups and the ruthenium centre were taken. The metal complexes were attached to AuNP13, AuNP50 and AuNP100via thiol groups using a method of precoating the nanoparticles with a fluorinated surfactant. The luminescence lifetime of the longer spacer unit complex, RuS12, was enhanced by 70% upon attachment to the AuNP when compared to the increase of the short and medium linker unit complexes, RuS1 (20%) and RuS6 (40%) respectively. The effect of the surfactant in the lifetime increase of the ruthenium coated AuNPs was shown to be larger for the medium spacer probe, RuS6. There was no effect of the change of the size of the AuNPs from 13 to 50 or 100 nm.

Lifeact is a 17-residue peptide that can be employed in cell microscopy as a probe for F-actin when fused to fluorescent proteins, but therefore is not suitable for all cell types. We have conjugated fluorescently labelled Lifeact to three different cell-penetrating systems (a myristoylated carrier (myr), the pH low insertion peptide (pHLIP) and the cationic peptide TAT) as a strategy to deliver Lifeact into cells and developed new tools for actin staining with improved synthetic accessibility and low toxicity, focusing on their suitability in platelets and megakaryocytes. Using confocal microscopy, we characterised the cell distribution of the new hybrids in fixed cells, and found that both myr– and pHLIP–Lifeact conjugates provide efficient actin staining upon cleavage of Lifeact from the carriers, without affecting cell spreading. This new approach could facilitate the design of new tools for actin visualisation.

A new complex [Ru(bpy)(2)(bpySH)](PF(6))(2), RuBpySH, has been prepared bearing two anchoring groups for surface attachment, where bpy is 2,2'-bipyridyl and bpySH is 5,5'-bis(mercaptomethyl)-2,2'-bipyridine. Monolayers of RuBpySH have been formed on micro and macro platinum electrodes by spontaneous adsorption from micromolar solutions of the complex in 50:50 v/v water/acetone. The monolayers can be reversibly switched between the Ru(2+) and the Ru(3+) forms. Cyclic voltammetry is well-defined with a peak-to-peak splitting of 30 +/- 5 mV and a full width at half-maximum of 110 +/- 10 mV being observed for scan rates up to 5 V s(-1) where the supporting electrolyte is 0.1 M tetrabutylammonium tetrafluoroborate in acetonitrile. Adsorption is irreversible in this system, and the saturation coverage obtained is 8.1 +/- 0.4 x 10(-11) mol cm(-2) when the complex concentration in the deposition solution is between 10 microM and 1.0 mM. The dynamics of adsorption depend markedly on the bulk concentration and are described in terms of irreversible adsorption. Dry monolayers display luminescence properties similar to those of powder samples of the complex, indicating that the monolayer has characteristics of the solid-state sample rather than the solution sample of the complex. Significantly, efficient electrochemiluminescence is generated using tripropylamine as the coreactant. The rate of electron transfer across the electrode/monolayer interface has been probed using high scan rate cyclic voltammetry. The standard heterogeneous electron-transfer rate constant, k degrees , is 0.9 +/- 0.1 x 10(4) s(-1), and there is weak adsorbate-electrode electronic communication.

Gold nanoparticles are efficiently labelled with a luminescent ruthenium complex, producing 13 and 100 nm diameter, monodisperse red-emissive imaging probes with luminescence lifetimes prolonged over the molecular unit. Single, 100 nm particles are observed in whole cell luminescence imaging which reveals their biomolecular association with chromatin in the nucleus of cancer cells.

The bis(beta-diketone) ligands 1,3-bis(3-phenyl-3-oxopropanoyl)benzene, H(2)L(1) and 1,3-bis(3-phenyl-3-oxopropanoyl) 5-ethoxy-benzene, H(2)L(2), have been prepared for the examination of dinuclear lanthanide complex formation and investigation of their properties as sensitizers for lanthanide luminescence. The ligands bear two conjugated diketonate binding sites linked by a 1,3-phenylene spacer. The ligands bind to lanthanide(III) or yttrium(III) ions to form neutral homodimetallic triple stranded complexes [M(2)L(1)(3)] where M = Eu, Nd, Sm, Y, Gd and [M(2)L(2)(3)], where M = Eu, Nd or anionic quadruple-stranded dinuclear lanthanide units, [Eu(2)L(1)(4)](2-). The crystal structure of the free ligand H(2)L(1) has been determined and shows a twisted arrangement of the two binding sites around the 1,3-phenylene spacer. The dinuclear complexes have been isolated and fully characterized. Detailed NMR investigations of the complexes confirm the formation of a single complex species, with high symmetry; the complexes show clear proton patterns with chemical shifts of a wide range due to the lanthanide paramagnetism. Addition of Pirkle's reagent to solutions of the complexes leads to splitting of the peaks, confirming the chiral nature of the complexes. Electrospray and MALDI mass spectrometry have been used to identify complex formulation and characteristic isotope patterns for the different lanthanide complexes have been obtained. The complexes have high molar absorption coefficients (around 13 x 10(4) M(-1)cm(-1)) and display strong visible (red or pink) or NIR luminescence upon irradiation at the ligand band around 350 nm, depending on the choice of the lanthanide. Emission quantum yield experiments have been performed and the luminescence signals of the dinuclear complexes have been found to be up to 11 times more intense than the luminescence signals of the mononuclear analogues. The emission quantum yields and the luminescence lifetimes are determined to be 5% and 220 micros for [Eu(2)L(1)(3)], 0.16% and 13 micros for [Sm(2)L(1)(3)], and 0.6% and 1.5 micros for [Nd(2)L(1)(3)]. The energy level of the ligand triplet state was determined from the 77 K spectrum of [Gd(2)L(1)(3)]. The bis-diketonate ligand is shown to be an efficient sensitizer, particularly for Sm and Nd. Photophysical studies of the europium complexes at room temperature and 77 K show the presence of a thermally activated deactivation pathway, which we attribute to ligand-to-metal charge transfer (LMCT). Quenching of the luminescence from this level seems to be operational for the Eu(III) complex but not for complexes of Sm(III) and Nd(III), which exhibit long lifetimes. The quadruple-stranded europium complex has been isolated and characterized as the piperidinium salt of [Eu(2)L(1)(4)](2-). Compared with the triple-stranded Eu(III) complex in the solid state, the quadruple-stranded complex displays a more intense emission signal with a distinct emission pattern indicating the higher symmetry of the quadruple-stranded complex.

A multifunctionalised podand cyclodextrin ligand, β-CD-(urebpy)7, with urea--bipyridine binding sites leads to ruthenium and osmium, {Ru[β-CD-(urebpy)7]}[PF6]2 {Os[β-CD-(urebpy)7]}[PF6]2, cyclodextrins. The bipyridine ligands are preorganised by the cyclodextrin cavity encapsulating the ruthenium and osmium core to give photoactive metallocyclodextrins. The podate cyclodextrin complexes show characteristic ruthenium and osmium tri-bipyridine luminescence. It is demonstrated that the ruthenium cyclodextrins participate in sensing schemes through both the cyclodextrin cavity and the urea cage at the bottom of the cyclodextrin rim. Luminescence quenching of the ruthenium emission is observed by addition of anthraquinone guests in the cyclodextrin cavity or addition of dihydrogen phosphate anion.

Lanthanide complexes of the macrocyclic ligands 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N′-diacetic acid (H2(dacda)) and 1,4,7,10-tetraoxa-13-azacyclopentadecane-13-acetic acid (H(macma)) have been isolated and characterised. The photophysical properties of the red and green emissive, Eu(III) and Tb(III), respectively, complexes have been elucidated. Upon addition of mono- or bi-dentate aromatic carboxylates or dibenzoylmethide in solutions of the Eu(III) macrocycles triggering of the lanthanide emission is observed. The formation of the ternary complex between the lanthanide macrocycle and the sensitiser is controlled by the available coordinaton sites of the lanthanide macrocycle prior to the binding event.

No abstract

General discussion on luminescence sensing and imaging.

The actin nodule is a novel F-actin structure present in platelets during early spreading. However, only limited detail is known regarding nodule organization and function. Here we use electron microscopy, SIM and dSTORM super-resolution, and live-cell TIRF microscopy to characterize the structural organization and signalling pathways associated with nodule formation. Nodules are composed of up to four actin-rich structures linked together by actin bundles. They are enriched in the adhesion-related proteins talin and vinculin, have a central core of tyrosine phosphorylated proteins and are depleted of integrins at the plasma membrane. Nodule formation is dependent on Wiskott–Aldrich syndrome protein (WASp) and the ARP2/3 complex. WASp−/− mouse blood displays impaired platelet aggregate formation at arteriolar shear rates. We propose actin nodules are platelet podosome-related structures required for platelet–platelet interaction and their absence contributes to the bleeding diathesis of Wiskott–Aldrich syndrome., During early platelet spreading a novel F-actin structure forms, called the actin nodule. Here Poulter et al. demonstrate that actin nodule formation depends on WASp and the Arp2/3 complex, and using super-resolution microscopy they show that nodules bear a structural resemblance to podosomes.