The 2018 correlative microscopy techniques roadmap.

Developments in microscopy have been instrumental to progress in the life sciences, and many new techniques have been introduced and led to new discoveries throughout the last century. A wide and diverse range of methodologies is now available, including electron microscopy, atomic force microscopy, magnetic resonance imaging, small-angle x-ray scattering and multiple super-resolution fluorescence techniques, and each of these methods provides valuable read-outs to meet the demands set by the samples under study. Yet, the investigation of cell development requires a multi-parametric approach to address both the structure and spatio-temporal organization of organelles, and also the transduction of chemical signals and forces involved in cell-cell interactions.

Predictive Strength of Photophysical Measurements for in Vitro Photobiological Activity in a Series of Ru(II) Polypyridyl Complexes Derived from π-Extended Ligands.

This study investigates the correlation between photocytotoxicity and the prolonged excited-state lifetimes exhibited by certain Ru(II) polypyridyl photosensitizers comprised of π-expansive ligands. The eight metal complexes selected for this study differ markedly in their triplet state configurations and lifetimes. Human melanoma SKMEL28 and human leukemia HL60 cells were used as in vitro models to test photocytotoxicity induced by the compounds when activated by either broadband visible or monochromatic red light.

Improving Poor Man's Kramers-Kronig analysis and Kramers-Kronig constrained variational analysis.

We report a considerable improvement of Poor Man's Kramers-Kronig analysis and Kramers-Kronig constrained variational analysis. Whereas the first method is an alternative to the well-established conventional Kramers-Kronig analysis, but fully analytical, the second method allows to capture subtle spectral features that might get lost by conventional dispersion analysis using oscillator models. Since both methods share the same physical foundation, an improvement in the Kramers-Kronig conformity will be a benefit for either.

Fabrication of micro-patterned substrates for plasmonic sensing by piezo-dispensing of colloidal nanoparticles.

In this work we describe a very fast and flexible method for fabrication of plasmon-supporting substrates with micro-patterning capability, which is optimized for plasmonic sensing. We combined a wet chemistry approach to synthesize metallic nanoparticles with a piezo-dispensing system enabling deposition of nanoparticles on the substrates with micrometer precision. In this way, an arbitrary pattern consisting of 200 μm small spots containing plasmonic nanostructures can be produced.

Arylic versus Alkylic-Hydrophobic Linkers Determine the Supramolecular Structure and Optoelectronic Properties of Tripodal Amphiphilic Push-Pull Thiazoles.

The supramolecular structures and their constituents essentially determine the optoelectronic properties of thin films. The introduction of amphiphilicity to the constituents and interface assembly is one established technique to control supramolecular structures and resulting material properties. To yield amphiphilicity, rather hydrophobic chromophores are linked to hydrophilic head groups via flexible alkyl chains.

Assembly of T-Shaped Amphiphilic Thiazoles on the Air-Water Interface: Impact of Polar Chromophore Moieties, as Well as Dipolarity and π-Extension of the Chromophore on the Supramolecular Structure.

The supramolecular structure essentially determines the properties of organic thin films. In this work, we systematically investigate the influence of the chromophore on the supramolecular structure formation at air-water interfaces by means of the Langmuir-Blodgett technique. Therefore, we focus on the recently introduced class of double-anchor T-shaped amphiphilic dyes, namely, 4-hydroxy-thiazole chromophores that are centrally equipped with an amphiphilicity-inducing hexanoic acid.

Multimode Fabry⁻Perot Interferometer Probe Based on Vernier Effect for Enhanced Temperature Sensing.

New miniaturized sensors for biological and medical applications must be adapted to the measuring environments and they should provide a high measurement resolution to sense small changes. The Vernier effect is an effective way of magnifying the sensitivity of a device, allowing for higher resolution sensing. We applied this concept to the development of a small-size optical fiber Fabry⁻Perot interferometer probe that presents more than 60-fold higher sensitivity to temperature than the normal Fabry⁻Perot interferometer without the Vernier effect.

A novel multidrug-resistant PVL-negative CC1-MRSA-IV clone emerging in Ireland and Germany likely originated in South-Eastern Europe.

This study investigated the recent emergence of multidrug-resistant Panton-Valentine leukocidin (PVL)-negative CC1-MRSA-IV in Ireland and Germany. Ten CC1-MSSA and 139 CC1-MRSA isolates recovered in Ireland between 2004 and 2017 were investigated. These were compared to 21 German CC1-MRSA, 10 Romanian CC1-MSSA, five Romanian CC1-MRSA and two UAE CC1-MRSA, which were selected from an extensive global database, based on similar DNA microarray profiles to the Irish isolates.

Plasmonic Nanosensor Array for Multiplexed DNA-based Pathogen Detection.

In this research we introduce a plasmonic nanoparticle based optical biosensor for monitoring of molecular binding events. The sensor utilizes spotted gold nanoparticle arrays as sensing platform. The nanoparticle spots are functionalized with capture DNA sequences complementary to the analyte (target) DNA.

Ab Initio Prediction of Fluorescence Lifetimes Involving Solvent Environments by Means of COSMO and Vibrational Broadening.

The fluorescence lifetime is a key property of fluorophores that can be utilized for microenvironment probing, analyte sensing, and multiplexing as well as barcoding applications. For the rational design of lifetime probes and barcodes, theoretical methods have been developed to enable the ab initio prediction of this parameter, which depends strongly on interactions with solvent molecules and other chemical species in the emitteŕs immediate environment. In this work, we investigate how a conductor-like screening model (COSMO) can account for variations in fluorescence lifetimes that are caused by such fluorophore-solvent interactions.

Molecular Analysis of Two Different MRSA Clones ST188 and ST3268 From Primates ( spp.) in a United States Primate Center.

Methicillin-resistant (MRSA) were identified in macaques, their environmental facility, and nasal cultures of personnel from the Washington National Primate Research Center [WaNPRC] and included MRSA ST188 SCC IV and MRSA ST3268 SCC V. The aim of the current study was to determine the carriage of virulence genes, antibiotic resistance genes, and other characteristics of the primate MRSA isolates to determine if there were any obvious differences that would account for differences in transmission within the WaNPRC facility. In total, 1,199 samples from primates were tested for the presence of MRSA resulting in 158 MRSA-positive samples.

Sample-Size Planning for Multivariate Data: A Raman-Spectroscopy-Based Example.

The goal of sample-size planning (SSP) is to determine the number of measurements needed for statistical analysis. This SSP is necessary to achieve robust and significant results with a minimal number of measurements that need to be collected. SSP is a common procedure for univariate measurements, whereas for multivariate measurements, like spectra or time traces, no general sample-size-planning method exists.

Design of a scalable AuNP catalyst system for plasmon-driven photocatalysis.

In this work we present a simple, fast and cost-efficient synthesis of a metal nanoparticle catalyst on a glass support for plasmon driven heterogeneous photocatalysis. It is based on efficient mixing of metal salts as particle precursors with porous glass as the supporting material in a mixer ball mill, and the subsequent realization of a complete catalyst system by laser sintering the obtained powder on a glass plate as the support. By this, we could obtain catalyst systems with a high particle proportion and an even spatial particle distribution in a rapid process, which could be applied to various kinds of metal salt resulting in plasmon active metal nanoparticles.

Fabrication of self-assembled spherical Gold Particles by pulsed UV Laser Treatment.

We report on the fabrication of spherical Au spheres by pulsed laser treatment using a KrF excimer laser (248 nm, 25 ns) under ambient conditions as a fast and high throughput fabrication technique. The presented experiments were realized using initial Au layers of 100 nm thickness deposited on optically transparent and low cost Borofloat glass or single-crystalline SrTiO substrates, respectively. High (111)-orientation and smoothness (RMS ≈ 1 nm) are the properties of the deposited Au layers before laser treatment.

Nanoparticles Can Wrap Epithelial Cell Membranes and Relocate Them Across the Epithelial Cell Layer.

Although the link between the inhalation of nanoparticles and cardiovascular disease is well established, the causal pathway between nanoparticle exposure and increased activity of blood coagulation factors remains unexplained. To initiate coagulation tissue factor bearing epithelial cell membranes should be exposed to blood, on the other side of the less than a micrometre thin air-blood barrier. For the inhaled nanoparticles to promote coagulation, they need to bind lung epithelial-cell membrane parts and relocate them into the blood.

Removing interference-based effects from the infrared transflectance spectra of thin films on metallic substrates: a fast and wave optics conform solution.

A hybrid formalism combining elements from Kramers-Kronig based analyses and dispersion analysis was developed, which allows removing interference-based effects in the infrared spectra of layers on highly reflecting substrates. In order to enable a highly convenient application, the correction procedure is fully automatized and usually requires less than a minute with non-optimized software on a typical office PC. The formalism was tested with both synthetic and experimental spectra of poly(methyl methacrylate) on gold.

Complementary studies of lipid membrane dynamics using iSCAT and super-resolved fluorescence correlation spectroscopy.

Observation techniques with high spatial and temporal resolution, such as single-particle tracking based on interferometric scattering (iSCAT) microscopy, and fluorescence correlation spectroscopy applied on a super-resolution STED microscope (STED-FCS), have revealed new insights of the molecular organization of membranes. While delivering complementary information, there are still distinct differences between these techniques, most prominently the use of fluorescent dye tagged probes for STED-FCS and a need for larger scattering gold nanoparticle tags for iSCAT. In this work, we have used lipid analogues tagged with a hybrid fluorescent tag-gold nanoparticle construct, to directly compare the results from STED-FCS and iSCAT measurements of phospholipid diffusion on a homogeneous supported lipid bilayer (SLB).

Simultaneous isolation and detection of single breast cancer cells using surface-enhanced Raman spectroscopy.

Nowadays, cancer is one of the most dangerous and deadly disease all around the world. Cancer that is diagnosed at early stages is more likely to be treated successfully. Treatment of progressed cancer is very difficult, and generally surviving rates are much lower.

Plasmon response evaluation based on image-derived arbitrary nanostructures.

The optical response of realistic 3D plasmonic substrates composed of randomly shaped particles of different size and interparticle distance distributions in addition to nanometer scale surface roughness is intrinsically challenging to simulate due to computational limitations. Here, we present a Finite Element Method (FEM)-based methodology that bridges in-depth theoretical investigations and experimental optical response of plasmonic substrates composed of such silver nanoparticles. Parametrized scanning electron microscopy (SEM) images of surface enhanced Raman spectroscopy (SERS) active substrate and tip-enhanced Raman spectroscopy (TERS) probes are used to simulate the far-and near-field optical response.

Introducing double polar heads to highly fluorescent Thiazoles: Influence on supramolecular structures and photonic properties.

Hypothesis: Supramolecular structures determine properties of optoelectronically active materials and can be tailored via the Langmuir-Blodgett (LB) technique. Interactions between dyes can cause high crystallinities of Langmuir monolayers, thus rendering retaining their integrity during the LB-deposition challenging. However, increasing degrees of freedom exclusively at the polar anchoring moieties of dyes might improve processability without perturbing the dye's optoelectronic properties nor the function-determining crystallinity of the layer.

Localized surface plasmon resonance based biosensing.

Bioanalytical sensing based on the principle of localized surface plasmon resonance experiences is currently an extremely rapid development. Novel sensors with new kinds of plasmonic transducers and innovative concepts for the signal development as well as read-out principles were identified. This review will give an overview of the development of this field.

Thermally Switchable Fluorescence Resonance Energy Transfer via Reversible Diels-Alder Reaction of π-Conjugated Oligo-(Phenylene Ethynylene)s.

The combination of reversible, dynamic covalent bonds and π-conjugated oligo-(phenylene ethynylene)s is utilized for exchange reactions between two acceptors and one donor containing copolymer in the solid state upon thermal treatment. The specific molecular design of the polymers allows upon thermally triggering the reshuffling of the π-conjugated donor and acceptor moieties. Depending on the nature of the acceptor, an increased and a decreased fluorescence resonance energy transfer (FRET), respectively, can be observed for the mixing of the copolymers or the demixing of a donor-acceptor copolymer.

Direct detection of the photoinduced charge-separated state in a Ru(ii) bis(terpyridine)-polyoxometalate molecular dyad.

Observation of photoinduced intramolecular charge-separation is difficult for photosensitizer-POM dyads because of rapid backward electron transfer. We report here for the first time on a long-lived charge-separated state (τ = 470 ns) observed in a Ru(ii) bis(terpyridine)-based dyad. Charge-separation occurs despite virtually no driving force and the short intrinsic excited-state lifetime of the photosensitizer.

Unusually Short-Lived Solvent-Dependent Excited State in a Half-Sandwich Ru(II) Complex Induced by Low-Lying MC States.

A ruthenium complex with a half-sandwich geometry ([(p-cymene)Ru(Cl)(curcuminoid)]) was synthesized, characterized, and investigated regarding its ultrafast photophysics. These photophysical investigations of the complex revealed a weak and short-lived emission from the initially populated MLCT state and solvent-dependent photoinduced dynamics, where the secondarily populated MC state is stabilized by nonpolar solvents. Overall the decay of the dd-MC state to the ground state is completed within picoseconds.

Investigation of Microalgal Carotenoid Content Using Coherent Anti-Stokes Raman Scattering (CARS) Microscopy and Spontaneous Raman Spectroscopy.

The yield of high-value products, such as pigments that could be extracted from microalgae, is affected by various nutritional and physical factors. Consequently, there is a need for fast visualization techniques that investigate the responses of individual microalgal cells to changing environmental conditions without introducing perturbations. Here, we apply CARS microscopy to map the distribution of pigments in the diatoms Ditylum brightwellii and Stephanopyxis turris and report their relative change in response to varying light cycles using a marker-based watershed analysis of the acquired images.