Supposedly identical microplastic particles substantially differ in their material properties influencing particle-cell interactions and cellular responses.

Microplastics and its putative adverse effects on environmental and human health increasingly gain scientific and public attention. Systematic studies on the effects of microplastics are currently hampered by using rather poorly characterised particles, leading to contradictory results for the same particle type. Here, surface properties and chemical composition of two commercially available nominally identical polystyrene microparticles, frequently used in effect studies, were characterised. We show distinct differences in monomer content, ζ-potentials and surface charge densities. Cells exposed to particles showing a lower ζ-potential and a higher monomer content displayed a higher number of particle-cell-interactions and consequently a decrease in cell metabolism and proliferation, especially at higher particle concentrations. Our study emphasises that no general statements can be made about the effects of microplastics, not even for the same polymer type in the same size class, unless the physicochemical properties are well characterised.

Spectral field mapping in plasmonic nanostructures with nanometer resolution.

Plasmonic nanostructures and -devices are rapidly transforming light manipulation technology by allowing to modify and enhance optical fields on sub-wavelength scales. Advances in this field rely heavily on the development of new characterization methods for the fundamental nanoscale interactions. However, the direct and quantitative mapping of transient electric and magnetic fields characterizing the plasmonic coupling has been proven elusive to date. Here we demonstrate how to directly measure the inelastic momentum transfer of surface plasmon modes via the energy-loss filtered deflection of a focused electron beam in a transmission electron microscope. By scanning the beam over the sample we obtain a spatially and spectrally resolved deflection map and we further show how this deflection is related quantitatively to the spectral component of the induced electric and magnetic fields pertaining to the mode. In some regards this technique is an extension to the established differential phase contrast into the dynamic regime.

The role of colloidal plasmonic nanostructures in organic solar cells.

Plasmonic particles can contribute via multiple processes to the light absorption process in solar cells. These particles are commonly introduced into organic solar cells via deposition techniques such as spin-coating or dip-coating. However, such techniques are inherently challenging to achieve homogenous surface coatings as they lack control of inter-particle spacing and particle density on larger areas. Here we introduce interface assisted colloidal self-assembly as a concept for the fabrication of well-defined macroscopic 2-dimensional monolayers of hydrogel encapsulated plasmonic gold nanoparticles. The monolayers showed a pronounced extinction in the visible wavelength range due to localized surface plasmon resonance with excellent optical homogeneity. Moreover this strategy allowed for the investigation of the potential of plasmonic monolayers at different interfaces of P3HT:PCBM based inverted organic solar cells. In general, for monolayers located anywhere underneath the active layer, the solar cell performance decreased due to parasitic absorption. However with thick active layers, where low hole mobility limited the charge transport to the top electrode, the plasmonic monolayer near that electrode spatially redistributed the light and charge generation close to the electrode led to an improved performance. This work systematically highlights the trade-offs that need to be critically considered for designing an efficient plasmonically enhanced organic solar cell.

Scaling properties of the shear modulus of polyelectrolyte complex coacervates: a time-pH superposition principle.

We analyze the scaling properties of pH-dependent shear modulus spectra of complex coacervates made of weak polyanions and strong polycations. For the first time, we report on a "time-pH superposition principle". This principle implies that the charge density in complex coacervates made of not fully charged polyions only influences the time scale of the relaxation dynamics, but not the mechanisms of the underlying dynamics.

Influence of chemical treatments on adhesion properties of hemp fibres.

In addition to be an environmentally friendly material, hemp fibres are also inexpensive reinforcements in thermoplastics or concrete composites, due to their intrinsic mechanical, thermal and acoustic properties. The morphology of hemp fibres has been chemically modified in order to enhance the matrix/fibre interface and has been examined by Scanning Electron Microscopy (SEM). In this paper, Gas Chromatography (GC) and Atomic Force Microscopy (AFM) were used to investigate the influence of treatments on the composition of hemp fibres and also on the micro-adhesive interactions between a silica colloidal probe and the surface of the fibres using Chemical Force Microscopy (CFM). Microscopy studies and chemical analysis showed that each treatment tends to lead to a morphology of interconnected web-like structure of hemp fibres. It was found that on an average, the adhesion force, contribution of capillary force and Van der Waals' forces, is higher in the case of NaOH treatment.

Bacterial protein patterning by micro-contact printing of PLL-g-PEG.

Biomimetic micro-patterned surfaces of three S-layer (fusion) proteins, wild type (SbpA), enhanced green fluorescence protein (SbpA-EGFP) and streptavidin (SbpA-STV), were built by microcontact printing of poly-L-lysine grafted polyethylene glycol (PLL-g-PEG). The functionality of the adsorbed proteins was studied with atomic force microscopy and fluorescence microscopy. Atomic force microscopy (AFM) measurements showed that wild-type SbpA recrystallized on PLL-g-PEG free areas, while fluorescent properties of SbpA-EGFP and the interaction of SbpA-streptavidin heterotetramers with biotin were not affected due to the adsorption on the micro patterned substrates.

Experimental evidence of the electrostatic contribution to the bending rigidity of charged membranes.

We address the issue of the origin of the bending rigidity of a charged membrane formed from amphiphilic molecules. Electrostatic effects are investigated by direct measurement of the force necessary to deform a catanionic membrane as function of the ionic strength of the medium by means of an atomic force microscope (AFM). Using continuum mechanical modeling of membrane deformation, we derive the bending rigidity of the catanionic membranes and monitor for the first time its decrease in response to increasing salt concentration.

Direct method to study membrane rigidity of small vesicles based on atomic force microscope force spectroscopy.

Mechanical properties of lipidic membranes such as their bending rigidity are governing liposome morphology and play an important role in processes like membrane fusion and adhesion. Force versus deformation measurements are the most direct means to determine this, but so far experimental data is scarce and mainly stems from techniques that are limited to giant vesicles. We present atomic force microscope force spectroscopy as a method allowing force-deformation measurements of submicron vesicles. Bending rigidities of small unilamellar dipalmitoylphosphatidylcholine (DPPC) liposomes (R<200 nm) can be derived from the force-deformation data using analytical models based on shell theory and are in good agreement with independent measurements.

Freestanding polyelectrolyte multilayers as functional and construction elements.

This article reviews the progress in the field of polyelectrolyte multilayer membranes with special attention to freestanding membranes. These can be prepared both in the form of hollow capsules and as flat membrane sheets. While (bio) functionality, or bioactivity as it is known, from solid supported multilayers is maintained, additional applications arise for the freestanding membranes in the fields of encapsulation, separation and micromechanics. The production processes and functionalities achieved for capsules and flat sheets. The integration of membranes into larger scale structures is essential for their use and an overview of existing strategies is given. In particular, the way in which arrays of micro-compartments can be built up is shown, and their potential for sensing and combinatorial chemistry discussed. Recent results on the applications of such systems as membrane sensors in the case of flat membrane sheets are also discussed.

Adhesion of polyelectrolyte microcapsules through biotin-streptavidin specific interaction.

Adhesion of PAH/PSS and PDADMAC/PSS capsules through electrostatic and specific interactions has been investigated using reflective interference contrast microscopy (RICM). Adhesion of capsules via electrostatic interactions was found to be spontaneous and strong. Capsules functionalized with poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) did not exhibit significant adhesion (as determined by the adhesion area) to streptavidin-coated substrates, whereas capsules functionalized with biotinylated PLL-g-PEG showed a significantly larger adhesion area. Using continuum mechanical models, the total adhesion energies for these cases were calculated and were found to correspond to several tens of individual biotin-streptavidin pairs. The application of specific interactions such as the biotin-streptavidin system for controlled capsule adhesion has been demonstrated in this study.

Salt softening of polyelectrolyte multilayer capsules.

The changes in the morphology and the mechanical properties of hollow polyelectrolyte multilayer capsules made from poly(styrenesulfonate)/poly(allylamine hydrochloride) in response to added salt were investigated. We found that capsules shrink in response to salt exposure. The effect depends strongly on the nature of the salt added and follows trends of the Hoffmeister series, with weakly hydrated cations inducing the strongest shrinking. For NaCl, we have investigated additional effects on capsule mechanical properties that are occurring above a 3 M salt concentration and we found that the morphological changes are accompanied by a pronounced softening of the capsule wall material, which we can quantify by analyzing the force response of capsules in the prebuckling regime. This shows that salts can act as plasticizers in the multilayers and induce annealing effects.

Elastic properties of polyelectrolyte capsules studied by atomic-force microscopy and RICM.

Mechanical properties of polyelectrolyte multilayer capsules were studied using a new method combining atomic-force microscopy and reflection interference contrast microscopy. By measuring the force vs. deformation for poly(styrene sulfonate)/poly(allylamine) capsules the existence of different deformation regimes depending on the applied deformation was shown. The present paper focuses on the small-deformation regime. The elastic response of the deformed capsule was studied as a function of the wall thickness and the capsule size, and showed the theoretically expected variations. The Young modulus obtained from the experiments ranges between 1.3 and 1.9 GPa.

Spinodal dewetting in liquid crystal and liquid metal films

Theory predicts that dewetting of a homogeneous liquid film from a solid surface may proceed via unstable surface waves on the liquid. This phenomenon, usually termed spinodal dewetting, has been sought after in many systems. Observations in liquid crystal and liquid metal films showed that, as expected, the emerging structures were similar to those found for spinodal decomposition in mixtures. Certain differences, however, could be attributed to peculiarities of the wetting forces in these two dissimilar systems, thereby demonstrating the role of nonlinearities inherent in the wetting forces.

Expression of DNA excision-repair-cross-complementing proteins p80 and p89 in brain of patients with Down Syndrome and Alzheimer's disease.

Although deficient DNA repair was proposed for neurodegenerative disorders including Down syndrome (DS), repair proteins for nucleotide excision repair have not been studied in brain yet. As one of the hypotheses for the pathogenesis of brain damage in DS and Alzheimer's disease (AD), is oxidative stress, and cells of patients with DS were shown to be more susceptible to ionizing irradiation. We decided to study expression of excision repair-cross-complementing (ERCC) gene products, proteins 80 and 89, representatives of repair genes known to be involved in the repair of different types of DNA damage. ERCC2-protein 80 kDa and ERCC3-protein p89 were determined in five individual brain regions of controls, aged DS and AD patients. Although different in the individual regions, DNA repair proteins were consistently higher in temporal and frontal lobes of patients with DS and higher in all brain regions of patients with AD. Our results are the first to describe DNA repair gene protein patterns in human brain regions providing the basis for further studies in this area. We showed that DNA repair genes ERCC2 and ERCC3 (excision-repair-cross-complementing) for nucleotide excision repair were increased at the protein level with the possible biological meaning that this increase may be compatible with and indicate ongoing (oxidative?) DNA damage.

[Chronic sclerosing osteomyelitis. Apropos of 4 cases and the value of the treatment by closed intramedullary reaming]. / L'ostéomyélite chronique sclérosante. A propos de 4 cas et intérêt du traitement par alésage centro-médullaire à foyer fermé.

Chronic sclerosing osteomyelitis is a rare variety of primary osteomyelitis located principally on the diaphysis of the long bones in adults. Pain is the main symptom, but biological signs are negative or normal, and histological examination is non-specific. X-rays are very stereotyped with enlargement of the cortex of diaphyseal bone. This disease is note worthy by its difficult diagnosis, and is often misdiagnosed as bone tumor, malignant or benign, especially osteoid osteoma. Four observations are reported and in one case, after 13 years, an abscess developed, bearing out the oneness of chronic, primary osteomyelitis. This form deserves its individualization because of its treatment by closed intra-medullary reaming which proves to be effective after an average follow-up of 10 years.

Recurrent posterior instability of the shoulder.

Seven cases of recurrent posterior instability of the shoulder were reviewed, three with recurrent subluxation and four with recurrent posterior dislocations. All were treated surgically, one by inverted Putti-Platt, one by glenoplasty and five by posterior bone block procedures. The follow-up goes from three to 17.5 years (mean 8.5 years). Clinical history and physical examination were the most accurate diagnostic methods. There were three excellent, one fair, and one poor results with two failures. The poor result and failure cases are due to technical errors, particularly because of wrong positioning of the graft in posterior bone block procedures. We suggest a bone graft with a projection of at least 15 mm beyond the glenoid rim to obtain a good result with this technique. Osteoarthritis does not seem to develop at long-term in our patients even with a poor result except for those with iatrogenic origin. The functional results are stable over time except for patients with osteoarthritis.

[Surgical treatment of metastases of the humerus]. / Traitement chirurgical des métastases de l'humérus.

Surgical treatment of metastasis disease of the humerus was applied for 46 lesions among 42 patients, i-e 22% of overall osteosyntheses for skeletal metastasis. Two patients only are still alive at 3 and 4 years. The mean survival time is 8.1 months and at 3 months 50% died. Metastasis disease of the humerus becomes evident late during the evolution of the primary cancer, but 26% are revealing lesions. For 9.5% the primary tumor remains unknown. After review of the surgical methods generally used, indirect osteosynthesis by intra-medullary pinning according to Hackethal, without bone cement, is alleged. So the arm is immediately mobilized and a complementary irradiation is applied in post-operative. Prophylactic fixation of impending fractures is encouraged in order to suppress pain, and for better function. This paper demonstrates the changing concept of internal fixation of pathologic fractures and recommends intra-medullary nailing or pinning.

[Benign tumors of the spine in the adolescent. Surgical considerations apropos of 4 cases]. / Tumeurs bénignes du rachis de l'adolescent. Considérations chirurgicales à propos de 4 cas.

About 4 observations of benign tumours of the spine of the adolescent, we have studied the surgical aspect of the treatment of these lesion. The choice of the surgical approach is fundamental in view of the necessity of a complete exeresis, which implies techniques of spinal reconstruction and stabilization. Those problems are illustrated by: 2 cases of aneurysmal cyst, 1 case of eosinophilic granuloma, and 1 case of osteochondroma.

[Sternoclavicular dislocations. Observations on the treatment and result of 49 cases]. / Les disjonctions sterno-claviculaires. Considérations sur le traitement et les résultats de 49 cas.

Over a period of 19 years, 49 dislocations of the sternoclavicular joint were treated. Two were epiphyseal separations. The dislocation was an isolated injury in only 41% of the patients. There were associated injuries to the scapula in 55% and to the thorax in 37%. Forty dislocations were anterior, 8 retrosternal and one merely unstable. Seventeen were treated by operation, 15 by closed reduction and 17 were left untreated. We have been able to review 55% of these patients with an average follow up of 6.7 years; 15 were between 2 and 6 years after injury, and 12 between 6 and 16 years. The end result was achieved by 3 months; 42% of patients had an excellent result, 58% were satisfied and 25% disappointed with the final outcome. Operative treatment gave 66% of excellent results, whereas immobilisation, particularly with unreduced dislocations, accounted for most of those judged unsatisfactory. Closed treatment should be undertaken initially, but if reduction is not achieved an operation should be carried out. If old unreduced dislocations are unsatisfactory they should be stabilised by myoplasty, or by excision of the inner end of the clavicle if the articular surface is damaged.