•The Dr. Probe software for multislice STEM simulations is introduced.•Reference is given of methods and approximations applied in the software.•Basic simulation features are demonstrated.•Signal ...variance from frozen-lattice calculations limits atom counting accuracy.•Strategies are discussed enabling bias-free atom counting.
The Dr. Probe software for multislice simulations of STEM images is introduced, and reference is given of the applied methods. Major program features available with the graphical user interface version are demonstrated by means of a few examples for bright-field and dark-field STEM imaging as well as simulations of diffraction patterns. The numerical procedure applied for the simulation of thermal-diffuse scattering by the frozen-lattice approach is described in detail. Intensity variations occurring in simulations with atomic-column resolution due to frozen-lattice variations are discussed in the context of atom counting. It is found that a significant averaging over many lattice configurations with different random atomic displacements is required to prevent atom-counting bias from simulations. A strategy is developed for the assessment of the amount of required averaging based on the estimated signal variance and the expected signal gain per atom in a column.
Recently, plasmonic copper sulfide (Cu2–x S) nanocrystals (NCs) have attracted much attention as materials for photothermal therapy (PTT). Previous reports have correlated photoinduced cell death to ...the photothermal heat mechanism of these NCs, and no evidence of their photodynamic properties has been reported yet. Herein we have prepared physiologically stable near-infrared (NIR) plasmonic copper sulfide NCs and analyzed their photothermal and photodynamic properties, including therapeutic potential in cultured melanoma cells and a murine melanoma model. Interestingly, we observe that, besides a high PTT efficacy, these copper sulfide NCs additionally possess intrinsic NIR induced photodynamic activity, whereupon they generate high levels of reactive oxygen species. Furthermore, in vitro and in vivo acute toxic responses of copper sulfide NCs were also elicited. This study highlights a mechanism of NIR light induced cancer therapy, which could pave the way toward more effective nanotherapeutics.
The use of magnetic nanoparticles in oncothermia has been investigated for decades, but an effective combination of magnetic nanoparticles and localized chemotherapy under clinical magnetic ...hyperthermia (MH) conditions calls for novel platforms. In this study, we have engineered magnetic thermoresponsive iron oxide nanocubes (TR-cubes) to merge MH treatment with heat-mediated drug delivery, having in mind the clinical translation of the nanoplatform. We have chosen iron oxide based nanoparticles with a cubic shape because of their outstanding heat performance under MH clinical conditions, which makes them benchmark agents for MH. Accomplishing a surface-initiated polymerization of strongly interactive nanoparticles such as our iron oxide nanocubes, however, remains the main challenge to overcome. Here, we demonstrate that it is possible to accelerate the growth of a polymer shell on each nanocube by simple irradiation of a copper-mediated polymerization with a ultraviolet light (UV) light, which both speeds up the polymerization and prevents nanocube aggregation. Moreover, we demonstrate herein that these TR-cubes can carry chemotherapeutic doxorubicin (DOXO-loaded-TR-cubes) without compromising their thermoresponsiveness both in vitro and in vivo. In vivo efficacy studies showed complete tumor suppression and the highest survival rate for animals that had been treated with DOXO-loaded-TR-cubes, only when they were exposed to MH. The biodistribution of intravenously injected TR-cubes showed signs of renal clearance within 1 week and complete clearance after 5 months. This biomedical platform works under clinical MH conditions and at a low iron dosage, which will enable the translation of dual MH/heat-mediated chemotherapy, thus overcoming the clinical limitation of MH: i.e., being able to monitor tumor progression post-MH-treatment by magnetic resonance imaging (MRI).
In the recent two decades the technique of high-resolution transmission electron microscopy experienced an unprecedented progress through the introduction of hardware aberration correctors and by the ...improvement of the achievable resolution to the sub-Ångström level. The important aspect that aberration correction at a given resolution requires also a well defined amount of optical stability has received little attention so far. Therefore we investigate the qualification of a variety of high-resolution electron microscopes to maintain an aberration corrected optical state in terms of an optical lifetime. We develop a comprehensive statistical framework for the estimation of the optical lifetime and find remarkably low values between tens of seconds and a couple of minutes. Probability curves are introduced, which inform the operator about the chance to work still in the fully aberration corrected state.
•We investigate the temporal stability of optical aberrations in HRTEM.•We develop a statistical framework for the estimation of optical lifetimes.•We introduce plots showing the success probability for aberration-free work.•Optical lifetimes in sub-Ångström electron microscopy are surprisingly low.•The success of aberration correction depends strongly on the optical stability.
We present the synthesis of colloidally stable ultrasmall (diameter of 1.5 ± 0.6 nm) and fluorescent copper clusters (Cu-clusters) exhibiting outstanding quantum efficiencies (up to 67% in THF and ...approximately 30% in water). For this purpose, an amphiphilic block copolymer poly(ethylene glycol)-block-poly(propylene sulfide) (MPEG-b-PPS) was synthesized by living anionic ring-opening polymerization. When CuBr is mixed with the living polymer chains in THF, the formation of Cu-clusters is detected by the appearance of the fluorescence. The cluster growth is quenched by the addition of water, followed by THF removal. The structural features of the MPEG-b-PPS copolymer control the cluster formation and the stabilization: the poly(propylene sulfide) segment acts as coordinating and reducing agent for the copper ions in THF, and imparts a hydrophobic character. This hydrophobic block protects the Cu-clusters from water exposure, thus allowing to obtain a stable emission in water. The PEG segment instead provides the hydrophilicity, rendering the Cu-clusters water-soluble. To obtain fluorescent and stable Cu-clusters exhibiting outstanding quantum efficiencies, the removal of the excess of free polymer and copper salt was crucial. The Cu-clusters are also colloidally and optically stable in physiological media and showed bright fluorescence even when taken up by HeLa cells, being noncytotoxic when administered at a Cu dose between 10 nM and 1.6 μM. Given the very small size of the Cu-clusters, localization and fluorescent staining of cell nucleus is achieved, as demonstrated by confocal cell imaging performed at different Cu-cluster doses and at different incubation temperatures.
The application of well‐defined poly(furfuryl glycidyl ether) (PFGE) homopolymers and poly(ethylene oxide)‐b‐poly(furfuryl glycidyl ether) (PEO‐b‐PFGE) block copolymers synthesized by living anionic ...polymerization as self‐healing materials is demonstrated. This is achieved by thermo‐reversible network formation via (retro) Diels‐Alder chemistry between the furan groups in the side‐chain of the PFGE segments and a bifunctional maleimide crosslinker within drop‐cast polymer films. The process is studied in detail by differential scanning calorimetry (DSC), depth‐sensing indentation, and profilometry. It is shown that such materials are capable of healing complex scratch patterns, also multiple times. Furthermore, microphase separation within PEO‐b‐PFGE block copolymer films is indicated by small angle X‐ray scattering (lamellar morphology with a domain spacing of approximately 19 nm), differential scanning calorimetry, and contact angle measurements.
Films of poly(furfuryl glycidyl ether) (PFGE) and poly(ethylene oxide)‐b‐poly(furfuryl glycidyl ether) PEO‐b‐PFGE block copolymers are prepared and reversibly crosslinked by Diels‐Alder chemistry. The self‐healing of damaged surfaces is studied in detail with help of differential scanning calorimetry, depth‐sensing indentation, small angle X‐ray scattering, and profilometry.
Treatment of food-producing animals with veterinary medicinal products (VMPs) can result in residues in foodstuffs (e.g. eggs, meat, milk, or honey) representing a potential consumer health risk. To ...ensure consumer safety, worldwide regulatory concepts for setting safe limits for residues of VMPs e.g. as tolerances (US) or maximum residue limits (MRLs, EU) are used. Based on these limits so-called withdrawal periods (WP) are determined. A WP represents the minimum period of time required between the last administration of the VMP and the marketing of foodstuff. Usually, WPs are estimated using regression analysis based on residue studies. With high statistical confidence (usually 95% in the EU and 99% in the US) the residues in almost all treated animals (usually 95%) have to be below MRL when edible produce is harvested. Here, uncertainties from both sampling and biological variability are taken into account but uncertainties of measurement associated with the analytical test methods are not systematically considered. This paper describes a simulation experiment to investigate the extent to which relevant sources of measurement uncertainty (accuracy and precision) can impact the length of WPs. A set of real residue depletion data was artificially 'contaminated' with measurement uncertainty related to permitted ranges for accuracy and precision. The results show that both accuracy and precision had a noticeable effect on the overall WP. Due consideration of sources of measurement uncertainty may improve the robustness, quality and reliability of calculations upon which regulatory decisions on consumer safety of residues are based.
ε-caprolactone-p-coumaric acid copolymers at different mole ratios (ε-caprolactone:p-coumaric acid 1:0, 10:1, 8:1, 6:1, 4:1, and 2:1) were synthesized by melt-polycondensation and using ...4-dodecylbenzene sulfonic acid as catalyst. Chemical analysis by NMR and GPC showed that copolyesters were formed with decreasing molecular weight as p-coumaric acid content was increased. Physical characteristics, such as thermal and mechanical properties, as well as water uptake and water permeability, depended on the mole fraction of p-coumaric acid. The p-coumarate repetitive units increased the antioxidant capacity of the copolymers, showing antibacterial activity against the common pathogen Escherichia coli. In addition, all the synthesized copolyesters, except the one with the highest concentration of the phenolic acid, were cytocompatible and hemocompatible, thus becoming potentially useful for skin regeneration applications.
We present results of a comprehensive investigation of two phenomena arising in superconductor(S)/ferromagnet(F) heterostructures of Nb on FePd with a lateral magnetic domain pattern: ...domain-superconductivity and spin-triplet Cooper pair generation. Resistivity measurements in a magnetic field applied out-of-plane to a Nb/FePd (S/F) sample with high magnetocrystalline anisotropy give evidence of stray field generated domain-wall- and reverse-domain-superconductivity. A corresponding bilayer comprising low magnetocrystalline anisotropy exhibits spin-triplet Cooper pair generation and a notable high variation of the S critical temperature due to spin-triplet generation (ΔTc) of 100 mK in an in-plane applied field. Using reference samples we can clearly distinguish stray field from proximity effects. The relevance of the characteristic S and F length scales related to the observed proximity effects is discussed.
During the last few decades considerable scientific effort has been devoted to the synthesis, self-assembly, and application of ABC triblock terpolymers with various building blocks. Such materials ...show high potential in the fields of materials science and life sciences. In particular, poly(ethylene oxide) (PEO) is a versatile building block and related materials featuring PEO segments are often exploited due to its solubility in a wide range of solvents, its non-toxicity, biocompatibility, and the so called "stealth effect". This review presents a short summary of possible synthetic routes for the synthesis of PEO-containing triblock terpolymers, as well as different applications in the bulk and in solution - including the preparation of porous materials, hybrid systems, and carriers for controlled drug delivery.
This review presents a short summary of possible synthetic routes for the synthesis of poly(ethylene oxide) (PEO) containing triblock terpolymers, as well as different applications in the bulk or in solution - including the preparation of porous materials, hybrid systems, and carriers for controlled drug delivery.
PDF
