Disulfide-Cross-Linked Tetra-PEG Gels.

The preparation of polymer gels via cross-linking of four-arm star-shaped poly(ethylene glycol) (Tetra-PEG) precursors is an attractive strategy to prepare networks with relatively well-defined topologies. Typically, Tetra-PEG gels are obtained by cross-linking heterocomplementary reactive Tetra-PEG precursors. This study, in contrast, explores the cross-linking of self-reactive, thiol-end functional Tetra-PEG macromers to form disulfide-cross-linked gels. The structure of the disulfide-cross-linked Tetra-PEG gels was studied with multiple-quantum NMR (MQ-NMR) spectroscopy and small-angle neutron scattering (SANS) experiments. In line with earlier simulation studies, these experiments showed a strong dependence of the relative fractions of the different network connectivities on the concentration of the thiol-end functional Tetra-PEG macromer that was used for the synthesis of the networks. Disulfide-cross-linked Tetra-PEG gels prepared at macromer concentrations below the overlap concentration (c = 0.66c*) primarily feature defect connectivity motifs, such as primary loops and dangling ends. For networks prepared at macromer concentrations above the overlap concentration, the fraction of single-link connectivities was found to be similar to that in amide-cross-linked Tetra-PEG gels obtained by heterocomplementary cross-linking of N-hydroxysuccinimide ester and amine functional Tetra-PEG macromers. Since disulfide bonds are susceptible to reductive cleavage, these disulfide-cross-linked gels are of interest, e.g., as reduction-sensitive hydrogels for a variety of biomedical applications.

Real and In Silico Microgels Show Comparable Bulk Moduli Below and Above the Volume Phase Transition.

The compressibility of soft colloids influences their phase behavior and flow properties, especially in concentrated suspensions. Particle compressibility, which is proportional to the reciprocal of the bulk modulus K, is a key parameter for soft polymer-based particles that can be compressed in crowded environments. Here, microgels with different degrees of cross-linking, i.e., softness, are investigated below and above their volume phase transition temperature (VPTT). By combining molecular dynamics simulations with small-angle neutron scattering with contrast variation, a change in the particle bulk moduli of two orders of magnitude is observed. The degree of cross-linking has a significant impact on the bulk modulus of the swollen microgel, while above the VPTT the values of K are almost independent of the cross-linking density. The excellent agreement between experimental results and simulations also highlight that the model microgels from computer simulations possess both the internal architecture and the elastic properties of real polymeric networks. This paves the way to a systematic use of simulations to investigate the behavior of dense microgel suspensions below and above their VPTT.

Measuring the counterion cloud of soft microgels using SANS with contrast variation.

The behavior of microgels and other soft, compressible colloids depends on particle concentration in ways that are absent in their hard-particulate counterparts. For instance, poly-N-isopropylacrylamide (pNIPAM) microgels can spontaneously deswell and reduce suspension polydispersity when concentrated enough. Despite the pNIPAM network in these microgels is neutral, the key to understanding this distinct behavior relies on the existence of peripheric charged groups, responsible for providing colloidal stability when deswollen, and the associated counterion cloud. When in close proximity, clouds of different particles overlap, effectively freeing the associated counterions, which are then able to exert an osmotic pressure that can potentially cause the microgels to decrease their size. Up to now, however, no direct measurement of such an ionic cloud exists, perhaps even also for hard colloids, where it is referred to as an electric double layer. Here, we use small-angle neutron scattering with contrast variation with different ions to isolate the change in the form factor directly related to the counterion cloud, and obtain its radius and width. Our results highlight that the modeling of microgel suspensions must unavoidably and explicitly consider the presence of this cloud, which exists for nearly all microgels synthesized today.

An EU landmark for AI governance.

A groundbreaking draft law adopted with overwhelming majority by the European Parliament provides a glimpse into the future of governance of artificial intelligence (AI). The AI Act (AIA) aims to safeguard fundamental rights and ensure the ethical development of AI in Europe and beyond. It is the most ambitious framework to date designed to guide the development and usage of AI. The vote echoes a growing chorus of researchers from various disciplines calling for guardrails to govern powerful AI. Although AIA's final form will emerge from talks with the European Council and the Commission, the decision by Europe's influential law-making body offers a timely opportunity for the AI research community to brace for impact, which is expected to reverberate across borders.

Neat Protein Single-Chain Nanoparticles from Partially Denatured BSA.

The main challenge for the preparation of protein single-chain nanoparticles (SCNPs) is the natural complexity of these macromolecules. Herein, we report the suitable conditions to produce "neat" bovine serum albumin (BSA) single-chain nanoparticles (SCNPs) from partially denatured BSA, which involves denaturation in urea and intramolecular cross-linking below the overlap concentration. We use two disuccinimide ester linkers containing three and six methylene spacer groups: disuccinimidyl glutarate (DSG) and disuccinimidyl suberate (DSS), respectively. Remarkably, the degree of internal cross-linking can be followed simply and efficiently via 1H NMR spectroscopy. The associated structural changes-as probed by small-angle neutron scattering (SANS)-reveal that the denatured protein has a random-like coil conformation, which progressively shrinks with the addition of DSG or DSS, thus allowing for size control of the BSA-SCNPs with radii of gyration down to 5.4 nm. The longer cross-linker exhibits slightly more efficiency in chain compaction with a somewhat stronger size reduction but similar reactivity at a given cross-linker concentration. This reliable method is applicable to a wide range of compact proteins since most proteins have appropriate reactive amino acids and denature in urea. Critically, this work paves the way to the synthesis of "neat", biodegradable protein SCNPs for a range of applications including nanomedicine.

Experimental determination of the bulk moduli of hollow nanogels.

The softness of an object can be quantified by one of the fundamental elastic moduli. The bulk modulus of the particle is most appropriate in the presence of isotropic compressions. Here, we use small-angle neutron scattering with contrast variation to directly access the bulk modulus of polymeric nanocapsules - pNIPAM-based hollow nanogels. We show that the size of the cavity is the most important quantity that determines the softness of hollow nanogels. During initial compression, the polymer collapses into the cavity and leads to a large change in the particle volume, resulting in a very small initial bulk modulus. Once the cavity is partially occupied by the polymer, the hollow nanogels become significantly stiffer since now the highly crosslinked network has to be compressed. Furthermore, we show that the larger the cavity, the softer the nanogel.

Resolving the different bulk moduli within individual soft nanogels using small-angle neutron scattering.

The bulk modulus, K, quantifies the elastic response of an object to an isotropic compression. For soft compressible colloids, knowing K is essential to accurately predict the suspension response to crowding. Most colloids have complex architectures characterized by different softness, which additionally depends on compression. Here, we determine the different values of K for the various morphological parts of individual nanogels and probe the changes of K with compression. Our method uses a partially deuterated polymer, which exerts the required isotropic stress, and small-angle neutron scattering with contrast matching to determine the form factor of the particles without any scattering contribution from the polymer. We show a clear difference in softness, compressibility, and evolution of K between the shell of the nanogel and the rest of the particle, depending on the amount of cross-linker used in their synthesis.

How NFTs could transform health information exchange.

[Figure: see text].

Amyloid ß 42 fibril structure based on small-angle scattering.

Amyloid fibrils are associated with a number of neurodegenerative diseases, including fibrils of amyloid ß42 peptide (Aß42) in Alzheimer's disease. These fibrils are a source of toxicity to neuronal cells through surface-catalyzed generation of toxic oligomers. Detailed knowledge of the fibril structure may thus facilitate therapeutic development. We use small-angle scattering to provide information on the fibril cross-section dimension and shape for Aß42 fibrils prepared in aqueous phosphate buffer at pH = 7.4 and pH 8.0 under quiescent conditions at 37 °C from pure recombinant Aß42 peptide. Fitting the data using a continuum model reveals an elliptical cross-section and a peptide mass-per-unit length compatible with two filaments of two monomers, four monomers per plane. To provide a more detailed atomistic model, the data were fitted using as a starting state a high-resolution structure of the two-monomer arrangement in filaments from solid-state NMR (Protein Data Bank ID 5kk3). First, a twofold symmetric model including residues 11 to 42 of two monomers in the filament was optimized in terms of twist angle and local packing using Rosetta. A two-filament model was then built and optimized through fitting to the scattering data allowing the two N-termini in each filament to take different conformations, with the same conformation in each of the two filaments. This provides an atomistic model of the fibril with twofold rotation symmetry around the fibril axis. Intriguingly, no polydispersity as regards the number of filaments was observed in our system over separate samples, suggesting that the two-filament arrangement represents a free energy minimum for the Aß42 fibril.

Regulating AI in medicine in the United States and Europe.

The regulatory landscape for artificial intelligence (AI) is shaping up on both sides of the Atlantic, urgently awaited by the scientific and industrial community. Commonalities and differences start to crystallize in the approaches to AI in medicine.

Similarities and Differences in the Effects of Toxic Concentrations of Cadmium and Chromium on the Structure and Functions of Thylakoid Membranes in Chlorella variabilis.

Trace metal contaminations in natural waters, wetlands, and wastewaters pose serious threats to aquatic ecosystems-mainly via targeting microalgae. In this work, we investigated the effects of toxic amounts of chromium and cadmium ions on the structure and function of the photosynthetic machinery of Chlorella variabilis cells. To halt the propagation of cells, we used high concentrations of Cd and Cr, 50-50 mg L-1, in the forms of CdCl2 x 2.5 H2O and K2Cr2O7, respectively. Both treatments led to similar, about 50% gradual diminishment of the chlorophyll contents of the cells in 48 h, which was, however, accompanied by a small (~10%) but statistically significant enrichment (Cd) and loss (Cr) of ß-carotene. Both Cd and Cr inhibited the activity of photosystem II (PSII)-but with more severe inhibitions with Cr. On the contrary, the PsbA (D1) protein of PSII and the PsbO protein of the oxygen-evolving complex were retained more in Cr-treated cells than in the presence of Cd. These data and the higher susceptibility of P700 redox transients in Cr-treated cells suggest that, unlike with Cd, PSII is not the main target in the photochemical apparatus. These differences at the level of photochemistry also brought about dissimilarities at higher levels of the structural complexity of the photosynthetic apparatus. Circular dichroism (CD) spectroscopy measurements revealed moderate perturbations in the macro-organization of the protein complexes-with more pronounced decline in Cd-treated cells than in the cells with Cr. Also, as reflected by transmission electron microscopy and small-angle neutron scattering, the thylakoid membranes suffered shrinking and were largely fragmented in Cd-treated cells, whereas no changes could be discerned with Cr. The preservation of integrity of membranes in Cr-treated cells was most probably aided by high proportion of the de-epoxidized xanthophylls, which were absent with Cd. It can thus be concluded that beside strong similarities of the toxic effects of Cr and Cd, the response of the photosynthetic machinery of C. variabilis to these two trace metal ions substantially differ from each other-strongly suggesting different inhibitory and protective mechanisms following the primary toxic events.

Digital tools against COVID-19: taxonomy, ethical challenges, and navigation aid.

Data collection and processing via digital public health technologies are being promoted worldwide by governments and private companies as strategic remedies for mitigating the COVID-19 pandemic and loosening lockdown measures. However, the ethical and legal boundaries of deploying digital tools for disease surveillance and control purposes are unclear, and a rapidly evolving debate has emerged globally around the promises and risks of mobilising digital tools for public health. To help scientists and policy makers to navigate technological and ethical uncertainty, we present a typology of the primary digital public health applications that are in use. These include proximity and contact tracing, symptom monitoring, quarantine control, and flow modelling. For each, we discuss context-specific risks, cross-sectional issues, and ethical concerns. Finally, recognising the need for practical guidance, we propose a navigation aid for policy makers and other decision makers for the ethical development and use of digital public health tools.

Inhibition of Chemoresistance in Primary Tumor Cells by Camellia sinensis non fermentatum Extract Noviphenone (NPE®).

BACKGROUND/AIM: Despite improvements in cancer therapy, life expectancy after tumor recurrence remains low. Relapsed cancer is characterized by drug resistance, often mediated through overexpression of multidrug resistance (MDR) genes. Camellia sinensis non fermentatum extract is known for its anticancer properties in several cancer cell lines and might improve cancer therapy outcome after tumor recurrence. MATERIALS AND METHODS: Embryonal rhabdomyosarcoma cell lines, alveolar rhabdomyosarcoma cell lines and primary rhabdomyosarcoma MAST139 cells were used to test NPE® effects on cell viability in combination with chemotherapeutic agents. Cell viability was measured by the WST-1 assay and CV staining. Gene expression levels of chemotherapy-induced efflux pumps and their activity was assessed upon NPE® treatment by measuring doxorubicin retention through evaluation of the autofluorescence signal. RESULTS: Administration of increasing doxorubicin concentrations triggered immediate adaptation to the drug, which was surprisingly overcome by the addition of NPE®. Investigating the mechanism of immediate adaptation, MDR1 gene overexpression was observed upon doxorubicin treatment. Although NPE® did not alter pump gene expression, it was able to reduce pump activity, thus allowing the chemotherapeutic agent to stay inside the cells to exert its full anticancer activity. CONCLUSION: NPE® might improve chemotherapeutic treatment by re-sensitizing relapsed tumors to anticancer drugs. Fighting MDR represents the key to overcome tumor relapse and improve the overall survival of cancer patients.

Anisotropic Diffusion and Phase Behavior of Cellulose Nanocrystal Suspensions.

In this paper, we use dynamic light scattering in polarized and depolarized modes to determine the translational and rotational diffusion coefficients of concentrated rodlike cellulose nanocrystals in aqueous suspension. Within the range of studied concentrations (1-5 wt %), the suspension starts a phase transition from an isotropic to an anisotropic state as shown by polarized light microscopy and viscosity measurements. Small-angle neutron scattering measurements also confirmed the start of cellulose nanocrystal alignment and a decreasing distance between the cellulose nanocrystals with increasing concentration. As expected, rotational and translational diffusion coefficients generally decreased with increasing concentration. However, the translational parallel diffusion coefficient was found to show a local maximum at the onset of the isotropic-to-nematic phase transition. This is attributed to the increased available space for rods to move along their longitudinal axis upon alignment. This increased parallel diffusion coefficient thus confirms the general idea that rodlike particles gain translational entropy upon alignment while paying the price for losing rotational degrees of freedom. Once the concentration increases further, diffusion becomes more hindered even in the aligned regions due to a reduction in the rod separation distance. This leads once again to a decrease in translational diffusion coefficients. Furthermore, the relaxation rate for fast mode translational diffusion (parallel to the long particle axis) exhibited two regimes of relaxation behavior at concentrations where significant alignment of the rods is measured. We attribute this unusual dispersive behavior to two length scales: one linked to the particle length (at large wavevector q) and the other to a twist fluctuation correlation length (at low wavevector q) along the cellulose nanocrystal rods that is of a larger length when compared to the actual length of rods and could be linked to the size of aligned domains.

Short- and long-term effects of two emollients on itching and skin restoration in xerotic eczema.

Pruritus is associated with various skin diseases, dry skin, and with it an impaired skin barrier function. The study objective was to investigate short-term and long-term effects of two emollients on symptoms and skin barrier functions in xerotic eczema. Randomized, double-blind, study enrolling females/males, with bilateral itching. Two emollients, containing lactic acid and refined almond oil with/without polidocanol were administered on left versus right body sides. Itching severity, skin moisture, lipid content, and pH were assessed on Day 1, within 30-120 min after first administration, and on Days 7 and 14, and compared with baseline assessments. Severity of itching decreased 30 min after first administration of both emollients compared with baseline (p < .0001) and reached a maximum reduction of 63% (p < .0001) and 69% (p < .0001) on Day 14. Skin moisture and lipid content increased after first application, and further ameliorated within 14 days of treatment (p < .0001). Both emollients were tolerated well, and only a few adverse events were reported. This study confirmed the clinical efficacy of the two study emollients to substantially reduce itching already after first administration, and restore skin barrier integrity and thus should be considered as therapeutic approach for xerotic eczema.

Prevention of Acute Radiation-Induced Skin Reaction with NPE® Camellia Sinensis Nonfermentatum Extract in Female Breast Cancer Patients Undergoing Postoperative Radiotherapy: A Single Centre, Prospective, Open-Label Pilot Study.

BACKGROUND: To assess effectiveness of NPE, a proprietary Camellia sinensis nonfermentatum (CSNF) extract, in prevention and recovery of acute radiation-induced skin reaction (ARSR) and skin care during postoperative whole breast radiotherapy (RT). METHODS: Twenty patients were enrolled in this single centre, prospective, open-label pilot study. The outcomes of 20 prospective data sets were compared with 100 retrospectively collected matched data sets derived from hospital records. The preventive CSNF gel (2.5%) was administered 1 to 2 hours before each session on the irradiated fields. The care CSNF lotion (0.4%) was administered as 7-day pretreatment after each RT session, twice daily between RT sessions, and 4 to 8 weeks thereafter. The control group was treated according to the hospital care guidelines. The primary endpoint was time to ARSR ≥ Grade 2 (CTCAE v4.03); secondary endpoints were frequencies of ARSR grades 1, 2, 3, and 4, recovery of ARSR, frequencies of interruption and RT stop, complications and required rescue interventions, and tolerability of CSNF. RESULTS: Time to ARSR ≥ G2 (censoring) was significantly longer (p = 0.014) in the CSNF group. The hazard ratio was 2.33 (95% CI: 1.15-4.72), demonstrating a 50% decrease in the risk of developing ARSR ≥ G2. There was a trend to faster recovery from ARSR G2 in the CSNF group (100% versus 47%; p = 0.078). The proportion of patients requiring rescue treatment during RT and follow-up was markedly higher in the control compared to the CSNF group (1% to 51% versus 0% to 15%). CSNF gel and lotion were well tolerated both during and after RT. CONCLUSIONS: This pilot study provides the first evidence on the potential pharmacological effectiveness of CSNF extract in prevention of RT-induced ARSR and recovery of skin irritation in patients undergoing postoperative whole breast RT and may reflect a novel concept for prevention of RT-induced ARSR and care of irritated skin.

Rivaroxaban for Thromboprophylaxis After Nonelective Orthopedic Trauma Surgery in Switzerland.

This study investigated the effectiveness and the outcomes of rivaroxaban vs the standard of care for venous thromboembolic prophylaxis in patients undergoing fracture-related surgery. A total of 413 patients undergoing fracture-related surgery from 9 Swiss orthopedic and trauma centers were enrolled. The authors selected the type of venous thromboembolic prophylaxis according to standardized medical practice at the participating centers before the inclusion of patients: 208 patients received rivaroxaban and 205 received the standard of care. Data on symptomatic thromboembolic and bleeding events, surgery-related complications, death, adverse events, time to mobilization, and hospital discharge were collected. Symptomatic thromboembolic events were reported in 1 patient (0.5%) and 2 patients (1.0%) and treatment-emergent major bleeding events were reported in 1 patient (0.5%) and 2 patients (1.0%) receiving rivaroxaban and the standard of care, respectively. The durations of hospital stay and venous thromboembolic prophylaxis were similar in the 2 groups. In both groups, adverse events related to venous thromboembolic prophylaxis were reported in 12 patients. The proportion of patients with minor and major fracture surgery was 74.3% and 25.7%, respectively. In patients undergoing minor fracture surgery receiving rivaroxaban (n=167) and the standard of care (n=140), no symptomatic thromboembolic events and no major bleeding events were reported. Outcomes of this study indicate that rivaroxaban might be an appropriate oral alternative for venous thromboembolic prophylaxis in routine medical care after fracture-related major and minor surgery. Reported results were comparable to those from other large-scale, noninterventional and randomized controlled studies. [Orthopedics. 2017; 40(2):109-116.].

The role of ions in the self-healing behavior of soft particle suspensions.

Impurities in crystals generally cause point defects and can even suppress crystallization. This general rule, however, does not apply to colloidal crystals formed by soft microgel particles [Iyer ASJ, Lyon LA (2009) Angew Chem Int Ed 48:4562-4566], as, in this case, the larger particles are able to shrink and join the crystal formed by a majority of smaller particles. Using small-angle X-ray scattering, we find the limit in large-particle concentration for this spontaneous deswelling to persist. We rationalize our data in the context of those counterions that are bound to the microgel particles as a result of the electrostatic attraction exerted by the fixed charges residing on the particle periphery. These bound counterions do not contribute to the suspension osmotic pressure in dilute conditions, as they can be seen as internal degrees of freedom associated with each microgel particle. In contrast, at sufficiently high particle concentrations, the counterion cloud of each particle overlaps with that of its neighbors, allowing these ions to freely explore the space outside the particles. We confirm this scenario by directly measuring the osmotic pressure of the suspension. Because these counterions are then no longer bound, they create an osmotic pressure difference between the inside and outside of the microgels, which, if larger than the microgel bulk modulus, can cause deswelling, explaining why large, soft microgel particles feel the squeeze when suspended with a majority of smaller particles. We perform small-angle neutron scattering measurements to further confirm this remarkable behavior.