On the uncertainty of the correlation between nanoparticle avidity and biodistribution

The specific delivery of a drug to its site of action also known as targeted drug delivery is a topic in the field of pharmaceutics studied for decades. One approach extensively investigated in this context is the use ligand functionalized nanoparticles. These particles are modified to carry receptor specific ligands, enabling them to accumulate at a desired target site. However, while this concept initially appears straightforward to implement, in-depth research has revealed several challenges hindering target site specific particle accumulation - some of which remain unresolved to this day. One of these challenges consists in the still incomplete understanding of how nanoparticles interact with biological systems. This knowledge gap significantly compromises the predictability of particle distribution in biological systems, which is critical for therapeutic efficacy. One of the most crucial steps in delivery is the attachment of nanoparticles to cells at the target site. This attachment occurs via the formation of multiple ligand receptor bonds. A process also referred to as multivalent interaction. While multivalency has been described extensively for individual molecules and macromolecules respectively, little is known on the multivalent binding of nanoparticles to cells. Here, we will specifically introduce the concept of avidity as a measure for favorable particle membrane interactions. Also, an overview about nanoparticle and membrane properties affecting avidity will be given. Thereafter, we provide a thorough review on literature investigating the correlation between nanoparticle avidity and success in targeted particle delivery. In particular, we want to analyze the currently uncertain data on the existence and nature of the correlation between particle avidity and biodistribution.

Impact of interferon-γ on the target cell tropism of nanoparticles

Interferon-γ (IFN-γ) is well known to reduce the infectivity of viral pathogens by altering their tissue tropism. This effect is induced by upregulation of cholesterol 25-hydroxylase (CH25H). Given the similarity of viral pathogens and ligand-functionalized nanoparticles in the underlying strategy of receptor-mediated cell recognition, it appears conceivable that IFN-γ exceeds similar effects on nanoparticles. Concretely, IFN-γ-induced activation of CH25H could decrease nanoparticle avidity for target cells via depletion of clathrin-coated pits. We hypothesized that this effect would cause deterioration of target-cell specific accumulation of nanoparticles. To prove our hypothesis, we investigated the cell tropism of angiotensin II functionalized nanoparticles (NPLys-Ang II) in a co-culture system of angiotensin II subtype 1 receptor (AT1R) positive rat mesangial target cells (rMCs) and AT1R-negative HeLa off-target cells. In the presence of IFN-γ we observed an up to 5-fold loss of target cell preference for NPLys-Ang II. Thus, our in vitro results suggest a strong influence of IFN-γ on nanoparticle distribution, which is relevant in the context of nanotherapeutic approaches to cancer treatment, as IFN-γ is strongly expressed in tumors. For the target cell tropism of viruses, our results provide a conclusive hypothesis for the underlying mechanism behind non-directed viral distribution in the presence of IFN-γ.

How clathrin-coated pits control nanoparticle avidity for cells

The paramount relevance of clathrin-coated pits (CCPs) to receptor-mediated endocytosis of nanoparticles, extracellular vesicles, and viruses has made them the focus of many studies; however, the role of CCP geometry in the ligand-receptor interactions between multivalent nanoparticles and cells has not been investigated. We hypothesized the general dependence of nanoparticle binding energy on local membrane curvature to be expandable to the specific case of ligand-functionalized nanoparticles binding cell membranes, in the sense that membrane structures whose curvature matches that of the particle (e.g., CCPs) signficantly contribute to binding avidity. We investigated this hypothesis with nanoparticles that bind multivalently to angiotensin II receptor type 1, which is subject to clathrin-mediated endocytosis. When we used cholesterol extraction to prevent the action of CCPs, we found a 67 to 100-fold loss in avidity. We created a theoretical model that predicts this decrease based on the loss of ligand-receptor interactions when CCPs, which perfectly match nanoparticle geometry, are absent. Our findings shed new light on how cells "see" nanoparticles. The presence or absence of CPPs is so influential on how cells interact with nanoparticles that the number of particles required to be visible to cells changes by two orders of magnitude depending on CCP presence.

In-beam superfluid-helium ultracold neutron source for the ESS

This paper discusses design principles and possible performances of an “in-beam” ultracold neutron (UCN) source for the European Spallation Source (ESS). The key components of the proposed neutron delivery system are nested-mirror optics (NMO), which image the bright neutron emission surface of the large liquid-deuterium moderator, studied within the HighNESS project, onto a remotely located superfluid-helium converter. Bandpass supermirrors, with optional polarization capability, enable the selective transport of those neutrons that are most effective for UCN production, exploiting the single-phonon conversion process that is possible for neutrons having wavelengths within a narrow range centered on 8.9 A ˚. NMO are capable of extracting and refocusing neutrons with small transport losses under the large solid angle available at the ESS Large Beam Port (LBP), allowing the converter to be placed far away from the high-radiation area in the ESS shielding bunker, where the source stays accessible for trouble-shooting while facilitating a low-background environment for nearby UCN experiments. Various configurations of the beam and converter are possible, including a large-volume converter – with or without a magnetic reflector – for a large total UCN production rate, or a beam focused onto a small converter for highest possible UCN density. The source performances estimated by first simulations of a baseline version presented in this paper, including a saturated UCN density on the order of 10 5 cm − 3 , motivate further study and the development of NMO beyond the first prototypes that have been recently investigated experimentally.

Approaches to high-density storage experiments with in-situ production and detection of ultracold neutrons

Low counting statistics is one of the most important challenges in modern experiments with ultracold neutrons (UCN). UCN densities in superthermal sources based on superfluid helium are normally much higher than those after UCN delivery to ex-situ volumes. Therefore, and due to the vanishing neutron absorption of 4He, storage-based experiments performed in-situ promise significant sensitivity gains. Scalable measurements offer a promising path to simultaneously address the inefficient use of cold neutron beams as precursors for UCN production in 4He, by recuperating the unused beam fraction, and confront the practical challenges of large-scale UCN infrastructure. We suggest strategies for the development of modular cryogenic cells, propose a novel approach for in-situ UCN detection, and discuss the ultimate statistical reach of such a multiplexed experiment for measuring the neutron’s permanent electric dipole moment (EDM). While dedicated research and development are needed to evaluate the feasibility for many requirements, a neutron EDM measurement with sensitivity well beyond 10 − 28 e  cm seems possible. Such an experiment could be pursued at any compatible cold neutron beamline, e.g., at the Institut Laue–Langevin, or later using the ANNI facility or large beam port (LBP) at the European Spallation Source.

Very cold and ultra cold neutron sources for ESS

The goal of the “Workshop on Very Cold and Ultra Cold Neutron Sources for ESS” was to discuss scientific cases, ideas and possibilities for the implementation of sources of Very Cold and Ultra Cold neutrons at the European Spallation Source. The ESS facility, presently under construction, offers several possibilities for in-pile UCN or VCN sources, in primis thanks to the available space below the spallation target where additional neutron sources can be placed to complement those above the target. Neutron beams can be extracted over a wide angular range with a grid of forty-two beamports with 6° average angular separation, allowing future instruments to be installed which may view either the upper or lower moderator systems. Of greatest interest for fundamental physics is the so-called Large Beamport foreseen for the NNBAR experiment. This beamport is also particularly well suited to feed a UCN source, for which several ideas were presented that employ either superfluid helium or solid deuterium as established neutron converter materials. Concepts for VCN sources make use of novel materials for VCN production and/or advanced reflectors to increase yields in the coldest part of the neutron spectrum from a cryogenic neutron source. In this paper we discuss these ideas and the possible locations of UCN and VCN sources at ESS.

Concept and strategy of SuperSUN: A new ultracold neutron converter

A new source of ultracold neutrons (UCNs), developed at the Institut Laue-Langevin (ILL) and named SuperSUN, is currently being commissioned. Its operational principle is the conversion of cold neutrons, delivered by ILL’s existing beam H523, to UCNs in a vessel filled with superfluid helium-4, wherein the neutron’s energy and momentum are transferred by inelastic scattering to phonons in the superfluid. The inverse Boltzmann-suppressed process is negligible at temperatures below 0.6 K, enabling long storage times and high in-situ UCN densities as demonstrated at the ILL for two prototype sources. These two prototypes are installed at secondary beams behind crystal monochromators, whereas a primary beam with a white cold spectrum illuminates the SuperSUN conversion volume. This provides not only higher intensity around the wavelength 0.89 nm where the dominant single-phonon process for UCN production takes place, but also a contribution to UCN production by multi-phonon processes. In the first phase of the project, material walls will trap the UCNs, while in the second phase an octupole magnet will generate a 2.1 T magnetic field at the edge of the conversion volume. For low-field-seeking UCNs, this field increases the trapping potential and reduces wall losses so that the accumulated UCNs are spin-polarized as a result. SuperSUN aims to deliver the highest possible UCN densities to external storage experiments, the first of which will be the PanEDM experiment measuring the neutron’s permanent electric dipole moment.

Airway Delivery of Hydrogel-Encapsulated Niclosamide for the Treatment of Inflammatory Airway Disease

Repurposing of the anthelminthic drug niclosamide was proposed as an effective treatment for inflammatory airway diseases such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease. Niclosamide may also be effective for the treatment of viral respiratory infections, such as SARS-CoV-2, respiratory syncytial virus, and influenza. While systemic application of niclosamide may lead to unwanted side effects, local administration via aerosol may circumvent these problems, particularly when the drug is encapsulated into small polyethylene glycol (PEG) hydrospheres. In the present study, we examined whether PEG-encapsulated niclosamide inhibits the production of mucus and affects the pro-inflammatory mediator CLCA1 in mouse airways in vivo, while effects on mucociliary clearance were assessed in excised mouse tracheas. The potential of encapsulated niclosamide to inhibit TMEM16A whole-cell Cl- currents and intracellular Ca2+ signalling was assessed in airway epithelial cells in vitro. We achieved encapsulation of niclosamide in PEG-microspheres and PEG-nanospheres (Niclo-spheres). When applied to asthmatic mice via intratracheal instillation, Niclo-spheres strongly attenuated overproduction of mucus, inhibited secretion of the major proinflammatory mediator CLCA1, and improved mucociliary clearance in tracheas ex vivo. These effects were comparable for niclosamide encapsulated in PEG-nanospheres and PEG-microspheres. Niclo-spheres inhibited the Ca2+ activated Cl- channel TMEM16A and attenuated mucus production in CFBE and Calu-3 human airway epithelial cells. Both inhibitory effects were explained by a pronounced inhibition of intracellular Ca2+ signals. The data indicate that poorly dissolvable compounds such as niclosamide can be encapsulated in PEG-microspheres/nanospheres and deposited locally on the airway epithelium as encapsulated drugs, which may be advantageous over systemic application.

Computing and Detector Simulation Framework for the HIBEAM/NNBAR Experimental Program at the ESS

The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source focusing on searches for baryon number violation via processes in which neutrons convert to antineutrons. This paper outlines the computing and detector simulation framework for the HIBEAM/NNBAR program. The simulation is based on predictions of neutron flux and neutronics together with signal and background generation. A range of diverse simulation packages are incorporated, including Monte Carlo transport codes, neutron ray-tracing simulation packages, and detector simulation software. The common simulation package in which these elements are interfaced together is discussed. Data management plans and triggers are also described.

Development of high intensity neutron source at the European Spallation Source

The European Spallation Source being constructed in Lund, Sweden will provide the user community with a neutron source of unprecedented brightness. By 2025, a suite of 15 instruments will be served by a high-brightness moderator system placed above the spallation target. The ESS infrastructure, consisting of the proton linac, the target station, and the instrument halls, allows for implementation of a second source below the spallation target. We propose to develop a second neutron source with a high-intensity moderator able to (1) deliver a larger total cold neutron flux, (2) provide high intensities at longer wavelengths in the spectral regions of Cold (4–10 Å), Very Cold (10–40 Å), and Ultra Cold (several 100 Å) neutrons, as opposed to Thermal and Cold neutrons delivered by the top moderator. Offering both unprecedented brilliance, flux, and spectral range in a single facility, this upgrade will make ESS the most versatile neutron source in the world and will further strengthen the leadership of Europe in neutron science. The new source will boost several areas of condensed matter research such as imaging and spin-echo, and will provide outstanding opportunities in fundamental physics investigations of the laws of nature at a precision unattainable anywhere else. At the heart of the proposed system is a volumetric liquid deuterium moderator. Based on proven technology, its performance will be optimized in a detailed engineering study. This moderator will be complemented by secondary sources to provide intense beams of Very- and Ultra-Cold Neutrons.

The PanEDM neutron electric dipole moment experiment at the ILL

The neutron's permanent electric dipole moment dn is constrained to below 3 × 10−26e cm (90% C.L.) [1, 2], by experiments using ultracold neutrons (UCN). We plan to improve this limit by an order of magnitude or more with PanEDM, the first experiment exploiting the ILL's new UCN source SuperSUN. SuperSUN is expected to provide a high density of UCN with energies below 80 neV, implying extended statistical reach with respect to existing sources, for experiments that rely on long storage or spin-precession times. Systematic errors in PanEDM are strongly suppressed by passive magnetic shielding, with magnetic field and gradient drifts at the single fT level. A holding-field homogeneity on the order of 10−4 is achieved in low residual fields, via a high static damping factor and built-in coil system. No comagnetometer is needed for the first order-of-magnitude improvement in dn, thanks to high magnetic stability and an assortment of sensors outside the UCN storage volumes. PanEDM will be commissioned and upgraded in parallel with SuperSUN, to take full advantage of the source's output in each phase. Commissioning is ongoing in 2019, and a new limit in the mid 10−27e cm range should be possible with two full reactor cycles of data in the commissioned apparatus.

Design of the magnet system of the neutron decay facility PERC

The PERC (Proton and Electron Radiation Channel) facility is currently under construction at the research reactor FRM II, Garching. It will serve as an intense and clean source of electrons and protons from neutron beta decay for precision studies. It aims to contribute to the determination of the Cabibbo-Kobayashi-Maskawa quark-mixing element Vud from neutron decay data and to search for new physics via new effective couplings. PERC's central component is a 12 m long superconducting magnet system. It hosts an 8 m long decay region in a uniform field. An additional high-field region selects the phase space of electrons and protons which can reach the detectors and largely improves systematic uncertainties. We discuss the design of the magnet system and the resulting properties of the magnetic field.

Preface

This volume contains the written proceedings of PPNS-2018, the international workshop on “Particle Physics at Neutron Sources” hosted by the LPSC in Grenoble, France from May 24th–26th, 2018.

New Neutron Lifetime Measurements with the Big Gravitational Trap and Review of Neutron Lifetime Data

Neutron lifetime is one of the most important physical constants which determines parameters of the weak interaction and predictions of primordial nucleosynthesis theory. In our experiment we measure the storage time of UCN in the material trap coated with a hydrogen-free fluorine-containing polymer (Fomblin grease UT-18). The stability of this coating to multiple thermal cycles between 80 K and 300 K was tested. The achieved storage time is only 1.5% less than free neutron lifetime. Using additional surface, which can be plunged into the trap to change the collision frequency of UCN with walls, we calculate free neutron lifetime by extrapolation to zero collision frequency. The result of the measurements with this new experimental setup is

Polarized proton spin density images the tyrosyl radical locations in bovine liver catalase

A tyrosyl radical, as part of the amino acid chain of bovine liver catalase, supports dynamic proton spin polarization (DNP). Finding the position of the tyrosyl radical within the macromolecule relies on the accumulation of proton polarization close to it, which is readily observed by polarized neutron scattering. The nuclear scattering amplitude due to the polarization of protons less than 10 Å distant from the tyrosyl radical is ten times larger than the amplitude of magnetic neutron scattering from an unpaired polarized electron of the same radical. The direction of DNP was inverted every 5 s, and the initial evolution of the intensity of polarized neutron scattering after each inversion was used to identify those tyrosines which have assumed a radical state. Three radical sites, all of them close to the molecular centre and the haem, appear to be equally possible. Among these is tyr-369, the radical state of which had previously been proven by electron paramagnetic resonance.

Polarized neutron Laue diffraction on a crystal containing dynamically polarized proton spins

A polarized neutron Laue diffraction experiment on a single crystal of neodymium-doped lanthanum magnesium nitrate hydrate containing polarized proton spins is reported. By using dynamic nuclear polarization to polarize the proton spins, it is demonstrated that the intensities of the Bragg peaks can be enhanced or diminished significantly, whilst the incoherent background, due to proton spin disorder, is reduced. It follows that the method offers unique possibilities to tune continuously the contrast of the Bragg reflections and thereby represents a new tool for increasing substantially the signal-to-noise ratio in neutron diffraction patterns of hydrogenous matter.

Superthermal source of ultracold neutrons for fundamental physics experiments

Ultracold neutrons (UCNs) play an important role for precise measurements of the properties of the neutron and its interactions. During the past 25 years, a neutron turbine coupled to a liquid deuterium cold neutron source at a high-flux reactor has defined the state of the art for UCN production, despite a long history of efforts towards a new generation of UCN sources. This Letter reports a world-best UCN density available for users, achieved with a new source based on conversion of cold neutrons in superfluid helium. A conversion volume of 5 liters provides at least 274,000 UCN in a single accumulation run. Cyclically repeated operation of the source has been demonstrated, as well.

Superfluid-helium converter for accumulation and extraction of ultracold neutrons

We report the first successful extraction of accumulated ultracold neutrons (UCN) from a converter of superfluid helium, in which they were produced by downscattering neutrons of a cold beam from the Munich research reactor. Windowless UCN extraction is performed in vertical direction through a mechanical cold valve. This prototype of a versatile UCN source is comprised of a novel cryostat designed to keep the source portable and to allow for rapid cooldown. We measured time constants for UCN storage and extraction into a detector at room temperature, with the converter held at various temperatures between 0.7 and 1.3 K. The UCN production rate inferred from the count rate of extracted UCN is close to the theoretical expectation.

A Superconducting Magnet UCN Trap for Precise Neutron Lifetime Measurements

Finite-element methods along with Monte Carlo simulations were used to design a magnetic storage device for ultracold neutrons (UCN) to measure their lifetime. A setup was determined which should make it possible to confine UCN with negligible losses and detect the protons emerging from β-decay with high efficiency: stacked superconducting solenoids create the magnetic storage field, an electrostatic extraction field inside the storage volume assures high proton collection efficiency. Alongside with the optimization of the magnetic and electrostatic design, the properties of the trap were investigated through extensive Monte Carlo simulation.

First Ever Storage of Ultracold Neutrons in a Magnetic Trap Made of Permanent Magnets

Further improvement in the accuracy of any neutron lifetime experiment by means of ultracold neutrons (UCN) in material bottles is limited due to unavoidable systematic effects when the UCN are reflected from the walls. However, such effects can be excluded in principle if magnetic trapping of UCN is used. The storage of UCN in a small magnetic trap made of permanent magnets was demonstrated for the first time ever. The measured storage time in this feasibility study was (882 ± 16) s. At this level of accuracy no depolarization was observed.

Is the unitarity of the quark-mixing CKM matrix violated in neutron beta-decay?

We report on a new measurement of neutron beta-decay asymmetry. From the result A(0) = -0.1189(7), we derive the ratio of the axial vector to the vector coupling constant lambda = g(A)/g(V) = -1.2739(19). When included in the world average for the neutron lifetime tau = 885.7(7) s, this gives the first element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix V(ud). With this value and the Particle Data Group values for V(us) and V(ub), we find a deviation from the unitarity condition for the first row of the CKM matrix of Delta = 0.0083(28), which is 3.0 times the stated error.

[Acute pyelonephritis in children with minimal or normal urine findings]

BACKGROUND

Over the past years we have seen several children with serious bacterial infections in whom the focus of the infection was found in the kidneys despite of normal or minimal urine findings.

MATERIAL AND METHODS

We review the cases of all children hospitalised at our paediatric department from 1995-2000 with normal or minimal urine findings, and in whom acute pyelonephritis was diagnosed by means of computerized tomographic imaging of the kidneys.

RESULTS

All 10 children (aged 9 months to 9 years) had focal areas of decreased enhancement in the kidney parenchyma. All received intravenous antibiotic treatment. Vesicouretheral reflux was detected in four patients and required surgical intervention in one. One patient had considerable renal scarring and decreased renal function on dimercaptosuccinic acid (DMSA) scintigraphy.

INTERPRETATION

In children with suspected serious bacterial infection, it is important to have the possibility of renal infection in mind in spite of normal urine findings. The importance of establishing the right diagnosis lies in the fact that patients with pyelonephritis need further investigation and follow-up.

Effect of the lipoxygenase inhibitor N-hydroxy-N-(6-methoxy-3,4-dihydro-2-naphthylmethyl)urea on bronchoconstriction and lung vascular permeability in anaphylactic guinea pigs

Narrowing of the airway lumen as a result of plasma exudation could augment airflow obstruction after allergen-induced bronchoconstriction. Because leukotrienes are putative mediators of bronchial asthma, the effects of a lipoxygenase inhibitor, VZ564 (N-hydroxy-N-(6-methoxy-3,4-dihydro-2- naphthylmethyl) urea. CAS 147495-99-6), on increased pulmonary permeability and bronchoconstriction during anaphylactic reaction were studied in guinea pigs and compared to the effects of the phosphodiesterase inhibitor theophylline. An anaphylactic reaction was induced by ovalbumin challenge (0.2 mg/kg i.v.) in passively sensitized and antihistamine (mepyramine)-pretreated guinea pigs; bronchoconstriction was measured as increased intratracheal pressure; lung vascular permeability was evaluated as extravasation of Evans blue dye up to 10 min after antigenic challenge. Ovalbumin challenge induced an increase in intratracheal pressure by 31 +/- 3 mmHg; the pulmonary permeability index was higher in ovalbumin-challenged versus saline (sham)-challenged guinea pigs (1.49 +/- 0.17 vs 0.56 +/- 0.04, p < 0.05). VZ564 and theophylline dose-dependently reduced increased pulmonary permeability and bronchoconstriction. VZ564 (10 and 46.4 mg/kg p.o., given 1 h before ovalbumin challenge) inhibited increased lung permeability by 42% and 95% and reduced bronchoconstriction by 61% at the higher dose. Theophylline (1 and 10 mg/kg i.v., given 10 min before ovalbumin challenge) diminished increased pulmonary permeability by 88% and reduced bronchoconstriction by 63% at the higher dose. In conclusion, the novel lipoxygenase inhibitor VZ564 inhibits after oral application important symptoms of asthma, namely bronchoconstriction and alveolar exudation of plasma in anaphylactic guinea pigs. The acute effects of VZ564 in this experimental model are comparable with the effects of the well known antiasthmatic substance theophylline.

(dA-dT) dependent inactivation of the DNA template properties by interaction with netropsin and distamycin A

The inhibitory effect of the polypeptide antibiotics netropsin and distamycin A on DNA dependent nucleic acid synthesis has been shown to be related to the base composition of the template DNA. A number of natural DNA's of quite different dA-dT content as well as poly (dI-dC)-poly (dI-dC), poly (dA-dT)-poly (dA-dT), poly (dA) - poly (dT) and poly (dG) - poly (dC) has been studied as templates in DNA and in part in RNA polymerase reaction. The highest binding efficiency of netropsin existing for (dA-dT) - containing DNA polymers and the less pronounced interaction with the (dI-dC)-containing polymer shown by the melting and CD spectrral behaviour of the complexes are entirely reflected in the template inactivation. The same is evident for distamycin A. However, in contrast to netropsin the antibiotic distamycin A exhibits some binding tendency to poly (dG) - poly (dC). Binding effects of a netropsin derivative to DNA and (dA-dT) -containing polymers suggest the importance of hydrogen bonds of the peptide groups in the complex formation.