In Vitro and In Vivo Characterization of PLLA-316L Stainless Steel Electromechanical Devices for Bone Tissue Engineering—A Preliminary Study

Bone injuries represent a major social and financial impairment, commonly requiring surgical intervention due to a limited healing capacity of the tissue, particularly regarding critical-sized defects and non-union fractures. Regenerative medicine with the application of bone implants has been developing in the past decades towards the manufacturing of appropriate devices. This work intended to evaluate medical 316L stainless steel (SS)-based devices covered by a polymer poly (L-lactic acid) (PLLA) coating for bone lesion mechanical and functional support. SS316L devices were subjected to a previously described silanization process, following a three-layer PLLA film coating. Devices were further characterized and evaluated towards their cytocompatibility and osteogenic potential using human dental pulp stem cells, and biocompatibility via subcutaneous implantation in a rat animal model. Results demonstrated PLLA-SS316L devices to present superior in vitro and in vivo outcomes and suggested the PLLA coating to provide osteo-inductive properties to the device. Overall, this work represents a preliminary study on PLLA-SS316L devices’ potential towards bone tissue regenerative techniques, showing promising outcomes for bone lesion support.     

Optimized EPI for fMRI using a slice-dependent template-based gradient compensation method to recover local susceptibility-induced signal loss

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Most functional magnetic resonance imaging (fMRI) experiments use gradient-echo echo planar imaging (GE EPI) to detect the blood oxygenation level-dependent (BOLD) effect. This technique may fail in the presence of anatomy-related susceptibility-induced field gradients in the human head. In this work, we present a novel 3D compensation method in combination with a template-based correction that can be optimized over particular regions of interest to recover susceptibility-induced signal loss without acquisition time penalty.     

Plug-plug kinetic capillary electrophoresis: method for direct determination of rate constants of complex formation and dissociation

We present a method for direct determination of rate constants of complex formation, k(on), and dissociation, k(off). The method is termed plug-plug kinetic capillary electrophoresis (ppKCE). To explain the concept of the method, we consider the formation of a noncovalent complex C between molecules A and B; A is assumed to migrate slower in electrophoresis than B. In ppKCE, a short plug of A is injected into a capillary, followed by a short plug of B. When a high voltage is applied, the electrophoretic zone of B moves through that of A, allowing for the formation of C. When the zones of A and B are separated, C starts dissociating. The features of the resulting electropherogram are defined by both binding and dissociation. We developed a unique mathematical approach that allows finding k(on) and k(off) from a single electropherogram without nonlinear regression analysis. The approach uses algebraic functions with the only input parameters from electropherograms being areas and migration times of electrophoretic peaks. In this work, we explain theoretical bases of ppKCE and prove the principle of the method by finding k(on) and k(off) for a protein-ligand complex. The unique capability of the method to directly determine both k(on) and k(off) along with its simplicity make ppKCE highly attractive to a broad community of molecular scientists.     

Convergence of the discrete dipole approximation. I. Theoretical analysis

We perform a rigorous theoretical convergence analysis of the discrete dipole approximation (DDA). We prove that errors in any measured quantity are bounded by a sum of a linear term and a quadratic term in the size of a dipole d when the latter is in the range of DDA applicability. Moreover, the linear term is significantly smaller for cubically than for noncubically shaped scatterers. Therefore, for small d, errors for cubically shaped particles are much smaller than for noncubically shaped ones. The relative importance of the linear term decreases with increasing size; hence convergence of DDA for large enough scatterers is quadratic in the common range of d. Extensive numerical simulations are carried out for a wide range of d. Finally, we discuss a number of new developments in DDA and their consequences for convergence.     

Designing solution-processable air-stable liquid crystalline crosslinkable semiconductors

Organic electronics technology, in which at least the semiconducting component of the integrated circuit is an organic material, offers the potential for fabrication of electronic products by low-cost printing technologies, such as ink jet, gravure offset lithography and flexography. The products will typically be of lower performance than those using the present state of the art single crystal or polysilicon transistors, but comparable to amorphous silicon. A range of prototypes are under development, including rollable electrophoretic displays, active matrix liquid crystal (LC) displays, flexible organic light emitting diode displays, low frequency radio frequency identification tag and other low performance electronics. Organic semiconductors that offer both electrical performance and stability with respect to storage and operation under ambient conditions are required. This work describes the development of reactive mesogen semiconductors, which form large crosslinked LC domains on polymerization within mesophases. These crosslinked domains offer mechanical stability and are inert to solvent exposure in further processing steps. Reactive mesogens containing conjugated aromatic cores, designed to facilitate charge transport and provide good oxidative stability, were prepared and their liquid crystalline properties evaluated. The organization and alignment of the mesogens, both before and after crosslinking, were probed by grazing incidence wide-angle X-ray scattering of thin films. Both time-of-flight and field effect transistor devices were prepared and their electrical characterization reported.     

Optical vortices in twisted elliptical optical fibers with torsional stress

In the present paper we have derived the analytical expressions for the modes of twisted elliptical fibers with torsional mechanical stress at various relationships of the fiber parameters. It was shown that circularly polarized optical vortices with the topological charges ±1 can propagate in elliptical fibers as generic modes if ellipticity and the twist-induced circular birefringence suppress the spin-orbit interaction. A comparison of the obtained results with the corresponding results for spun elliptical fibers is made.     

Pathogen‐Mimicking MnO Nanoparticles for Selective Activation of the TLR9 Pathway and Imaging of Cancer Cells

Here, design of the first pathogen‐mimicking metal oxide nanoparticles with the ability to enter cancer cells and to selectively target and activate the TLR9 pathway, and with optical and MR imaging capabilities, is reported. The immobilization of ssDNA (CpG ODN 2006) on MnO nanoparticles is performed via the phosphoramidite route using a multifunctional polymer. The multifunctional polymer used for the nanoparticle surface modification not only affords a protective organic biocompatible shell but also provides an efficient and convenient means for loading immunostimulatory oligonucleotides. Since fluorescent molecules are amenable to photodetection, a chromophore (Rhodamine) is introduced into the polymer chain to trace the nanoparticles in Caki‐1 (human kidney cancer) cells. The ssDNA coupled nanoparticles are used to target Toll‐like receptors 9 (TLR9) receptors inside the cells and to activate the classical TLR cascade. The presence of TLR9 is demonstrated independently in the Caki‐1 cell line by western blotting and immunostaining techniques. The magnetic properties of the MnO core make functionalized MnO nanoparticles potential diagnostic agents for magnetic resonance imaging (MRI) thereby enabling multimodal detection by a combination of MR and optical imaging methods. The trimodal nanoparticles allow the imaging of cellular trafficking by different means and simultaneously are an effective drug carrier system.     

Shocks in homogeneous and heterogeneous populations

A system subject to a point process of shocks is considered. Shocks occur in accordance with a non-homogeneous Poisson process. Different criterions of system failures are discussed in a homogeneous case. Two natural settings are analyzed. Heterogeneity is modeled by an unobserved univariate random variable (frailty). It is shown that reliability (safety) analysis for a heterogeneous case can differ dramatically from that for a homogeneous setting. A shock burn-in procedure for a heterogeneous population is described. The corresponding bounds for the failure rates are obtained.     

Coupling tolerances of high-index silicon-oxynitride waveguides with small bending radii

Silicon-oxynitride waveguides gained by plasma-enhanced chemical vapour deposition are very attractive for the fabrication of passive optical components used in optical networks. The low-loss and compact devices with small bending radii are achieved with a new high-index waveguide design. At the same time this feature increases the requirements on the fibre-to-chip coupling compared to common fibre-matched waveguides. In this paper, we discuss the junction of the high-index optical components to fibre systems and their coupling tolerances. The presented solution is based on using high numerical aperture fibres. Furthermore, the option of higher automation and reliability is given by the coupling with tapered fibres because they allow better positioning tolerances.     

EPR Relaxation‐Enhancement‐Based Distance Measurements on Orthogonally Spin‐Labeled T4‐Lysozyme

Lanthanide‐induced enhancement of the longitudinal relaxation of nitroxide radicals in combination with orthogonal site‐directed spin labeling is presented as a systematic distance measurement method intended for studies of bio‐macromolecules and bio‐macromolecular complexes. The approach is tested on a water‐soluble protein (T4‐lysozyme) for two different commercially available lanthanide labels, and complemented by previously reported data on a membrane‐inserted polypeptide. Single temperature measurements are shown to be sufficient for reliable distance determination, with an upper measurable distance limit of about 5–6 nm. The extracted averaged distances represent the closest approach in Ln^III–nitroxide distance distributions. Studies of conformational changes and of bio‐macromolecule association‐dissociation are proposed as possible application area of the relaxation‐enhancement‐based distance measurements.