Modeling of non‐Fickian diffusion and dissolution from a thin polymeric coating: An application to drug‐eluting stents

In this paper, we present a general model for non‐Fickian diffusion and drug dissolution from a controlled drug delivery device coated with a thin polymeric layer. First, we study the stability and deduce an analytic solution to the problem. Then, we consider this solution and provide suitable boundary conditions to replace the problem of mass transport in the coating of a coronary drug‐eluting stent. With this approach, we reduced the computational cost of performing numerical simulations in complex 3‐dimensional geometries. The model for mass transport by a coronary drug‐eluting stent is coupled with a non‐Newtonian blood model flow. In order to show the effectiveness of the method, numerical experiments and a model validation with experimental data are also included. In particular, we investigate the influence of the non‐Newtonian flow regime on the drug deposition in the arterial wall.     

Self‐Assembly of Poly‐Adenine‐Tailed CpG Oligonucleotide‐Gold Nanoparticle Nanoconjugates with Immunostimulatory Activity

Synthetic unmethylated cytosine–guanine (CpG) oligodeoxynucleotides (CpG ODNs) possess high immunostimulatory activity and have been widely used as a therapeutic tool for various diseases including infection, allergies, and cancer. A variety of nanocarriers have been developed for intracellular delivery of CpG ODNs that are otherwise nonpermeable through the cellular membrane. For example, previous studies showed that gold nanoparticles (AuNPs) could efficiently deliver synthetic thiolated CpG ODNs into cultured cells and induce expression of proinflammatory cytokines. Nevertheless, the necessity of using thiolated CpG ODNs for the modification of AuNPs inevitably complicates the synthesis of the nanoconjugates and increases the cost. A new approach is demonstrated for facile assembly of AuNP‐CpG nanoconjugates for cost‐effective drug delivery. It is found that non‐thiolated, diblock ODNs containing a CpG motif and a poly‐adenine (polyA) tail can readily self‐assemble on the surface of AuNPs with controllable and tunable density. Such nanoconjugates are efficiently delivered into RAW264.7 cells and induce immune response in a Toll‐like receptor 9 (TLR9)‐dependent manner. Under optimal conditions, polyA‐CpG‐AuNPs show significantly higher immunostimulatory activity than their thiolated counterpart. In addition, the immunostimulatory activity of CpG‐AuNPs can be modulated by varying the length of the polyA tail. In vivo induction of immune responses in mice is demonstrated by using polyA‐tailed CpG‐AuNP nanoconjugates.     

Self‐Collapsing of Single Molecular Poly‐Propylene Oxide (PPO) in a 3D DNA Network

On the basis of DNA self‐assembly, a thermal responsive polymer polypropylene oxide (PPO) is evenly inserted into a rigid 3D DNA network for the study of single molecular self‐collapsing process. At low temperature, PPO is hydrophilic and dispersed uniformly in the network; when elevating temperature, PPO becomes hydrophobic but can only collapse on itself because of the fixation and separation of DNA rigid network. The process has been characterized by rheological test and Small Angle X‐Ray Scattering test. It is also demonstrated that this self‐collapsing process is reversible and it is believed that this strategy could provide a new tool to study the nucleation‐growing process of block copolymers.     

Roll‐to‐roll coating of flexible glass

Flexible glass is a relatively new kind of substrate with a unique combination of properties that are, in different aspects, ideal for numerous applications. The material has aroused significant interest and has prompted activities in R&D communities dedicated to topics such as flexible electronics, flexible OLED and flexible PV. As a result, device demonstrators of considerable maturity have been created, some of which were even manufactured using a roll‐to‐roll (R2R) process. So far, these activities have not resulted in marketable final products that are produced in an industrial context. The key prerequisite for a widespread industrial adoption of R2R processing of flexible glass substrates is the availability of suitable and proven manufacturing equipment. The tools need to be able to handle and process this delicate material, taking into account its mechanical properties, which differ significantly from the typical flexible substrates such as paper, polymer film, or metal foil. This article discusses specific equipment aspects that need to be considered in the R2R handling of flexible glass, both in general and by taking the example of a roll‐to‐roll lab coating system. This tool has been designed specifically for handling flexible glass and will be available to the interested community from October 2016. Furthermore, it is shown how different processes such as R2R sputtering, evaporation, and flash lamp annealing can be used for potential flexible glass applications in flexible electronics, architecture, and energy conversion devices. Beyond that, related layer stacks deposited by vacuum coating will be discussed.     

Assessment of the Cytocompatibility of Poly‐(N‐hexylvinylpyridinium) Used as an Antibacterial Implant Coating

Medical implants made of titanium have a wide variety of applications, ranging from replacement of a single tooth to extraoral maxillofacial prosthetic rehabilitation or hip endoprosthesis. The long‐term success of such osseointegrated titanium implants is endangered by inflammation of periimplant hard or soft tissues caused by a bacterial infection. Therefore, implants should ideally inhibit bacterial adhesion and growth, but allows strong attachment of connective tissues or epithelium at the same time. Antimicrobial polymers like poly(vinyl‐N‐hexylpyridinium bromide) (hexyl‐PVP) are a promising approach as implant coatings to inhibit bacterial adhesion, but little is known about the biocompatibility of these polymers. The aim of the present study was to develop a method for evaluation of the cell acceptance of hexyl‐PVP or copolymers of vinyl‐N‐hexylpyridinium bromide and (4‐vinylbenzyl)phosphonic acid diethylester (poly((hexyl‐VP)‐co‐VBP)) as coating on titanium disks. Primary human gingival fibroblasts were used and biocompatibility was assessed by cell adhesion and proliferation. The cell morphology of the fibroblasts on these surfaces was analyzed by scanning electron microscopy (SEM) and was used as additional criterion. The results indicate no significant differences in adhesion or proliferation rate between primary human gingival fibroblasts seeded on polymer‐coated titanium disks and uncoated titanium disks as a control. Although SEM micrographs displayed moderate differences in cell morphology between the two groups, application of hexyl‐PVP or the corresponding copolymers as antibacterial coatings for medical implants or devices appears to be promising.     

Development of an universal affinity fusion tag (Poly‐DOPA) for immobilizing recombinant proteins on biomaterials

The covalent and non‐covalent immobilization of growth factors such as recombinant human bone morphogenetic protein 2 (rhBMP‐2) on metals and bone replacement materials in bioactive form is a recent development. Up to now the immobilization technology usually involved the chemical modification and activation of the biomaterial surface followed by attachment of the bioactive protein. Here we suggest an alternative method in which an affinity tag fused to an active protein will allow immobilization without additional chemistry. For biomaterials such as minerals, metals (titanium, steel, CoCrMo), glass ceramics, teflon and possibly bone and teeth ideal adhesion molecules would be the foot proteins (Mefps) of the mussel M. edulis which contain the rare amino acid dihydroxy phenylalanine (DOPA). Recently it could be shown by Messersmith's group that a single DOPA‐molecule can be non‐covalently bound to titanium dioxide surface with a dissociation energy of 22.2 kcal/mol (Lee, H.; Scherer, N. F.; Messersmith, P. B. Proc. Natl. Acad. Sci. U. S. A 2006, 103, 12999–13003).We therefore propose the DOPA‐tag as a general and versatile affinity tag for the immobilization of proteins on biomaterials.     

Thermal conductivity of zirconia‐based ceramics for thermal barrier coating

Lowering the thermal conductivity of thermal barrier coatings used to protect blade and vane airfoils represents an important challenge for gas turbine designers and manufacturers. Dense zirconia‐based materials have been prepared by solid state reaction methods to determine their thermal properties up to 1000 °C. Partially stabilised zirconias having a thermal conductivity 40 % lower than the thermal conductivity of the most widely used system (ZrO₂‐8wt.%Y₂O₃) have been obtained.     

Simulation and preliminary experimental results for an active neutron counter using a neutron generator for a fissile material accounting

An active neutron coincidence counter using a neutron generator as an interrogation source has been suggested. Because of the high energy of the interrogation neutron source, 2.5 MeV, the induced fission rate is strongly affected by the moderator design. MCNPX simulation has been performed to evaluate the performance achieved with these moderators. The side- and bottom-moderator are significantly important to thermalize neutrons to induce fission. Based on the simulation results, the moderators are designed to be adapted to the experimental system. Their preliminary performance has been tested by using natural uranium oxide powder samples. For a sample of up to 3.5 kg, which contains 21.7 g of ²³⁵U, 2.64 cps/g-²³⁵U coincidence events have been measured. Mean background error was 9.57 cps and the resultant coincidence error was 13.8 cps. The experimental result shows the current status of an active counting using a neutron generator which still has some challenges to overcome. However, the controllability of an interrogation source makes this system more applicable for a variety of combinations with other non-destructive methods like a passive coincidence counting especially under a harsh environment such as a hot cell. More precise experimental setup and tests with higher enriched samples will be followed to develop a system to apply it to an active measurement for the safeguards of a spent fuel treatment process.     

Blends of linear and peroxide‐modified branched polylactide for extrusion coating

The purpose of the present work was to improve melt rheological properties of linear poly(L‐lactide) (PLLA) by melt blending with peroxide‐modified branched PLLA for extrusion coating. Peroxide‐modified PLLA, ie, PLLA melt extruded with 0.3 wt% of tert‐Butyl‐peroxybenzoate (TBPB); 2,5‐dimethyl‐2,5‐(tert‐butylperoxy)‐hexane (Lupersol 101 [LOL1]); and benzoyl peroxide was added to linear PLLA in ratios of 5, 15, and 30 wt%. All blends showed increased zero shear viscosity, elastic feature (storage modulus, decreased tan delta), and shear sensitivity. The blends' properties were mostly dependent on the peroxide applied for the modification and, to some extent, on the amount of added peroxide‐modified PLLA. Rheological models suggest that all blend compositions are mainly immiscible. Thermal properties were unchanged; all materials remained amorphous, though the enthalpy of cold crystallization was slightly increased. Extrusion coating on paperboard was conducted with PLLA and peroxide‐modified PLLA blends (90:10). All blends were processable; however, only that made with 2,5‐dimethyl‐2,5‐(tert‐butylperoxy)‐hexane (LOL1) afforded a smooth high‐quality coating surface with improved line speed. Adhesion levels between fibre and plastic and heat seal performance were marginally reduced compared with pure PLLA (3051D). The water vapour transmission measurements with 2,5‐dimethyl‐2,5‐(tert‐butylperoxy)‐hexane (LOL1) showed acceptable water transmission levels, being only slightly higher than for neat PLLA coating.     

Partition experimental designs for sequential processes: Part II—second‐order models

Second‐order experimental designs are employed when an experimenter wishes to fit a second‐order model to account for response curvature over the region of interest. Partition designs are utilized when the output quality or performance characteristics of a product depend not only on the effect of the factors in the current process, but the effects of factors from preceding processes. Standard experimental design methods are often difficult to apply to several sequential processes. We present an approach to building second‐order response models for sequential processes with several design factors and multiple responses. The proposed design expands current experimental designs to incorporate two processes into one partitioned design. Potential advantages include a reduction in the time required to execute the experiment, a decrease in the number of experimental runs, and improved understanding of the process variables and their influence on the responses. Copyright © 2002 John Wiley & Sons, Ltd.     

Partition experimental designs for sequential processes: Part I—First‐order models

The output quality or performance characteristics of a product often depend not only on the effect of the factors in the current process but on the effect of factors from preceding processes. Statistically‐designed experiments provide a systematic approach to study the effects of multiple factors on process performance by offering a structured set of analyses of data collected through a design matrix. One important limitation of experimental design methods is that they have not often been applied to multiple sequential processes. The objective is to create a first‐order experimental design for multiple sequential processes that possess several factors and multiple responses. The first‐order design expands the current experimental designs to incorporate two processes into one partitioned design. The designs are evaluated on the complexity of the alias structure and their orthogonality characteristics. The advantages include a decrease in the number of experimental design runs, a reduction in experiment execution time, and a better understanding of the overall process variables and their influence on each of the responses. Copyright © 2001 John Wiley & Sons, Ltd.