CCVD Synthesis of Carbon‐Encapsulated Cobalt Nanoparticles for Biomedical Applications

Carbon‐encapsulated ferromagnetic Cobalt nanoparticles (Co@C) have been synthesized by catalytic chemical vapour deposition (CCVD). The nanoparticles, mainly ranging between 10 and 15 nm, are tightly encapsulated by 2–3 concentric graphitic carbon shells and protected from oxidation. Because of their magnetic properties (saturation magnetization of 106 emu/g and a coercivity HC of 250 Oe), Co@C nanoparticles have been investigated for hyperthermia application. Although the observed values of the specific absorption rate (28.7 W/gCo@C at 30 kA/m and 215.4 W/gCo@C at 70 kA/m) are slightly lower than required in actual hyperthermia therapies, the observed strong heating effect provides a very promising starting point for future clinical application. It is also demonstrated that these nanoparticles can at the same time be used for magnetic resonance imaging (MRI) with an efficiency comparable to commercially available T2 contrast agents.     

A novel nano drug delivery system based on tigecycline-loaded calciumphosphate coated with poly-dl-lactide-co-glycolide

The purpose of the study presented in this paper has been to examine the possibility of the synthesis of a new nanoparticulate system for controlled and systemic drug delivery with double effect. In the first step, a drug is released from bioresorbable polymer; in the second stage, after resorption of the polymer, non-bioresorbable calcium phosphate remains the chief part of the particle and takes the role of a filler, filling a bone defect. The obtained tigecycline-loaded calcium-phosphate(CP)/poly(dl-lactide-co-glycolide)(PLGA) nanoparticles contain calcium phosphate coated with bioresorbable polymer. The composite was analyzed by FT-IR, XRD and AFM methods. The average particle size of the nanocomposite ranges between 65 and 95 nm. Release profiles of tigecycline were obtained by UV–VIS spectroscopy in physiological solution at 37°C. Experimental results were analyzed using Peppas and Weibull mathematical models. Based on kinetic parameters, tigecycline release was defined as non-Fickian transport. The cytotoxicity of the nanocomposite was examined on standard cell lines of MC3T3-E1, in vitro. The obtained low values of lactate dehydrogenase (LDH) activity (under 37%) indicate low cytotoxicity level. The behaviour of the composite under real-life conditions was analyzed through implantation of the nanocomposite into living organisms, in vivo. The system with the lowest tigecycline content proved to be an adequate system for local and controlled release. Having in mind the registered antibiotics concentration in other tissues, delivery systems with a higher tigecycline content show both local and systemic effects.     

Development and characterization of thermosensitive hydrogels based on poly(N‐isopropylacrylamide) and calcium alginate

This work refers to the synthesis and characterization of thermosensitive hydrogels based on interpenetrating polymer networks (IPNs) of poly(N‐isopropylacrylamide) (PNIPAAm) and calcium alginate in the form of films. The influence of the crosslinking degree of PNIPAAm and alginate content on thermal, swelling, mechanical, and morphological properties of hydrogels is investigated in detail. Characterization of pure PNIPAAm hydrogels and IPN hydrogels was performed by FTIR, DSC, DMA, and SEM. In addition, the studies of equilibrium swelling behavior as well as swelling, deswelling, and reswelling kinetics are performed. The results obtained imply the benefits of synthesizing IPNs based on PNIPAAm and calcium alginate over pure PNIPAAm hydrogels. The presence of calcium alginate contributes to the improvement of mechanical properties, the deswelling rate of hydrogels, and the network porosity, without altering the thermosensitivity of PNIPAAm significantly. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Hyperbranched polycarbosiloxanes and polycarbosilanes via bimolecular non-linear hydrosilylation polymerization

The syntheses and selected structure–property relationships of two series of polycarbosiloxanes (HB-PCSOX) and polycarbosilanes (HB-PCS) prepared by the platinum-catalyzed bimolecular non-linear hydrosilylation polymerizations of commercially available 1,3-diallyl- or 1,3-divinyl- disiloxanes or disilanes and tri- or tetra-functional siloxysilanes or silanes (i.e., A_x + B_y polymerization systems where x = 2 and y = 3 or 4) are described. The polymerizations were controlled to avoid gelation and ensure preparation of non-crosslinked soluble polymer products by adjusting the molar ratios of the reacting A (allylsilyl, Si–CH₂–CHCH₂, or vinylsilyl, Si–CHCH₂) and B (silyl, Si–H) reactive functional groups such that r ≤ 1/[(x ? 1)(y ? 1)] or r ≥ (x ? 1)(y ? 1) where r = [A]/[B]. The polymers were characterized by IR, ¹H, ¹³C and ²⁹Si NMR, SEC, DSC and TGA. Their molecular weights were found to increase in the following order of the side-group substitution in the 1,3-divinyldisiloxane monomer used: EtO > Me > MePh > Ph₂, consistent with the increased electron-donation to the vinyl groups causing their increased reactivity in hydrosilylation. These polymers represent unique yet easily and economically available multifunctional nanoscopic dendritic building blocks for more complex 3D nano-structured materials for a variety of applications in electronics, photonics, lithography, specialty coatings, etc.     

Susceptibility to contact insecticides of granary weevil Sitophilus granarius (L.) (Coleoptera: Curculionidae) originating from different locations in the former Yugoslavia

The insecticides dichlorvos, malathion, chlorpyrifos-methyl, pirimiphos-methyl, deltamethrin and cypermethrin were applied to filter paper to assess their toxicity to granary weevil Sitophilus granarius adults. Based on discriminating doses obtained from tests on a susceptible laboratory population, the susceptibility of 12 populations originating from different storage facilities (11 in Serbia and 1 in Bosnia-Herzegovina) was tested. The facilities included silos, floor stockpiles and attic stockpiles. Weevils originating from Apatin, Belgrade Port, Bijeljina and Kikinda were submitted to toxicity testing, and determination of ld-p lines, LD values and levels of susceptibility/resistance. Chlorpyrifos-methyl proved the most toxic and cypermethrin the least toxic insecticides against all populations. Dichlorvos, malathion and pirimiphos-methyl had the least toxic effect on weevils originating from Belgrade Port and Kikinda, While deltamethrin was most toxic to weevils from Belgrade Port, and least toxic to weevils from Kikinda. The resistance ratios (RR) for deltamethrin at the LD₅₀ and LD₉₅ levels 48 h after exposure to treated filter paper were 11.2 and 14.5 for Bijeljina weevils, and 20.9 and 25.5 for Kikinda weevils.     

Direct gold and copper wires bonding on copper

The key to bonding to copper die is to ensure bond pad cleanliness and minimum oxidation during wire bonding process. This has been achieved by applying a organic coating layer to protect the copper bond pad from oxidation. During the wire bonding process, the organic coating layer is removed and a metal to metal weld is formed. This organic layer is a self-assembled monolayer. Both gold and copper wires have been wire-bonded successfully to the copper die even without prior plasma cleaning. The ball diameter for both wires are 60 μm on a 100 μm fine pitch bond pad. The effectiveness of the protection of the organic coating layer starts from the wafer dicing process up to the wire bonding process and is able to protect the bond pad for an extended period after the first round of wire bond process. In this study, oxidization of copper bond pad at different packaging processing stages, dicing and die attach curing, have been explored. The ball shear strength for both gold and copper ball bonds achieved are 5 and 6 g/mil² respectively. When subjected to high temperature storage test at 150 °C, the ball bonds formed by both gold and copper wire bond on the organic coated copper bondpad are thermally stable in ball shear strength up to a period of 1440 h. The encapsulated daisy chain test vehicle with both gold and copper wires bonding have passed 1000 cycles of thermal cycling test (−65 to 150 °C). It has been demonstrated that orientation imaging microscopy technique is able to detect early levels of oxidation on the copper bond pad. This is extremely important in characterization of the bondability of the copper bond pad surface.     

The Cyclic Cystine Ladder of Theta‐Defensins as a Stable,Bifunctional Scaffold: A Proof‐of‐Concept Study Using the Integrin‐Binding RGD Motif.

Peptides have the specificity and size required to target the protein–protein interactions involved in many diseases. Some cyclic peptides have been utilised as scaffolds for peptide drugs because of their stability; however, other cyclic peptide scaffolds remain to be explored. θ‐Defensins are cyclic peptides from mammals; they are characterised by a cyclic cystine ladder motif and have low haemolytic and cytotoxic activity. Here we demonstrate the potential of the cyclic cystine ladder as a scaffold for peptide drug design by introducing the integrin‐binding Arg‐Gly‐Asp (RGD) motif into the θ‐defensin RTD‐1. The most active analogue had an IC₅₀ of 18 nM for the α_vβ₃ integrin as well as high serum stability, thus demonstrating that a desired bioactivity can be imparted to the cyclic cystine ladder. This study highlights how θ‐defensins can provide a stable and conformationally restrained scaffold for bioactive epitopes in a β‐strand or turn conformation. Furthermore, the symmetry of the cyclic cystine ladder presents the opportunity to design peptides with dual bioactive epitopes to increase activity and specificity.     

Process innovation through Integration approaches at multiple scales: a perspective

Process innovation can be efficiently enabled by considering it as a holistic procedure, which applies integration—starting from molecules and extending through process tasks, unit operations, plant-wide and finally at enterprise level. It is only through such a comprehensive approach that truly breakthrough process innovations are possible and realisable in a highly competing and enormously complex system environment with multiple counter balancing objectives.     

Computing the electromagnetic field of the system of arbitrarily positioned conductors in horizontally stratified multilayer medium

This paper presents a novel computational methodology, based on the finite element technique, for the analysis of electromagnetic field due to system of arbitrarily positioned current‐carrying conductors in horizontally stratified multilayer medium, having arbitrary number of layers with different characteristics (including air). Each soil layer is horizontally unbounded, homogenous and isotropic, whereas conductors can penetrate different layers and extend into the air. The effect of the stratified multilayer medium is taken into account by using the originally developed fixed image method. Complete electromagnetic coupling between grounding system conductors (satisfying thin‐wire approximation) is taken into account, whereas attenuation and phase shift effects are approximated. The electric and magnetic field in stratified multilayer medium are computed from the scalar electric and vector magnetic potentials, using the said fixed image method and approximations to the attenuation and phase shift effects. Copyright © 2014 John Wiley & Sons, Ltd.