Vacuum Infiltration Method Research Articles

Bottleneck removal of paclitaxel biosynthetic pathway by overexpression of DBTNBT gene under methyl-β-cyclodextrin and coronatine elicitation in Taxus baccata L.

Paclitaxel is a highly functionalized diterpenoid that is broadly used for the treatment of several cancer types. This valuable specialized metabolite naturally exists in the inner bark of Taxus species in low amounts. The limited-scale production of paclitaxel in Taxus cell cultures has necessitated the use of several elicitors. Recently, methyl-β-cyclodextrin (CD) and coronatine (COR) have been considered to be highly effective elicitors in producing plant specialized metabolites. Given the limited production of paclitaxel due to the rate limiting enzymes' function, bottleneck removal is conducive to the production of more significant amounts of paclitaxel. In the present study, the full length of DBTNBT coding sequence (CDS), as one of the paclitaxel pathway bottlenecks, was integrated downstream of the CaMV 35S promoter (pCAMBIA1304-DBTNBT) and transiently expressed in Taxus baccata leaves via Agrobacterium tumefaciens and vacuum infiltration method. Paclitaxel production and the expression level of several involved genes were evaluated through different treatments. The transient overexpression of the DBTNBT gene, associated with dual elicitation, resulted in 7.4-fold more paclitaxel production compared with the no-inoculation/no-elicitation control. These ratios were 2.1 and 1.8 in the CD + COR and pCAM treatments, respectively. Among T13αH, T14βH, DBAT, BAPT, DBTNBT, and ABC genes, the most increased expression level belonged to the DBTNBT gene, followed by ABC and BAPT genes. It seems as though in the near future, bottleneck removal could be used on a large scale in Taxus metabolic engineering, resulting in the relative removal of some other bottlenecks and an increase in the final paclitaxel production.

Mechanical behavior of entangled metallic wire materials-polyurethane interpenetrating composites

Composite materials exhibit the impressive mechanical properties of high damping and stiffness, which cannot be attained by employing conventional single materials. Along these lines, a novel material architecture is presented in this work in order to fabricate composites with enhanced mechanical characteristics. More specifically, entangled metallic wire materials were used as the active matrix, whereas polyurethane was employed as the reinforcement elements. As a result, an entangled metallic wire material-polyurethane composite with high damping and stiffness was prepared by enforcing the vacuum infiltration method. On top of that, the mechanical properties (loss factor, energy consumption, and average stiffness) of the proposed composite materials were characterized by performing dynamic tests, and its fatigue characteristics were verified by the micro-interface bonding, as well as the macro-damage factor. The impact of the density, preloading spacing, loading amplitude, and exciting frequency on the mechanical properties of the composites were also thoroughly analyzed. The extracted results indicate that the mechanical properties of the composites were significantly enhanced than those of the pure materials due to the introduction of interface friction. Moreover, the average stiffness of the composites was about 10 times the respective value of the entangled metallic wire material. Interestingly, a rise in the loading period leads to some failure between the composite interfaces, which reduces the stiffness property but enhances the damping dissipation properties. Finally, a comprehensive dynamic mechanical model of the composites was established, while it was experimentally verified. The proposed composites possess higher damping features, i.e., stiffness characteristics, and maintain better fatigue characteristics, which can broaden the application range of the composites. In addition, we provide a theoretical and experimental framework for the research and applications in the field of metal matrix composites.

An Investigation of Production and Properties of RHA Reinforced Hybrid Composites by Vacuum Infiltration Method

The harmful effect of agricultural waste has been intensified over the last decade and impacts the environment every passing day. Rice husk waste is a major problem in Turkey and the far east countries. Due to the economic dependence of the mass cultivation and the production of rice, the disposal of the waste appears both time and money consuming. Alternative methods sought over the years and the implementation of the rice husk in the production of composites is seen as a promising method. RHA is a burning residue of rice husk and the implementation of RHA in the production of aluminum composites gained attention in recent years. In this study, aluminum composites having 5 wt.% Al2O3 reinforcement and 5 wt.% Al2O3/0.5, 1.0, and 1.5 wt.% RHA reinforcement were produced by vacuum infiltration process which is a cheap and cost-effective route. AA7075 alloy without any reinforcement was produced for comparison. Solution heat treatment at 480 °C for 2 hours was applied and then quenched following by aging heat treatment at 120 °C for 8 hours. The microstructure, microhardness, and wear tests of all composites were investigated. Increasing RHA content up to 1 wt.% and aging heat treatment increased the hardness of composites. Abrasion coefficient decreased by increasing RHA content.

Properties of Reinforced Polymer Composite Produced from Coconut Fiber

This study aimed at the production of reinforced polymer composites from coconut fibers and plastics. Coir Fiber (CF) sheets with dimensions of 200 x 200 x 12 mm (+ 3mm) were used as the natural fiber, whereas a thermosetting plastic or an elastomer (unsaturated polyester [UPE] or silicon rubber [SIR]) was used as the binder in the matrix. Processing was performed using the vacuum infiltration method, wherein the liquid polymer was made to infiltrate the cellulose of the natural structure of the CFs and disperse within the CF matrix. The effect of production variables on thermal, sound, and flexural properties was evaluated. Material characterization tests revealed that the addition of the UPE and SIR as reinforcing materials enhanced the thermal conductivity of the CFs. UPE improved the modulus of rupture of the CFs. The study further revealed that CF/SIR composites showed high ductility. Analysis of the sound absorption properties of the composites revealed that the noise reduction coefficient (NRC) of the CF/400 wt% SIR composite was the highest. Moreover, the CF/SIR composites showed higher sound absorption efficiency (α) values at high frequencies than those of the CF/UPE composites. However, the polymers had no effect on the NRC of the neat CFs when added in a low concentration (200 wt%). This study shows that coconut husk waste can be used to produce reinforced polymer composites with desirable thermal conductivity and sound absorption characteristics.

Vacuum infiltration molding and mechanical property of short carbon fiber reinforced Ti-based metallic glass matrix composite

• New vacuum infiltration method using Cu-mold-prepared CF preform is developed. • Electroless-Cu-plated layer dissolves to improve the wettability during infiltration. • Interface microstructure control is achieved by Cu-layer and short-term infiltration. • Ti-based CFRMGMC has obviously improved plasticity together with high-strength. • Randomly and uniformly distributed short CF leads to brittle-ductile transition. The molding process is the key technology for the development of carbon fiber reinforced metallic glass matrix composites (CFRMGMCs), which not only needs to tackle the challenge of the mixing uniformity of carbon fibers, but also should take into account the rapid cooling technology to obtain a fully glassy matrix. Herein, a new vacuum pressure infiltration molding method is developed to fabricate a Ti-based CFRMGMC, in which a copper mold is performed as the container for carbon fiber preforms in addition to being used as a rapid cooling device. In order to prevent the interface reaction between carbon fiber and metal liquid, an electroless copper layer is plated on the surface of carbon fiber. It is found that the thin copper layer is dissolved in the glassy matrix and no crystalline phase is formed on the interface between the fiber and the matrix, showing a good effect on the control of interface microstructure. Meanwhile, electroless copper layer also effectively improves the wettability between the carbon fiber and the titanium alloy melt, thereby improving the infiltration forming ability of the composite material and reducing the tendency to form macroscopic defects. The as-prepared Ti-based CFRMGMC shows a significantly improved plasticity of ∼5 % and a high yield strength of 1880 MPa. The toughening mechanism can be attributed to the random distribution of short carbon fibers in different directions, which originates from the preparing process of carbon fiber preforms. This multi-directional posture is frozen in the glassy matrix and stimulates the multiple shear band behavior of the CFRMGMC. This work sheds lights on the use of carbon fiber in bulk metallic glasses, and is of great significance to the lightweight development and the interface reaction control of CFRMGMCs.

Interaction between Dickeya dianthicola and Pectobacterium parmentieri in Potato Infection under Field Conditions.

Dickeya and Pectobacterium spp. both cause blackleg and soft rot of potato, which can be a yield-reducing factor to potato production. The purpose of this study was to examine the interaction between these two bacterial genera causing potato infection, and subsequent disease development and yield responses under field conditions. Analysis of 883 potato samples collected in Northeastern USA using polymerase chain reaction determined that Dickeya dianthicola and P. parmentieri were found in 38.1% and 53.3% of all samples, respectively, and that 20.6% of samples contained both D. dianthicola and P. parmentieri. To further investigate the relationship between the two bacterial species and their interaction, field trials were established. Potato seed pieces of “Russet Burbank”, “Lamoka”, and “Atlantic” were inoculated with bacterial suspension of D. dianthicola at 107 colony-forming unite (CFU)/mL using a vacuum infiltration method, air dried, and then planted in the field. Two-year results showed that there was a high correlation (p < 0.01) between yield loss and percent of inoculated seed pieces. In a secondary field trial conducted in 2018 and 2019, seed pieces of potato “Shepody”, “Lamoka” and “Atlantic” were inoculated with D. dianthicola, P. parmentieri, or mixture of both species, and then planted. In 2019, disease severity index, as measured by the most sensitive variety “Lamoka”, was 16.2 with D. dianthicola inoculation, 10.4 with P. parmentieri, 25.4 with inoculation with both bacteria. Two-year data had a similar trend. Thus, D. dianthicola was more virulent than P. parmentieri, but the co-inoculation of the two species resulted in increased disease severity compared to single-species inoculation with either pathogen.

Supramolecular hydrogel-infiltrated ceramics composite coating with combined antibacterial and self-lubricating performance.

Inspired by the structure and dynamic weeping lubricating mechanism of articular cartilage, a novel composite coating composed of a textured Y2O3-stabilized ZrO2 (YSZ) ceramics reservoir and silver nanoparticles (AgNPs) hybrid supramolecular hydrogel was developed on the basis of a soft/hard combination strategy. The precursor solution including the poly(ethylene glycol) (PEG)-modified AgNPs and α-cyclodextrins (α-CDs) could be infiltrated deep into (50-60 μm) the pores of a textured YSZ ceramics substrate by a vacuum infiltration method, in situ forming a supramolecular hydrogel within the pores through host-guest inclusion between α-CDs and PEG chains distributed onto the surface of AgNPs. The AgNPs hybrid hydrogel showed thixotropic and thermoresponsive gel-sol transition behavior, low cytotoxicity, and excellent drug-loading capacity, as well as significant antibacterial properties. The textured YSZ ceramics not only provided a hard supporting skeleton and stable reservoir to protect the supramolecular hydrogel from destruction under load-bearing or shear condition, but also allowed retaining the stimuli-responsive gel-sol transition property and drug-release capability of the infiltrated hydrogel, endowing the composite coating with excellent antibacterial properties, and self-lubrication and wear-resistance performance. The composite coating in this work brings a new insight into the design of antibacterial and self-lubricating ceramic coatings for artificial joint applications.

Strawberry-like carbonized cotton Cloth@Polyaniline nanocomposite for high-performance symmetric supercapacitors

In order to control the microstructure of polyaniline (PANI) and enhance the interfacial bonding between PANI and carbon substrate, a vacuum infiltration method is put forward to prepare functionalized carbonized cotton cloth (FCC)@PANI nanocomposite. In which, FCC is soaked in dilute PANI solution under vacuum to achieve the permeation adsorption of PANI. After the solvent evaporated, strawberry-like FCC@PANI nanocomposite is produced with PANI nanoparticles embedding on the fiber surface. This novel method effectively avoids the generation of PANI nanofibers and their agglomeration, even at a high PANI loading of 28.1 wt%. Serving as electrodes in symmetric supercapacitors, the optimum FCC@PANI composite exhibits the maximum capacitance of 350.8 F g−1 (1859.2 mF cm−2) at 1 A g−1, and a high capacitance retention of 90.8% for 10,000 cycles. The performance is much better than that of optimized FCC/PANI composite synthesized by in-situ polymerization, due to the low internal resistance, fast transfer of electrons/ions and a strong interfacial bonding interaction. In view of the easy operation and scalability, vacuum infiltration method has a promising prospect for preparing carbon fabrics/PANI composite electrodes in large scale.

Transformation of Amorphadiene Synthase and Antisilencing P19 Genes into Artemisia annua L. and its Effect on Antimalarial Artemisinin Production.

Purpose: The low content of artemisinin related to the biosynthetic pathway is influenced by the role of certain enzymes in the formation of artemisinin. The regulation of genes involved in artemisinin biosynthesis through genetic engineering is a choice to enhance the content. This research aims to transform ads and p19 gene as an antisilencing into Artemisia annua and to see their effects on artemisinin production. Methods: The presence of p19 and ads genes was confirmed through polymerase chain reaction (PCR) products and sequencing analysis. The plasmids, which contain ads and/or p19 genes, were transformed into Agrobacterium tumefaciens, and then inserted into leaves and hairy roots of A. annua by vacuum and syringe infiltration methods. The successful transformation was checked through the GUS histochemical test and the PCR analysis. Artemisinin levels were measured using HPLC. Results: The percentages of the blue area on leaves by using vacuum and syringe infiltration method and on hairy roots were up to 98, 92.55%, and 99.00% respectively. The ads-p19 sample contained a higher level of artemisinin (0.18%) compared to other samples. Transformed hairy root with co-transformation of ads-p19 contained 0.095% artemisinin, where no artemisinin was found in the control hairy root. The transformation of ads and p19 genes into A. annua plant has been successfully done and could enhance the artemisinin content on the transformed leaves with ads-p19 up to 2.57 folds compared to the untransformed leaves, while for p19, cotransformed and ads were up to 2.25, 1.29, and 1.14 folds respectively. Conclusion: Antisilencing p19 gene could enhance the transformation efficiency of ads and artemisinin level in A. annua.

Highly Conductive PDMS Composite Mechanically Enhanced with 3D-Graphene Network for High-Performance EMI Shielding Application

A highly conductive three-dimensional (3D) graphene network (GN) was fabricated by chemical vapor deposition on a 3D nickel fiber network and subsequent etching process. Then a lightweight and flexible polydimethylsiloxane (PDMS)/GN composite was prepared by a vacuum infiltration method by using the graphene network as a template. The composite showed the superior electrical conductivity of 6100 S/m even at a very low loading level of graphene (1.2 wt %). As a result, an outstanding electromagnetic interference (EMI) shielding effectiveness (SE) of around 40 and 90 dB can be achieved in the X-band at thicknesses of 0.25 and 0.75 mm, respectively, which are much higher than most of the conductive polymers filled with carbon. The 3D graphene network can also act as a mechanical enhancer for PDMS. With a loading level of 1.2 wt %, the composite shows a significant increase by 256% in tensile strength.

Expression of gus and gfp genes in amphidiploid spelt wheat (Triticum spelta L.) after Agrobacterium-mediated transformation

Мета. Дослідити експресію генів gus та gfp в калюсних експлантах амфідиплоїдної пшениці спельти ( Triticum spelta L.) після Agrobacterium -опосередкованої генетичної трансформації. Методи. Для трансформації було обрано сорт пшениці спельти озимої ‘Європа’. Як експланти використовували калюси, отримані зі зрілих зародків. Прекультивацію калюсів здійснювали на живильному середовищі МС (Мурасіге–Скуга), доповненому 2 мг/л 2,4-Д (2,4-дихлорфеноксиоцтова кислота) та 10 мг/л нітратом срібла. Для генетичної трансформації використовували Agrobacterium tumefaciens Conn., штам GV3101, та генетичну конструкцію з репортерними генами gus (ген бета-глюкуронідази (-glucuronidase)) та gfp (ген зеленого флюоресцентного білка (Green Fluorescent Protein, GFP)). Калюси трансформували шляхом інокуляції з агробактеріями та вакуумною інфільтрацією. Далі їх ко-культивували на середовищі МС із 2 мг/л 2,4-Д та 10 мг/л AgNO 3 , але без антибіотиків. Експресію гена gus перевіряли за допомогою гістохімічного, а гена gfp – візуального аналізу (флуоресценція білка GFP в УФ світлі). Рівні експресії генів gfp та gus оцінювали за допомогою програмного забезпечення ImajeJ. Інтеграцію генів gfp та gus в геном спельти перевіряли методом ПЛР . Результати. Генетична трансформація калюсних експлан­тів спельти шляхом їхньої інокуляції в живильному середовищі з агробактеріями та вакуумною інфільтрацією відбувалась з різною частотою. Рівень експресії гена gus за вакуумної інфільтрації становив 4,66 ± 0,74%, за інокуляції – 4,00 ± 0,91%; а гена gfp за вакуумної інфільтрації – 3,66 ± 0,74%, за інокуляції – 4,66 ± 1,39%. Рівень експресії гена gfp був вищим у разі використання інокуляції з агробактеріями, а гена gus – при ва­ку­умній інфільтрації. За допомогою ПЛР-аналізу було під­тверджено інтеграцію генів gfp та gus в геном калюсів спельти. Довжина ПЛР продукту із праймерами до гена gus становила 240 п. н., а до гена gfp – 717 п. н. Висновки. Використання методів вакуумної інфільтрації та інокуляції для генетичної трансформації спельти дали різні результати. Частота генетичної трансформації коливалась від 3,66 до 4,66%. Agrobacterium -опосередкована генетична трансформація амфідиплоїдної пшениці спельти дозволяє дослідити експресію репортерних генів gus та gfp за використання калюсних експлантів, отриманих із зрілих зародків.

High-performance epoxy composites reinforced with three-dimensional Al2O3 ceramic framework

High-performance epoxy composites are prepared by a vacuum infiltration method using a functionalized 3D-Al2O3 skeleton as the reinforcement and conducting framework. The preformed, porous thermal conducting framework acts as a highway for phonon transfer and can resist a high external loading to protect the epoxy composites. Consequently, a remarkable thermal conductivity of 4.356 W·m−1·K−1 is achieved for the 3D-43 vol%Al2O3/epoxy composite, which is 2.7 times higher than that achieved for epoxy composites with conventional randomly dispersed 40 vol% Al2O3 particles. The thermal conductivity of the composites with lower interface resistance was higher than that of 3D-43 vol% Al2O3/epoxy composite with non-functionalization (3.796 W·m−1·K−1), because of the enhanced Al2O3/epoxy interface adhesion. Moreover, the 3D skeleton provides a dual advantage in its prominent reinforcement and toughening of the epoxy composites. The inclusion of 80 vol% of Al2O3 preform dramatically enhanced the flexural strength (352 MPa) by 318%, compared to that of neat epoxy.

Functional analysis of coilin in virus resistance and stress tolerance of potato Solanum tuberosum USING CRISPR/Cas9 editing

The role of the nuclear protein coilin in the mechanisms of resistance of potato Solanum tuberosum cultivar Chicago to biotic and abiotic stresses was studied using the CRISPR/Cas9 technology. For the coilin gene editing, a complex consisting of the Cas9 endonuclease and a short guide RNA was immobilized on gold or chitosan microparticles and delivered into apical meristem cells by bioballistics or vacuum infiltration methods, respectively. Editing at least one allele of the coilin gene considerably increased the resistance of the edited lines to infection with the potato virus Y and their tolerance to salt and osmotic stress.

Screening of a multi-virus resistant RNAi construct in cowpea through transient vacuum infiltration method.

Plant viruses are the most devastating pathogens causing substantial economic losses in many crops. Current viral disease management relies on prophylactics, roguing and insect vector control, since in most crops resistant gene pools for resistance breeding are unavailable. RNA interference, a sequence dependent gene silencing mechanism holds great potential in imparting virus resistance. In this study, the efficacy of a RNAi gene construct developed against four viruses commonly infesting tomato and chilli viz., capsicum chlorosis virus, groundnut bud necrosis virus, cucumber mosaic virus and chilli veinal mottle virus was evaluated. A 3546bp dsRNA-forming construct comprising sense-intron-antisense fragments in binary vector pBI121 (hpRNAi-MVR) was mobilized into Agrobacterium tumefaciens. Cowpea (Vigna unguiculata) was used as an indicator plant for GBNV agroinfiltration to evaluate the efficacy of hpRNAi-MVR construct in conferring GBNV resistance. The type of agroinfiltration, bacterial concentration and incubation-temperatures were optimized. Vacuum infiltration of three pulses of 20-30s at 66.66kPa were effective than syringe infiltration. Of the five Agrobacterial concentrations, OD600 0.5 was more efficient. Incubation temperature of 31 ± 1°C was favorable for development of disease symptoms than 20 ± 1°C and 26 ± 1°C. ELISA revealed a 35% decline in viral load in hpRNAi-MVR infiltrated plants compared to vector control plants. Quantitative real time PCR results have shown a viral gene silencing to the extent of 930-990 folds in hpRNAi-MVR infiltrated plants compared to vector control. This approach is simple, rapid and efficient to screen the efficacy of RNAi constructs developed for the RNAi mediated plant virus management.

Functional Analysis of Coilin in Virus Resistance and Stress Tolerance of Potato Solanum tuberosum using CRISPR-Cas9 Editing.

The role of the nuclear protein coilin in the mechanisms of resistance of potato Solanum tuberosum cultivar Chicago to biotic and abiotic stresses was studied using the CRISPR-Cas9 technology. For the coilin gene editing, a complex consisting of the Cas9 endonuclease and a short guide RNA was immobilized on gold or chitosan microparticles and delivered into apical meristem cells by bioballistics or vacuum infiltration methods, respectively. Editing at least one allele of the coilin gene considerably increased the resistance of the edited lines to infection with the potato virus Y and their tolerance to salt and osmotic stress.

Enhancing the cycle life of Li-S batteries by designing a free-standing cathode with excellent flexible, conductive, and catalytic properties

Poor electrical conductivity of sulfur, sluggish redox kinetics, dissolution of intermediate polysulfides, and expansion in volume upon cycling are the main drawbacks that hamper the practical application of Li-S batteries. By taking advantages of the high conductivity and favorable catalytic activity of RuO2, we design a 3D carbon nanotube film with embedded RuO2 nanoparticles as a freestanding type of chemisorptive and catalyst-like cathode for Li-S batteries, which can be facilely prepared by a surfactant-assisted vacuum infiltration method. Both experimental and theoretical results reveal the excellent capability of RuO2 for anchoring polysulfides and accelerating the kinetics of polysulfides catalytic redox reactions. Besides, the 3D freestanding cathode is beneficial to overcoming pulverization during volume changes, especially for long-term cycling. At a high areal sulfur loading of 2 mg cm−2, favorable initial capacities of 750 and 1060 mA h g−1 respectively at 2 and 0.5 C are achieved. More attractively, the capacity after 1000 cycles maintains 405 mA h g−1 at 0.5 C with a loss in capacity of only 0.06% per cycle. Additionally, such freestanding cathode allows the batteries to be tested under various bending stages, hence encouraging more research works on fabrication of other 3D nanostructure families as high-performance cathodes for Li-S batteries.

Hierarchical formation mechanism of anisotropic magnetite microflakes and their superior microwave attenuation properties

In the preparation of the α-Fe2O3 particles, the size, thickness, morphology and size distribution were controlled by adding silicon and magnesium salts as surfactants, and finally the fine hexagonal α-Fe2O3 microflakes with a diameter of 1.8 μm and a thickness of 200 nm were obtained. This synthesis method provides some ideas for the manufacture of well-defined α-Fe2O3 particles. In-plane aligned composites made from reduced microflakes were prepared by a vacuum infiltration method. The hysteresis loops of the composites with in-plane alignment of the microflakes were obtained by applying the external magnetic field parallel and perpendicular to the composite sample plane. It is obviously exhibited that the composites are easily magnetized along the sample plane. According to the results of magnetic and microwave measurement, aligned composites have higher permeability and magnetic loss, which lead to a better microwave absorption performance than that of random composites. Especially when the thickness is 5 mm, the minimum RL value of aligned composites (−41.67 dB) is enhanced by 258%, compared with that of random composites (−16.11 dB). This would open up the possibility of using the in-plane alignment method to improve the microwave absorbing property and expand the range of practical applications of absorbers.

The phase change property of lauric acid confined in carbon nanotubes as nano-encapsulated phase change materials

Lauric acid (LA) impregnates in carbon nanotubes (CNTs), resulting in nano-encapsulated phase change materials (PCMs). TEM and DSC results both indicate that the filling of LA into CNTs is realized by the vacuum infiltration method. A further study of nano-encapsulated PCMs at the molecular level is investigated by molecular dynamics simulations. From the axial view of CNTs, LA molecules always keep a circular distribution inside CNTs with a radius of about 4.8 A. The analysis on radial distribution function, the end-to-end distance and the torsion angle simultaneously verifies that the order degree of LA molecules is improved due to the nano-confined effect of CNTs. The diffusion coefficient of LA is enhanced in CNTs. The energy flux and thermal conductivity of LA molecules in CNTs are higher than those of pure LA at the same temperature. These results fully indicate the heat and mass transfer of LA in CNTs could be enhanced. The current research could contribute to a deep understanding nanoscale thermal science and to potential application in heat dissipation of nanodevices.

Porous ZnO/2–Hydroxyethyl Methacrylate Eluting Coatings for Ureteral Stent Applications

High-surface-area porous coatings represent an interesting option to fabricate eluting stents with additional functionalities, as controlled drug delivery and antibacterial resistance properties. ZnO is a biocompatible material available in various high-surface-area morphologies, with promising antibacterial properties. Hydrophilic 2-hydroxyethyl methacrylate (HEMA) polymers (pHEMA) have been widely investigated for their biomedical applications, thanks to their biocompatibility, absence of toxicity, and tunable swelling properties. This work aims to demonstrate the use of porous ZnO/polymer bilayer coatings for future drug eluting stent applications. Sputtered mesoporous ZnO layers were coated with pHEMA and p(HEMA-co-acrylic acid (AA)) films through vacuum infiltration and drop-casting methods. The last approach was found to be the most suitable one for achieving a good polymer infiltration within the ZnO matrix and to avoid the mechanical detachment of the porous film from the substrate. The corresponding release properties were evaluated by loading a fluorescent dye in the host ZnO matrix, before drop-casting the polymer coating. For pure ZnO, the release of the dye was completed after 2 h. For ZnO/pHEMA, the sustained release of the molecule was achieved with only 30% released after 2 h and 100% released after seven days. In this case, the pH-triggered delivery properties were also demonstrated by switching from neutral to acidic pH conditions. No significant changes were obtained for the ZnO/p(HEMA-co-AA) system, which exhibited a faster swelling behavior and a release profile similar to pure ZnO.

Study on the technology and performance of 3D-reticulated porous SiC/Fe composite material

ABSTRACT3D-reticulated porous (3D-RP) SiC ceramic was fabricated by polymer sponge replica technique with SiC ceramic slurry (77 wt% solid content). Furthermore, pure alumina slurry and alumina slurry with Y2O3/CeO2 were used to fill up the triangle hollows in coated sponge by vacuum infiltration method respectively. The results show that the compressive strength of 3D-RP SiC ceramic, infiltrated by the alumina slurry or alumina slurry with Y2O3/CeO2, was significantly improved in comparison with those of non-infiltrated ones. Subsequently, 3D-RP SiC/Fe composite material was prepared successfully by casting technique. The microstructure and abrasive resistance of 3D-RP SiC/Fe composite materials based on the different 3D-RP SiC ceramics were discussed in detail. The results show that an excellent interface bonding between 3D-RP SiC ceramic and iron matrix formed and intermediate products not measured in the interface. Moreover, the abrasive resistance of SiC/Fe composite material, especially, 3D-RP SiC ceramics with addition of Y2O3/CeO2 and Ni respectively, is observably superior to that of gray cast iron. The wear mechanism of 3D-RP SiC/Fe composite material is predominantly oxidative wear and adhesive wear, together with partial abrasive wear if under a high load.