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Macroporous and nanometre scale fibrous PLA and PLA-HA composite scaffolds fabricated by a bio safe strategy

RSC ADVANCES 2014年第106期4卷 61491-61502页

作者： Salerno, Aurelio Fernandez-Gutierrez, Mar Roman del Barrio, Julio San Domingo Pascual, Concepcion CSIC ICMAB Inst Mat Sci Barcelona Bellaterra 08193 Spain CSIC Inst Polymer Sci & Technol E-28006 Madrid Spain CIBER BBN Hlth Inst Carlos III Zaragoza Spain

The present study deals with the design, fabrication and characterization of porous scaffolds for tissue engineering made of polylactic acid (PLA) and PLA containing hydroxyapatite (HA) nanoparticles. The main novelty relies on the fact that the fabrication of the scaffolds has been achieved avoiding totally the use of toxic chemicals. In particular, the scaffolds are obtained by combining both thermal induced phase separation (TIPS) using ethyl lactate (EL) solutions and supercritical CO2 (scCO(2)) drying processes. Furthermore, gelatin particles have been used as a leachable porogen and combined with the previous processes to improve the control of the pore structure features of the scaffolds. The results show that the developed technique allows for the fabrication of porous PLA scaffolds with HA concentrations up to 30 wt%. Furthermore, these scaffolds are characterized by an overall porosity as high as 98% and a double scale pore structure. In particular, the appropriate control of the TIPS process and the scCO(2) drying allowed for the development of nanoscale fibrous PLA and PLA-HA structures starting from PLA/EL solutions. Concomitantly, the proper selection of the size range of gelatin particles as well as their spatial distribution in the mixture allowed imprinting an interconnected network of large pores inside the scaffolds.

关键词： programmable logic arrays fabrication Online resources THERMALLY INDUCED PHASE SEPARATION Structural properties Toxic chemicals Nanometers Porous size range Tissue Engineering Pore structure

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Load Sharing Strategy for Autonomous AC Microgrids Based on FPGA Implementation of ADALINE&FLL

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IEEE TRANSACTIONS ON ENERGY CONVERSION 2014年第3期29卷 663-672页

作者： Guzman, Cristina Cardenas, Alben Agbossou, Kodjo Univ Quebec Trois Rivieres Hydrogen Res Inst Trois Rivieres PQ G9A 5H7 Canada Univ Quebec Trois Rivieres Dept Genie Elect & Genie Informat Trois Rivieres PQ G9A 5H7 Canada

Paralleled operation of voltage-source inverters (VSIs) is currently achieved by using voltage/frequency droop control techniques which requires the knowledge of the system parameters. Otherwise, centralized control techniques with robust communication among VSIs controllers are also used. This paper presents a new control strategy which allows the load sharing between the power sources of an ac microgrid without centralized controller or any communication among the VSIs;only local measurements of voltage and output current are used. The dispatchable sources (e.g., fuel cells) of the microgrid are operated using voltage control with a direct droop scheme, and the nondispatchables or intermittent ones (e.g., wind turbine generators) are operated using power control with a complementary inverse droop scheme (D-Droop + I-Droop). The number of operating sources can be changed online without any modification needed on the VSI controllers. The proposed VSI controllers are based on the variable frequency adaptive linear neuron with frequency-locked loop for the VSIs system synchronization, voltage/power and signal estimation. Experimental results using field-programmable gate array devices for the implementation of each VSI control in themicrogrid test bench demonstrated the validity of the proposition.

关键词： Distributed power generation frequency-locked loops neural networks power generation control programmable logic arrays smart grids very large scale integration voltage control

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Melt Rheological Investigation of Polylactide-Nanographite Platelets Biopolymer Composites

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POLYMER ENGINEERING AND SCIENCE 2014年第1期54卷 175-188页

作者： Narimissa, Esmaeil Gupta, Rahul K. Kao, Nhol Choi, Hyoung J. Jollands, Margaret Bhattacharya, Sati N. RMIT Univ RMPC Sch Civil Environm & Chem Engn Melbourne Vic 3000 Australia Inha Univ Dept Polymer Sci & Engn Inchon 402751 South Korea

This study is an analytical investigation of processability of biopolymer-carbon based nanofiller composites primarily through rheological investigation of samples. The composites were fabricated via dry mixing and melt-blending of biodegradable polylactide (PLA) and nanographite platelets (NGP) in a Brabender twin screw extruder. A range of different nanofiller contents (1, 3, 5, 7, and 10 wt %) were studied for NGP containing composites. The morphology was studied with X-ray diffraction and transmission electron microscopy techniques and showed poor dispersion, with agglomerates, tactoids, and exfoliated layers present. Mechanical properties showed an optimum at 3 wt % filler. Results showed that the composites exhibited higher elastic and viscous moduli than neat PLA. The rheological percolation threshold predicted by changes in slope () as well as liquid-solid transition theory of samples was found around 3 wt % through the change from liquid-like behavior to pseudo-solid-like behavior at terminal region during dynamic oscillatory measurements. NGP nanofillers were found to enhance the viscoelastic and mechanical properties of PLA at low concentrations;however, an efficient dispersion of nanofillers within polymer by melt intercalation method of mixing was not achieved. POLYM. ENG. SCI., 54:175-188, 2014. (c) 2013 Society of Plastics Engineers

关键词： Composites programmable logic arrays NORTH GALACTIC POLE dry mixing Blood Platelets Transmission electron microscopy NANOFILLER Biopolymers Mechanical properties

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Structure and blood compatibility of highly oriented PLA/MWNTs composites produced by solid hot drawing

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JOURNAL OF BIOMATERIALS APPLICATIONS 2014年第7期28卷 978-989页

作者： Li, Zhengqiu Zhao, Xiaowen Ye, Lin Coates, Phil Caton-Rose, Fin Martyn, Michasel Sichuan Univ Polymer Res Inst State Key Lab Polymer Mat Engn China Chengdu 610064 Peoples R China Univ Bradford Sch Engn Design & Technol Bradford BD7 1DP W Yorkshire England

Highly oriented poly(lactic acid) (PLA)/multi-walled carbon nanotubes (MWNTs) composites were fabricated through solid hot drawing technology in an effort to improve the mechanical properties and blood biocompatibility of PLA as blood-contacting medical devices. It was found that proper MWNTs content and drawing orientation can improve the tensile strength and modulus of PLA dramatically. With the increase in draw ratio, the cold crystallization peak became smaller, and the glass transition and the melting peak of PLA moved to high temperature, while the crystallinity increased, and the grain size decreased, indicating the stress-induced crystallization of PLA during drawing. MWNTs showed a nucleation effect on PLA, leading to the rise in the melting temperature, increase in crystallinity and reduction of spherulite size for the composites. Moreover, the intensity of (002) diffraction of MWNTs increased with draw ratio, indicating that MWNTs were preferentially aligned and oriented during drawing. Microstructure observation demonstrated that PLA matrix had an ordered fibrillar bundle structure, and MWNTs in the composite tended to align parallel to the drawing direction. In addition, the dispersion of MWNTs in PLA was also improved by orientation. Introduction of MWNTs and drawing orientation could significantly enhance the blood compatibility of PLA by prolonging kinetic clotting time, reducing hemolysis ratio and platelet activation.

关键词： blood compatibility composites mechanical properties multi-walled carbon nanotubes orientation Poly (lactic acid) solid hot drawing Multi-Walled Nanotube Composites programmable logic arrays blood compatibility Crystallinity poly(lactic acid) Mechanical properties

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Biorenewable Blends of Polyamide-11 and Polylactide

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POLYMER ENGINEERING AND SCIENCE 2014年第7期54卷 1523-1532页

作者： Patel, Rakhi Ruehle, David A. Dorgan, John R. Halley, Peter Martin, Darren Colorado Sch Mines Dept Chem & Biol Engn Golden CO 80401 USA Univ Queensland Australian Inst Bioengn & Nanotechnol Sch Chem Engn Brisbane Qld 4072 Australia

Polyamide-11(PA11) is melt blended with polylactide (PLA) using 0.00 to 0.10 wt% titanium isopropoxide catalyst to investigate potential compatibilizing reactions. Blend properties are characterized by differential scanning calorimetry (DSC), thermogravimetric analysis, dynamic mechanical thermal analysis, and tensile and impact testing. DSC shows two separate glass transition temperatures indicating only partial miscibility. Base etching to remove PLA domains followed by field emission scanning electron microscopy confirms the two phase nature of the blends. Storage and tensile moduli of the blends increase monotonically with increasing PLA content. Interchange reactions during reactive mixing were investigated by 13 degrees C-NMR spectroscopy but the analysis shows little evidence of interchange reactions. This is true irrespective of catalyst level and mixing time over the temperature range from 185 degrees C to 225 degrees C. At the upper end of the temperature range investigated, significant degradation is observed. The combined results indicate that degradation reactions dominate over compatibilizing interchain transreactions. (C) 2013 Society of Plastics Engineers

关键词： programmable logic arrays CAPACITY EXPANSION MIXING TIME Exchange reaction Blends Differential scanning calorimetry Polylactides glass transition temperature TEMPERATURE RANGE field emission scanning electron microscopy nuclear magnetic resonance spectroscopy

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Preparation and performance evaluation of castor oil-based polyurethane prepolymer/polylactide blends

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JOURNAL OF MATERIALS SCIENCE 2014年第23期49卷 8016-8030页

作者： Gurunathan, T. Mohanty, Smita Nayak, Sanjay K. Cent Inst Plast Engn & Technol ARSTPS Madras 600032 Tamil Nadu India Cent Inst Plast Engn & Technol LARPM Bhubaneswar 751024 Orissa India

Polylactide (PLA) is an important biodegradable polymer, used for numerous applications ranging from industrial packaging to tissue engineering. However, its inherent brittleness and limited thermal stability have restricted its penetration to niche markets. In this communication, the authors demonstrate that blending of PLA with castor oil-based polyurethane prepolymer (COPUP), with the addition of COPUP, dispersed in the PLA matrix can overcome the inherent brittleness of the matrix polymer. NCO-terminated COPUP was successfully synthesized and subsequently mixed with variable concentration of PLA matrix using melt blending technique. The interfacial compatibilization between COPUP and PLA phase happened by the reaction of -NCO groups with terminal hydroxyl groups of PLA was confirmed by FT-IR peak deconvolution technique. As indicated by the results of DMA and DSC, the glass transition temperature (T (g)) of both PLA and COPUP shifted closer together, indicating that the blend compatibility increased. The tensile properties and notched Izod impact strength of the PLA and toughened PLA are also investigated. With the addition of 30 % COPUP concentration, the elongation at break of the blend reached 377.46 %, and a notched Izod impact 269.62 J m(-1). With improved toughness, the PLA/COPUP blends could be used as replacements for some traditional petroleum-based polymers.

关键词： COPUP PLA FT-IR programmable logic arrays industrial packaging preparation Performance Evaluation IZOD-IMPACT STRENGTH

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Formulation- Properties Versatility of Wood Fiber Biocomposites Based on Polylactide and Polylactide/ Thermoplastic Starch Blends

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POLYMER ENGINEERING AND SCIENCE 2014年第6期54卷 1325-1340页

作者： Mihai, Mihaela Legros, Nathalie Alemdar, Ayse Natl Res Council Canada Quebec City PQ J4B 6Y4 Canada FPInnovat Wood Biomat Dept Quebec City PQ G1P 4R4 Canada

This article discusses the interrelation between formulation, processing, and properties of biocomposites composed of a bioplastic reinforced with wood fibers. Polylactide (PLA) and polylactide/thermoplastic starch blends (PLA/TPS) were used as polymeric matrices. Two grades of PLA, an amorphous and a semicrystalline one, were studied. TPS content in the PLA/TPS blends was set at 30, 50, and 70 wt%. Two types of wood fiber were selected, a hardwood (HW) and a softwood (SW), to investigate the effect of the fiber type on the biocomposite properties. Finally, the impact of different additives on biocomposite properties was studied with the purpose to enhance the bioplastic/wood fiber adhesion and, therefore, the final mechanical performance. The biocomposites containing 30 wt% of wood fibers were obtained by twin-screw extrusion. The properties of the biocomposites are described in terms of morphology, thermal, rheological, and mechanical properties. Furthermore, the biocomposites were tested for humidity and water absorption and biodegradability. An almost 100% increase in elastic modulus and 25% in tensile strength were observed for PLA/wood fiber biocomposite with the best compatibilization strategy used. The presence of the TPS in the biocomposites at 30 and 50 wt% maintained the tensile strength higher or at least equal as for the virgin PLA. These superior tensile results were due to the inherent affinity between the matrices and wood fibers improved by the addition of a combination of coupling and a branching agent. In addition to their outstanding mechanical performance, the biocomposites showed high biodegradation within 60 days. POLYM. ENG. SCI., 54:1325-1340, 2014. (c) Her Majesty the Queen in Right of Canada 2013

关键词： Wood fibres Fiber programmable logic arrays Blends BIOCOMPOSITE Polylactides Tensile Strength transaction processing system

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An unnatural amino acid based fluorescent probe for phenylalanine ammonia lyase

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ORGANIC & BIOMOLECULAR CHEMISTRY 2014年第31期12卷 5818-5821页

作者： Tian, Zhenlin Zhu, Weiping Xu, Yufang Qian, Xuhong E China Univ Sci & Technol Sch Pharm Shanghai Key Lab Chem Biol State Key Lab Bioreactor Engn Shanghai 200237 Peoples R China

A fluorescent probe (2a-LP) based on an unnatural amino acid (UAA) is developed for the detection of phenylalanine ammonia lyase (PAL). In the presence of PAL, 2a-LP is catalytically deaminated to ortho-amino-transcinnamic acid (o-a-CA), which shows a remarkable "off-on" fluorescence signal Thus, the probe 2a-LP enables direct visualization of the PAL activity in tomato under UV illumination and has potential in vitro assays.

关键词： unnatural fluorescent lyase SHCBP1 gene programmable logic arrays Phenylalanine Ammonia-Lyase utilised agricultural area Lyases LRIT1 gene Fluorescence

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Biodegradability of Nonwoven Flax Fiber Reinforced Polylactic Acid Biocomposites

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POLYMER COMPOSITES 2014年第11期35卷 2094-2102页

作者： Alimuzzaman, Shah Gong, R. H. Akonda, Mahmudul Univ Manchester Sch Mat Manchester M13 9PL Lancs England Tilsatec Ltd Tilsatec Adv Mat Wakefield England

Biocomposites of flax reinforced polylactic acid (PLA) were made using a new technique incorporating an air-laying nonwoven process. PLA and flax fibers were mixed and converted to the webs in the air-laying process. Prepregs were then made from the fiber webs by thermal consolidation. The prepregs were finally converted to composites by compression molding. This study was investigated the biodegradability and water absorption properties of the composites. The composites were incubated in compost under controlled conditions. The percentage weight loss and the reduction in mechanical properties of PLA and biocomposites were determined at different time intervals. It was found that with increasing flax content, the mechanical properties of the biocomposites decreased more during the burial trial. The increasing of flax content led to the acceleration of weight loss due to preferential degradation of flax. This was further confirmed by the surface morphology of the biodegraded composites from scanning electron microscope image analysis. Morphological observations indicated severe disruption of biocomposites structure between 60 and 120 days of incubation. (C) 2014 Society of Plastics Engineers

关键词： Composites Time intervals programmable logic arrays Prepregs Flax BIOCOMPOSITE Surface morphology biodegradability fiber flax poly(lactic acid) Mechanical properties

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Biodegradable nanoparticles composed of enantiomeric poly(γ-glutamic acid)-graft-poly(lactide) copolymers as vaccine carriers for dominant induction of cellular immunity

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BIOMATERIALS SCIENCE 2014年第4期2卷 530-537页

作者： Akagi, Takami Zhu, Ye Shima, Fumiaki Akashi, Mitsuru Osaka Univ Grad Sch Engn Dept Appl Chem Suita Osaka 5650871 Japan

The design of particulate materials with controlled degradation at desired sites is important in applications for drug/vaccine/gene delivery systems. Amphiphilic biodegradable polymeric nanoparticles are promising vaccine delivery carriers due to their ability to stably maintain antigens, provide tailored release kinetics, effectively target, and function as adjuvants. In this study, we report that stereocomplex nanoparticles (SC NPs) composed of enantiomeric poly(gamma-glutamic acid)-graft-poly(lactide) (gamma-PGA-PLA) copolymers are excellent protein delivery carriers for vaccines that can deliver antigenic proteins to dendritic cells (DCs) and elicit potent immune responses. We prepared ovalbumin (OVA)-encapsulated gamma-PGA-PLA SC NPs (OVA-SC NPs) and isomer NPs. These NPs were efficiently taken up by DCs and also affected the intracellular degradation of the encapsulated OVA. The degradation of OVA encapsulated into the SC NPs was attenuated as compared to free OVA and the corresponding isomer NPs. Interestingly, immunization with OVA-SC NPs predominantly induced antigen-specific cellular immunity. The crystalline structure of inner NPs consisting of PLA had a significant impact on the degradation profiles of NPs and the release/degradation behavior of encapsulated antigens and thus the efficiency of immune induction. Our findings suggest that the.-PGA-PLA SC NPs are suitable for protein-based vaccines that are used to induce cellular immunity, such as for infectious diseases, cancer, allergies and autoimmune diseases.

关键词： Ovum programmable logic arrays Encapsulated Mass Scandium antigens Cellular Immunity Vaccines particulate materials Autoimmune Disease

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