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Optimization of adhesive conditions for neural differentiation of murine embryonic stem cells using hydrogels functionalized with continuous Ile-Lys-Val-Ala-Val concentration gradients

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ACTA BIOMATERIALIA 2015年 21卷 55-62页

作者： Yang, Yueh-Hsun Khan, Zara Ma, Cheng Lim, Hyun Ju Callahan, Laura A. Smith Univ Texas Med Sch Houston Vivian L Smith Dept Neurosurg Houston TX USA Univ Texas Brown Fdn Inst Mol Med Ctr Stem Cell & Regenerat Med Houston TX USA Univ Texas Hlth Sci Ctr Houston Dept Nanomed & Biomed Engn Houston TX 77030 USA Univ Texas Hlth Sci Ctr Houston Grad Sch Biomed Sci Houston TX 77030 USA

Stem cell therapies, which aim to restore neurological function after central nervous system injury, have shown increased efficacy when a tissue engineering matrix is implanted with cells compared to implantation of the cells alone. However, much work still needs to be done to characterize materials that can be used to facilitate and direct the differentiation of implanted cells. In the current study, polyethylene glycol hydrogels functionalized with continuous Ile-Lys-Val-Ala-Val (IKVAV) concentration gradients were fabricated and utilized to systematically study and optimize the adhesive conditions for neural differentiation of mouse embryonic stem cells in two- and three-dimensional environments. The results suggest that 570 mu M and 60 mu M are the optimal IKVAV concentrations for 2D and 3D neural differentiation, respectively, to maximize mRNA expression of neuron-specific markers and neurite extension while minimizing apoptotic activities in cultured cells compared to those exposed to higher IKVAV concentrations. The combinatorial approach presented in this work demonstrates that hydrogels functionalized with bioactive peptides provide a defined and tunable platform that can be employed to characterize and improve culture conditions for superior survival, maturation and integration of implanted cells, leading to enhanced restoration of neurological function for those receiving stem cell therapies after traumatic brain and spinal cord injuries. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Neural differentiation Embryonic stem cell Tissue engineering Gradient hydrogel combinatorial methods

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combinatorial synthesis and high-throughput characterization of the thin film materials system Co-Mn-Ge: Composition, structure, and magnetic properties

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PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 2015年第9期212卷 1969-1974页

作者： Salomon, Steffen Hamann, Sven Decker, Peer Savan, Alan Meshi, Louisa Ludwig, Alfred Ruhr Univ Bochum Inst Mat D-44801 Bochum Germany Ben Gurion Univ Negev Dept Mat Engn IL-653 Beer Sheva Israel

Co- Mn-Ge is a system of interest for magnetocaloric applications as a solid state magnetic refrigerant. A thin him materials lihrary COVering a large fraction of the Co Mn Ge ternary composition space as fahricated hy sputter deposition. Alter deposition. it was annealed at 600 degrees C lor 3 h and cmenched subsequently. An energy-dispersive X-ray spectroscopy and X-ray diffraction-based cluster analysis revealed he regions oh existence or he CoMnGe and the Co(2)NinGe single phase (treas. Furthermore. high intensity diffraction peaks revealed the presence oh the hexagonal (Co. Mr)7Ge,, phase in a region that also featured the CoMnGe phase. In this region. a non-linear. symmetric. and hysteretic shin. of the (200) diffraction peak of the (Co. NlnI-Ge,, phase as observed by temperature-dependent X-ray diffraction for CotttMmtGe44. indicating a structural phase transition taking place hemeen 35 and 375 K upon heating and 325 and 300 K Upon cooling. This coincides with a magnetic transition near 325 K from the ferromagnetic to the paramagnetic state. I lowever. no Magnetostructural coupling was identined 111 the temperature range from 330 to 300 K upon coolillg. Magnetostriction and an undetected structural transition of the CoMnGe phase were ruled out as probable causes or the non-linear shifts. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

关键词： combinatorial methods high-throughput magnetocaloric sputter deposition thin films

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Electrodeposition of cobalt-nickel material libraries

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PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 2015年第6期212卷 1216-1222页

作者： Grill, Carina Daniela Kollender, Jan Philipp Hassel, Achim Walter Johannes Kepler Univ Linz Inst Chem Technol Inorgan Mat A-4040 Linz Austria

Cobalt-nickel material libraries were electrodeposited in two different types of modified Hull cells. Chloride and sulphate based electrolyte baths, the influence of the overall applied current density, cobalt concentration in the bath and addition of citrate as complexing agent were studied. The experiments suggested a higher cobalt content in the deposits for relatively low overall applied current densities and higher Co2+ concentrations in the electrolyte bath. For the vast majority of the cobalt-nickel material libraries, a transition from anomalous to normal co-deposition behaviour was found as a result of the current density gradient establishing in the Hull cell during electroplating. Further examination was carried out by scanning electron microscopy (SEM), revealing a changing surface morphology within a material library depending on the cobalt content and the current density. X-ray diffraction (XRD) showed separate and mixed face-centred cubic (fcc) and hexagonal close-packed (hcp) crystallographic structures. Cobalt-nickel composition gradient obtained from two different Hull cell modifications including SEM micrographs of the material library deposited in the lying Hull cell.

关键词： cobalt combinatorial methods electrodeposition electroplating Hull cells nickel

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Controlled facile synthesis and photocatalytic activity of ultrafine high crystallinity TiO₂ nanocrystals with tunable anatase/rutile ratios

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APPLIED SURFACE SCIENCE 2014年 294卷 36-41页

作者： Gao, Yina Wang, Hong Wu, Jie Zhao, Ruohui Lu, Yanfang Xin, Baifu Heilongjiang Univ Minist Educ Key Lab Funct Inorgan Mat Chem Harbin 150080 Peoples R China Heilongjiang Univ Coll Heilongjiang Prov Key Lab Chem Engn Proc & Technol High Efficiency Harbin 150080 Peoples R China Heilongjiang Univ Sch Chem & Mat Sci Harbin 150080 Peoples R China

The superfine high crystallinity TiO2 nanocrystals with tunable anatase/rutile ratios have been synthesized in an ethanol aqueous solution of HCl and sodium dodecylbenzene sulfonate (DBS) by a "low temperature dissolution-reprecipitation process" (LTDRP) and solvethermal treatment composite method. The effect of the synthesis parameters on the crystal structure, crystal size and the photocatalytic properties of the TiO2 nanocrystallines were investigated. The growth and aggregation of TiO2 nanocrystallines can be inhibited, and the high crystallinity spherical nanoparticles with small size are generated in the presence of DBS. The ratios of anatase and rutile can be easily controlled by sample adjusting aging time. The pure phase anatase is obtained by solvethermal treatment without aging process, the contents and the crystallite size of rutile are increased with increase of the aging time and only rutile exists while aging time is 16 h or more. The well-crystallized TiO2 nanocrystals exhibit higher photocatalytic activities. Their high photocatalytic activities could be attributed to high crystallinity, small crystal size (approximately 5 nm for anatase and 8 to 15 nm for rutile), the synergistic effect between anatase and rutile and strong electron-withdrawing characteristic of the sulfoacid radical of DBS. (C) 2014 Published by Elsevier B. V.

关键词： Anatase-rutile combinatorial methods Controlled Synthesis Photocatalysis

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Primary human chondrocyte extracellular matrix formation and phenotype maintenance using RGD-derivatized PEGDM hydrogels possessing a continuous Young's modulus gradient

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ACTA BIOMATERIALIA 2013年第4期9卷 6095-6104页

作者： Callahan, Laura A. Smith Ganios, Anna M. Childers, Erin P. Weiner, Scott D. Becker, Matthew L. Univ Akron Dept Polymer Sci Akron OH 44325 USA Summa Hlth Syst Dept Orthoped Surg Akron OH USA Austen Bioinnovat Inst Akron Ctr Biomat Med Akron OH USA Akron Funct Mat Ctr Akron OH USA

Efficient ex vivo methods for expanding primary human chondrocytes while maintaining the phenotype is critical to advancing the sourcing of autologous cells for tissue engineering applications. While there has been significant research reported in the literature, systematic approaches are necessary to determine and optimize the chemical and mechanical scaffold properties for hyaline cartilage generation using limited cell numbers. Functionalized hydrogels possessing continuous variations in physico-chemical properties are, therefore, an efficient three-dimensional platform for studying several properties simultaneously. Herein we describe a polyethylene glycol dimethacrylate (PEGDM) hydrogel system with a modulus gradient (similar to 27,000-3800 Pa) containing a uniform concentration of arginine-glycine-aspartic acid (RGD) peptide to enhance cell adhesion in order to correlate primary human osteoarthritic chondrocyte proliferation, phenotype maintenance, and extracellular matrix (ECM) production with hydrogel properties. Cell number and chondrogenic phenotype (CD14:CD90 ratios) were found to decline in regions with a higher storage modulus (>13,100 Pa), while regions with a lower storage modulus maintained their cell number and phenotype. Over 3 weeks culture hydrogel regions possessing a lower Young's modulus experienced an increase in ECM content (similar to 200%) compared with regions with a higher storage modulus. Variations in the amount and organization of the cytoskeletal markers actin and vinculin were observed within the modulus gradient, which are indicative of differences in chondrogenic phenotype maintenance and ECM expression. Thus scaffold mechanical properties have a significant impact in modulating human osteoarthritic chondrocyte behavior and tissue formation. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Cartilage Tissue engineering Hydrogel combinatorial methods Gradient

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Combining indentation and diffusion couple techniques for combinatorial discovery of high temperature shape memory alloys

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ACTA MATERIALIA 2013年第15期61卷 5735-5742页

作者： Shastry, V. V. Divya, V. D. Azeem, M. A. Paul, A. Dye, D. Ramamurty, U. Indian Inst Sci Dept Mat Engn Bangalore 560012 Karnataka India Univ London Imperial Coll Sci Technol & Med Dept Mat London SW7 2AZ England King Abdulaziz Univ Ctr Excellence Adv Mat Res Jeddah 21589 Saudi Arabia

We demonstrate the possibility of accelerated identification of potential compositions for high-temperature shape memory alloys (SMAs) through a combinatorial material synthesis and analysis approach, wherein we employ the combination of diffusion couple and indentation techniques. The former was utilized to generate smooth and compositionally graded inter-diffusion zones (IDZs) in the Ni-Ti-Pd ternary alloy system of varying IDZ thickness, depending on the annealing time at high temperature. The IDZs thus produced were then impressed with an indenter with a spherical tip so as to inscribe a predetermined indentation strain. Subsequent annealing of the indented samples at various elevated temperatures, T-a, ranging between 150 and 550 degrees C allows for partial to full relaxation of the strain imposed due to the shape memory effect. If T-a is above the austenite finish temperature, A(f), the relaxation will be complete. By measuring the depth recovery, which serves as a proxy for the shape recovery characteristic of the SMA, a three-dimensional map in the recovery temperature composition space is constructed. A comparison of the published Af data for different compositions with the Ta data shows good agreement when the depth recovery is between 70% and 80%, indicating that the methodology proposed in this paper can be utilized for the identification of promising compositions. Advantages and further possibilities of this methodology are discussed. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Shape memory alloys High temperature Indentation Austenite to martensite phase transformation combinatorial methods

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Maximizing phenotype constraint and extracellular matrix production in primary human chondrocytes using arginine-glycine-aspartate concentration gradient hydrogels

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ACTA BIOMATERIALIA 2013年第7期9卷 7420-7428页

作者： Callahan, Laura A. Smith Childers, Erin P. Bernard, Sharon L. Weiner, Scott D. Becker, Matthew L. Univ Akron Dept Polymer Sci Akron OH 44325 USA Summa Hlth Syst Dept Orthoped Surg Akron OH 44325 USA Austen Bioinnovat Inst Akron Ctr Biomat Med Akron OH 44308 USA

New systematic approaches are necessary to determine and optimize the chemical and mechanical scaffold properties for hyaline cartilage generation using the limited cell numbers obtained from primary human sources. Peptide functionalized hydrogels possessing continuous variations in physico-chemical properties are an efficient three-dimensional platform for studying several properties simultaneously. Herein, we describe a polyethylene glycol dimethacrylate (PEGDM) hydrogel system possessing a gradient of arginine-glycine-aspartic acid peptide (RGD) concentrations from 0 mM to 10 mM. The system is used to correlate primary human osteoarthritic chondrocyte proliferation, phenotype maintenance and extracellular matrix (ECM) production to the gradient hydrogel properties. Cell number and chondrogenic phenotype (CD14:CD90 ratios) were found to decline in regions with higher RGD concentrations, while regions with lower RGD concentrations maintained cell number and phenotype. Over three weeks of culture, hydrogel regions containing lower RGD concentrations experience an increase in ECM content compared to regions with higher RGD concentrations. Variations in actin amounts and vinculin organization were observed within the RGD concentration gradients that contribute to the differences in chondrogenic phenotype maintenance and ECM expression. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Cartilage Tissue engineering Hydrogel combinatorial methods Gradient

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Does a Photocatalytic Synergy in an Anatase-Rutile TiO2 Composite Thin-Film Exist?

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CHEMISTRY-A EUROPEAN JOURNAL 2012年第41期18卷 13048-13058页

作者： Kafizas, Andreas Carmalt, Claire J. Parkin, Ivan P. UCL Dept Chem Mat Chem Res Ctr London WC1H 0AJ England

It has often been suggested that anataserutile mixtures/composites synergistically enhance photocatalysis. However, in the case of dense thin-films containing an intimate mix of both anatase and rutile phases, such an effect has not been observed. In synthesising combinatorial films with graded film thickness and phase, and applying established photocatalytic mapping methods, we were able to assess how dense thin-films of intimately mixed anataserutile mixtures affect photocatalytic performance. We found that no photocatalytic synergy between anataserutile composites (29=rutile?%=83) within such dense thin-film systems exists. In fact, an increased presence of rutile caused the photocatalytic activity to fall. This was explained by the unfavourable energetics in the multiple electron transfers required between several neighbouring rutile and anatase sites for the photo-generated electron to reach the materials surface;encouraging the trapping of electrons within the bulk and increasing the likelihood of charge recombination. The decrease in photocatalytic activity was found to vary linearly with rutile component.

关键词： anatase-rutile composites combinatorial methods photocatalysis materials science thin films

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combinatorial Characterization of Chemiresistive Films Using Microhotplates

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IEEE SENSORS JOURNAL 2012年第5期12卷 1459-1460页

作者： Hertz, Joshua L. Lahr, David L. Semancik, Steve NIST Gaithersburg MD 20899 USA

When producing chemical sensors, especially in thin film form, there are often a large variety of processing variables that are believed to impact the ultimate performance of the materials. It is thus advantageous to find methods for simultaneous, high-throughput characterization of many process variables. Here, we report on a method for using MEMS-based microhotplates to create and characterize arrays of chemiresistive SnO2 thin films. The microhotplates are used both to control the thermal process variables at each element of the array during film growth by CVD as well as subsequently to operate the sensors. Example chemiresistive properties of the films at 200 degrees C were characterized during exposure to CH3OH and NO2. Through the use of a fractional factorial experiment design, the effects of 4 different process variables (growth temperature, thickness, presence of a dopant and use of rapidly pulsed heating during growth) were reliably determined using only 8 films and the associated statistical modeling of the results.

关键词： Chemiresistance combinatorial methods microhotplate tin oxide

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Analysis of effect of high-power amplifier modelling on the performance of orthogonal frequency division multiplexing transceiver for wireless communications

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IET SCIENCE MEASUREMENT & TECHNOLOGY 2012年第3期6卷 159-167页

作者： Madani, M. H. Abdipour, A. Mohammadi, A. Amirkabir Univ Technol Radio Commun Ctr Excellence Dept Elect Engn Microwave Millimetre Wave & Wireless Commun Res L Tehran Iran

This study presents an exact theoretical analysis of performance degradation in OFDM system when the signal including phase noise is passed through a dynamic non-linear circuit such as HPA. The HPA is modelled using a memory polynomial model. The theoretical analysis shows that the detected data symbol at the receiver include common phase error, intersubcarrier interference and intermodulation components. The analytical expressions for intermodulation term are derived using combinatorial methods. Using the derived expressions, a closed form SNR at the output, degradation factor and hence, the probability of error can be evaluated theoretically. The results show that when the OFDM signal with phase noise passes through dynamic non-linear circuit, the phase noise expansion occurs. This expansion is related to the memory length of non-linear device and causes higher degradation in OFDM signal. By use of this exact analysis, designers can choose optimum parameters and operating point of HPA for a desired performance of OFDM transceiver. This reduces energy consumption. To verify the accuracy of the analysis, a comparison between the theoretical and simulated results is presented. The comparison shows that the BER of analytical results closely matches with the simulation results of the OFDM system.

关键词： data symbol orthogonal frequency division multiplexing transceiver Electromagnetic compatibility and interference dynamic nonlinear circuit error probability combinatorial mathematics intersubcarrier interference HPA error statistics phase noise expansion intersymbol interference intermodulation components intermodulation term nonlinear device Modulation and coding methods OFDM modulation OFDM transceiver combinatorial mathematics memory polynomial model OFDM signal power amplifiers wireless communications radio transceivers energy consumption reduction degradation factor common phase error high-power amplifier modelling Radio links and equipment phase noise SNR combinatorial methods radio networks Amplifiers Other topics in statistics

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