Publications

Molecularly Imprinted Intelligent Scaffolds for Tissue Engineering Applications

by Neves, MI; Wechsler, ME; Gomes, ME ; Reis, RL; Granja, PL; Peppas, NA

TISSUE ENGINEERING PART B-REVIEWS; Volume: 23; Issue: 1; Pages: 27-43; DOI: 10.1089/ten.teb.2016.0202; Published: FEB 2017

The development of molecularly imprinted polymers (MIPs) using biocompatible production methods enables the possibility to further exploit this technology for biomedical applications. Tissue engineering (TE) approaches use the knowledge of the wound healing process to design scaffolds capable of modulating cell behavior and promote tissue regeneration. Biomacromolecules bear great interest for TE, together with the established recognition of the extracellular matrix, as an important source of signals to cells, both promoting cell-cell and cell-matrix interactions during the healing process. This review focuses on exploring the potential of protein molecular imprinting to create bioactive scaffolds with molecular recognition for TE applications based on the most recent approaches in the field of molecular imprinting of macromolecules. Considerations regarding essential components of molecular imprinting technology will be addressed for TE purposes. Molecular imprinting of biocompatible hydrogels, namely based on natural polymers, is also reviewed here. Hydrogel scaffolds with molecular memory show great promise for regenerative therapies. The first molecular imprinting studies analyzing cell adhesion report promising results with potential applications for cell culture systems, or biomaterials for implantation with the capability for cell recruitment by selectively adsorbing desired molecules.

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Direct Observation of Poly(Methyl Methacrylate) Removal from a Graphene Surface

by Wang, XH; Dolocan, A; Chou, H; Tao, L; Dick, A; Akinwande, D; Wilison, CG

CHEMISTRY OF MATERIALS; Volume: 29; Issue: 5; Pages: 2033-2039; DOI: 10.1021/acs.chemmater.6b03875; Published: MAR 14 2017

Poly(methyl methacrylate) (PMMA) is commonly used as a temporary support layer for chemical vapor deposition (CVD) graphene transfer; it is then removed by a chemical or thermal treatment. Regardless of the method used for PMMA removal, polymer residues are left on the graphene surface, which alter its intrinsic properties. A method based on isotope labeling of PMMA and time-of-flight secondary ion mass spectrometry (ToF-SIMS) has now been developed to identify, locate, and quantify these residues. It is shown that vacuum annealing does not completely remove the PMMA residues but, instead, transforms them into amorphous carbon. In contrast, air annealing under optimized conditions generates a PMMA-free surface with limited damage to the graphene structure. This cleaned graphene surface demonstrates low friction which is comparable with that of pristine graphene film.

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Using module-based learning methods to introduce sustainable manufacturing in engineering curriculum

by Sengupta, D; Huang, YL ; Davidson, CI ; Edgar, TF; Eden, MR; El-Halwagi, MM

INTERNATIONAL JOURNAL OF SUSTAINABILITY IN HIGHER EDUCATION; Volume: 18; Issue: 3; Pages: 307-328; DOI: 10.1108/IJSHE-05-2015-0100; Published: 2017

Purpose – Sustainable manufacturing may be defined as the creation of manufactured products that use processes that are non-polluting, conserve energy and natural resources, and are economically sound and safe for employees, communities and consumers. Recently, there have been several industrial and governmental endeavors to launch sustainable manufacturing initiatives. To support such initiatives and to prepare the next generation of scientists and engineers, academic institutions have a responsibility to introduce educational programs and tools in the area of sustainable manufacturing. The purpose of this paper is to report on the approach, progress and contributions of a US National Science Foundation-sponsored project titled: “The Sustainable Manufacturing Advances in Research and Technology Coordination Network (SMART CN)”.

Design/methodology/approach – The project aims to bridge the gap between the academic knowledge discovery and industrial technology innovation for sustainable manufacturing. Toward this goal, various research and educational activities have been undertaken to introduce Sustainable Manufacturing Case Studies for use by academic instructors to a diverse group of undergraduate, graduate and industry professionals.

Findings – In this paper, the need for education on sustainable manufacturing has been focused upon, followed by approaches toward addressing these needs, concluding with examples of case studies developed through the SMART-CN project framework.

Originality/value – This work provides the engineering community with structured modules for introducing the topic of sustainable manufacturing in the curriculum.

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Effect of droplet size, droplet placement, and gas dissolution on throughput and defect rate in UV nanoimprint lithography

by Jain, A; Spann, A; Bonnecaze, RT

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B; Volume: 35; Issue: 1; Article Number: 011602; DOI: 10.1116/1.4971771; Published: JAN-FEB 2017

Simulation of multidrop spreading in ultraviolet nanoimprint lithography is performed to study the effects of droplet size, droplet arrangement, droplet placement error, and gas diffusion on filling-time and defects. Simulations are carried out for square, hexagonal, and modified hexagonal arrangements of up to 1024 droplets ink-jetted on a substrate to determine the optimum arrangement for minimum imprint time. The effect of error in droplet placement by the inkjet dispenser on the imprint time for different droplet sizes is also investigated. The square droplet arrangement leads to the shortest fluid filling time for a flat template. The filling time increases significantly for droplet placement errors of more than 0.01% relative to the width of the substrate. A model is presented to study the diffusion of gas encapsulated between droplets into the resist. A dimensionless parameter alpha similar to mu D/k(H)gamma H-o measures the relative importance gas diffusion to hydrodynamics, where D is the gas diffusion constant, k(H) is the Henry’s law constant, mu is the resist viscosity, and gamma is the surface tension of the imprint resist. For small values of alpha, gas diffusion is slower than resist spreading and defect size is diffusion-controlled while for larger values, gas diffusion is faster than resist spreading and the defect size is hydrodynamically controlled. Scaling laws are developed to extrapolate predictions on filling time, residual layer thickness, and defects here for hundreds to a thousand droplets to tens and hundreds of thousands of droplets. (C) 2016 American Vacuum Society.

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Volatility of amines for CO2 capture

by Du, Y; Yuan, Y; Rochelle, GT

INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL; Volume: 58; Pages: 1-9; DOI: 10.1016/j.ijggc.2017.01.001; Published: 2017

Volatility is a critical criterion for amine selection for CO2 capture from low pressure gas streams. The Henry’s law constant (Ham) in water of 24 novel amines, including 18 tertiary amines, 3 hindered amines, 2 ether amines, and 1 pyridine derivative was measured at 40 degrees C using a hot gas FTIR. 14 of them have a Ham less than 2-amino-2-methyl-1-propanol (AMP). A group contribution model that correlates Ham to molecular structure was developed based on the data from this work and data from literature. Non-cyclic groups and cyclic groups have significant effect on the volatility of the amine. The amine partial pressure (P-am) of tertiary and hindered amines was also measured in a blend with PZ at 40 degrees C and their normal CO2 loading range for flue gas CO2 capture. With increased pK(a), the Pam of tertiary and hindered amines becomes a stronger function of CO2 loading. These results at nominal lean loading were correlated with Ham of the amine. (C) 2017 Elsevier Ltd. All rights reserved.

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Effectiveness of absorber intercooling for CO2 absorption from natural gas fired flue gases using monoethanolamine solvent

by Rezazadeh, F; Gale, WF; Rochelle, GT; Sachde, D

INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL; Volume: 58; Pages: 246-255; DOI: 10.1016/j.ijggc.2017.01.016; Published: 2017

Chemical absorption using aqueous amine is one of the most feasible options for post-combustion CO2 capture. One of the main challenges of this technology is its high energy requirements. Absorber intercooling was considered as a viable method to offer benefits in terms of solvent absorption capacity and mass transfer efficiency in CO2 absorption processes. However, the effectiveness of absorber intercooling on overall energy requirements depends on other factors such as lean loading and liquid to gas ratio. This study evaluates the benefits of using two different configurations of absorber intercooling, i.e. in-and-out and recycled intercooling when using 30 wt% aqueous monoethanolamine (MEA) to capture 90% CO2 from a natural gas fired turbine with 4 mol% CO2. The Lean CO2 loading was varied from 0.15 to 0.42 (mol CO2/mol MEA) to determine the lean loading at which the application of intercooling is most significant. Absorber intercooling provides the most benefit at lean loading from 0.30 to 0.34. The use of in-and-out and recycle intercooling at 0.34 lean loading, provided 15.6 and 15.8% reduction in the total equivalent work associated with 32.0% and 36.6% reduction in required packing area when using 1.2 times the minimum liquid flow rate. At lean loading greater than 0.34, the benefit of absorber intercooling is a trade-off between reduction of solvent flow rate and total energy requirement and the drawback of greater packing area in the absorber. The greatest saving in total equivalent work, 17%, was observed at the 0.36 lean loading associated with nearly 60% more packing area when using 1.2 times the minimum solvent flow rate. At very low lean loading and very high lean loading absorber intercooling does not offer significant benefit. (C) 2017 Elsevier Ltd. All rights reserved.

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Development of a P((MAA-co-NVP)-g-EG) Hydrogel Platform for Oral Protein Delivery: Effects of Hydrogel Composition on Environmental Response and Protein Partitioning

by Steichen, S; O'Connor, C; Peppas, NA

MACROMOLECULAR BIOSCIENCE; Volume: 17; Issue: 1; Article Number: UNSP 1600266; DOI: 10.1002/mabi.201600266; Published: JAN 2017

Hydrogels based upon terpolymers of methacrylic acid, N-vinyl pyrrolidone, and poly(ethylene glycol) are developed and characterized for their ability to respond to changes in environmental pH and to partition protein therapeutics of varying molecular weights and isoelectric points. P((MAA-co-NVP)-g-EG) hydrogels are synthesized with PEG-based cross-linking agents of varying length and incorporation densities. The composition is confirmed using FT-IR spectroscopy and shows peak shifts indicating hydrogen bonding. Scanning electron microscopy reveals microparticles with an irregular, planar morphology. The pH-responsive behavior of the hydrogels is confirmed under equilibrium and dynamic conditions, with the hydrogel collapsed at acidic pH and swollen at neutral pH. The ability of the hydrogels to partition model protein therapeutics at varying pH and ionic strength is evaluated using three model proteins: insulin, porcine growth hormone, and ovalbumin. Finally, the microparticles are evaluated for adverse interactions with two model intestinal cell lines and show minimal cytotoxicity at concentrations below 5 mg mL(-1).

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Integrative FourD omics approach profiles the target network of the carbon storage regulatory system

by Sowa, SW; Gelderman, G; Leistra, AN; Buvanendiran, A; Lipp, S; Pitaktong, A; Romeo, T; Baldea, M; Contreras, LM

NUCLEIC ACIDS RESEARCH; Volume: 45; Issue: 4; Pages: 1673-1686; DOI: 10.1093/nar/gkx048; Published: FEB 28 2017

Multi-target regulators represent a largely untapped area for metabolic engineering and anti-bacterial development. These regulators are complex to characterize because they often act at multiple levels, affecting proteins, transcripts and metabolites. Therefore, single omics experiments cannot profile their underlying targets and mechanisms. In this work, we used an Integrative FourD omics approach (INFO) that consists of collecting and analyzing systems data throughout multiple time points, using multiple genetic backgrounds, and multiple omics approaches (transcriptomics, proteomics and high throughput sequencing crosslinking immunoprecipitation) to evaluate simultaneous changes in gene expression after imposing an environmental stress that accentuates the regulatory features of a network. Using this approach, we profiled the targets and potential regulatory mechanisms of a global regulatory system, the well-studied carbon storage regulatory (Csr) system of Escherichia coli, which is widespread among bacteria. Using 126 sets of proteomics and transcriptomics data, we identified 136 potential direct CsrA targets, including 50 novel ones, categorized their behaviors into distinct regulatory patterns, and performed in vivo fluorescence-based follow up experiments. The results of this work validate 17 novel mRNAs as authentic direct CsrA targets and demonstrate a generalizable strategy to integrate multiple lines of omics data to identify a core pool of regulator targets.

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Effect of fixed charge group concentration on equilibrium ion sorption in ion exchange membranes

by Kamcev, J; Paul, DR; Freeman, BD

JOURNAL OF MATERIALS CHEMISTRY A; Volume: 5; Issue: 9; Pages: 4638-4650; DOI: 10.1039/c6ta07954g; Published: 2017

Despite their increasing importance in many energy and water purification applications, few systematic studies of ion sorption in ion exchange membranes exist where fixed charge group concentration and water content are varied independently. Such studies are critical for developing fundamental structure/property relations important for rationally tailoring such materials. Here, cation and anion exchange membranes having different fixed charge group concentrations but similar water content were synthesized to investigate the influence of fixed charge group concentration on equilibrium ion sorption in such materials. Co-ion sorption decreased with increasing membrane fixed charge group concentration, as expected, presumably due to enhanced Donnan exclusion. However, the extent to which co-ion sorption was suppressed was different for the cation and anion exchange membranes, despite similar changes in membrane fixed charge group concentration. A thermodynamic model, based on Donnan theory and Manning’s counter-ion condensation theory, was used to interpret the data. The model predicted equilibrium co-ion concentrations in the anion exchange membranes with no adjustable parameters. However, good agreement between the model and experimental data for the cation exchange membranes was only obtained by treating the Manning parameter as an adjustable constant, presumably due to phase separation during polymerization, which produced inhomogeneous membranes.

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