scholarly journals Development of Nanoporous Ultrathin Membranes For Implantable Drug Delivery

2008 ◽  
Vol 2 (2) ◽  
Author(s):  
Eric E. Nuxoll ◽  
Marc A. Hillmyer ◽  
Ronald A. Siegel
Keyword(s):  
Composite Membrane ◽  
Mechanical Tests ◽  
Plasma Etch ◽  
Molecule Transport ◽  
Etch Stop ◽  
Bottom Side ◽  
Oxygen Plasma Etch ◽  
Small Molecule Transport ◽  
Physiological Sensing ◽  
Ultrathin Membranes

For drug release or physiological sensing with advanced functionality, an implanted device must have an interface that permits passage of drugs or analytes while blocking immunoproteins and other physiological fouling agents. To this end, we have developed a composite membrane which integrates the nanoscale size selectivity of block-copolymers with the mechanical strength and order of micromachined silicon. A silicon wafer was coated with low-stress silicon nitride (LSN) and patterned with 20μm squares on the bottom side by photolithography. These squares were etched through the underlying silicon, using the LSN on the top side as an etch-stop. Poly(styrene)-poly(isoprene)-poly(lactide) (PS-PI-PLA) triblock terpolymer was spin-coated onto the top-side LSN surface and annealed under vacuum. The PLA domains self-assembled into cylinders perpendicular to the coating, nearly spanning it. The PLA was etched away, leaving 40nm pores in the polymer film. The device was subjected to hydrofluoric acid to remove the LSN capping the microscale pores and a final, brief oxygen plasma etch removed any PS capping the nanoscale pores. The resulting composite membrane consists of a 80nm thick PS layer with 40nm wide pores overlaying a 100μm thick silicon support with 20μm wide pores. Preliminary mechanical tests have demonstrated the membrane’s robustness. Such membranes should provide immuno-isolation without retarding small molecule transport and should integrate well with the burgeoning number of BioMEMS devices under development.

scholarly journals Multi-Scale Modeling of Aqueous-Phase Methane Diffusion in Silicate Channels

2021 ◽  
Author(s):  
Tom Pace ◽  
Hadi Rahmaninejad ◽  
Bin Sun ◽  
Peter Kekenes-Huskey
Keyword(s):  
Molecular Dynamics ◽  
Multi Scale ◽  
Relative Contribution ◽  
Kinetic Information ◽  
Two Factors ◽  
Molecule Transport ◽  
Potentials Of Mean Force ◽  
Methane Diffusion ◽  
Dynamics Simulations ◽  
Small Molecule Transport

Silica-based materials including zeolites are commonly used for wide ranging applications including separations and catalysis.<br>Substrate transport rates in these materials often significantly influence the efficiency of such applications.<br>Two factors that contribute to transport rates include<br>1) the porosity of the silicate matrix and<br>2) non-bonding interactions between the diffusing species and the silicate surface.<br>Here, we utilize computer simulation to resolve the relative contribution of these factors to effective methane transport rates in a silicate channel.<br>Specifically, we develop a `homogenized' model of methane transport valid at micron and longer length scales that incorporates atomistic-scale kinetic information.<br>The atomistic-scale data are obtained from extensive molecular dynamics simulations that yield local diffusion coefficients and potentials of mean force.<br>With this model, we demonstrate how nuances in silicate hydration and silica/methane interactions impact 'macroscale' methane diffusion rates in bulk silicate materials.<br>This hybrid homogenization/molecular dynamics approach will be of general use for describing small molecule transport in materials with detailed molecular interactions.<br><br>

Preparation and characterization of crosslinked poly(vinylimidazolium) anion exchange membranes for artificial photosynthesis

2019 ◽  
Vol 7 (41) ◽  
pp. 23818-23829 ◽  
Author(s):  
Blaine M. Carter ◽  
Laura Keller ◽  
Matthias Wessling ◽  
Daniel J. Miller
Keyword(s):  
Ionic Conductivity ◽  
Ion Exchange ◽  
Water Content ◽  
Small Molecule ◽  
Artificial Photosynthesis ◽  
Anion Exchange Membranes ◽  
Molecule Transport ◽  
Small Molecule Transport ◽  
Low Alcohol

The dependence of small molecule transport on the water content of ion exchange materials frustrates the development of membranes with both high ionic conductivity and low alcohol permeability for artificial photosynthesis devices.

Low k Film Etch in Applied Materials eMxP+ Chamber

1998 ◽  
Vol 544 ◽  
Author(s):  
Melissa Yu ◽  
Hongching Shan ◽  
Ashley Taylor
Keyword(s):  
Dielectric Constant ◽  
Etch Rate ◽  
Process Conditions ◽  
Plasma Etch ◽  
Absolute Value ◽  
Lower Dielectric Constant ◽  
Profile Control ◽  
Etch Stop ◽  
Anisotropic Etch ◽  
Low K

ABSTRACTThe materials with lower dielectric constant ( low k ) have been attracting attention recently because the low k material has the potential to be used in place of SiO2 in ULSI. In this work, we focused on evaluating organic low k material performance with plasma etch in the Applied Material's eMxP+ anisotropic etch chamber. The films studied were Dow Chemical BCB and Silk, Allied Signal Flare 2.0, and Du Pont FPI. The feature sizes of the wafer s were 0.25 to 1 micron trenches. Du Pont FPI resulted in the highest achieved etch rate of more than lum/min, followed by BCB, and Flare. The microloading study indicated that the etch rate microloading is less than 10% between lum and 0.25 urn feature sizes, which suggests that the chance of etch stop for a high aspect ratio features will be small. The profile could vary from bowing to vertical, to tapering by using different process conditions, mainly by temperature. The FP1 profile was more tapered than those of BCB and Flare when the same process was used to etch the same type of patterned wafer having these three different low k films. The detailed study showed that the trend of etch rate and profile for BCB and Flare film etch were similar, but that the absolute value for profile, as well as the trend of etch rate uniformity and profile were somewhat different. In conclusion, low k materials can be etched in AMAT traditional dielectric chamber (eMxP+) with a good etch rate and profile control.

scholarly journals Quantitative Small Molecule Transport after Nanosecond Electric Field Exposures - Experiments and Models

2017 ◽  
Vol 112 (3) ◽  
pp. 219a
Author(s):  
Esin B. Sözer ◽  
C. Florencia Pocetti ◽  
Zachary A. Levine ◽  
P. Thomas Vernier
Keyword(s):  
Electric Field ◽  
Small Molecule ◽  
Molecule Transport ◽  
Small Molecule Transport

scholarly journals Synthetic auxotrophy remains stable after continuous evolution and in co-culture with mammalian cells

2020 ◽  
Author(s):  
Aditya M. Kunjapur ◽  
Michael G. Napolitano ◽  
Eriona Hysolli ◽  
Karen Noguera ◽  
Evan M. Appleton ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Culture ◽  
Mammalian Cell ◽  
Mammalian Cells ◽  
Mammalian Cell Culture ◽  
Normal Growth ◽  
Evolutionary Stability ◽  
Continuous Evolution ◽  
Molecule Transport ◽  
Small Molecule Transport

AbstractUnderstanding the evolutionary stability and possible context-dependence of biological containment techniques is critical as engineered microbes are increasingly under consideration for applications beyond biomanufacturing. While batch cultures of synthetic auxotrophic Escherichia coli previously exhibited undetectable escape throughout 14 days of monitoring, the long-term effectiveness of synthetic auxotrophy is unknown. Here, we report automated continuous evolution of a synthetic auxotroph using custom chemostats that supply a decreasing concentration of essential biphenylalanine (BipA). After 100 days of evolution in three separate trials, populations exhibit no observable escape and are capable of normal growth rates at 10-fold lower BipA concentration than the ancestral synthetic auxotroph. Allelic reconstruction of three proteins implicated in small molecule transport reveals their contribution to increased fitness at low BipA concentrations. Mutations do not appear in orthogonal translation machinery nor in synthetic auxotrophic markers. Based on its evolutionary stability, we introduce the progenitor synthetic auxotroph directly to mammalian cell culture. We observe containment of bacteria without detrimental effects on HEK293T cells. Overall, our findings reveal that synthetic auxotrophy is effective on timescales and in contexts that enable diverse applications.One Sentence SummaryTo ascertain whether life inevitably finds a way, we continuously evolve an Escherichia coli strain that was not able to escape from engineered biocontainment before, and we find that it does not escape even after 100 days of evolution, nor does it escape when added to mammalian cell culture.

scholarly journals Depletion of a Toxoplasma porin leads to defects in mitochondrial morphology and contacts with the ER

2021 ◽  
Author(s):  
Natalia Mallo ◽  
Jana Ovciarikova ◽  
Erica S. Martins-Duarte ◽  
Stephan C. Baehr ◽  
Marco Biddau ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Protein Import ◽  
Morphological Changes ◽  
Anion Channel ◽  
Multiple Roles ◽  
Mitochondrial Morphology ◽  
Voltage Dependent Anion Channel ◽  
Voltage Dependent ◽  
Molecule Transport ◽  
Small Molecule Transport

The Voltage Dependent Anion channel (VDAC) is a ubiquitous channel in the outer membrane of the mitochondrion with multiple roles in protein, metabolite and small molecule transport. In mammalian cells, VDAC, as part of a larger complex including the inositol triphosphate receptor, has been shown to have a role in mediating contacts between the mitochondria and endoplasmic reticulum (ER). We identify VDAC of the pathogenic apicomplexan Toxoplasma gondii and demonstrate its importance for parasite growth. We show that VDAC is involved in protein import and metabolite transfer to mitochondria. Further, depletion of VDAC resulted in significant morphological changes of the mitochondrion and ER, suggesting a role in mediating contacts between these organelles in T. gondii.

scholarly journals Intervertebral Disc Degeneration Is Associated With Aberrant Endplate Remodeling and Reduced Small Molecule Transport

2020 ◽  
Vol 35 (8) ◽  
pp. 1572-1581 ◽  
Author(s):  
Beth G Ashinsky ◽  
Edward D Bonnevie ◽  
Sai A Mandalapu ◽  
Stephen Pickup ◽  
Chao Wang ◽  
...  
Keyword(s):  
Intervertebral Disc ◽  
Disc Degeneration ◽  
Small Molecule ◽  
Intervertebral Disc Degeneration ◽  
Molecule Transport ◽  
Small Molecule Transport

scholarly journals Rapid toxin sequestration modifies poison frog physiology

2021 ◽  
pp. jeb.230342
Author(s):  
Lauren A. O'Connell ◽  
Jeremy D. O'Connell ◽  
Joao A. Paulo ◽  
Sunia A. Trauger ◽  
Steven P. Gygi ◽  
...  
Keyword(s):  
Small Molecule ◽  
Chemical Defenses ◽  
Protein Abundance ◽  
Poison Frog ◽  
Poison Frogs ◽  
Toxin Binding ◽  
Physiological Adaptations ◽  
Molecule Transport ◽  
Protein Classes ◽  
Small Molecule Transport

Poison frogs sequester chemical defenses from their diet of leaf litter arthropods for defense against predation. Little is known about the physiological adaptations that confer this unusual bioaccumulation ability. We conducted an alkaloid-feeding experiment with the Diablito poison frog (Oophaga sylvatica) to determine how quickly alkaloids are accumulated and how toxins modify frog physiology using quantitative proteomics. Diablito frogs rapidly accumulated the alkaloid decahydroquinoline within four days, and dietary alkaloid exposure altered protein abundance in the intestines, liver, and skin. Many proteins that increased in abundance with decahydroquinoline accumulation are plasma glycoproteins, including the complement system and the toxin-binding protein saxiphilin. Other protein classes that change in abundance with decahydroquinoline accumulation are membrane proteins involved in small molecule transport and metabolism. Overall, this work shows poison frogs can rapidly accumulate alkaloids, which alter carrier protein abundance, initiate an immune response, and alter small molecule transport and metabolism dynamics across tissues.

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