4 Generation of pH gradients

Berkelman, Tom

doi:10.1016/s0149-6395(05)80007-8

Cited by 5 publications

(5 citation statements)

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“…While DC electrolysis will, by definition, generate large pH changes between the cathode and anode, proposed DC implantable technologies mitigate this by reversing electrolytic reactions via charge balancing the metal electrodes (Fridman and Della Santina, 2013a) or by chemically and physically buffering the electrode/tissue interface (Ackermann et al, 2011). Ionic DC delivery could still influence pH at the microfluidic/tissue interface as sustained ionic current acts as an ion pump that over time might change the H + /OH − concentrations at the tissue/device interface, and a locally sustained electric field can create a pH gradient even in the absence of electrolysis (Macounová et al, 2000; Berkelman, 2005). Given that these effects have historically been masked by pH changes from DC electrolysis there has not yet been an exploration of their significance in-vivo .…”

Section: Non-metal-electrode Based DC Safety Considerationsmentioning

confidence: 99%

Implantable Direct Current Neural Modulation: Theory, Feasibility, and Efficacy

Aplin

Fridman

2019

Front. Neurosci.

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Implantable neuroprostheses such as cochlear implants, deep brain stimulators, spinal cord stimulators, and retinal implants use charge-balanced alternating current (AC) pulses to recover delivered charge and thus mitigate toxicity from electrochemical reactions occurring at the metal-tissue interface. At low pulse rates, these short duration pulses have the effect of evoking spikes in neural tissue in a phase-locked fashion. When the therapeutic goal is to suppress neural activity, implants typically work indirectly by delivering excitation to populations of neurons that then inhibit the target neurons, or by delivering very high pulse rates that suffer from a number of undesirable side effects. Direct current (DC) neural modulation is an alternative methodology that can directly modulate extracellular membrane potential. This neuromodulation paradigm can excite or inhibit neurons in a graded fashion while maintaining their stochastic firing patterns. DC can also sensitize or desensitize neurons to input. When applied to a population of neurons, DC can modulate synaptic connectivity. Because DC delivered to metal electrodes inherently violates safe charge injection criteria, its use has not been explored for practical applicability of DC-based neural implants. Recently, several new technologies and strategies have been proposed that address this safety criteria and deliver ionic-based direct current (iDC). This, along with the increased understanding of the mechanisms behind the transcutaneous DC-based modulation of neural targets, has caused a resurgence of interest in the interaction between iDC and neural tissue both in the central and the peripheral nervous system. In this review we assess the feasibility of in-vivo iDC delivery as a form of neural modulation. We present the current understanding of DC/neural interaction. We explore the different design methodologies and technologies that attempt to safely deliver iDC to neural tissue and assess the scope of application for direct current modulation as a form of neuroprosthetic treatment in disease. Finally, we examine the safety implications of long duration iDC delivery. We conclude that DC-based neural implants are a promising new modulation technology that could benefit from further chronic safety assessments and a better understanding of the basic biological and biophysical mechanisms that underpin DC-mediated neural modulation.

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Section: Non-metal-electrode Based DC Safety Considerationsmentioning

confidence: 99%

Implantable Direct Current Neural Modulation: Theory, Feasibility, and Efficacy

Aplin

Fridman

2019

Front. Neurosci.

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“…The reader is referred to excellent reviews for further details. 71 − 74 Our approach of using only cellulose hydrogels along with buffers is presented in the next section.…”

Section: Recent Advances In Generating Immobilized Ph Gradients Using Polyacrylamide Hydrogelsmentioning

confidence: 99%

“…Generation of pH gradients inside the proposed hydrogel-based bioreactor is essential for simulating the human gut environment and multi-strain probiotic production. Immobilized pH gradients generated using immobilines covalently grafted onto polyacrylamide gels with their use in isoelectric focusing for protein separation is a well-established technology, which is reviewed in detail by many authors. − The details of the immobiline structure along with some examples of acidic and basic acrylamido buffers and their use to generate immobilized pH gradients for isoelectric focusing of proteins are shown in detail in Figure . The reader is referred to excellent reviews for further details. − Our approach of using only cellulose hydrogels along with buffers is presented in the next section.…”

Section: Recent Advances In Generating Immobilized Ph Gradients Using...mentioning

confidence: 99%

“…Immobilized pH gradients generated using immobilines covalently grafted onto polyacrylamide gels with their use in isoelectric focusing for protein separation is a well-established technology, which is reviewed in detail by many authors. − The details of the immobiline structure along with some examples of acidic and basic acrylamido buffers and their use to generate immobilized pH gradients for isoelectric focusing of proteins are shown in detail in Figure . The reader is referred to excellent reviews for further details. − Our approach of using only cellulose hydrogels along with buffers is presented in the next section.…”

Section: Recent Advances In Generating Immobilized Ph Gradients Using...mentioning

confidence: 99%

“…Existing approaches in the literature − on creating immobilized pH gradients using immobilines covalently grafted onto polyacrylamide gels and their use in isoelectric focusing for protein separation. This figure is adapted and redrawn with permission from refs − .…”

Section: Recent Advances In Generating Immobilized Ph Gradients Using...mentioning

confidence: 99%

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Perspective on Constructing Cellulose-Hydrogel-Based Gut-Like Bioreactors for Growth and Delivery of Multiple-Strain Probiotic Bacteria

Mettu

Hathi

Athukoralalage

et al. 2021

J. Agric. Food Chem.

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The current perspective presents an outlook on developing gut-like bioreactors with immobilized probiotic bacteria using cellulose hydrogels. The innovative concept of using hydrogels to simulate the human gut environment by generating and maintaining pH and oxygen gradients in the gut-like bioreactors is discussed. Fundamentally, this approach presents novel methods of production as well as delivery of multiple strains of probiotics using bioreactors. The relevant existing synthesis methods of cellulose hydrogels are discussed for producing porous hydrogels. Harvesting methods of multiple strains are discussed in the context of encapsulation of probiotic bacteria immobilized on cellulose hydrogels. Furthermore, we also discuss recent advances in using cellulose hydrogels for encapsulation of probiotic bacteria. This perspective also highlights the mechanism of probiotic protection by cellulose hydrogels. Such novel gut-like hydrogel bioreactors will have the potential to simulate the human gut ecosystem in the laboratory and stimulate new research on gut microbiota.

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Bioseparations, Separation Methods in Proteomics

Garfin

Ahuja²

2007

Kirk-Othmer Encyclopedia of Chemical Technology

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Bioseparations entail separations of proteins and other materials from biological matrices. In the last few decades, proteins have gained significant importance. For example, monoclonal antibodies and recombinant antibodies are now among the largest classes of proteins that have received FDA approval for therapeutics and diagnostics. The protein engineering market in 2006 was worth almost 67 billion dollars and is predicted to rise to 118 billion dollars by 2011. Development of protein and peptide therapeutics is revolutionizing the biotech and pharmaceutical markets, spurring the creation of next‐generation products with reduced immunogenicity, improved safety and greater effectiveness. Oncology is the dominant therapy for both monoclonal antibodies and other types of engineered proteins. Proteomics is concerned with the global investigation of gene and cell functions at the protein level. The goals of proteomics are determination of protein expression levels, post‐translational modifications, protein localization, and protein–protein interactions. One of the important goals of proteomics that deserves special mention here is the discovery and identification of protein biomarkers of disease states. Of all the biomolecules, proteins present the greatest challenges in bioseparations. The main focus of this article is on the important bioseparations techniques that are most useful for separations and characterization of proteins.

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4 Generation of pH gradients

Cited by 5 publications

References 104 publications

Implantable Direct Current Neural Modulation: Theory, Feasibility, and Efficacy

Implantable Direct Current Neural Modulation: Theory, Feasibility, and Efficacy

Perspective on Constructing Cellulose-Hydrogel-Based Gut-Like Bioreactors for Growth and Delivery of Multiple-Strain Probiotic Bacteria

Bioseparations, Separation Methods in Proteomics

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