Synthesis and Characterization of a Hydrogel with Controllable Electroosmosis: A Potential Brain Tissue Surrogate for Electrokinetic Transport

Faraji, Amir H.; Cui, Jonathan J.; Guy, Yifat; Li, Ling; Gavigan, Colleen A.; Strein, Timothy G.; Weber, Stephen G.

doi:10.1021/la202198k

Cited by 21 publications

(34 citation statements)

References 55 publications

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“…In the case of the neutral hydrogel (MA wt% = 0), the water transport was negligible. The flux increased in proportional to the electric field regardless of the composition of the hydrogels, as expected from the following equation of EOF through a fluid conduit

U_{eo} = k_{eo} E

k_{eo} = - \frac{ε ζ}{η}

where U eo [µL cm −2 min −1 ] is the electroosmotic flow rate, E [V mm −1 ] is the electric field applied to the conduit, ε [F m −1 ] is the dielectric constant of the solvent (water), ζ [mV] is the zeta potential of the negative charge fixed in the conduit media, and η [Pa s] is the viscosity of the solvent (water). The value of k eo [µL mm cm −2 min −1 V −1 ] is the ratio of U eo and E , and can be regarded as a standardized indicator of the EOF strength of the conduit material.…”

Section: Resultsmentioning

confidence: 75%

“…In this paper, we report that electroosmotic flow (EOF) can be induced in a soft CL in order to maintain the moisture of the lens. EOF is the motion of water induced by an applied voltage across a fluid conduit like a capillary tube or a porous material such as hydrogels . When the fluid conduit contains fixed electrical charges, the dominant electromigration of the mobile counter‐ions produces net water flow .…”

Section: Introductionmentioning

confidence: 99%

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Self‐Moisturizing Smart Contact Lens Employing Electroosmosis

Kusama

Sato

Yoshida

et al. 2019

Adv Materials Technologies

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dry eye syndrome, it is important to keep the lens moist and maintain tears between the CL and the ocular surface, which is here referred to TCO (the initial letters of tear, contact lens, and ocular). Conventional rehydration by regular eye drops, the electrical stimulation of the lacrimal gland, [17] and treatment with a punctum plug [18] will increase the total tear fluid in eye, but cannot directly address the maintenance of the amount of TCO. The only example so far of a smart CL for maintaining the TCO is that of Lee et al., who developed a CL coated with single layer of graphene which decreases the moisture evaporation. [19] Hence, there is still a high demand to develop a CL equipped with an antidehydration function.In this paper, we report that electroosmotic flow (EOF) can be induced in a soft CL in order to maintain the moisture of the lens. EOF is the motion of water induced by an applied voltage across a fluid conduit like a capillary tube [20,21] or a porous material such as hydrogels. [22,23] When the fluid conduit contains fixed electrical charges, the dominant electromigration of the mobile counterions produces net water flow. [24,25] For example, due to the large amount of carboxyl groups in keratin in the stratum corneum of the skin, the transdermal iontophoretic current is known to be accompanied by the EOF from anode to cathode, which assists the penetration of drugs into the skin. [26][27][28] Here, we first developed charge-fixed hydrogel materials and studied their properties as the fluid conduit for EOF generation. The density of the fixed charge was optimized by adjusting the mechanical strength and the efficiency of EOF generation (EOF strength). It was successfully demonstrated that the upward EOF within the soft CL can maintain moisture of the lens itself and also the TCO as illustrated in Figure 1, by in situ monitoring of conductance and by microscope observations. As an example of a built-in power source for EOF generation, the mounting of batteries (Mg/O 2 battery and fructose/O 2 enzymatic battery) was also demonstrated. Results and Discussion EOF Generation in Charged HydrogelsThe hydrogel materials composed of 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), and methacrylic acid (MA) were prepared using a the copolymerization ratio of Contact lenses (CLs) can be a cause of "dry eye syndrome" that can lead to corneal wounds and inflammation as well as a feeling of discomfort. To prevent the dry eye, it is important to keep the lens moist and maintain tears between the CL and the ocular surface. Here, the use of electroosmotic flow (EOF) in a CL is reported as a novel mechanism for antidehydration. A CL made from a charged hydrogel has served as the fluid conduit for EOF generation. The charge density of the gel is optimized by varying the composition ratio of anionic monomer having carboxyl group, by taking into account the efficiency of EOF generation and the mechanical strength of the hydrogels. By in situ monitoring of conductance and by microscope observations,...

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U_{eo} = k_{eo} E

k_{eo} = - \frac{ε ζ}{η}

Section: Resultsmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Self‐Moisturizing Smart Contact Lens Employing Electroosmosis

Kusama

Sato

Yoshida

et al. 2019

Adv Materials Technologies

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“…32 Two juxtaposed media with different ζ-potentials create pressure in an electric field. 39 When the hydrogel's ζ-potential magnitude is less than that of the capillary, there is the possibility of transport by pressure-induced flow arising from the larger ζ-potential in the pipette.…”

Section: Resultsmentioning

confidence: 99%

Iontophoresis From a Micropipet into a Porous Medium Depends on the ζ-Potential of the Medium

et al. 2012

Self Cite

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Iontophoresis uses electricity to deliver solutes into living tissue. Often, iontophoretic ejections from micropipettes into brain tissue are confined to millisecond pulses for highly localized delivery, but longer pulses are common. As hippocampal tissue has a ζ-potential of approximately –22 mV, we hypothesized that, in the presence of the electric field resulting from the iontophoretic current, electroosmotic flow in the tissue would carry solutes considerably farther than diffusion alone. A steady state solution to this mass transport problem predicts a spherically symmetrical solute concentration profile with the characteristic distance of the profile depending on the ζ-potential of the medium, the current density at the tip, the tip size and the solute electrophoretic mobility and diffusion coefficient. Of course, the ζ-potential of the tissue is defined by immobilized components of the extracellular matrix as well as cell-surface functional groups. As such, it cannot be changed at will. Therefore, the effect of the ζ-potential of the porous medium on ejections is examined using poly(acrylamide-co-acrylic acid) hydrogels with various magnitudes of ζ-potential, including that similar to hippocampal brain tissue. We demonstrated that nearly neutral fluorescent dextran (3 and 70 kD) solute penetration distance in the hydrogels and OHSCs depends on the magnitude of the applied current, solute properties, and, in the case of the hydrogels, the ζ-potential of the matrix. Steady state solute ejection profiles can be predicted semi-quantitatively.

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“…A clean plastic Petri dish was held securely in place over the objective lens and filled with 1.2 mL HBSS. The dish could hold an insert membrane containing OHSCs or a ∼2 cm × 2 cm square of hydrogel (25% w/w acrylic acid, prepared as previously described 42 ). The insert membrane with tissues was on top of the HBSS while the gel sits in the HBSS.…”

Section: ■ Methodsmentioning

confidence: 99%

Electroosmotic Push–Pull Perfusion: Description and Application to Qualitative Analysis of the Hydrolysis of Exogenous Galanin in Organotypic Hippocampal Slice Cultures

Rupert

Sandberg

et al. 2013

ACS Chem. Neurosci.

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We demonstrate here a method that perfuses a small region of an organotypic hippocampal culture with a solution containing an enzyme substrate, a neuropeptide. Perfusate containing hydrolysis products is continually collected and subsequently analyzed for the products of the enzymatic degradation of the peptide substrate. The driving force for perfusion is an electric field. The fused silica capillaries used as "push" and "pull" or "source" and "collection" capillaries have a ζ-potential that is negative and greater in magnitude than the tissue's ζ-potential. Thus, depending on the magnitudes of particular dimensions, the electroosmotic flow in the capillaries augments the fluid velocity in the tissue. The flow rate is not directly measured; however, we determine it using a finite-element approach. We have determined the collection efficiency of the system using an all d-amino acid internal standard. The flow rates are low, in the nL/min range, and adjustable by controlling the current or voltage in the system. The collection efficiency of the d-amino acid peptide internal standard is variable, increasing with increased current and thus electroosmotic flow rate. The collection efficiency can be rationalized in the context of a Peclet number. Electroosmotic push-pull perfusion of the neuropeptide galanin (gal1-29) through the extracellular space of an organotypic hippocampal culture results in its hydrolysis by ectopeptidase reactions occurring in the extracellular space. The products of hydrolysis were identified by MALDI-MS. Experiments at two levels of current (8-12 μA and 19-40 μA) show that the probability of seeing hydrolysis products (apparently from aminopeptidases) is greater in the Cornu Ammonis area 3 (CA3) than in the Cornu Ammonis area 1 (CA1) in the higher current experiments. In the lower current experiments, shorter peptide products of aminopeptidases (gal13-29 to gal20-19) are seen with greater frequency in CA3 than in CA1 but there is no statistically significant difference for longer peptides (gal3-29 to gal12-29).

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Synthesis and Characterization of a Hydrogel with Controllable Electroosmosis: A Potential Brain Tissue Surrogate for Electrokinetic Transport

Cited by 21 publications

References 55 publications

Self‐Moisturizing Smart Contact Lens Employing Electroosmosis

Self‐Moisturizing Smart Contact Lens Employing Electroosmosis

Iontophoresis From a Micropipet into a Porous Medium Depends on the ζ-Potential of the Medium

Electroosmotic Push–Pull Perfusion: Description and Application to Qualitative Analysis of the Hydrolysis of Exogenous Galanin in Organotypic Hippocampal Slice Cultures

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