Effect of Cross-Linking on the Diffusion of Water, Ions, and Small Molecules in Hydrogels

Wu, Y.; Joseph, Sony; Aluru, N. R.

doi:10.1021/jp808145x

Cited by 176 publications

(158 citation statements)

References 109 publications

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“…28 It is described by the mesh size which is affected by the degree of (physical) crosslinking of hydrogels. 29 General physical crosslinking in hydrogels results from the random entanglement of disordered chains.…”

Section: Influence Of Layer Preparation Conditions On the Release Andmentioning

confidence: 99%

Controlled antibody release from gelatin for on-chip sample preparation

Zhang¹,

Wasserberg²,

Breukers³

et al. 2016

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A practical way to realize on-chip sample preparation for point-of-care diagnostics is to store the required reagents on a microfluidic device and release them in a controlled manner upon contact with the sample. For the development of such diagnostic devices, a fundamental understanding of the release kinetics of reagents from suitable materials in microfluidic chips is therefore essential. Here, we study the release kinetics of fluorophore-conjugated antibodies from (sub-) µm thick gelatin layers and several ways to control the release time. The observed antibody release is well-described by a diffusion model. Release times ranging from ~20 s to ~650 s were determined for layers with thicknesses (in the dry state) between 0.25 µm and 1.5 µm, corresponding to a diffusivity of 0.65 µm 2 /s (in the swollen state) for our standard layer preparation conditions. By modifying the preparation conditions, we can influence the properties of gelatin to realize faster or slower release. Faster drying at increased temperatures leads to shorter release times, whereas slower drying at increased humidity yields slower release. As expected in a diffusive process, the release time increases with the size of the antibody. Moreover, the ionic strength of the release medium has a significant impact on the release kinetics. Applying these findings to cell counting chambers with on-chip sample preparation, we can tune the release to control the antibody distribution after inflow of blood in order to achieve homogeneous cell staining. IntroductionOne of the major fields of applications for microfluidics is in vitro diagnostics, with great potential particularly in point-of-care diagnostics. 1-3 Many process steps and sensing principles have been realized on microfluidic devices. 4 Recently, on-chip sample preparation using reagents stored in microfluidic devices has received more and more attention. 5 On-chip sample preparation can eliminate the dependence on external instrumentation for reagent delivery as well as benchtop sample treatment, thus integrating the complete test into one disposable. 6 To realize on-chip sample preparation, reagents are integrated in microfluidic devices and released upon contact with the inflowing sample. Compared with liquid reagents 7-10 , integrating dry reagents in microfluidic devices is beneficial for long-term storage and convenient for transportation, due to the better stability of reagents in the dry state. 11 However, the controlled dissolution of the reagent and on-chip mixing with the added sample is challenging. Especially in applications where the inflowing sample passes a reservoir of the reagent and slowly dissolves or washes out the stored reagent 12-15 , very precise control of the sample flow and the reagent release process is required. In contrast, mixing between sample and reagents in stopped flow applications can be realized simply by releasing the reagent with sufficient delay after the sample inflow has stopped at the required position on the chip. 16 To realize controlled reagen...

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Section: Influence Of Layer Preparation Conditions On the Release Andmentioning

confidence: 99%

Controlled antibody release from gelatin for on-chip sample preparation

Zhang¹,

Wasserberg²,

Breukers³

et al. 2016

Analyst

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“…The measured equilibrium water content (EWC) of hydrogels, as reported in Figure 4.10, offer a good indicator for the diffusivity of solutes within their structure, with diffusivity increasing with water content [124]. Hydrogels soaked in water had a 97 % water content (4.8 % crosslinker, n = 9), which corresponds well to the literature for identical hydrogels [113].…”

Section: Hydrogel Water Contentsupporting

confidence: 73%

“…Several studies have quantified KCl aq flux through hydrogels as well [98,123,124], and determined theoretical models for ion transport [125]. Capillary pore diffusion and solution-diffusion models were used to describe solute diffusion through PMMA and other materials used as dialysis membranes [126].…”

Section: Solute Diffusionmentioning

confidence: 99%

A Bio-inspired Excitable Cardiac Cell Membrane from Electroactive Polymers: Ion Transport Studies

Moored

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The heart is an incredibly efficient biological pump, which contracts as a whole from the coordinated effort of millions of excitable cells called cardiac myocytes. These cells are considered excitable since they possess the ability to respond to a threshold activation signal, but only if sufficient time has passed and they have recovered from their previous excitation. Excitable cells also have the capacity to propagate an activation signal to their neighboring cells, and collectively are referred to as an excitable medium. Numerous examples of excitable media exist in nature, including the heart, forest fires, the intestine, nerves, and certain kinds of chemical reactions. Engineered artificial excitable media, however, have never been developed before.The long-term goal of this project, therefore, is to develop the first such artificial excitable medium from an array of artificial excitable cells, called gel-cells. The conceptual design of the gel-cell consists of a thin electroactive ion-gating membrane (polypyrrole), sandwiched between two layers of hydrated polymer (hydrogel) loaded with different concentrations of potassium chloride (KCl aq ) electrolytes. The voltage controlled artificial membrane initially confines ions to the upper chamber of the gelcell, and releases them upon membrane opening into the lower chamber, a process similar to membrane activation in cardiac myocytes. Potassium sensing electrodes embedded throughout the gel-cell provide feedback on the location and concentration of ions within the gel-cell, becoming markers for its activation. The scope of the research presented here was to construct the biomimetic cell membrane portion of the gel-cell, and study ion transport through its assembly.First, the electrochemical response of polypyrrole (PPy) was characterized via cyclic voltammetry, and its membrane morphology and thickness were observed via scanning electron microscopy. Experimentally obtained membrane thickness values were then compared to model predictions, which were subsequently improved by updating membrane density and structure assumptions. Hydrogel pore size approximations were correlated to equilibrium water content calculations, and KCl aq concentrations were quantified using electrochemical impedance spectroscopy. Time-resolved KCl aq flux experiments were performed on PPy membranes in solution, providing real-time concentration profiles of KCl aq as it passes through the membrane. From the parameter space tested, the optimal membrane preparation and gating potentials were selected which produced the highest flux rates. Time-lapse flux experiments (providing piece-wise concentration profiles for KCl aq ) were then performed on PPy membranes in both solution and hydrogel. Ion transport through two nearly identical membranes produced under different deposition conditions (PPy a and PPy b ) were compared in solution. The slightly denser and thicker membrane (PPy b ) produced nearly an order of magnitude higher flux rates than PPy a , suggesting that an active comp...

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“…(b) Regression analysis of the relationship between extract concentration and genotoxicity, based on significant correlation among these two variables. structure 13,52,53 . The elution of unreacted components from hydrogels is influenced by several factors including the chemical composition of components in hydrogel synthesis, the conversion during polymerization reaction and the degree of crosslinking of the polymeric network 13 .…”

Section: Comet Assaymentioning

confidence: 99%

Synthesis, Swelling Properties and Evaluation of Genotoxicity of Hydrogels Based on (Meth)acrylates and Itaconic Acid

et al. 2016

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In this study we prepared hydrogels based on 2-hydroxyethyl methacrylate (HEMA): PHEMA homopolymer and two terpolymers of HEMA, itaconic acid (IA) and two poly(alkylene glycol) (meth) acrylates (PAGM): poly(ethylene glycol) 6 acrylate (P(HEMA/IA/PAGM1)) and poly(propylene glycol) 5 methacrylate (P(HEMA/IA/PAGM2)). Hydrogels were synthesized by gamma-irradiated radical polymerization and subjected to swelling measurements and genotoxicity evaluation. Swelling studies confirmed that these hydrogels deserve consideration as biomaterials due to their ability to swell in phosphate buffer but maintaining physical integrity for a prolonged contact time after equilibrium state has been reached. Comet assay showed certain genotoxic effect following cell exposure to extracts of hydrogels, which was dependent on the concentration of extracts, chemical composition of hydrogels and the degree of crosslinking. The influence of concentration on genotoxicity was the most pronounced. The synthesis of these novel HEMA-based hydrogels should be optimized so as to reduce their toxicity and enable the use in clinical practice.

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Effect of Cross-Linking on the Diffusion of Water, Ions, and Small Molecules in Hydrogels

Cited by 176 publications

References 109 publications

Controlled antibody release from gelatin for on-chip sample preparation

Controlled antibody release from gelatin for on-chip sample preparation

A Bio-inspired Excitable Cardiac Cell Membrane from Electroactive Polymers: Ion Transport Studies

Synthesis, Swelling Properties and Evaluation of Genotoxicity of Hydrogels Based on (Meth)acrylates and Itaconic Acid

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