Entrapment of islets into reversible disulfide hydrogels

Hisano, Nobuharu; Morikawa, Noriyuki; Iwata, Hiroo; Ikada, Yoshito

doi:10.1002/(sici)1097-4636(199804)40:1<115::aid-jbm13>3.0.co;2-n

Cited by 52 publications

(54 citation statements)

References 20 publications

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“…14 Very recently, solubilized polyacrylamide chain containing thiol groups which was obtained from the reduction process was re-oxidized and crosslinked back for the entrapment of islets cells for re-fillable bioartificial pancreas. 15 As shown in Figure 1, synthesized poly(NIPAAm) gel network could be dissolved into water soluble polymer chains by treating with a reducing agent, DTT. However, the reductive cleavage reaction of disulfide linkage in the poly-(NIPAAm) gel did not yield a complete dissolution of the gel.…”

Section: Resultsmentioning

confidence: 99%

Reduction/Oxidation Induced Cleavable/Crosslinkable Temperature-Sensitive Hydrogel Network Containing Disulfide Linkages

Lee

Park

1998

Polym J

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ABSTRACT:Temperature-sensitive poly(N-isopropylacrylamide) [poly(NIPAAm)] was crosslinked with a small amount of N,N'-cystamine-bis-acrylamide which contains a disulfide linkage between two vinyl groups. The hydrogel network could be dissolved into water soluble polymer chains by the reduction of a disulfide bond to two thiol groups. The cleavage of crosslink points led to the experimental determination of the polymer molecular weight (M.) and the amount of free thiol concentration in the polymer backbone. This permitted the calculation of an average molecular weight between crosslinks (M,) which has been theoretically predicted by a Flory-Rehner equation based on either swelling or tensile experiments. The experimentally measured M, values agree well with those obtained from the swelling experiment. When the reduced poly(NIPAAm) was re-oxidized in a dilute aqueous solution, time dependent evolution of inter-and intra-molecularly disulfide linked poly(NIPAAm) species could be observed.KEY WORDS Poly(N-isopropylacrylamide) I Disulfide I Hydrogel I Lower Critical Solution Temperature I Reversible Gels I Hydrogels are crosslinked polymer chain networks that swell in aqueous or biological solution. The structure of three dimensional polymer network has been mostly characterized from its equilibrium swelling capacity in aqueous water milieu. 1 The degree of swelling for nonionic polymer hydrogels is determined by counter-balancing of mixing and elastic free energies that act in an opposite direction. 2 The most critical factor affecting the swelling property is the crosslinking density that has been more conveniently defined as an average molecular weight between crosslinks (Me). From the classical model of rubber elasticity, a Flory-Rehner equation was first introduced to estimate the Me, and later, a modified Bray-Merrill equation was developed. 3 • 4 The latter equation applies for crosslinking reactions of polymer in solid and solution states as well as the polymerization and subsequent network formation of various hydrophilic vinyl monomers in the presence of a small amount of crosslinker. The above equations were used to evaluate the theoretical calculation of Me by simply measuring the equilibrium swelling capacity of hydrogel network. Crosslinking of polymer chains such as poly(vinyl alcohol) by radiation or chemical means easily permits the calculation of Me because M" value of the polymer is known. 5 However, when vinyl monomers are used for the network formation, M" value is not available. This problem limited the use of the above equation for free radically polymerized hydrogels based on vinyl monomers such as acrylamide and 2-hydroxyethylmethacrylate. 6 Water soluble poly(N-isopropylacrylamide) [poly-(NIPAAm)] has been extensively studied for its unique coil to globular conformation change with increasing the temperature above its lower critical solution temperature (LCST). 7 -1° Crosslinked poly(NIP A Am) network that exhibits a volume phase transition at the LCST has also received much attention for i...

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Section: Resultsmentioning

confidence: 99%

Reduction/Oxidation Induced Cleavable/Crosslinkable Temperature-Sensitive Hydrogel Network Containing Disulfide Linkages

Lee

Park

1998

Polym J

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“…The polyacrylamide hydrogels were used to entrap islets of hamster by re-formation of disulfide bonds on the copolymer. In vitro results demonstrated the insulin release from the islet-entrapped copolymer continued up to one month [23]. Recently, the three-dimensional (3D)-engineered tissues composed of cells and ECM were developed by Matsusaki et al Template hydrogels were prepared by disulfide-crosslinked poly(g-glutamic acid) hydrogels and mouse L929 fibroblast cells as model cells were seeded on the template hydrogels.…”

Section: Discussionmentioning

confidence: 99%

In situ gelling properties of chitosan-thioglycolic acid conjugate in the presence of oxidizing agents

2009

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“…One electron transfer from ABS -ion (from ABSH) to oxygen determines the rate of air oxidation of the thiol. 34 This reaction rate increases with increasing pH. At pH 7, re-gelation occurred in less than 24 h, depending on the concentration.…”

Section: Synthesis Of Poly(aam-co-bac) Hydrogelsmentioning

confidence: 99%

Refilling of Ocular Lens Capsule with Copolymeric Hydrogel Containing Reversible Disulfide

2004

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Polymer solutions can fill any potential irregular cavity using minimally invasive techniques and thus have potential uses in ophthalmology. We prepared acrylamide hydrogels containing disulfide bonds by free radical polymerization in aqueous ethanol. The hydrogels were liquefied using dithiothreitol to yield water-soluble acrylamide copolymers containing pendant thiol (-SH) groups. The weight average molecular weights of the copolymers ranged from 1.43 x 10(5) to 9.22 x 10(5) daltons by GPC. Ellman's analysis and Raman spectroscopy confirmed the presence of -SH. The aqueous solutions of these purified thiol-containing copolymers were oxidized with 3,3'-dithiodipropionic acid or air to reform the hydrogels. The moduli of the reformed hydrogels ranged from 0.27 to 1.1 kPa depending on concentration and thiol content. Rapid endocapsular gelation yielded optically clear gel within the lens capsular bag. This technique now enables us to validate methods to determine the biomechanics of the lens and its role in accommodation.

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Entrapment of islets into reversible disulfide hydrogels

Cited by 52 publications

References 20 publications

Reduction/Oxidation Induced Cleavable/Crosslinkable Temperature-Sensitive Hydrogel Network Containing Disulfide Linkages

Reduction/Oxidation Induced Cleavable/Crosslinkable Temperature-Sensitive Hydrogel Network Containing Disulfide Linkages

In situ gelling properties of chitosan-thioglycolic acid conjugate in the presence of oxidizing agents

Refilling of Ocular Lens Capsule with Copolymeric Hydrogel Containing Reversible Disulfide

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