A highly sensitive cell assay for validation of purification regimes of alginates

Leinfelder, Ulrich; Brunnenmeier, Frank; Cramer, Hubert; Schiller, Jürgen; Arnold, Klaus; Vásquez, Julio A.; Zimmermann, U.

doi:10.1016/s0142-9612(03)00299-0

Cited by 43 publications

(34 citation statements)

References 39 publications

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“…One of the main requirements for long-term alginate-based transplantation is the stability of the microcapsules. This is achieved by cross-linking ultra-highϪ viscosity alginate of clinical grade (i.e., free of mitogenic and cytotoxic ingredients as well as of gram-negative and gram-positive bacterial spores) (19,20) with Ba 2ϩ and by simultaneously incorporating stabilizing agents such as proteins into the microcapsules (17). As shown elsewhere (16), HSA can preserve insulin secretion for up to 3 weeks in tissue culture when this microcapsule design is used for encapsulation of rat islets.…”

Section: Discussionmentioning

confidence: 99%

“…Microencapsulation was performed using ultrahighϪviscosity alginate of clinical grade (viscosity of a 0.1% wt/vol solution in distilled water was 20 -30 mPa ⅐ s). The extraction and purification protocol has been described elsewhere (19,20). For microcapsule formation, the alginate was dissolved in sterile, endotoxin-free 0.9% NaCl solution at a concentration of 0.7% (wt/vol).…”

Section: Methodsmentioning

confidence: 99%

“…The islet-containing microcapsules were dropped into a 20-mmol/l BaCl 2 solution adjusted to 290 mOsm with appropriate amounts of NaCl and buffered to pH 7.0 with 5 mmol/l histidine. After 20 min, the islet-containing microcapsules were washed three times with 0.9% NaCl solution and treated with 6 mmol/l Na 2 SO 4 saline solution for 30 min at 37°C to precipitate excess Ba 2ϩ ions (20). The microcapsules obtained by this encapsulation procedure had a diameter of ϳ700 -800 m and on average contained one islet or, in rare cases, two or three.…”

Section: Methodsmentioning

confidence: 99%

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Long-Term Graft Function of Adult Rat and Human Islets Encapsulated in Novel Alginate-Based Microcapsules After Transplantation in Immunocompetent Diabetic Mice

Schneider¹,

Feilen²,

et al. 2005

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We describe the results of the first study to show that adult rat and human islets can be protected against xenogenic rejection in immunocompetent diabetic mice by encapsulating them in a novel alginate-based microcapsule system with no additional permselective membrane. Nonencapsulated islets lost function within 4 -8 days after being transplanted into diabetic Balb/c mice, whereas transplanted encapsulated adult rat or human islets resulted in normoglycemia for >7 months. When rat islet grafts were removed 10 and 36 weeks after transplantation, the mice became immediately hyperglycemic, thus demonstrating the efficacy of the encapsulated islets. The explanted capsules showed only a mild cellular reaction on their surface and a viability of >85%, and responded to a glucose stimulus with a 10-fold increase in insulin secretion. Furthermore, transplanted mice showed a slight decrease in the glucose clearance rate in response to intraperitoneal glucose tolerance tests 3-16 weeks after transplantation; after 16 weeks, the rate remained stable. Similar results were obtained for encapsulated human islets. Thus we provide the first evidence of successful transplantation of microencapsulated human islets. In conclusion, we have developed a novel microcapsule system that enables survival and function of adult rat and human islets in immunocompetent mice without immunosuppression for >7 months. Diabetes 54:687-693, 2005

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Long-Term Graft Function of Adult Rat and Human Islets Encapsulated in Novel Alginate-Based Microcapsules After Transplantation in Immunocompetent Diabetic Mice

Schneider¹,

Feilen²,

et al. 2005

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“…Although it is recognized that other purification protocols have been published, 24,27,28,31,33,34 we decided not to include them in this study for economical and practicality reasons. Specifically, although Zimmermann et al 34 published a purification method that used free-flow electrophoresis, we chose not to reproduce the described protocol because the procedure is expensive and difficult to perform on a large scale.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of alginate purification methods: Effect on polyphenol, endotoxin, and protein contamination

Dusseault

Tam

Ménard

et al. 2005

J Biomedical Materials Res

137

106

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Alginate, a polysaccharide extracted from brown seaweed, is widely used for the microencapsulation of islets of Langerhans, allowing their transplantation without immunosuppression. This natural polymer is known to be largely contaminated. The implantation of islets encapsulated using unpurified alginate leads to the development of fibrotic cell overgrowth around the microcapsules and normalization of the blood glucose is restricted to a very short period if it is achieved at all. Several research groups have developed their own purification method and obtained relatively good results. No comparative evaluation of the efficiencies of these methods has been published. We conducted an evaluative study of five different alginate preparations: a pharmaceutical-grade alginate in its raw state, the same alginate after purification according to three different published methods, and a commercially available purified alginate. The results showed that all purification methods reduced the amounts of known contaminants, that is, polyphenols, endotoxins, and proteins, although with varying efficiencies. Increased viscosity of alginate solutions was observed after purification of the alginates. Despite a general efficiency in decreasing contamination levels, all of the purified alginates contained relatively high residual amounts of protein contaminants. Because proteins may be immunogenic, these residual proteins may have a role in persisting microcapsule immunogenicity.

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“…Alginates, which exhibit an M:G ratio of 70:30 yield best transplantation results [16,[18][19][20]. Sources of this material are peeled stipes of Laminaria pallida and particularly of Lessonia nigrescens, both harvested from the sea [10].…”

Section: Requirements For Producing Clinical-grade Alginatesmentioning

confidence: 99%

Homogeneously Cross-Linked Scaffolds Based on Clinical-Grade Alginate for Transplantation and Tissue Engineering

Zimmermann¹,

Leinfelder²,

Hillgärtner³

et al. 2003

Cartilage Surgery and Future Perspectives

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A highly sensitive cell assay for validation of purification regimes of alginates

Cited by 43 publications

References 39 publications

Long-Term Graft Function of Adult Rat and Human Islets Encapsulated in Novel Alginate-Based Microcapsules After Transplantation in Immunocompetent Diabetic Mice

Long-Term Graft Function of Adult Rat and Human Islets Encapsulated in Novel Alginate-Based Microcapsules After Transplantation in Immunocompetent Diabetic Mice

Evaluation of alginate purification methods: Effect on polyphenol, endotoxin, and protein contamination

Homogeneously Cross-Linked Scaffolds Based on Clinical-Grade Alginate for Transplantation and Tissue Engineering

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