A new method for encapsulation of living cells: preliminary results with PC12 cell line.
ABSTRACT A new method is described for encapsulation of living cells. PC12 rat adrenal pheochromocytoma cells, which have been shown to synthesize, store and release dopamine were employed. The particles are made first and the cells then incorporated in a gentle mechanical procedure. The morphology (by light and electron microscopic observation), stability, rheology, texture and permeability of these microcapsules provided by Kappa Biotech were investigated. Membrane permeability studies demonstrated exclusion of 69,000 Da human serum albumin, but equilibrium of D-glucose and inulin was within 24h, indicating a molecular weight cut-off in the 5000-70,000 Da range. The viability and the function of the encapsulated cells were evaluated by measuring the spontaneous release of dopamine by high performance liquid chromatography with electrochemical detection. The results show that dopamine-secreting cells can be sequestered in a semi-permeable capsule and still display good viability and proliferation for at least 1 month.
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ABSTRACT: Cell encapsulation in microcapsules allows the in situ delivery of secreted proteins to treat different pathological conditions. Spherical microcapsules offer optimal surface-to-volume ratio for protein and nutrient diffusion, and thus, cell viability. This technology permits cell survival along with protein secretion activity upon appropriate host stimuli without the deleterious effects of immunosuppressant drugs. Microcapsules can be classified in 3 categories: matrix-core/shell microcapsules, liquid-core/shell microcapsules, and cells-core/shell microcapsules (or conformal coating). Many preparation techniques using natural or synthetic polymers as well as inorganic compounds have been reported. Matrix-core/shell microcapsules in which cells are hydrogel-embedded, exemplified by alginates capsule, is by far the most studied method. Numerous refinement of the technique have been proposed over the years such as better material characterization and purification, improvements in microbead generation methods, and new microbeads coating techniques. Other approaches, based on liquid-core capsules showed improved protein production and increased cell survival. But aside those more traditional techniques, new techniques are emerging in response to shortcomings of existing methods. More recently, direct cell aggregate coating have been proposed to minimize membrane thickness and implants size. Microcapsule performances are largely dictated by the physicochemical properties of the materials and the preparation techniques employed. Despite numerous promising pre-clinical results, at the present time each methods proposed need further improvements before reaching the clinical phase.Biotechnology Progress 07/2009; 25(4):946-63. · 1.85 Impact Factor
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ABSTRACT: Adhesion molecules composed of Gly-Arg-Gly-Asp-Ser (GRGDS) peptides and cell recognition ligands were inculcated into thermo-reversible hydrogel composed of N-isopropylacrylamide, with a small amount of succinyl poly(ethylene glycol) (PEG) acrylate (MW 3400) used as a biomimetic extracellular matrix (ECM). The GRGDS-containing p(NiPAAm-co-PEG) copolymer gel was studied in vitro for its ability to promote cell spreading and to increase the viability of cells by introducing PEG spacers. Hydrogel lacking the adhesion molecules proved to be a poor ECM for adhesion, permitting only a 20% spread of the seeded cells after 10 days. When PEG spacer arms, immobilized by a peptide linkage, had been integrated into the hydrogel, conjugation of RGD promoted cell spread by 600% in a 10-day trial. In addition, in a serum-free medium, only GRGDS peptides conjugated with the spacer arm were able to promote cell spread. In terms of the cell viability, GRGDS peptides conjugated with the PEG-carrying copolymer gel specifically mediated cell spread. This result supports the theory that specific recognition is the result of interaction between the integrin families on the fibroblast, and the RGD sequence on the p(NiPAAm-co-PEG) copolymer gel.Bioscience Biotechnology and Biochemistry 12/2004; 68(11):2224-9. · 1.27 Impact Factor
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ABSTRACT: Human parathyroid glands were encapsulated using the alginate-PLL system in this study. In order to improve the mechanical strength and the biocompatibility, the microcapsules were fabricated with a three-layer structure that consisted of alginate/photosensitive poly(L-lysine)/short chain alginate-co-MPEG. These modified microcapsules were used for encapsulating human parathyroid tissue. In vitro experiments revealed that microencapsulated parathyroid glands maintained differentiative properties in culture, and the capsular membrane was freely permeable to the human parathyroid hormone. For in vivo experiments, these capsules were transplanted into parathyroidectomized SD-rats. After parathyroidectomy, serum calcium decreased from 2.25 to 1.68 mmol/L and remained in a constantly low concentration until transplantation. Parathyroidectomized SD-rats were normocalcemic after transplant of encapsulated parathyroid tissue. The microcapsules were then explanted at 12 weeks for examination. Histological evaluations of excised transplants revealed that the microcapsules remained intact structurally and were free of cell adhesions. The results demonstrated that human parathyroid tissue microencapsulated by this system retains stability and is functional both in vitro and in vivo. This encapsulating system will have valuable application for endocrine surgery in the future.Artificial Organs 07/2004; 28(6):537-42. · 1.96 Impact Factor