Pancreatic Cell Immobilization in Alginate Beads Produced by Emulsion and Internal Gelation
Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, BC, Canada. Biotechnology and Bioengineering
(Impact Factor: 4.13).
02/2011; 108(2):424-34. DOI: 10.1002/bit.22959
Alginate has been used to protect transplanted pancreatic islets from immune rejection and as a matrix to increase the insulin content of islet progenitor cells. The throughput of alginate bead generation by the standard extrusion and external gelation method is limited by the rate of droplet formation from nozzles. Alginate bead generation by emulsion and internal gelation is a scaleable alternative that has been used with biological molecules and microbial cells, but not mammalian cells. We describe the novel adaptation of this process to mammalian cell immobilization. After optimization, the emulsion process yielded 90 ± 2% mouse insulinoma 6 (MIN6) cell survival, similar to the extrusion process. The MIN6 cells expanded at the same rate in both bead types to form pseudo-islets with increased glucose stimulation index compared to cells in suspension. The emulsion process was suitable for primary pancreatic exocrine cell immobilization, leading to 67 ± 32 fold increased insulin expression after 10 days of immobilized culture. Due to the scaleability and broad availability of stirred mixers, the emulsion process represents an attractive option for laboratories that are not equipped with extrusion-based cell encapsulators, as well as for the production of immobilized or encapsulated cellular therapeutics on a clinical scale.
Available from: Tohid Pirbodaghi
- "Alginate is a naturally derived polymer, which can physically cross-link with divalent ions to provide an ideal three-dimensional scaffold for cells that allows bidirectional diffusion of nutrients and waste products. Alginate particles are typically produced by ejecting drops of alginate solution into a bath of divalent ions resulting in millimeter-sized polydisperse beads (Maguire et al. 2006; Hoesli et al. 2011; Mazzitelli et al. 2011). However, for use as carriers of drugs, proteins, or cells, it is desirable to precisely control particle size and monodispersity . "
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ABSTRACT: An improved internal gelation approach is developed to encapsulate single mammalian cells in monodisperse alginate microbeads as small as 26 μm in diameter and at rates of up to 1 kHz with high cell viability. The cell damage resulting from contact with calcium carbonate nanoparticles as gelation reagents is eliminated by employing a co-flow microfluidic device, and the cell exposure to low pH is minimized by a chemically balanced off-chip gelation step. These modifications significantly improve the viability of cells encapsulated in gelled alginate particles. Two different mammalian cell types are encapsulated with viability of over 84 %. The cells are functional and continue to grow inside the microparticles.
Available from: Tania Castillo
- "Moreover, there are several new strategies developed to improve the cell-alginate immobilization process (Hoesli et al., 2011), as well as immune protection and oxygen supply to avoid hypoxia problems during transplants (Ludwig et al., 2010). In the tissue engineering field, alginate has been used for bone regeneration therapy using coimmobilization of human osteoprogenitors and endothelial cells in studies in vivo and in vitro (Hernández et al., 2010). "
Available from: Michiel Pot
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ABSTRACT: Tissue/organ printing aims to recapitulate the intrinsic complexity of native tissues. For a number of tissues, in particular those of musculoskeletal origin, adequate mechanical characteristics are an important prerequisite for their initial handling and stability, as well as long-lasting functioning. Hence, organized implants, possessing mechanical characteristics similar to the native tissue, may result in improved clinical outcomes of regenerative approaches. Using a bioprinter, grafts were constructed by alternate deposition of thermoplastic fibers and (cell-laden) hydrogels. Constructs of different shapes and sizes were manufactured and mechanical properties, as well as cell viability, were assessed. This approach yields novel organized viable hybrid constructs, which possess favorable mechanical characteristics, within the same range as those of native tissues. Moreover, the approach allows the use of multiple hydrogels and can thus produce constructs containing multiple cell types or bioactive factors. Furthermore, since the hydrogel is supported by the thermoplastic material, a broader range of hydrogel types can be used compared to bioprinting of hydrogels alone. In conclusion, we present an innovative and versatile approach for bioprinting, yielding constructs of which the mechanical stiffness provided by thermoplastic polymers can potentially be tailored, and combined specific cell placement patterns of multiple cell types embedded in a wide range of hydrogels.
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