Evaluation of asymmetric poly(vinyl alcohol) membranes for use in artificial islets

Center for Biomedical Engineering, College of Medicine, National Taiwan University, Taipei, Taiwan, R.O.C.
Biomaterials (Impact Factor: 8.56). 12/1996; 17(22):2139-2145. DOI: 10.1016/0142-9612(96)00043-9
Source: PubMed


Islets of Langerhans surrounded by a semipermeable membrane to prevent the host immunosystem is a potential way to treat type I diabetes mellitus. In this study, a series of poly (vinyl alcohol) membranes were formed by adding polyethylene glycols to create pores in the skin layer. The permeability study showed the skin layer structure had an influence on the diffusion of low molecular weight glucose, vitamin B12 and insulin. The mass transfer coefficient was improved from 1.04 × 10−4 to 2.16 × 10−4cm/ sec for glucose, from 2.84 × 10−5 to 8.36 × 10−5 cm/sec for vitamin B12 and from 1.45 × 10−6 to 4.15 × 10−6 cm/sec for insulin, whereas the passage of immunoglobulin G was completely prevented, indicating that these membranes could be effective in protecting islets from immunorejection. Thus such a membrane is an alternative potential material for artificial islets. In addition, we examined the insulin secretory response of islets separated by a poly(vinyl alcohol) membrane. We found that the insulinsecretion rate is relatively rapid compared to the permeation rate of insulin; thus, the process of the artificial islets is insulin-diffusion-controlled.

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    • "Poly(vinyl alcohol) (PVA) has been developed for vari- 41 ous biomedical applications such as artificial pancreas [8], 42 hemodialysis [9] and implantable medical materials [10] "
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    ABSTRACT: The purpose of this study was to evaluate the behaviors of rat tooth germ (TG) cells cultured on poly(vinyl alcohol) (PVA). It was found that TG cells suspended and aggregated to form three-dimensional spheroids on PVA. Compared with traditional monolayered cells on tissue culture polystyrene, TG cell spheroids on PVA obviously increased the alkaline phosphatase activity, the degree of mineralization, and upregulated both osteopontin and dentin matrix protein 1 genes, regardless of the seeding density. Surprisingly, PVA appears to activate the alkaline phosphatase activity and mineralization effects on TG cell spheroids in the absence of a differentiation medium. Furthermore, the present study indicates that integrins may play an important role in the mineralization on TG cell spheroids by adding Arg-Gly-Asp (RGD) peptides. Therefore, the information presented here should help to clarify the role of PVA in the regulation of the mineralization, differentiation and integrin-mediation of TG cells.
    Acta biomaterialia 05/2009; 5(4):1064-74. DOI:10.1016/j.actbio.2008.11.023 · 6.03 Impact Factor
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    • "Transplantation of the cells encapsulated in polymer vehicles with semi-permeable membranes is an attractive method for in vivo delivery of proteins without the need for immunosuppressant drugs [1]. A number of polymer vehicles with various configurations have been reported [2] [3] [4] [5], and of these, spherical-and fiber-shaped vehicles were the most frequently investigated. The fibershaped vehicles have an important advantage over spherical-shaped vehicles in that they are easily removed from patients when either adverse effects are observed or after the cessation of function [4]. "
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    ABSTRACT: A jetting technique in a liquid-liquid co-flowing stream was applied to the preparation of mammalian cell-enclosing calcium-alginate (Ca-alg) hydrogel fibers of several hundred micrometers in cross-sectional diameter. One percent alginate aqueous solution was extruded from needles (270, 480, 940 microm inner diameter) into a co-flowing laminar stream of 100 mM aqueous calcium chloride solution. The extruded alginate solution was stretched by the CaCl(2) solution, which is known as a "jetting process", and the Ca-alg hydrogel fibers were formed by gelation of the alginate solution through the uptake of calcium ions in the CaCl(2) solution. The cross-sectional diameter of the hydrogel fibers could be controlled from approximately 100-800 microm by changing the velocities of the alginate and CaCl(2) solution, and the inner diameter of the needle. Approximately 95% of bovine carotid artery vascular endothelial cells remained alive after the process of preparing hydrogel fibers in a co-flowing stream, demonstrating that the cell-enclosing process scarcely influences the viability of the enclosed cells.
    Biotechnology Journal 09/2006; 1(9):1014-7. DOI:10.1002/biot.200600055 · 3.49 Impact Factor
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    • "One of the widely used polymers to be incorporated into chitosan is poly(vinyl alcohol), PVA, because of its biocompatible, nontoxic, and excellent mechanical properties . It exhibits minimal cell adhesion and protein adsorption (Burczak, Gamian, & Kochman, 1996; Chuang et al., 1999; Ishihara et al., 2002; Minoura et al., 1998; Yang, Yao, Chang, & Chen, 1996), and has been found to be biodegradable (Takasu, Aoki, Tsucyia, & Okada, 1999). Simple blends of CS and PVA have good mechanical properties, and applications of these CS/PVA blends have been reported (Chandy et al., 1992; Koyano et al., 2000; Miya, Iwamoto, & Mima, 1984; Nakatsuka et al., 1992; Wang, Turhan, & Gunasekaram, 2004). "
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    ABSTRACT: To increase the physicochemical compatibility between chitosan and poly(vinyl alcohol), chitosan-g-poly(vinyl alcohol)/poly(vinyl alcohol) (CS-g-PVA/PVA) blends were prepared via a two-step reaction. In the first step, chitosan-g-poly(vinyl acetate)/poly(vinyl acetate) (CS-g-PVAc/PVAc) blends were produced in situ by adding 100 g of VAc monomer to acetic aqueous solutions with different amounts of CS, using a ceric ion as the initiator. The polymerization was carried out at 60 °C for 2 h, where grafting of VAc monomers onto chitosan and homopolymerization of VAc monomers occurred simultaneously. Monomer conversion, grafting efficiency and grafting ratio were all measured by gravimetric analysis. In the second step, CS-g-PVA/PVA blends were obtained by converting PVAc chains to PVA through alcoholysis in an alkali methanol solution. After oven drying process, the morphology of CS-g-PVAc/PVAc and CS-g-PVA/PVA blends were observed to be particulate and dense membrane, respectively. The cellular and blood compatibility of pure PVA, pure chitosan, and CS-g-PVA/PVA blends were tested separately by the viability of osteoblasts and the adhesion of platelets. Our results showed the cellular compatibility of PVA was improved due to the incorporation of chitosan. For platelet adhesion, pure PVA offered a good blood-contact property, while pure chitosan did very poor. However, interesting enough, the blends of a small amount of CS-g-PVA with PVA further improved the blood compatibility. An optimum composition of CS-g-PVA/PVA blend was determined in this study for its use in blood-contacting biomedical devices.
    Carbohydrate Polymers 03/2006; 63(3-63):331-339. DOI:10.1016/j.carbpol.2005.08.023 · 4.07 Impact Factor
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