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  • 1
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recent studies indicate that polymer-encapsulated PC12 cells release sufficient amounts of dopamine to significantly alter behavioural paradigms in animals with unilateral lesions of dopaminergic midbrain neurons. Because cell fine structure provides a useful measure for assessment of storage function, exocytosis, metabolism, cell activity and cell viability, we examined the ultrastructure of PC12 cells grown in semi-permeable polymer capsules maintainedin vitro or implanted into the forebrain of rats or guinea pigs. Encapsulated PC12 cells remained viable and continued to divide for the entire evaluation period of six months. Overall morphologies of encapsulated PC12 cells were similar in both environments and they resembled PC12 cells grown in monolayer cultures. In short-term cultures, encapsulated PC12 cells typically contained abundant quantities of chromaffin cell-like granules. The encapsulated cells had initially abundant microvilli on their surfaces which decline in frequency over time. After long-term enclosure for ten weeks or more, fewer secretory granules were detected in the cytoplasm of cells in capsules culturedin vitro and in brain-implated capsules. Some cells in implanted capsules had long slender filipodia that were not present on PC12 cells in cultured capsules. The morphological changes of PC12 cells may correlate with altered growth conditions such as serum and oxygen concentrations, the presence or absence of growth factors in different environments, and with changes of cell interactions related to cell densities and build up of debris within the capsules over time. Since dopaminergic PC12 pheochromocytoma cells remain viable in semi-permeable polymer capsules for at least six months, such ‘cell-capsules’ could provide an alternative to dopamine-secreting embryonic neural grafts in dopamine replacement therapies.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 511-519 
    ISSN: 0021-9304
    Keywords: PEO chemistry ; cell adhesion ; model surface ; RGD peptide ; surface modification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The ability to study and regulate cell behavior at a biomaterial interface requires strict control over material surface chemistry. Perhaps the greatest challenge to researchers working in this area is preventing the fouling of a given surface due to uncontrolled protein adsorption. This work describes a method for coupling peptides to hydrophobic materials for the purpose of simultaneously preventing nonspecific protein adsorption and controlling cell adhesion. A hexapeptide containing the ubiquitous RGD cell-adhesion motif was coupled to polystyrene (PS) via a polyethylene oxide (PEO) tether in the form of a modified PEO/PPO/PEO triblock copolymer. Triblocks were adsorbed onto PS at a density of 3.3 ± (5.14 × 10-4) mg/m2 (1.4 × 105 ± 2.12 × 101 molecules/μm2), which was determined by isotope 125I labeling. The peptide, GRGDSY, was activated at the N terminus with N-Succinimidyl 3-(2-pyridyldithio) propionate and coupled to immobilized triblocks where the terminal hydroxyls had been converted to sulfhydryl groups. Surface peptide density was measured by amino acid analysis and found to be 1.4 × 104 ± 0.47 × 104 molecules/μm2. PS modified with PEO/PPO/PEO copolymers alone was found to be inert to cell adhesion both in the presence of serum proteins and when exposed to activated RGD peptide. In contrast, PS conjugated with RGD via end-group-activated PEO/PPO/PEO copolymers supported cell adhesion and spreading. The surface coupling scheme reported here should prove valuable for studying cell-ligand interactions under simplified and highly controlled conditions. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 511-519, 1998.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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