title: Characteristics of Poly-L-Ornithine-coated alginate microcapsules.
abstract: Poly-L-Lysine (PLL) is the most widely used biomaterial for providing perm-selectivity in alginate microcapsules for islet transplantation. We had previously reported that Poly-L-Ornithine (PLO) is less immunogenic than PLL, and in the present study, we have compared the physical characteristics of PLO- and PLL-coated hollow alginate microcapsules. Microspheres made with 1.5% alginate were divided into 2 groups that were first coated with either 0.1% PLO or PLL, followed by a second coating with 0.25% alginate. After liquefaction of the inner alginate core with sodium citrate, the microcapsules were washed with saline and used for experiments. Pore size exclusion studies were performed with FITC-labeled lectins incubated with encapsulated pig islets followed by examination for fluorescence activity. Mechanical strength was assessed by an osmotic pressure test and by 36 h of mechanical agitation of microcapsules with inert soda lime beads. The pore size exclusion limit of microcapsules after 20 min of coating was significantly smaller with PLO. While the mean +/- SEM diameter of PLL-coated microcapsules increased from 718+/-17 to 821 +/- 17 microm (p < 0.05) during 14 days incubation at 37 degrees C, the PLO group did not change in size. Also, PLL group had a higher percentage of broken capsules (52.7 +/- 4.9%) compared to 3.1 +/- 2.05% for PLO capsules (p < 0.0001,n = 6). We conclude that PLO-coated alginate microcapsules are mechanically stronger and provide better perm-selectivity than PLL-coated microcapsules.
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Marcus D
authors.initials: MD
authors.lastname: Darrabie
authors.forename: William F
authors.initials: WF
authors.lastname: Kendall
authors.forename: Emmanuel C
authors.initials: EC
authors.lastname: Opara
mesh_terms: D000464:Alginates / Q000032:analysis / Q000737:chemistry*; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods*; D002478:Cells, Cultured; D020099:Coated Materials, Biocompatible / Q000032:analysis / Q000737:chemistry*; D004548:Elasticity; D020723:Glucuronic Acid / Q000032:analysis / Q000737:chemistry; D006603:Hexuronic Acids / Q000032:analysis / Q000737:chemistry; D007515:Islets of Langerhans / Q000166:cytology* / Q000502:physiology*; D016381:Islets of Langerhans Transplantation / Q000295:instrumentation / Q000379:methods*; D008422:Materials Testing; D008863:Microspheres; D010316:Particle Size; D010455:Peptides / Q000032:analysis / Q000737:chemistry*; D016062:Porosity; D013314:Stress, Mechanical; D013552:Swine; D013718:Tensile Strength
chemical_list: D000464:Alginates; D020099:Coated Materials, Biocompatible; D006603:Hexuronic Acids; D010455:Peptides; C008973:polyornithine; D020723:Glucuronic Acid