title: Quantitative study of the production and properties of alginate/poly-L-lysine microcapsules.
abstract: Alginate-polylysine-alginate (APA) microcapsules are of particular interest for their application as implants or for bioreactor cultures. Although their formation has been widely studied, there is still a lack of quantitative data describing resistance, membrane thickness and permeability. In this study, the quantitative application of a Texture Analyser for the measurement of capsule deformation yielded important results that permit comparison with other polymer systems used for encapsulation. Furthermore, single-membrane and multi-membrane capsules were formed in order to improve the modulation of the capsule properties. For single-membrane capsules, resistance was mostly affected by the incubation time in poly-L-lysine (PLL), the PLL molecular weight and concentration. The increase in resistance from 0.1 +/- 0.01 g/capsules to 2 +/- 0.2 g/capsules was linked to a membrane thickening (35-120 microm) and a decrease in permeability (150 to 40 kD). Thus, it was not possible to modify resistance and membrane permeability independently. Multi-membrane capsules with a resistance comparable to single-membrane capsules could be formed using various combinations of PLL molecular weights, and enabled uncoupling of permeability and resistance properties.
authors.affiliation: Laboratory of Chemical and Biochemical Engineering, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Gugerli
authors.forename: E
authors.initials: E
authors.lastname: Cantana
authors.forename: C
authors.initials: C
authors.lastname: Heinzen
authors.forename: U
authors.initials: U
authors.lastname: von Stockar
authors.forename: I W
authors.initials: IW
authors.lastname: Marison
mesh_terms: D000464:Alginates / Q000138:chemical synthesis* / Q000737:chemistry*; D002214:Capsules / Q000138:chemical synthesis / Q000737:chemistry; D019343:Citric Acid; D019245:Compressive Strength; D004339:Drug Compounding; D008567:Membranes, Artificial; D008970:Molecular Weight; D009994:Osmolar Concentration; D010539:Permeability; D011107:Polylysine / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry*; D013314:Stress, Mechanical
chemical_list: D000464:Alginates; D002214:Capsules; D008567:Membranes, Artificial; C051546:alginate-polylysine-alginate; D011107:Polylysine; D019343:Citric Acid