title: Non-invasive evaluation of alginate/poly-l-lysine/alginate microcapsules by magnetic resonance microscopy.
abstract: In this report, we present data to demonstrate the utility of (1)H MR microscopy to non-invasively examine alginate/poly-l-lysine/alginate (APA) microcapsules. Specifically, high-resolution images were used to visualize and quantify the poly-l-lysine (PLL) layer, and monitor temporal changes in the alginate gel microstructure during a month long in vitro culture. The thickness of the alginate/PLL layer was quantified to be 40.6+/-6.2 microm regardless of the alginate composition used to generate the beads or the time of alginate/PLL interaction (2, 6, or 20 min). However, there was a notable difference in the contrast of the PLL layer that depended upon the guluronic content of the alginate and the alginate/PLL interaction time. The T(2) relaxation time and the apparent diffusion coefficient (ADC) of the alginate matrix were measured periodically throughout the month long culture period. Alginate beads generated with a high guluronic content alginate demonstrated a temporal decrease in T(2) over the duration of the experiment, while ADC was unaffected. This decrease in T(2) is attributed to a reorganization of the alginate microstructure due to periodic media exchanges that mimicked a regular feeding regiment for cultured cells. In beads coated with a PLL layer, this temporal decrease in T(2) was less pronounced suggesting that the PLL layer helped maintain the integrity of the initial alginate microstructure. Conversely, alginate beads generated with a high mannuronic content alginate (with or without a PLL layer) did not display temporal changes in either T(2) or ADC. This observation suggests that the microstructure of high mannuronic content alginate beads is less susceptible to culture conditions.
authors.affiliation: Division of Endocrinology, Department of Medicine, University of Florida, PO Box 100226, Gainesville, FL 32610-0226, USA. consti@medicine.ufl.edu
authors.forename: Ioannis
authors.initials: I
authors.lastname: Constantinidis
authors.forename: Samuel C
authors.initials: SC
authors.lastname: Grant
authors.forename: Susanne
authors.initials: S
authors.lastname: Celper
authors.forename: Isabel
authors.initials: I
authors.lastname: Gauffin-Holmberg
authors.forename: Kristina
authors.initials: K
authors.lastname: Agering
authors.forename: Jose A
authors.initials: JA
authors.lastname: Oca-Cossio
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Bui
authors.forename: Jeremy
authors.initials: J
authors.lastname: Flint
authors.forename: Christine
authors.initials: C
authors.lastname: Hamaty
authors.forename: Nicholas E
authors.initials: NE
authors.lastname: Simpson
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Blackband
mesh_terms: D000464:Alginates / Q000737:chemistry*; D002214:Capsules / Q000737:chemistry*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D006603:Hexuronic Acids / Q000032:analysis; D021621:Imaging, Three-Dimensional; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011107:Polylysine / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000464:Alginates; D002214:Capsules; D006603:Hexuronic Acids; C051546:alginate-polylysine-alginate; C007896:guluronic acid; D011107:Polylysine; C008324:mannuronic acid