title: Lipid-alginate interactions render changes in phospholipid bilayer permeability.
abstract: Lipid vesicles, e.g. liposomes, generally release their contents in a continuous manner. However, when these vesicles are entrapped in Ca-alginate and coated with poly(L-lysine), they release their contents in an unusual fashion, in 'bursts'. Molecular-level studies indicated that lipid-alginate interactions are responsible for changes in the barrier properties of lipid vesicles. Differential scanning calorimetry revealed that exposure of liposomes to alginate resulted in a 4-fold reduction in the phase transition enthalpy, with no change in the melting temperature. Size-exclusion chromatography of liposomes-in-alginate gave an additional liposomal peak with a smaller elution volume. These studies suggested that alginate is inserted into the lipid bilayer of vesicles. Lipid-alginate interactions were highly dependent on phospholipid head group charge and the phase transition temperature of the phospholipid. Based on these interactions, a mechanism to explain the 'burst' from these entrapped liposomes is suggested.
authors.affiliation: Department of Chemical Engineering, M.I.T., Cambridge, MA 02139.
authors.forename: S
authors.initials: S
authors.lastname: Cohen
authors.forename: M C
authors.initials: MC
authors.lastname: Bañó
authors.forename: M
authors.initials: M
authors.lastname: Chow
authors.forename: R
authors.initials: R
authors.lastname: Langer
mesh_terms: D000464:Alginates / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D002784:Cholesterol / Q000737:chemistry; D066298:In Vitro Techniques; D008051:Lipid Bilayers; D008081:Liposomes; D008244:Lysophosphatidylcholines / Q000737:chemistry; D008563:Membrane Lipids / Q000737:chemistry*; D010539:Permeability; D011107:Polylysine / Q000737:chemistry; D013329:Structure-Activity Relationship
chemical_list: D000464:Alginates; D008051:Lipid Bilayers; D008081:Liposomes; D008244:Lysophosphatidylcholines; D008563:Membrane Lipids; D011107:Polylysine; D002784:Cholesterol; D002118:Calcium