title: Lipogels: single-lipid-bilayer-enclosed hydrogel spheres.
abstract: We have fabricated Lipogels consisting of a single POPC lipid bilayer supported by a micrometer-sized, thermoresponsive, hydrophobically modified (HM), hydrogel sphere. The hydrogel consists of a lightly cross-linked poly(N-isopropylacrylamide) (pNIPAM) core surrounded by a highly cross-linked acrylic acid (AA)-rich p(NIPAM-co-AA) shell. The lipid bilayer was assembled by binding liposomes to HM microgels, followed by several cycles of freeze-thaw. The pNIPAM volume phase transition (VPT) at ∼32 °C was present both before and after hydrophobic modification and after lipid bilayer coating. Fluorescence studies confirmed the fusion of liposomes into a continuous single bilayer. At a temperature above the VPT, it was found that the volume decrease in the hydrogel was coupled to the appearance of highly curved obtrusions of the uncompromised lipid bilayer into the surroundings. It is anticipated that these properties of Lipogels will prove to be useful in drug delivery applications and in fundamental biophysical studies of membranes.
authors.affiliation: Department of Chemistry, University of Toronto, Mississauga, Ontario, Canada.
authors.forename: Qasim
authors.initials: Q
authors.lastname: Saleem
authors.forename: Baoxu
authors.initials: B
authors.lastname: Liu
authors.forename: Claudiu C
authors.initials: CC
authors.lastname: Gradinaru
authors.forename: Peter M
authors.initials: PM
authors.lastname: Macdonald
mesh_terms: D000178:Acrylamides / Q000737:chemistry*; D000179:Acrylates / Q000737:chemistry*; D000180:Acrylic Resins; D016503:Drug Delivery Systems / Q000379:methods*; D005456:Fluorescent Dyes / Q000032:analysis; D005615:Freezing; D020100:Hydrogels / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008863:Microspheres; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry* / Q000378:metabolism; D011108:Polymers / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D000178:Acrylamides; D000179:Acrylates; D000180:Acrylic Resins; D005456:Fluorescent Dyes; D020100:Hydrogels; D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D011108:Polymers; C052970:poly-N-isopropylacrylamide; C036658:acrylic acid; C028694:1-palmitoyl-2-oleoylphosphatidylcholine