Lamellar Biogels: Fluid-Membrane-Based Hydrogels Containing Polymer Lipids

Abstract

A class of lamellar biological hydrogels comprised of fluid membranes of lipids and surfactants with small amounts of low molecular weight poly(ethylene glycol)-derived polymer lipids (PEG-lipids) were studied by x-ray diffraction, polarized light microscopy, and rheometry. In contrast to isotropic hydrogels of polymer networks, these membrane-based birefringent liquid crystalline biogels, labeled L-alpha,g, form the gel phase when water is added to the liquid-like lamellar L-alpha phase, which reenters a liquid-like mixed phase upon further dilution. Furthermore, gels with larger water content require less PEG-lipid to remain stable. Although concentrated (approximately 50 weight percent) mixtures of free PEG (molecular weight, 5000) and water do not gel, gelation does occur in mixtures containing as little as 0.5 weight percent PEG-lipid. A defining signature of the L-alpha,g regime as it sets in from the fluid lamellar L-alpha phase is the proliferation of layer-dislocation-type defects, which are stabilized by the segregation of PEG-lipids to the defect regions of high membrane curvature that connect the membranes.

Neurofilament sidearms modulate parallel and crossed-filament orientations inducing nematic to isotropic and re-entrant birefringent hydrogels

“…As can be seen in Fig. 4e, the B G phase has a significantly larger elastic modulus (between a factor of 15 to 30) as compared to the I G and N G hydrogels, which have moduli comparable to other typical physical hydrogels 24 . The large value of G 0 , ranging between E3,000 and 7,000 Pa over a frequency range of 0.01-10 Hz, for the B G physical gel stabilized by electrostatic interactions at low C S (discussed in detail below), is comparable to the modulus of typical chemically crosslinked polyacrylamide hydrogels 25 .…”

Local entropic effects of polymers grafted to soft interfaces

“…is of order h i and Z (0) N is defined in equation (4). One can notice that due to the linearity of equation (1), each term of the perturbative expansion obeys an Edwards equation…”

“…Adhesion of membranes on a substrate plays a role in biological phenomena such as endocytosis and exocytosis [2], it is also of relevance in biotechnological processes, such as drug delivery by liposomes [36]. A second important case of constraint membranes corresponds to lamellar L α phases, where the membranes are confined by interactions with their neighbors in the lamella stack [4,37].…”

“…Polymers grafted to the bilayers can induce gelation [4] or other phase changes [5,6] in liquid lamellar phases. They stabilize monodisperse vesicles [7] and modify the geometry of monolamellar [8,9] and multilamellar cylindrical vesicles [10].…”

Novel polymer-free iridescent lamellar hydrogel for two-dimensional confined growth of ultrathin gold membranes

“…In contrast to the conventional isotropic hydrogels with fibre/ polymer chains-based network, a few of anisotropic hydrogels with one-dimensional periodic lamellar structure have been discovered and received particular attentions, which expand our understanding and knowledge about hydrogels [10][11][12] . A lamellar biological hydrogel comprised of fluid membranes of lipids and surfactants with small amounts of poly(ethylene glycol)-derived polymer lipids was firstl reported by C. R. Safinya et al 10 The lamellar hydrogel with the maximum water spacing of B40 nm between adjacent layers exhibits birefringent liquid crystalline behaviour.…”