Self-Assembly Formation of Lipid Bilayer Coatings on Bare Aluminum Oxide: Overcoming the Force of Interfacial Water

Abstract

Widely used in catalysis and biosensing applications, aluminum oxide has become popular for surface functionalization with biological macromolecules, including lipid bilayer coatings. However, it is difficult to form supported lipid bilayers on aluminum oxide, and current methods require covalent surface modification, which masks the interfacial properties of aluminum oxide, and/or complex fabrication techniques with specific conditions. Herein, we addressed this issue by identifying simple and robust strategies to form fluidic lipid bilayers on aluminum oxide. The fabrication of a single lipid bilayer coating was achieved by two methods, vesicle fusion under acidic conditions and solvent-assisted lipid bilayer (SALB) formation under near-physiological pH conditions. Importantly, quartz crystal microbalance with dissipation (QCM-D) monitoring measurements determined that the hydration layer of a supported lipid bilayer on aluminum oxide is appreciably thicker than that of a bilayer on silicon oxide. Fluorescence recovery after photobleaching (FRAP) analysis indicated that the diffusion coefficient of lateral lipid mobility was up to 3-fold greater on silicon oxide than on aluminum oxide. In spite of this hydrodynamic coupling, the diffusion coefficient on aluminum oxide, but not silicon oxide, was sensitive to the ionic strength condition. Extended-DLVO model calculations estimated the thermodynamics of lipid-substrate interactions on aluminum oxide and silicon oxide, and predict that the range of the repulsive hydration force is greater on aluminum oxide, which in turn leads to an increased equilibrium separation distance. Hence, while a strong hydration force likely contributes to the difficulty of bilayer fabrication on aluminum oxide, it also confers advantages by stabilizing lipid bilayers with thicker hydration layers due to confined interfacial water. Such knowledge provides the basis for improved surface functionalization strategies on aluminum oxide, underscoring the practical importance of surface hydration.

Construction of Cell–Extracellular Matrix Microenvironments by Conjugating ECM Proteins on Supported Lipid Bilayers

“…Different from conventional vesicle fusion method, which involves the spontaneous adsorption and rupture of phospholipid vesicles, and is limited to only a subset of lipid compositions and solid supports (Huang et al, 2010a,b,c), the SALB formation method is based on the reverse-phase evaporation phenomenon and involves lipid deposition onto a hydrophilic solid surface in an alcohol (Tabaei et al, 2014). The SALB method has been applied successfully to a wide variety of substrates, such as Au, Al 2 O 3 , and graphene, which are intractable to the conventional method (Tabaei et al, 2014;Jackman et al, 2015). The ECM proteins of type I collagen and fibronectin were chemical conjugated on SALB-assisted SLBs.…”

Hydrodynamic Propulsion of Liposomes Electrostatically Attracted to a Lipid Membrane Reveals Size-Dependent Conformational Changes

“…39 The above mentioned studies demonstrate the potential of combined diffusivity and drift velocity measurements to extract properties of particles that are confined to a mobile interface, but did not specifically address that liposomes may deform in response to interfacial interactions, as previously observed at solid interfaces. [40][41][42][43][44][45][46] Inspired by the design of lipid nanoparticles that has been proven efficient in various drug delivery applications, we here apply this approach to determine both the size and conformational changes of individual membrane-adhering liposomes induced by direct membrane-membrane interactions controlled by electrostatic attraction between oppositely charged lipid bilayers in close contact. 47,48 The observed dependence of liposome deformation on size and membrane rigidity is discussed in the context of understanding how to optimize lipid nanoparticle formulations.…”

Fabrication of ZnO nanoparticles by solution-combustion method for the photocatalytic degradation of organic dye

“…The microscopic analysis outcome of the MSA is usually visualized as aggregations of nanofibers [9], nanorods, [10] nanotubes [11], or nanospheres [12]. MSA has been commonly observed in nature, for instance, in the formation of the various intriguing biomolecules, such as the DNA nucleobases, proteins, viruses, and lipid bilayers [13][14][15][16]. A growing interest has been dedicated over the past decades to two-dimensional (2D) self-assembly of supramolecular architectures at solid surfaces due to its impact for developing new nanomaterials [17].…”