Oxide-Dependent Adsorption of a Model Membrane Phospholipid, Dipalmitoylphosphatidylcholine:  Bulk Adsorption Isotherms

Abstract

The importance of substrate chemistry and structure on supported phospholipid bilayer design and functionality is only recently being recognized. Our goal is to investigate systematically the substrate-dependence of phospholipid adsorption with an emphasis on oxide surface chemistry and to determine the dominant controlling forces. We obtained bulk adsorption isotherms at 55 degrees C for dipalmitoylphosphatidylcholine (DPPC) at pH values of 5.0, 7.2, and 9.0 and at two ionic strengths with and without Ca(2+), on quartz (alpha-SiO(2)), rutile (alpha-TiO(2)), and corundum (alpha-Al(2)O(3)), which represent a wide a range of points of zero charge (PZC). Adsorption was strongly oxide- and pH-dependent. At pH 5.0, adsorption increased as quartz < rutile approximately corundum, while at pH 7.2 and 9.0, the trend was quartz approximately rutile < corundum. Adsorption decreased with increasing pH (increasing negative surface charge), although adsorption occurred even at pH > or = PZC of the oxides. These trends indicate that adsorption is controlled by attractive van der Waals forces and further modified by electrostatic interactions of oxide surface sites with the negatively charged phosphate ester (-R(PO(4)-)R'-) portion of the DPPC headgroup. Also, the maximum observed adsorption on negatively charged oxide surfaces corresponded to roughly two bilayers, whereas significantly higher adsorption of up to four bilayers occurred on positively charged surfaces. Calcium ions promote adsorption beyond a second bilayer, regardless of the sign of oxide surface charge. We develop a conceptual model for the structure of the electric double layer to explain these observations.

Cell membrane disruption induced by amorphous silica nanoparticles in erythrocytes, lymphocytes, malignant melanocytes, and macrophages

“…In addition to the particulate silica, the interactions of silica substrates with PC liposomes [70] have been studied by quartz crystal microbalance (QCM) [71][72][73] and AFM [62,74]. These studies indicate that affinity of the bare silica surface for neutral PCs is rather weak and mainly attributed to van der Waals forces [58][59][60][61][62]68], which is consistent with the results of our AFM measurements shown in Fig. 5d.…”

“…It is noted that a major constituent of cell membranes is phosphatidylcholine (PC), which has a zwitterionic head group of the phosphate ester (ÀR(PO 4 À )R 0 À) and the quaternary amine (ÀN(CH 3 ) 3 + ) moieties and is more commonly found in the exoplasmic leaflet of a cell membrane. The interactions of silica particles with protein-free bilayers of PC have been investigated by the leakage of entrapped tracers from liposomes [56][57][58], the adsorption isotherms [57][58][59][60][61][62], the nuclear magnetic resonance (NMR) spectroscopy [63], the cryogenic transmission electron microscopy (Cryo-TEM) [64], the fluorescence microscopy and isothermal titration calorimetry [65], and the calorimetry, electrophoresis, dynamic light scattering (DLS), and Cryo-TEM [66,67]. The interactions of silica particles with supported membranes of PC have been studied by the electrochemistry and calorimetry [68] and the electrophysiology and fluorescence microscopy [69].…”

Interaction energies between oxide surfaces and multiple phosphatidylcholine bilayers from extended-DLVO theory

“…Furthermore, vesicle rupture and stability of stacked multiple bilayers on mineral surfaces may provide a model for evolution of pre-biotic, or early, cell membranes. Spontaneouslyformed and fabricated multiple SPBs on particles and planar surfaces of SiO 2 , TiO 2 , Al 2 O 3 , and mica have been reported previously [4,5,11,[13][14][15][16][17][18].…”

“…The diversity of current and potential applications for solid-supported phospholipid bilayers (SPBs) in areas such as biomedicine, biomineralization, biogeochemistry, materials science, and environmental remediation is established in the literature [1][2][3][4][5]. Efforts to produce and characterize SPBs have focused mainly on systems in which a single bilayer is deposited on the substrate.…”

Lipid-based Biomimetics in Drug and Vaccine Delivery

“…Glass microspheres coated with phospholipid layers evaluated the binding specificity of enzymes on cell surface (Obringer et al 1995) or quantified lipid-antibodies binding (Kiser et al, 1998). Recent work continues to investigate lipid-supporting particles based on minerals Nordlund et al 2009;Ahmed & Wunder, 2009;Xu et al, 2009;Oleson & Sahai, 2008;Pyiasena et al, 2008;Senarath-Yapa et al 2007;Moura & Carmona-Ribeiro, 2007;Parida et al, 2006), polymers Jha & Bose, 2009;Thevenot et al, 2008;Bershteyn et al 2008;Zuzzi et al, 2008;Troutier et al, 2005;Pereira et al, 2004), metals eg magnetoliposomes for biomedical applications or contrast agents in magnetic resonance imaging (Bulte & De Cuyper, 2003) or biological cells as templating cores to be dissolved to obtain capsules (Ge et al, 2003) or viruses for enhancing adenovirus tumor targeting in vivo (Singh et al, 2008). Polymer hollow capsules were produced by Möhwald and coworkers (Ge et al, 2003) from the polyelectrolyte layer-by-layer technique on biological cells.…”