title: Investigation of the interface in silica-encapsulated liposomes by combining solid state NMR and first principles calculations.
abstract: In the context of nanomedicine, liposils (liposomes and silica) have a strong potential for drug storage and release schemes: such materials combine the intrinsic properties of liposome (encapsulation) and silica (increased rigidity, protective coating, pH degradability). In this work, an original approach combining solid state NMR, molecular dynamics, first principles geometry optimization, and NMR parameters calculation allows the building of a precise representation of the organic/inorganic interface in liposils. {(1)H-(29)Si}(1)H and {(1)H-(31)P}(1)H Double Cross-Polarization (CP) MAS NMR experiments were implemented in order to explore the proton chemical environments around the silica and the phospholipids, respectively. Using VASP (Vienna Ab Initio Simulation Package), DFT calculations including molecular dynamics, and geometry optimization lead to the determination of energetically favorable configurations of a DPPC (dipalmitoylphosphatidylcholine) headgroup adsorbed onto a hydroxylated silica surface that corresponds to a realistic model of an amorphous silica slab. These data combined with first principles NMR parameters calculations by GIPAW (Gauge Included Projected Augmented Wave) show that the phosphate moieties are not directly interacting with silanols. The stabilization of the interface is achieved through the presence of water molecules located in-between the head groups of the phospholipids and the silica surface forming an interfacial H-bonded water layer. A detailed study of the (31)P chemical shift anisotropy (CSA) parameters allows us to interpret the local dynamics of DPPC in liposils. Finally, the VASP/solid state NMR/GIPAW combined approach can be extended to a large variety of organic-inorganic hybrid interfaces.
authors: UPMC Univ Paris 06 & CNRS, UMR 7574, Chimie de la Matière Condensée de Paris, Collège de France, 11, place Marcelin Berthelot, F-75005, Paris, France.
authors: Nicolas
authors: N
authors: Folliet
authors: Claire
authors: C
authors: Roiland
authors: Sylvie
authors: S
authors: Bégu
authors: Anne
authors: A
authors: Aubert
authors: Tzonka
authors: T
authors: Mineva
authors: Annick
authors: A
authors: Goursot
authors: Kaliaperumal
authors: K
authors: Selvaraj
authors: Luminita
authors: L
authors: Duma
authors: Frederik
authors: F
authors: Tielens
authors: Francesco
authors: F
authors: Mauri
authors: Guillaume
authors: G
authors: Laurent
authors: Christian
authors: C
authors: Bonhomme
authors: Christel
authors: C
authors: Gervais
authors: Florence
authors: F
authors: Babonneau
authors: Thierry
authors: T
authors: Azaïs
mesh_terms: D002214:Capsules / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D015394:Molecular Structure; D011789:Quantum Theory; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D002214:Capsules; D008081:Liposomes; D012822:Silicon Dioxide