Investigation of the Interface in Silica-Encapsulated Liposomes by Combining Solid State NMR and First Principles Calculations

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• 作者：Nicolas Folliet ; Claire Roiland ; Sylvie B茅gu ; Anne Aubert ; Tzonka Mineva ; Annick Goursot ; Kaliaperumal Selvaraj ; Luminita Duma ; Frederik Tielens ; Francesco Mauri ; Guillaume Laurent ; Christian Bonhomme ; Christel Gervais ; Florence Babonneau ; Thierry Aza茂s
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：October 26, 2011
• 年：2011
• 卷：133
• 期：42
• 页码：16815-16827
• 全文大小：1198K
• 年卷期：v.133,no.42(October 26, 2011)
• ISSN：1520-5126

文摘

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. {¹H鈥?sup>29Si}¹H and {¹H鈥?sup>31P}¹H 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 ³¹P 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鈥搃norganic hybrid interfaces.