Studies of Dipalmitoylphosphatidylcholine (DPPC) Monolayers Embedded with Endohedral Metallofullerene (Dy@C82)
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- 作者：Zhining Wang ; Xiaofang Li ; Shihe Yang
- 刊名：Langmuir
- 出版年：2009
- 出版时间：November 17, 2009
- 年：2009
- 卷：25
- 期：22
- 页码：12968-12973
- 全文大小：929K
- 年卷期：v.25,no.22(November 17, 2009)
- ISSN：1520-5827
文摘
Toxicological effects of carbon nanomaterials have attracted increasing attention. In this work, we studied the interaction between Dy@C82 and dipalmitoylphosphatidylcholine (DPPC) in a monolayer at the N2/Tris buffer interface by thermodynamic analysis of surface pressure−area (π−A) and surface potential−area (ΔV−A) isotherms. Dy@C82 was found to impact considerably more on the physical properties of the monolayers than C60 because of its elliptical structure and distinctive dipole. The addition of Dy@C82 essentially closed down the liquid expanded−liquid condensed (LE−LC) phase coexistence region of the mixed monolayers. Furthermore, Dy@C82 reduced elasticity of the monolayers, as indicated by the decreasing elastic modulus (Cs−1) with increasing molar ratio of Dy@C82 (XDy@C82). Brewster angle microscopy (BAM) and atomic force microscopy (AFM) revealed that the dispersion of Dy@C82 depend on the state of the mixed films. Dy@C82 formed flocs from aggregation of Dy@C82 towers in the LE and LE−LC coexistence regions, accompanied by gradual falling down of Dy@C82 from the towers and permeation of the falling metallofullerenes into the LE phase during their compression-induced reorientation process. In the LC and solid phases, the Dy@C82 flocs were dispersed into isolated towers, accompanied by the partial squeezing out of the embedded metallofullerenes to above the DPPC monolayer. The continuous falling down of Dy@C82 from the towers resulted in their height decrease but diameter enlargement. When the surface pressure was increased to the kink value (53 mN/m), Dy@C82 was almost completely extruded from the DPPC monolayers. These findings are believed to be important for understanding the impact of fullerenes, metallofullerenes, and nanomaterials in general on biological membranes.