Wang Z, Li X, Yang S. Studies of dipalmitoylphosphatidylcholine (DPPC) monolayers embedded with endohedral metallofullerene (Dy@C82).
LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009;
25:12968-12973. [PMID:
19739623 DOI:
10.1021/la9017932]
[Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Toxicological effects of carbon nanomaterials have attracted increasing attention. In this work, we studied the interaction between Dy@C(82) and dipalmitoylphosphatidylcholine (DPPC) in a monolayer at the N(2)/Tris buffer interface by thermodynamic analysis of surface pressure-area (pi-A) and surface potential-area (DeltaV-A) isotherms. Dy@C(82) was found to impact considerably more on the physical properties of the monolayers than C(60) because of its elliptical structure and distinctive dipole. The addition of Dy@C(82) essentially closed down the liquid expanded-liquid condensed (LE-LC) phase coexistence region of the mixed monolayers. Furthermore, Dy@C(82) reduced elasticity of the monolayers, as indicated by the decreasing elastic modulus (C(s)(-1)) with increasing molar ratio of Dy@C(82) (X(Dy@C82)). Brewster angle microscopy (BAM) and atomic force microscopy (AFM) revealed that the dispersion of Dy@C(82) depend on the state of the mixed films. Dy@C(82) formed flocs from aggregation of Dy@C(82) towers in the LE and LE-LC coexistence regions, accompanied by gradual falling down of Dy@C(82) 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@C(82) 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@C(82) 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@C(82) 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.
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