ABSTRACT
Fe3O4 nanoparticles (NPs) as a commonly used carrier in targeted drug delivery are widely used to carry drugs for the treatment of diseases. However, the mechanism of action of between Fe3O4 NPs and biological membranes is still unclear. Therefore, this article reports the influence of hydrophilic and hydrophobic Fe3O4 NPs on mixed 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) that were studied using the Langmuir-Blodgett (LB) film technique and an atomic force microscope (AFM). From surface pressure-area (π-A) isotherms, we have calculated the compression modulus. The results showed that hydrophobic Fe3O4 NPs enlarged the liquid-expanded (LE) and liquid-condensed (LC) phase of the mixed POPC/DPPC monolayers. The compressibility modulus of the mixed POPC/DPPC monolayer increases for hydrophilic Fe3O4 NPs, but the opposite happens for the hydrophobic Fe3O4 NPs. The adsorption of hydrophobic Fe3O4 NPs in mixed POPC/DPPC monolayers was much more than the hydrophilic Fe3O4 NPs. The interaction of hydrophilic Fe3O4 NPs with the head polar group of the mixed lipids increased the attraction force among the molecules, while the interaction of hydrophobic Fe3O4 NPs with the tail chain of the mixed lipids enhanced the repulsive force. The morphology of the monolayers was observed by AFM for validating the inferred results. This study is of great help for the application of Fe3O4 NPs in biological systems.
ABSTRACT
In this paper, the adsorption behavior of DNA on 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) mixed lipid monolayers had been studied at the air-water interface through the surface pressure-area curves (π-A), adsorption curves (π/π0-t), excess mean area (∆Aexc), excess Gibbs free energy (∆Gex) and the atomic force microscopy (AFM). π-A isotherms showed that the curves moved to larger mean molecular area after DNA added into subphase, however, the curves shifted to smaller mean molecular area when the concentration of DNA was higher than 1.2⯵g/mL. The result of adsorption curves indicated that DNA molecules were spread by combining with polar head groups of lipids except the concentration of DNA was 0.4⯵g/mL. ∆Aexc and ∆Gex demonstrated that DNA enlarged the interval between DPPC and POPC, and the strongest position happened at the concentration of DNA was 1.2⯵g/mL. These phenomena might be the steric hindrance between DNA molecules. Morphology of surface observed by AFM was agreement with the results above, which verified our conclusion from a more intuitive aspect. This work provides useful theoretical basis for the development of novel DNA delivery materials.
