Interaction Between Magnetic Nanoparticles And Phospholipid Molecules In Two-dimensional Monolayers

As the core of nanobiological materials,nanoparticles are widely used in industrial production,electronic products,biomedicine and other scientific fields due to their special electrical and optical properties.Due to its low toxicity,biocompatibility and chemical affinity,as well as certain targeting and large specific surface area,Fe₃O₄ magnetic nanoparticles play an important role in magnetic resonance imaging,targeted drug delivery,immobilized enzymes and the treatment of environmental pollution.However,Fe₃O₄ magnetic nanoparticles are easily oxidized and tend to aggregate together,resulting in weakened dispersibility and stability.Therefore,organic molecules（such as Oleic Acid）,polymers,surfactants or biomolecules are often used to modify the surface of Fe₃O₄ to form a dense protective monolayer and enhance the stability and dispersion of Fe₃O₄ magnetic nanoparticles.As a carrier of drug delivery,Fe₃O₄ magnetic nanoparticles will interact with the biofilm,adsorb on or through the cell membrane,and deposit in the target organs,causing potential health risks in applications such as biological imaging and drug delivery.Fe₃O₄ magnetic nanoparticles in industrial environment can reach the alveoli through respiration,affecting human health.Due to the complex structure of the biofilm and the lack of safe in vivo experimental technology,the interaction between Fe₃O₄ magnetic nanoparticles and the main phospholipids DPPC,DPPG and DOPC in the biofilm was studied by using Langmuir technology and Brewster Angle Microscope（BAM）,and the effect of Fe₃O₄ magnetic nanoparticles on the phospholipid monolayer was investigated.1.Interaction between DPPC and OA-Fe₃O₄ MNPs monolayers.By collecting theπ-A isotherms,π-t adsorption curves,compression expansion cycle curves and oscillation curves of DPPC monolayers with different concentrations of OA-Fe₃O₄ MNPs,and observing the surface morphology characteristics of DPPC monolayers in real time by BAM,the interaction between OA-Fe₃O₄ MNPs and DPPC molecules in two-dimensional monolayers on the gas-liquid interface was studied.The results showed that due to the addition of OA-Fe₃O₄ MNPs,the surface pressure of DPPC monolayers increased significantly,while the compressive modulus of DPPC monolayers decreased notably.In addition,the phase behavior of DPPC monolayers also changed.The stability of DPPC monolayers decreased with the increase of the concentration of OA-Fe₃O₄ MNPs.The order of OA-Fe₃O₄ MNPs and DPPC mixed monolayers was enhanced by compression,and some molecules were lost from the interface to the subphase during multiple compression-expansion processes.The response of the surface pressure of DPPC monolayers to the sinusoidal variation of mean molecular area was nonlinear.With the addition of OA-Fe₃O₄ MNPs into DPPC monolayers,the nonlinear response of monolayers to strain was weakened,but it always existed.2.Interaction between DPPG and OA-Fe₃O₄ MNPs monolayers.The interaction between OA-Fe₃O₄ MNPs and DPPG molecules in two-dimensional monolayers on the gas-liquid interface was studied by collecting theπ-A isotherms,π-t adsorption curves,compression expansion cycle curves and oscillation curves of DPPG monolayers with different concentrations of OA-Fe₃O₄ MNPs,and observing the surface morphology characteristics of DPPG monolayers in real time by BAM.The results showed that theπ-A isotherms moved to the direction of the increase of the molecular area with the increase of the content of OA-Fe₃O₄MNPs.The high concentration of OA-Fe₃O₄ MNPs easily leaded to the formation of complex between DPPG molecules and MNPs,which significantly increased the surface pressure and decreased the compression modulus(C_s^-1)of monolayers.Due to the emergence of OA-Fe₃O₄MNPs,the decreasing range of surface pressure of DPPG monolayer increased within 1 hour,indicating that the time stability of surface pressure of monolayer decreased.Some molecules were extruded from the interface during compression,thus,the expansion curve of the DPPG monolayer existed obvious hysteresis.DPPG monolayers showed nonlinear response to sinusoidal strain perturbation of the mean molecular area,OA-Fe₃O₄ MNPs did not change the viscoelastic characteristics and the time scale of relaxation process of DPPG monolayers.3.Interaction between DOPC and OA-Fe₃O₄ MNPs monolayers.By collecting theπ-A isotherms,π-t adsorption curves,compression expansion cycle curves and oscillation curves of DOPC monolayers with different concentrations of OA-Fe₃O₄ MNPs,and observing the surface morphology characteristics of DOPC monolayers in real time by BAM,the interaction between OA-Fe₃O₄ MNPs and DOPC molecules in two-dimensional monolayers on the gas-liquid interface was studied.The results showed that with the increasing of OA-Fe₃O₄ MNPs in the DOPC monolayer,the surface pressure increased and the modulus of monolayers decreased.The addition of OA-Fe₃O₄ MNPs made the monolayers more stable.The ordering of the mixed monolayers of OA-Fe₃O₄ MNPs and DOPC was enhanced by compression,and some molecules were extruded from the interface in the multiple compression-expansion.The response of the surface pressure of DOPC monolayers to the sinusoidal variation of molecular area was nonlinear,and OA-Fe₃O₄ MNPs did not change the nonlinear characteristics of rheological response of DOPC monolayers.