Construction Of Multilyered Composites From Poly(dopamine) Modified Carbon Nanotubes And The Interactions With Cells

Carbon nanotubes(CNTs) have attracted much attention because of their unique physical and chemical properties since discovery,which allows for great applications in the fields of electricity,optics and functional composites.However,CNTs are highly agglomerated and entangled due to the large π bond with high degree of delocalization and the large aspect ratio,limiting the application of CNTs greatly.Dopamine(3,4-dihydroxy-phenylalanine,DA)is an environmentally friendly biomolecule.It can self-polymerize under mild conditions and adhere to any substrate without changing the inherent properties.Poly(dopamine)(PDA)layer with active functional groups can be used as a secondary reaction platform and induce other functional polymers to further modification of materials.In this study,DA self-polymerization under alkaline aerobic conditions was carried out to coat the surface of CNTs.Then we evaluated the biocompatibility of the modified carbon nanotubes(CNT@PDA).Furthermore the CNT@PDA-polyelectrolyte multilayers were prepared by the layer-by-layer self-assembly technology.The interactions between the composite films and macrophages and neural stem cells were also evaluated to study its application in the field of neuroscience.Specific work is presented as follows:(1)CNTs modification via DA self-polymerization.The CNT@PDA particles were characterized by TEM and XPS.The results showed that poly(dopamine)was successfully coated on the surface of carbon nanotubes.At the same time,the biocompatibility of CNT@PDA particles was studied.We used macrophages as models and specially investigated the activation profile of macrophages and cellular events occurring when interfacing with CNT@PDA particles including cell viability,intracellular reactive oxygen species(ROS)production,phagocytic capacity,inflammatory response and gene expression.The results showed that CNT@PDA particles had no significant damage on macrophage activity.However,after treatment with CNT@PDA particles,macrophage phagocytic capacity for 0.1-1 μm microspheres particles decreased,and larger sizes were less internalized compared to smaller sizes.CNT@PDA particles promoted the secretion of pro-inflammatory factors to a certain extent.But the effects on macrophage gene expression were limited.(2)CNT@PDA-poly-lysine multilayers by the layer-by-layer self-assembly technology.They were characterized by UV,XPS and contact angle.Results showed that multilayers were constructed successfully.And the interaction between the PLL-CNT@PDA multilayers and macrophages was studied.We also chose the biocompatible PLLA film as the substrate of free-standing CNT multilayers to facilitate the evaluation of biocompatibility of CNT nanofilms.A 4-week subcutaneous implantation was performed to reveal plausible chronic foreign-body responses.Results showed that the PLL-CNT@PDA multilayers had no severe effect on macrophage activity.And we did not observe CNT@PDA particles in macrophage.Normal histology was observed in the subcutaneous muscle tissue contacting PLL-CNT@PDA film in vivo.These results indicated that PLL-CNT@PDA multilayer had good biocompatibility.(3)The CNT@PDA-Poly-dimethyl-diallyl-ammonium-chloride(PDDA)multilayer by the layer-by-layer self-assembly technology,and interaction with neural stem cells(NSCs).The results showed that PDDA-CNT@ PDA multilayers were beneficial to the differentiation of neural stem cell to neuron.Moreover,growth of neuronal axons and dendrites were promoted and the enrichment of astrocytes was affected to a certain extent.