The Influence Of Inorganic Surface Chirality On Protein Assemblies And Subsequent Cellular Behaviors

The interaction between biomolecule and the surface of mineral material must be the common event of the prebiotic chemistry.Since many mineral materials whose surfaces lack mirror or glide plane symmetry are inherently chiral,the investigation of the interaction between chiral inorganic surface and biosystem may give interesting insight for the origin of homochirality in nature.The surfaces of chiral inorganic materials which demonstrate their chirality upon formation of asymmetrical crystalline structures or contribute to the well-organized arrangement of their basic building blocks.Their chirality can be retained even under the harsh conditions such as high temperatures and a wide range of pH values compared to surfaces modified or adsorbed chiral organic molecular.Furthermore,because of the mechanical and thermal stability of chiral inorganic surfaces,there is an increasing interest about their applications,for example,it can be used as the interface of asymmetric synthesis,electrode material to discriminate enantiomers and enantiospecific autocatalytic surface for chiral molecules decomposition As we know,chiral inorganic materials such as quartz and calcite single crystals predate chiral organic compounds on Earth.Their enantiospecific surface chemistry may have played a role in the origins of biomolecular homochirality.The research of the interaction of chiral inorganic surface and biomolecules may provide useful evidence for understanding this scientific issue.To the best of our knowledge,however,the interaction between chiral inorganic surface and biomolecules or cells has never been explored.It has been found that the chiral organic molecules modified surfaces are able to govern the biological activities of attached proteins or modulate substrate-related cellular behaviors.While,most of them have only correlated surface chirality with the propensity for cell adhesion but have not studied the role that relevant protein played in the process.Considering the protein adsorption on the substrate surface is usually the first event that occurs before cell adhesion,our recent study systematically investigated the different assemblies of insulin on tartaric acid enantiomer modified mica surfaces which further modulates both proliferation and differentiation of PC12 cells.Those interactions between chiral organic molecules modified substrates and biosystem inspire us to introduce inorganic surface chirality into the study of protein assemblies and cell behaviors.The introduction of inorganic chiral surfaces may help to explain these effects from the spatial conformation points of view,and provide a new thinking to develop novel biocompatible materials for tissue engineering,moreover,it probably provides useful information to understand the origin of the high chiral preference in nature,since it's a possible mechanism leading to biohomochirality which is provided by minerals.Herein,we choose chiral TiO₂ nanofibers modified glass substrates as model chiral inorganic surface for the first time to investigate the influence of inorganic chiral surface on the protein assemblies and cellular behaviors,since Ti-based materials are known for their numerous and diverse applications,especially in biomedical applications.To our unexpected that inorganic surface chirality greatly influences assemblies of the model protein insulin.Insulin maintains its native ?-helical oligomers on the D-TiO₂ nanofibers-modified surface?D-surface?,while form ?-sheet-rich amyloid fibrils on the L-TiO₂ nanofibers-modified surface?L-surface?.The difference in the conformation of the adsorbed insulin originates from the surface topographic chirality.Insulin maintained native helical structures and retained its bioactivity on the D-surface after incubation,which further stimulated both proliferation and differentiation of PC12 cells.On the L-surface,however,insulin converted to an inactive ?-sheet-rich insoluble fibrils structure,which did not have obvious effects on PC12 cells proliferation and differentiation.Those findings will provide new insights into developing biocompatible materials and understanding how inorganic chiral surfaces regulate protein assembly and cellular behavior,besides,it is helpful for us to understand the origin of homochirality in living systems.