Preparation Of Photo/Electrical Responsive Thin Film And Its Regulation On Biomolecules

Surface properties of biomaterials are important factors to the interaction between materials and cell interface,its influences on biomolecules between materials and cells eventually regulates cell behaviors.Therefore,regulations of adsorbed biomolecules play important roles in improving biological properties of biomaterials.In recent years,stimuli responsive materials have been widely used in biological field,which can be used for accurate time-space regulation of biomolecules' adsorption,desorption and conformation.In this thesis,rare earth doping was used to improve the optical properties of photo-responsive nano-structured titanium dioxide,polydopamine was used as"binder"for immobilizing nano-structured titanium dioxide on polystyrene substrate to endue it light response performance,so that high-efficiency biomolecules and cells detachment could be realized.In addition,the adsorption and desorption of proteins and polysaccharides under electric field were investigated,we further evaluated the protein secondary conformation changes and follow-up cell responses on PDA with different redox states.Moreover,we improved the biocompatibility of Ppy caused by carrying biomolecules,successfully constructed a drug release system with the properties of promoting osteogenic differentiation and anti-inflammatory.Selective release of different biomolecules from the co-deposited composite Ppy coatings was also realized.The mechanism of such selective release of two model biomolecules was investigated.The main results are as following:1.Construction of photo-responsive thin film based on TiO2 and its regulation on proteins and cellsThe preparation of Eu-doped titanium dioxide nanodot film was achieved through phase separation induced self-assembly,with adding Eu(TMHD)3 during solution preparation.The morphology hardly changed after the addition of Eu,and it improved cell adhesion properties of titanium dioxide nanodots.Eu doping endued TiO2 unique photoluminescence properties,a strong luminescence intensity appeared at the wavelength of 614 nm under ultraviolet light,it also enhanced light absorption range and fluorescence lifetime,which was beneficial for photo-induced regulation of biomolecules on TiO2.The amount of adsorbed proteins can be characterized by the illumination intensity at 614 nm,and protein desorption was found under UV light.The Eu-doped TiO2 nanodot film exhibited good biocompatibility and a rapid detachment of cell sheets under UV illumination,the detached cells remained good viability.Polystyrene was first modified by polydopamine,then spin coating method was used to prepare TiO2/PDA composite film when the substrate was semi-wet,the obtained film was made up by densely stacked nano-particles.TiO2 was mostly on the top layer and PDA on the bottom layer,the composite film has good ultraviolet light transmittance,bonding strength and photoinduced hydrophilicity.TiO2/PDA composite film has good compatibility and can be used for direct and efficient cell harvest.2.Study on electrical responsive films and protein molecular regulation based on polydopaminePDA has not only outstanding performance as binder,but also good electrical responsiveness.A dense and uniform PDA film was prepared on the surface of Ti substrate by self-polymerization.The adsorption and desorption experiments of BSA and Starch biomolecules showed that PDA film can not only enhance the initial protein and polysaccharide adsorption properties of the substrate,but also enhance the surface protein adsorption and weaken the desorption effect of the polysaccharide under external electric field.There are three states of PDA under different electric field:original,oxidation,reduction states.These states can be reversibly conversed by the transformation of phenolic hydroxyl group and sulfhydryl group.Oxidation and reduction states showed better protein adsorption performance.BSA and BMP-2 were used for pre-adsorption before cell experiment,cell proliferation and differentiation enhancement were found owing to the proper regulation of protein conformation on PDA with different states.3.Study on polypyrrole based electrical responsive composite film and drug releaseStructured Ppy/Dex film was prepared by hot alkali treatment and anodizing method,the drug was successfully loaded in the film.After conjugation with ECM,a large area of ECM was immobilized on the surface with many exposed tips of nanofibers.The final exposure area and ECM/Ppy ratio of such Ppy/Dex/ECM composite film could be adjusted.The ECM complex improved the biocompatibility of Ppy film and provided a micro-environment that promoted osteogenic differentiation.In addition,the drug release under electrical stimuli not only enhance the differentiation but also greatly improve the anti-inflammatory function of the Ppy/Dex/ECM composite film,which makes it potential for implant surface modification applications.4.Study on polypyrrole based dual-molecules loaded electrical responsive film and selective releaseBS A and Hep co-loaded Ppy film was successfully prepared,the compatibility was improved by using Ppy film with sodium p-toluenesulfonate as dopant as the bottom layer.The content of BSA and Hep can be regulated by changing the deposition current and time.When positive electrical stimuli were applied,the change of pH value around BHP film made BSA turn positive,the electrostatic repulsion caused the release of BSA,the stronger the electric field was,the more amount of BSA released.At the same time,the release of Hep was inhibited.When negative electrical stimuli were applied,Hep showed a preferential release effect due to its low molecular weight and high electronegativity,the release of BSA was inhibited.As a result,selective release of two biomolecules was achieved under different external electric field.Further cell experiment showed that electrically controlled release of BSA promoted cell proliferation,the release of Hep promoted cell spreading and osteogenic differentiation.The release time point of Hep showed great influence on cell osteogenic differentiation,the ALP activity of pre-osteoblasts was most obviously promoted by releasing Hep at 1 and 3 days.In this thesis,different kinds of external(photo/electric)responsive films were designed,and the external field was used to control the adsorption,desorption and conformation of biomolecules on materials,in order to achieve efficient cell detachment,improve cell adhesion,proliferation,differentiation performance and relieve inflammation.We further explored the mechanism of selective release of bimolecules under electric field.These are of great importance for effective regulation of surface biomolecules and subsequent cell behavior.