Study Of Layer-by-layer Self-assembly Of Tannic Acid And Polyether Toward Neural Interface Application

Layer-by-layer assembly technique is a multi-functional method for surface modification,with great potentials for biological applications.This method is simple to operate,and can be used to construct a well-controlled nano-sized film with tunable chemical composition,morphology,thickness,structure and function by alternating deposition of different kinds of materialIn this paper,tannic acid?TA?and polyether,such as poloxamer 188?P188?,are assembled by hydrogen bonding to construct multifunctional layer-by-layer assembly on the surface of silicon,a material commonly used for implantable neural electrodes.The multilayer was designed to integrate antioxidation properties of TA with the cell membrane repair ability of P188 so that adverse biological events encountered by electrodes implantation in neural interface technology,such as blood-brain barrier damage and inflammatory reactions could be addressed.The solution behavior of TA and P188 mixture was first measured by dynamic light scattering?DLS?.Next,the multilayer assembling behavior,chemical composition and structure,surface wettability,antioxidation,cytotoxicity,biological activity,and drug loading capacity of the multilayers were characterized by UV-vis spectrophotometer,quartz crystal microbalances?QCM?,surface plasma resonance?SPR?,attenuated total reflection Fourier transform infrared spectroscopy?ATR-FTIR?,contact angle goniometer,optical microscopy,scanning electron microscopy?SEM?,laser scanning confocal microscopy?LSCM?,atomic force microscopy?AFM?,microplate reader,and so on.It has been found that the mixture of TA and P188 at concentrations of 0.05 mg/mL?pH3?became cloudy,and particles of 195 nm with a relatively narrow distribution were obtained,confirming complexation between TA and P188 at this condition.The turbidity and particle size of the mixture solution increased when the concentrations of TA and P188increased or the solution pH decreased.Besides,the mass fraction of TA affected the complexation,with the largest particle size achieved at TA mass fraction being 0.5.UV-vis spectra,QCM,SPR and ATR-FTIR confirmed the success of hydrogen bonding driven assembly of TA and P188 multilayers,and the growth followed an exponential pattern.Results from the stability studies revealed that the multilayer was relatively stable at pH 7.4,but disassembled at pH9.0 and 11.0.Unique morphology was observed for the TA/P188multilayers,where microdome-shaped surface features emerged and evolved with the number of assembled layers increased.The assembled multilayer was hydrophilic,with the overall contact angle being less than50°.The TA/P188 multilayer also exhibited radical scavenging capability,due to of the presence of TA.Furthermore,the antioxidation property of multilayers enhanced as the number of layers increased.Preliminary in vitro cytotoxicity studies showed that the morphology of cells exposed to?TA/P188?₈ either through direct contact or through elution test was similar to that of the untreated control group.It implied cytocompatibility of the multilayer within the scope of the present investigation.The WST-1 assay quantitatively supported such observations.It also showed that?TA/P188?_n multilayer film could protect cell to various extents from death induced by H₂O₂ treatment.In addition,it was found that the microdome-shaped surface features of the TA/P188 multilayers could function as reservoir for hydrophobic compounds,as demonstrated by the successful loading of hydrophobic nile red dye.