Enhanced And Electro-tunable Adhesion Of Bioinspired Edot Conducting Polymer To Bioelecotrodes

Poly(3,4-ethylene dioxythiophene)(PEDOT)has excellent potential in the application of implanted neural electrodes due to its flexibility,biocompatibility,water stability and charge storage capacity.However,the adhesion of PEDOT with metals and inorganic electrode substrates could not meet the requirement for long term electrical communication.Continual electro-recording and nerve stimulation would lead to debonding of the PEDOT materials and increasing of impedance.In this work,we provided a new type of conductive polymer film,which can tightly adhere to the polymer surface and electrode surface,inspired by the marine Mussel.Mussels can strongly attach to diverse substrates with high binding strength even on wet surfaces.It was found that the extraordinarily robust adhesion of Mussels was determined by the 3,4-dihydroxy-L-phenylalanine(DOPA)and lysine-enriched proteins near the plaque-substrate interface.Dopamine,which possessed similar molecular structure to DOPA,was introduced to improve the adhesion of the conductive polymer film.Dopamine can be easily deposited on virtually all types of inorganic and organic substrates,including superhydrophobic surfaces.Polydopamine is also a major pigment of naturally occurring melanin(eumelanin).Consequently,polydopamine displays excellent properties in optics,electricity and magnetics.Most importantly,it processes excellent biocompatibility.Thus,dopamine possesses great potential applications in the field of implanted neural electrodes.First of all,Poly(3,4-ethylene dioxythiophene-dopamine)(PEDOT-DA)with strong adhesion and highly conductive was prepared by electrochemical polymerization of EDOT,linked with dopamine side chain.We used tape adhesion test,weight test and ultrasonic wave test to evalutate the adhesion of a series of PEDOTs in dry and wet states.Among all the conducting polymers,PEDOT-DA showed the strongest bonding to electrodes both in dry and wet states.We further incuded PEDOT-DA as interfacial layer to enhance the adhesion between PEDOT and electrode substrates.Polydopamine and dopamine is prone to diffusion on substrates through noncovalent binding interaction such as metal coordination or chelating,hydrogen bonding,π-π stacking and quinhydrone charge-transfer complexes to yield an effective adlayer.Oxidation of dopamine to semidopaminequinone or dopaminequinone will form a strong irreversible covalent organic surfaces,the adhesion of polymer film rely mainly on molecular interactions,adhesion decreased rapidly.PEDOT-DA is electrochemical oxidized to PEDOT-DAQ,adhesion decreased sharply,which can control the polymer film’s adhesion and removal.At last,we tried to electrochemical deposit PEDOT on PEDOT-DA interface layer or introduce EDOT-DA to other EDOT copolymers,both of these methods can significantly enhance the interface adhesion of PEDOT polymer films with substrate.A new strong adhesion and nonspecific adhesion polymer electrode was prepared by introduce EDOT-DA to EDOT-PC polymer which posses nonspecific adhesion.This electrode has a very strong physical adhesion and nonspecific cell adhesion and can control the electrode polymer’s adhesion and removal by electrochemical oxidation.Electrical stimulation experiments was performed to validate the electrode’s stability and reliability in the long working term,taking into account the practical application environment.Accordingly,a strong adhesion and nonspecific adhesion bio-electrodes which can control the adhesion and removal of polymer film by electrochemical oxidation was maked.