Modulation Of Surface Potential Of P(VDF-TrFE)-based Funtional Films And Their Interaction With Cells

The interaction of biomaterials with cells plays a key role in cell behavior/tissue formation,and the surface potential of material is one of the important factors affecting their interaction.Constructing a suitable surface potential microenvironment for cell/tissue growth is an effective approach to promote the formation of bone tissue and osseointegration.However,how to rationally adopt the surface potential and its change to meet the requirement of cell growth is still a great challenge for the current research on biological materials.In this paper,the static and dynamic changes of the surface potential of the material are used to reveal the influence of surface potential on the cell behavior and the mechanism of action.Using a polyvinylidene fluoride trifluoroethylene polymer(P(VDF-TrFE))with excellent biocompatibility and ferroelectricity,a static modulation of stable surface potential is achieved by electrical poling treatment.Magnetostrictive cobalt ferrite(CoFe2O4)nanoparticles were introduced into P(VDF-TrFE),and a dynamic modulation of controllable surface potential was achieved by an external magnetic field.On this basis,the effects of static and dynamic changes in surface potential on cell behavior(adhesion,proliferation,differentiation,and mineralization)were investigated,and the mechanism of material-cell interaction mediated by static and dynamic surface potentials was explored.The main results are as follows:1.Preparation of P(VDF-TrFE)based thin film and its static or dynamic modulation of surface potentialA P(VDF-TrFE)ferroelectric thin film was prepared on Ti substrate by a solution casting method,and the prepared P(VDF-TrFE)thin film was poled by a contact poling method.The electric field intensity of poling treatment was controlled to obtain a P(VDF-TrFE)film with a wide range of surface potential changes(Kelvin potential:-3,106,391,915 mV),also,the surface potential was fairly stable(Almost no attenuation after 60 days soaking in PBS solution).Magnetostrictive CoFe2O4(CFO)nanoparticles were added into P(VDF-TrFE)solution,and CFO/P(VDF-TrFE)magnetoelectric thin films were prepared by solution casting on Ti substrate.After the poling treatment,the static surface potential of the CFO/P(VDF-TrFE)film was 97 mV(Kelvin potential).When an external magnetic field in the range of 0 to 3000 Oe is applied,the surface potential changes of the film is as much as 93 mV(magnetic-induced potential).2.Effect of static surface potential of P(VDF-TrFE)thin film on osteoblast differentiation and its mechanismThe MC3T3-E1 cells were grown on P(VDF-TrFE)thin films and it was found that as the surface potential of the thin film increased(-3,106,391,915 mV),the osteogenic differentiation capacity of the cells showed a parabola that first increased and then decreased.In the trend,cells with a surface potential of 391 mV exhibited the strongest osteogenic differentiation ability.Studies on the binding mechanism of fibronectin(FN)binding activity and molecular dynamics simulations show that the exposure of RGD adhesion sites and PHSRN coordination sites on FN with a surface potential of 391 mV The largest and shortest distances facilitate the formation of a completely bound state of the integrinα5β1 and FN(β1-RGD + a5-PHSRN),while the potential at the surface of the film is too low(106 mV)or too high(915 mV).The PHSRN coordination site on FN is not fully exposed,making α5β1 and FN only form a partially binding state(β1-RGD).Furthermore,gene and protein results showed that when α5β1 and RGD and PHSRN sites on FN are in a fully binding state,integrin-mediated FAK/ERK osteogenic differentiation signaling pathway can be effectively enhanced.Therefore,the present study reveals that the modulation of the static surface potential can change the conformation of the adsorbed protein and mediate the interaction with integrin,thereby affecting the degree of activation of the signaling pathway of osteogenic differentiation.3.Effect of dynamic surface potential of CFO/P(VDF-TrFE)thin film on osteogenic differentiation and its mechanismMC3T3-E1 cells were cultured on CFO/P(VDF-TrFE)thin films and the surface potential of the films was changed during cell culture by an external magnetic field.It was found that during the cell culture period(7 days),when the different intensities of magnetic fields were applied at different growth period,ie,the surface potential of the film was dynamically changed,the cells could exhibit stronger osteogenic differentiation ability.Under the condition of constant application of external magnetic field during cell culture,in the adhesion phase(0～1 day),the cell has the best adhesion effect when magnetic-induced potential of the film is 53 mV(2000 Oe);in the proliferation phase(2～4 days)When magnetic-induced potential of the film was 88 mV(2600 Oe),the cells had the best proliferation effect;in the differentiation stage(5-7 days),the osteogenic differentiation of cells was not sensitive to the changes of magnetic-induced potential of the film.Based on this result,dynamic magnetic fields were applied during cell culture to generate a dynamic change in the magnetic-induced potential on the surface of the film.The optimal surface potential was set during the adhesion phase and the proliferation phase,respectively,and after a 7-day cell culture,osteogenic differentiation of the cells was significantly enhanced.The FN binding activity assay and molecular dynamics simulations on its mechanism of action have shown that,at a magnetic-induced surface potential of 53 mV,the exposure of RGD sites on FN is maximized,resulting in binding of integrinα5β1 to FN(The strongest β1-RGD)enhances the cell’s ability to recognize and adhere;when the surface magnetic-indeced potential increases to 88 mV,the exposure of the PHSRN locus increases,making the binding of a5-PHSRN significantly stronger(β1-RGD + a5-PHSRN)forms a well-binding state,thereby enhancing cell proliferation and activation of osteogenic differentiation signalling pathways.Therefore,the present study reveals the modulation of dynamic surface potentials that can dynamically alter the conformation of adsorbed proteins,dynamically mediate the interaction with integrins,and achieve the most strongest effects,thereby comprehensively enhancing the activation degree of cellular osteogenic differentiation signaling pathway during cell growth.The first proposed strategy for dynamically modulating surface potential to mediate cellular osteogenic differentiation demonstrates its scientificity and effectiveness.