Enhancing osteogenic differentiation of BMSCs on high magnetoelectric response films.

High performance of biomaterial surfaces provides a sound basis to mediate cellular growth behavior. In this work, we attempted to incorporate both positive and negative magnetostriction particles of CoFe2O4 (CFO) and TbxDy1-xFe2 alloy (TD) into piezoelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) for forming high magnetoelectric effect films, on which osteogenic differentiation could be dynamically mediated by a magnetic-field-induced surface potential (φME).The negatively poled film with TD/CFO volume ratio of 1:4 (1T4C) showed a highest magnetoelectric effect with φME of -171 mV at 2800 Oe. Compared with CFO/P(VDF-TrFE) and TD/P(VDF-TrFE) films, the φME increased about 213% and 173%, respectively. This could result from that P(VDF-TrFE) dipole domains receive a larger off-axial stress caused by the distribution characteristic of CFO and TD in P(VDF-TrFE), consequently to facilitate P(VDF-TrFE) dipole domain rearrangement. When MSCs were cultured on 1T4C film for 7 or 14 days, the magnetic actuation was setup to begin at the 4th or 8th day after the culture. The 7-day osteogenic differentiation was hardly affected for magnetic actuation at 4th day, moreover, the 14-day differentiation was significantly enhanced for magnetic actuation at 8th day. The enhancement appears just at a relatively late period of the cell growth, probably because the cells need a steady change in cell membrane potential to disassociate pairs of ß-catenin and E-cadherin and activate osteogenic-related signaling pathway. This work could provide an alternative way to promote performance for magnetoelectric materials, and get insight into understanding of interactions of surface potential with cells.

Comprehensive Evaluation of Surface Potential Characteristics on Mesenchymal Stem Cells' Osteogenic Differentiation.

The surface electric potential of biomaterials has been extensively proven to play a critical role in stem cells' fate. However, there are ambiguous reports on the relation of stem cells' osteogenic capacity to surface potential characteristics (potential polarity and intensity). To address this, we adopted a surface with a wide potential range and both positive/negative polarity in a comprehensive view to get insight into surface potential-regulating cellular osteogenic differentiation. Tb xDy1- xFe2 alloy/poly(vinylidene fluoride-trifluoroethylene) magnetoelectric films were prepared, and the film could provide controllable surface potential characteristics with positive or negative polarity and potential (ϕME) intensity variation from 0 to ±120 mV as well as keep the surface chemical composition and microstructure unchanged. Cell culture results showed that osteogenic differentiation of mesenchymal stem cells on both positive and negative potential films was obviously upregulated when the /ϕME/ intensities were set from 0-55 mV. Differently, the highest upregulated osteogenic differentiation on the positive potential films corresponded to the /ϕME/ intensity from 35-55 mV and was better than that on the negative potential films whereas the highest on the negative potential films corresponded to the /ϕME/ intensity from 0-35 mV and was better than that on the positive potential films. This fact could illustrate why previous reports appeared ambiguously; i.e., the comparative result in osteogenic differentiation between the positive and negative potential films strongly depends on the selection of surface potential intensity. On the basis of assaying of the exposed functional sites (RGD and PHSRN) of the adsorbed fibronectin (FN) and the expression of cellular integrin α5 and ß1 subunits, the difference in the behavior between the positive and negative potential films was attributed to the distinct conformation of adsorbed fibronectin (FN) and the opposite changing trend with /ϕME/ for the two films, which triggers the osteogenesis-related FAK/ERK signaling pathway to a different extent. This study could provide new cognition for the in-depth understanding of the regulation mechanism underlying surface potential characteristics in cell behaviors.