Remnant polarization and structural arrangement in P(VDF-TrFE) electrospun fiber meshes affect osteogenic differentiation of human mesenchymal stromal cells

Many tissues and cells are influenced by mechano-electric stimulation, thus the application of piezoelectric materials has recently received considerable attention in tissue engineering. This report investigated electrospun fiber meshes based on poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)] as instructive biomaterials for osteogenic differentiation of human mesenchymal stromal cells (hMSCs). The influence played by methyl ethyl ketone (MEK), used as a solvent in place of dimethylformamide (DMF)/acetone mixture, and the effect of rotating velocity of the electrospinning collector on fiber morphology, mechanical and piezoelectric properties were studied. The solvent had noticeable effects on morphology and piezoelectric properties of electrospun fibers, with MEK outperforming DMF/acetone. By increasing the collector velocity up to 4000 rpm, the fiber diameter reduced and the mutual alignment of the fibers increased, corresponding to enhanced mechanical properties and piezo-active β-phase content. However, as a consequence of the diverse mechanical properties of random and aligned fibrous architectures, which ultimately affected the piezoelectric properties, randomly-oriented fibers exhibited higher remnant piezoelectric properties (Vout and d31 piezoelectric coefficient) than aligned ones. On these scaffolds, hMSCs showed an excellent capability of early osteogenic differentiation, leading to high calcium production. Fiber surface topology, fiber mesh morphology and remnant piezoelectric properties played a determinant role on hMSC osteogenic commitment.