ß-Phase poly(vinylidene fluoride) films encouraged more homogeneous cell distribution and more significant deposition of fibronectin towards the cell-material interface compared to α-phase poly(vinylidene fluoride) films.

The piezoelectric response from ß-phase poly(vinylidene fluoride) (PVDF) can potentially be exploited for biomedical application. We hypothesized that α and ß-phase PVDF exert direct but different influence on cellular behavior. α- and ß-phase PVDF films were synthesized through solution casting and characterized with FT-IR, XRD, AFM and PFM to ensure successful fabrication of α and ß-phase PVDF films. Cellular evaluation with L929 mouse fibroblasts over one-week was conducted with AlamarBlue® metabolic assay and PicoGreen® proliferation assay. Immunostaining of fibronectin investigated the extent and distribution of extracellular matrix deposition. Image saliency analysis quantified differences in cellular distribution on the PVDF films. Our results showed that ß-phase PVDF films with the largest area expressing piezoelectric effect elicited highest cell metabolic activity at day 3 of culture. Increased fibronectin adsorption towards the cell-material interface was shown on ß-phase PVDF films. Image saliency analysis showed that fibroblasts on ß-phase PVDF films were more homogeneously distributed than on α-phase PVDF films. Taken collectively, the different molecular packing of α and ß-phase PVDF resulted in differing physical properties of films, which in turn induced differences in cellular behaviors. Further analysis of how α and ß-phase PVDF may evoke specific cellular behavior to suit particular application will be intriguing.

α- and ß-poly(vinylidene fluoride) evoke different cellular behaviours.

α-Phase poly(vinylidene fluoride) (PVDF) has chains of zero dipole moments and is, therefore, nonpiezoelectric, while ß-phase PVDF has the most significant piezoelectric properties among the polymorphs due to its polar chains. Although many reports describe PVDF as a suitable biomaterial due to its stability and biocompatibility, few considered the specific effects that the different polymorphs exert on cellular behaviour. We hypothesized that α- and ß-phase PVDF will exert direct but different influences on cell attachment and metabolic activity. PVDF films were fabricated using N,N-dimethylformamide (DMF) and hexamethylphosphoramide (HMPA) by solvent casting. Samples were characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy and X-ray diffraction. Films containing 83.5% α-phase PVDF (DMF-PVDFα) and 91.4% of ß-phase PVDF (HMPA-PVDFß within the crystalline regions were produced and used to evaluate in vitro attachment and metabolic activity of L929 cells. Cell metabolic activity on both PVDF conformations increased 3-fold over the 1-week culture period, with higher cell metabolic activity observed on DMF-PVDFα on day 5 of culture, compared to HMPA-PVDFß. Cells grown on DMF-PVDFα were well-spread, flat and expressed spotted paxillin in focal adhesions that were mainly localized to perinuclear regions of the cells, while a high proportion of cells on HMPA-PVDFß were bulging, round and expressed relatively fewer paxillin spots. Our results suggest that α-phase PVDF supports higher cell metabolic activity and better cell spreading compared to ß-phase PVDF. Such variations can potentially be exploited for different biomedical applications.