Material characterisation and cellular behavior on different poly (vinylidene fluoride) polymorphs

• Main Author: Low, Adarina Yuen Kei.
• Other Authors: Boey Yin Chiang, Freddy
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Materials::Biomaterials
• Online Access: http://hdl.handle.net/10356/51164
• Institution: Nanyang Technological University

Poly (vinylidene fluoride) (PVDF) has attracted attention as a biomaterial because it is chemically inert, mechanically strong and stable over an extended period. PVDF exists in 4 polymorphs, with β-phase getting the most attention due to its piezoelectric property. However, questions on whether polymorphism can influence cellular behavior remain unanswered due to limited reports with conflicting conclusions. Understanding these influences is crucial for the advancement of PVDF as a biomaterial, and could introduce novel biomedical applications of PVDF. In this thesis, it was hypothesized that α and β-phase PVDF can exert direct but different influences on cellular behavior. In order to prove the hypothesis, the first objective was to understand the influence of fabrication parameters on polymorphism. Following that, the second objective was to fabricate predominantly α and β-phase films. Finally, the third objective was to carry out cell culture studies on predominantly α and β-phase PVDF films, using L929 mouse fibroblasts. Drying temperature was found to have the greatest influence on polymorph formation, and solvent properties altered the resulting polymorph produced with the same fabrication conditions. Although cationic salts of high valencies effectively increased β-phase content, this effect was not significantly affected by changing salt concentration. The amount of β-phase was quantified by Fourier transformed infra-red (FT-IR) spectrum and confirmed using X-ray diffraction (XRD). Surface topographies were assessed with scanning electron microscopy (SEM) and atomic force microscopy (AFM), while piezoelectric property was examined with piezoforce microscopy (PFM). Water contact angle was also done. Polymorphism, wettability and degree of crystallinity of PVDF did not influence the initial rate of cell adhesion from 0 to 12 h, but high surface roughness adversely decreased cell adhesion. Even though metabolic activity per cell was not significantly different between the two polymorphs studied, cell distributions at days 5 and 7 were different. Fibroblasts on α-phase PVDF were clustered and expressed fibronectin more evenly across the depth of the cell layer, while cell distribution on β-phase PVDF was more even while fibronectin was laid down nearer to the material surface.