Investigation Of Water Diffusion Process, Microphase Behavior And Biocompatibility After Plasma Surface Treatment Of Polyhydroxylkanoate

In the past decades, the family of polyhydroxyalkanoates (PHAs) has attracted a large volume of attention and widely studies, due to its microorganism synthesize, biodegradability, good biocompatibility and adjustable mechanical property, and shows the great potentials as the next generation green plastic in the fields of agriculture, packaging industry and regenerative medicine. Nowadays, one member of PHAs family, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) is fabricated into drug nano-carriers and biodegradable porous scaffolds in the tissue engineering application. In this dissertation, PHBHHx were extensively studied in the respects of water diffusion behaviors in the PHBHHx film, the relationship between mechanical properties and microphase structures of PHBHHx with different hydroxyhexanoate (HH) ratios and the biocompatibility evaluation of silk fibroin (SF) modified PHBHHx film radiated by the low temperature plasma. Correspondingly, the conclusions are obtained as follows:1. Three states of water were figured out during water diffusion process in PHBHHx, x= 12 mol% film. They are bulk water, bound water and free water.2. The water diffusion mechanism was suggested as:water molecules firstly diffuse into the micro-voids in bulk water form or are dispersed on the surface in free water form, and then penetrate into the polymer matrix in hydrogen bound water with the hydrophilic groups of PHBHHx, such as C=O and C-O-C. Moreover, water molecules diffuse into the loose amorphous phase and then into compact crystalline phase.3. Water diffusion coefficient in PHBHHx, x= 12 mol% was thus evaluated as 7.8±0.7×10-8 cm2s-1 at 293K.4. The C=O and CH groups on the backbone chain of PHBHHx polymer were proved in the two states of motions, one is fast motion with short 13C T1 and T1ρrelaxation time and the other is slow motion with long 13C T1 and T1ρrelaxation time. Moreover, PHBHHx, x= 18 mol% showed longer 13C T1 and T1ρof fast and slow motions than that of PHBHHx, x= 12 mol%, indicating the groups of C=O and CH of PHBHHx, x= 18 mol% were in a relatively flexible environment in comparison with PHBHHx, x= 12 mol%. In addition, there were differences of microphase in the scale of nanometer between PHBHHx, x= 12 and 18 mol%.5. The 12 dipolar filter pulse sequence can effectively suppress the rigid phase NMR signal, which is in a shorter T2 relaxation time than that of mobile phase, and preserve the signal of mobile phase. The optimal Ncycle time was 7 to the both of PHBHHx, x= 12 and 18 mol%, which can ideally preserve the mobile phase signal and weaken the rigid phase signal of PHBHHx polymer. Furthermore, T1 of mobile phase of PHBHHx, x= 18 mol% was shorter than that of PHBHHx, x= 12 mol%, and T2 of mobile phase of PHBHHx, x= 18 mol% was longer than that of PHBHHx, x= 12 mol%, demonstrating that protons in the mobile phase of PHBHHx, x= 18 mol% were in a more free environment that that of PHBHHx, x=12 mol%.6. After low temperature irradiation, the surface of PHBHHx, x= 12 mol% became more hydrophilic and rougher than before plasma treatment.7. The SF-coated PHBHHx films irradiated by the plasma were flushed by PBS buffer under the rate of physiological blood flow, proving that SF on the plasma treated surface have better immobilization strength than that on the surface without plasma treatment.8. A significant increase in the proliferation of hSMCs is presented on the SF-coated PHBHHx films with plasma treatment, and the cell sub-monolayer and the secreted ECM are also formed well on these films.