Study Of The Degradation Of Poly (L-Lactide)/Hydroxyapatite Biocomposite Materials By FTIR Imaging

FTIR spectroscopic imaging is a visualized tool for characterizing the distribution of different chemicals in heterogeneous materials. It is based on the combination of FTIR spectroscopy and bright field microscopy.As one of the most widely studied scaffold materials in bone tissue engineering, Poly-L-lactide/hydroxyapatite (PLLA/HA) biocomposite accord with the requirements of ideal scaffold materials for bone repair due to the good biocompatibility, biodegradablity and the mechanical properties. The biodegradation is a key factor to evaluate the material properties.PLLA/HA composites with high porosity were prepared using solvent-casting/salt-leaching method. The in vitro degradation behavior of the as-prepared samples were studied using micro-attenuated total reflectance-Fourier transform infrared spectroscopic imaging (Micro-ATR-FTIR-imaging), scanning electron microscopy (SEM) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR).The results show that the thorough degradation time for PLLA/HA composites with the weight ratio of 100/10,100/20,100/30,100/40 and 100/50 are respectively 98,105,91,91 and 77 days. The degradation process for the composites with a ratio from 100/30 to 100/50 exhibits a quadratic model based on ATR-FTIR results and the degradation half-lives for the three composites are 67,65 and 52 days, respectively.The degradation behavior of PLLA/HA is systematically investigated by ATR-FTIR imaging and the FTIR images are generated using the ratio A1035/A1750. The degradation process is monitored using the change of the color distribution of images. It shows that the composite materials with different viscosity coefficients of PLLA (η=1.22 andη=1.61) and with different content of HA exhibit a different degradation behavior in phosphate buffer solution (PBS) at 37℃. The ones with the ratio of 100/10 and 100/20 have large porosity but are degraded slow and the one with the ratio of 100/50 have a relative small porosity and is degraded fast. However, the ones with the ratio of 100/30 and 100/40 have good performance both in porosity and degradation, and they are suitable for the scaffold in bone tissue engineering. On the other hand, the result of the composite using high viscosity factor of PLLA (η=1.61, Mw=18500) shows an irregular degradation behavior and degraded more slower. In summary, the degradation ability of PLLA/HA composites with ratio of 100/40 is better than the one with the ratio of 100/30.In this dissertation the methodology of FTIR imaging was improved and the fields of applications were expanded. This developed technique promises to become a powerful tool for studying the other areas of biotechnology and the biomedical sciences.