Analysis of in vivo substitution of bone tissue by HAp/PLLA composite biomaterial with PLLA of different molecular weights using FTIR spectroscopy

Hydroxyapatite/poly-L-lactide (HAp/PLLA) composite biomaterial with PLLA of 50,000 and 430,000 g/mole molecular weight was studied in vivo. The biocomposite with PLLA of both molecular weights was implanted into mice and after 1 and 3 weeks removed from their organisms and analyzed by the FT-IR spectroscopy. After one week of testing in vivo, the implanted samples gave spectra in which absorption bands arising from new-formed functional groups of amine and peptide can be seen. Analysis of the spectra revealed faster formation of peptide compounds when the biocomposite with PLLA of lower molecular weight was used. After 3 weeks, the spectra of the biocomposite of both compositions were registered with pronounced absorption bands at about 3420 and 1650 cm(-1) assigned to new-generated collagen, a component of the extracellular connective-tissue matrix. Also, in the case of the biocomposite sample with PLLA of lower molecular weight, disappearance of the previously present absorption band at about 1760 cm(-1) originating from the C=O group of PLLA indicates complete bioresorption of the PLLA used. Analysis of the microstructures of the sample surfaces by scanning electron microscopy before and after implantation revealed bioresorption of the PLLA polymer phase in the system with PLLA of lower molecular weight and generation of collagen fibers at the sites of implanted bioresorptive PLLA. A mixture of autologous bone powder and HAp/PLLA biocomposite was also examined. After implantation, the same final products as in the case of HAp/PLLA composite biomaterial alone were found.