Bioactivity and biocompatibility of hydroxyapatite/DL-poly lactic acid composite: In vivo implantation

Xinyu WANG; Xuezhi SHAN; Ming WEI; Yingchao HAN; Shipu LI

ABSTRACT

BACKGROUND:

Hydrolysis in vivo is the key mechanism of degradation in DL-polylactic acid (PDLLA). When it is combined with hydroxyapatite (HA), could the biodegradation and weight loss rate be improved?

OBJECTIVE:

To observe the changes in the interface and structure of HA/PDLLA composite after in vivo implantation into rabbit femoral defects.

DESIGN:

Randomized grouping and controlled observation.

SETTING:

Biomedical Materials and Engineering Research Center, Wuhan University of Technology.MATERIALS Forty healthy adult Japan White Rabbits of 2.0-2.5 kg, either male or female were provided by the Animal Experimental Center of Hubei Province (No. SCXK. 2003-0005).

METHODS:

The experiment was conducted in Biomedical Materials and Engineering Research Center, Wuhan University of Technology from June 2005 to March 2006. ①The rabbits were randomly divided into two groups HA/PDLLA group and PDLLA control group with 20 animals in each group. After anesthetized with ketamine and proazamine, the sample rods of HA/PDLLA and PDLLA were respectively implanted into the drilled bone cavities (φ5 mm × 8 mm) among condyles of femur sites of the rabbits, and the rod could be slightly higher than the surface of bone substance. The samples were covered by periosteum and skin, and then the skin and periosteum were repositioned. ②The complete implants and peripheral bone tissues were taken out respectively after 3, 6, 12 and 24 weeks implantation. The changes in the interface and structure of HA/PDLLA composite after in vivo implantation were observed by using scanning electron microscope (SEM, JSM-5610LV, Japan).MAIN OUTCOME

MEASURES:

Changes in the interface and structure of HA/PDLLA composite after in vivo implantation.

RESULTS:

Totally 40 rabbits were involved in the result analysis. After the materials were implanted, HA granules shed from the material surface, some fibroblasts grew into the tissue and a little new osteotylus was formed, indicating HA/PDLLA composite had capabilities of bone-formation and bone-connection. After 24 weeks implantation, the material was divided and wrapped by tissues, neogenetic bone tissue grew into the material, and the fracture healed well,indicating HA/PDLLA composite had good biocompatibility. As for biodegradable PDLLA polymer, hydrolysis in vivo is the most main mechanism of degradation; the degradation speed was decreased owing to being compounded with HA.

CONCLUSION:

HA/PDLLA composite has capabilities of bone-formation and bone-connection; the biocompatibility of the composite is improved accordingly on account of the decrease of the degradation speed. HA/PDLLA composite is suitable for clinical application as absorbable materials for internal fixation.