GRAFTING POLYMERIZATION OF L-LACTIDE ON HYDROXYAPATITE NANOPARTICLES

Poly(lactid-glycolide acid)/hydroxyapatite (PLGA/HA) materials, as a class of composites,which have good bioactivity, absorbability and biodegradability, show promising applications in biomedical and tissue engineering fields. To improve the compatibility of HA and PLGA, the ring-opening polymerizations of L-lactic acid on three types of HA surfaces with different surface hydroxyl functionality : unmodified HA, HA modified with L-lactic acid, and HA modified with hexamethylene diisocyanate tethered ethylene glycol were carried out to produce poly(L-lactide acid) grafted hydroxyapatite (PLLA-g-HA). The results of FTIR, XPS, TEM and TGA show that PLLA was successfully grafted onto surface of HA by the above three methods. And the grafting rate of PLLA was dependent on the nature and steric environment of the hydroxyl groups on the HA surfaces, among which HA modified with (HMDI + EG) presented the best grafting percentage of 25%. The proportional change between inorganic and organic phase brought about little influence on PLLA grafting rate. The PLLA-g-HA can stably disperse in chloroform over 2 days without deposition. To investigate practicability of the composites used as bone guided regeneration membranes, tensile test after co-electrospinning shows that PLLA-g-HA/ PLAG nanofibrous membrane has better mechanical performance compared to HA/PLGA membrane, and its tensile force reaches maximum at 5% filling content.