Data supporting: The Apatite Forming Ability of Micro- and Nanocomposites of α-Tricalcium Phosphate/Poly (D,L-lactide-co-glycolide)

Bioresorbable composites consist of micro- and nano-sized α-tricalcium phosphate (α-TCP) particles in a poly(D,L-lactic-co-glycolic acid) (PLGA) matrix were compared for their ability to form bone-like apatite in simulated body fluid (SBF). Due to the uniform distribution of α-TCP nanoparticles over the nanocomposite surface, enhanced apatite formation was observed. Compared with microcomposite with the same α-TCP load, this enhanced apatite formation was achieved through faster and more uniform apatite nucleation. In the first stage of apatite formation, the presence of abundant high energy boundaries between α-TCP nanoparticles and PLGA matrix in nanocomposite provided a large number of suitable sites for calcium phosphate (CaP) nucleation. A homogenous distribution fo CaP nuclei formed after days. The resulting apatite crystals grew to form a flake-like apatite layer. In contrast, CaP nucleation was only observed on the micrometre-size α-TCP particles in the microcomposite over the same period. After 14 days, a dense, flake-like apatite was visible covering the surface of nanocomposite, whilst this suface layer was formed only on α-TCP particles of the microcomposite.

本研究以聚（DL-乳酸-羟基乙酸）共聚物（PLGA）为基体，负载微米级与纳米级α-磷酸三钙（α-TCP）颗粒制备的生物可吸收复合材料为研究对象，对比了二者在模拟体液（SBF）中形成类骨磷灰石的能力。由于α-TCP纳米颗粒在纳米复合材料表面分布更为均匀，该体系的磷灰石形成能力得到显著增强。与负载量相同的微米级复合材料相比，纳米复合材料可通过更快且更均匀的磷灰石成核过程实现这一性能提升。在磷灰石形成的初始阶段，纳米复合材料中α-TCP纳米颗粒与PLGA基体间存在大量高能界面，为磷酸钙（CaP）成核提供了大量适宜位点。数日后即可形成均匀分布的CaP晶核，最终生成的磷灰石晶体生长为片状磷灰石层。与之相对，同期内微米级复合材料仅在微米级α-TCP颗粒表面观察到CaP成核现象。培养14天后，纳米复合材料表面可观察到致密的片状磷灰石层完全覆盖其表面，而微米级复合材料的磷灰石表层仅形成于α-TCP颗粒表面。