Functionalization of oligo(poly(ethylene glycol)fumarate) hydrogels with finely dispersed calcium phosphate nanocrystals for bone-substituting purposes
Functionalization of oligo(poly(ethylene glycol)fumarate) hydrogels with finely dispersed calcium phosphate nanocrystals for bone-substituting purposes
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DOI：
10.1163/156856207794761998
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发表时间：
2007-01
期刊：
影响因子：
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通讯作者：
S. Leeuwenburgh;J. Jansen;A. Mikos
中科院分区：
文献类型：
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作者：
S. Leeuwenburgh;J. Jansen;A. Mikos
可加工成可注射水凝胶基质的可生物降解聚合物是用于骨替代目的的有希望的候选者。此外，通过将可降解磷酸钙（CaP）颗粒和生长因子掺入这些水凝胶基质中，可以设计出一种骨结构，刺激周围组织形成新骨，从而补偿可降解合成骨替代品结构完整性的损失。一般来说，纳米陶瓷增强聚合物合成的一个主要挑战是实现纳米颗粒在整个聚合物中的精细分散，因为当纳米颗粒聚集时，纳米复合材料的独特性能会丧失。在目前的研究中，采用物理或化学制备策略成功开发了由低聚（聚（乙二醇）富马酸酯）（OPF）基质和不同结晶度的CaP分散体组成的复合水凝胶。干燥的微米级 CaP 粉末的物理混合导致形成不可再现的复合材料，其中大且团聚的 CaP 微粒在整个 OPF 基质中高度不均匀分散。相反，使用化学混合策略制备了可重复且均质的水凝胶，在溶解的 OPF 大分子单体存在下形成 CaP 晶体。这种共沉淀技术使 CaP 晶体具有更高程度的分散性，从而可以在 OPF 等有机基质中获得更高的 CaP 含量。通过使用这些 CaP 悬浮液代替干燥粉末，分离的 CaP 晶体的纳米结构得以保留，导致 CaP 相的反应性更高，这些水凝胶的溶胀行为减少表明了这一点。这种效应很可能是由 Ca2+ 和未反应的 COOH 端基之间的物理化学相互作用引起的，从而导致复合水凝胶的物理交联增加。
Biodegradable polymers that can be processed into injectable hydrogel matrices are promising candidates for bone-substituting purposes. Furthermore, by incorporating degradable calcium phosphate (CaP) particles and growth factors into these hydrogel matrices, a bone construct can be designed which stimulates the formation of new bone by the surrounding tissue, thereby compensating for the loss of structural integrity of the degrading synthetic bone-substitute. Generally, a major challenge in synthesis of nanoceramic-reinforced polymers is the achievement of a fine dispersion of nanoparticles throughout the polymer, since the unique properties of nanocomposites are lost when nanoparticles aggregate. In the current study, composite hydrogels consisting of oligo(poly(ethylene glycol)fumarate) (OPF) matrices and CaP dispersions of varying crystallinity were successfully developed using physical or chemical preparation strategies. Physical mixing of dried, micrometer-sized CaP powders resulted into formation of irreproducible composites with a highly heterogeneous dispersion of large and agglomerated CaP microparticles throughout the OPF matrix. On the contrary, reproducible and homogeneous hydrogels were fabricated using a chemical mixing strategy, whereby CaP crystals were formed in the presence of dissolved OPF macromers. This co-precipitation technique resulted into a much higher degree of dispersion of the CaP crystals, which can enable higher CaP contents in organic matrices such as OPF. By using these CaP suspensions instead of dried powders, the nanosized structure of separated CaP crystals was preserved, resulting into a higher reactivity of the CaP phase, as indicated by a reduced swelling behavior of these hydrogels. This effect was most likely caused by a physicochemical interaction between Ca2+ and unreacted COOH end-groups, thereby leading to increased physical cross-linking of the composite hydrogels.