Rubini Katia, Boanini Elisa, Bigi Adriana
Department of Chemistry "Giacomo Ciamician", Alma Mater Studiorum-University of Bologna, 40126 Bologna, Italy.
J Funct Biomater. 2019 Feb 1;10(1):11. doi: 10.3390/jfb10010011.
Dicalcium phosphate dihydrate (DCPD) is one of the mineral phases indicated as possible precursors of biological apatites and it is widely employed in the preparation of calcium phosphate bone cements. Herein, we investigated the possibility to functionalize DCPD with aspartic acid (ASP) and poly-aspartic acid (PASP), as models of the acidic macromolecules of biomineralized tissues, and studied their influence on DCPD hydrolysis. To this aim, the synthesis of DCPD was performed in aqueous solution in the presence of increasing concentrations of PASP and ASP, whereas the hydrolysis reaction was carried out in physiological solution up to three days. The results indicate that it is possible to prepare DCPD functionalized with PASP up to a polyelectrolyte content of about 2.3 wt%. The increase of PASP content induces crystal aggregation, reduction of the yield of the reaction and of the thermal stability of the synthesized DCPD. Moreover, DCPD samples functionalized with PASP display a slower hydrolysis than pure DCPD. On the other hand, in the explored range of concentrations (up to 10 mM) ASP is not incorporated into DCPD and does not influence its crystallization nor its hydrolysis. At variance, when present in the hydrolysis solution, ASP, and even more PASP, delays the conversion into the more stable phases, octacalcium phosphate and/or hydroxyapatite. The greater influence of PASP on the synthesis and hydrolysis of DCPD can be ascribed to the cooperative action of the carboxylate groups and to its good fit with DCPD structure.
二水磷酸二钙（DCPD）是被认为可能是生物磷灰石前体的矿物相之一，并且它被广泛用于制备磷酸钙骨水泥。在此，我们研究了用天冬氨酸（ASP）和聚天冬氨酸（PASP）对DCPD进行功能化的可能性，它们作为生物矿化组织酸性大分子的模型，并研究了它们对DCPD水解的影响。为此，在存在浓度不断增加的PASP和ASP的水溶液中进行DCPD的合成，而水解反应在生理溶液中进行长达三天。结果表明，可以制备出PASP功能化的DCPD，其聚电解质含量高达约2.3 wt%。PASP含量的增加会导致晶体聚集、合成的DCPD反应产率降低以及热稳定性降低。此外，用PASP功能化的DCPD样品的水解速度比纯DCPD慢。另一方面，在探索的浓度范围内（高达10 mM），ASP不会掺入DCPD中，也不会影响其结晶和水解。不同的是，当存在于水解溶液中时，ASP，甚至更多的PASP，会延迟向更稳定相八钙磷酸钙和/或羟基磷灰石的转化。PASP对DCPD合成和水解的更大影响可归因于羧基的协同作用及其与DCPD结构的良好契合。
