Organic/Inorganic hydrogels by simultaneous selfassemblyand mineralization of aromatic shortpeptides

Self-assembled peptides and proteins have turned out to be excellent templates for the growth of inorganic minerals and can be used to emulate natural biomineralization processes. Doing this, researchers have developed complex sophisticated materials with properties, in some cases, similar to those found in nature. Of special interest is the development of scaffolds able to guide bone regeneration. The bone tissue comprises an organic matrix composed of aligned collagen fibers containing nanoapatite crystals oriented along the fiber direction. During bone mineralization, both processes, the self-assembly of collagen fibrils and mineralization occur simultaneously. Collagen fibers are able to control calcium phosphate nucleation and subsequent apatite crystal growth at a very limited range of collagen density and ionic concentration. In this study, we reproduced the simultaneity of both processes using an artificial peptide fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF) that has the ability to self-assemble in water after the addition of Ca2+ ions. Therefore, the peptide self-assembly process and the mineralization of apatite are Ca-demanding processes and occur simultaneously. The role of peptide and ionic concentrations has been investigated affording organic/inorganic hybrid hydrogels with different degrees of homogeneity and mineralization. Interestingly, at very low Ca2+ concentrations, we found that apatite nanocrystals are integrated into Fmoc-FF fibrils and oriented as in biologically mineralized collagen fibrils, the basic building blocks of bone.

自组装肽和蛋白质已被证明是无机矿物生长的优良模板，可用于模拟天然生物矿化过程。通过这种方式，研究人员开发出了复杂精密的材料，其性能在某些情况下与自然界中发现的材料相似。特别令人感兴趣的是能够引导骨再生的支架的开发。骨组织包含由排列整齐的胶原纤维组成的有机基质，这些胶原纤维中含有沿纤维方向取向的纳米磷灰石晶体。在骨矿化过程中，胶原纤维的自组装和矿化这两个过程同时发生。胶原纤维能够在非常有限的胶原密度和离子浓度范围内控制磷酸钙成核及随后的磷灰石晶体生长。在本研究中，我们使用一种人工肽——芴甲氧羰基-二苯丙氨酸（fluorenylmethoxycarbonyl-diphenylalanine, Fmoc-FF）重现了这两个过程的同步性，该肽在添加Ca²+离子后能够在水中自组装。因此，肽的自组装过程和磷灰石的矿化过程均为需钙过程且同时发生。研究人员已探究了肽和离子浓度的作用，得到了具有不同均匀度和矿化程度的有机/无机杂化水凝胶。有趣的是，在极低的Ca²+浓度下，我们发现纳米磷灰石晶体被整合到Fmoc-FF纤维中，并且其取向与生物矿化胶原纤维（骨的基本结构单元）中的取向一致。