Refining hydrogelator design: soft materials with improved gelation ability, biocompatibility and matrix for in situ synthesis of specific shaped GNP
作者:Dibyendu Das、Subhabrata Maiti、Sayanti Brahmachari、Prasanta Kumar Das
DOI:10.1039/c1sm05608e
日期:——
Despite the continuous surge in the development of new supramolecular gels, the prediction of a gelator's structure still remains elusive. It is also imperative to consolidate the existing inventory of gelators and devise ways to make the gels functional. In the present work, L-phenylalanine based poor (C-16) or non-gelating (C-12 tail) amphiphiles were converted to excellent gelators with the simple incorporation of N-terminal protected amino acid/dipeptide at the end of the alkyl tail. More than 6-fold enhancement in gelation efficiency was observed for amino acid/dipeptides incorporated at the tail of amphiphile in comparison to the corresponding unmodified alkyl tail. Interestingly, amphiphile with the tertiary butyloxycarbonyl (Boc) protected amino acid at the tail had better gelation ability than the amphiphile with the aromatic Fmoc (N-fluorenyl-9-methoxycarbonyl) protecting group. Spectroscopic investigations (XRD and FTIR) revealed that the modification at the tail compels the amphiphiles to take a different course of self-assembly than that adopted by their predecessors (alkyl tailed gelator, C-16). For example, in the case of the amphiphile having a dipeptide at the tail, formation of β-sheet structure through anti-parallel arrangement between the molecules results in notable improvement in its gelation ability. Most importantly, these tail modified amphiphiles were capable of in situ synthesis of gold nanoparticles (GNPs) of specific shape without the help of any external reducing agents in the newly developed soft materials. The biocompatibility of hydrogels is also crucial for their prolific biomedicinal functions. MTT assay showed dramatic improvement in the biocompatibility of the tail modified hydrogelators towards mammalian cells in comparison to the amphiphiles having no amino acid at the tail.
尽管新型超分子凝胶的发展持续激增,但凝胶剂结构的预测仍然难以捉摸。同样迫切的是整合现有凝胶剂清单,并设计方法使凝胶具有功能性。在本研究中,基于L-苯丙氨酸的不良(C-16)或非凝胶化(C-12尾部)的两性分子,通过简单地在烷基尾部末端引入N端保护的氨基酸/二肽,转化为优秀的凝胶剂。与未修饰的相应烷基尾部相比,在两性分子尾部引入氨基酸/二肽后,凝胶化效率提高了6倍以上。有趣的是,尾部带有叔丁氧羰基(Boc)保护氨基酸的两性分子比尾部带有芳香性Fmoc(N-芴基-9-甲氧羰基)保护基的两性分子具有更好的凝胶化能力。光谱学研究(XRD和FTIR)揭示,尾部的修饰迫使两性分子采取与前身(烷基尾部凝胶剂,C-16)不同的自组装途径。例如,在尾部具有二肽的两性分子中,通过分子间的反平行排列形成β-折叠结构,显著改善了其凝胶化能力。最重要的是,这些尾部修饰的两性分子能够在新型软材料中,无需任何外部还原剂的帮助,实现特定形状金纳米颗粒(GNPs)的原位合成。水凝胶的生物相容性对其丰富的生物医学功能也至关重要。MTT assay显示,与尾部没有氨基酸的两性分子相比,尾部修饰的水凝胶剂对哺乳动物细胞的生物相容性有了显著提高。