We report a series of bolaform homodiamides of N-protected alanines that exhibit efficient thermo-reversible gelation of a broad variety of solvents. Gelation of these solvents upon bath-sonication was also achieved. Overall superior gelation profiles were exhibited by gelators in which the aromatic moiety was bonded to the N-terminus of the alanine by amide bonds (rather than by carbamate bonds). Rigidification of aggressive, hydrogen-bonding solvents such as small-chain alcohols and alcohol–water mixtures was also achieved by these amide-gelators. AFM of chirally-pure samples showed the presence of nanofibers exhibiting helicity. The contributions of inter-molecular hydrogen bonding as well as π-stacking to the self-assembly of these gelators were assessed by variable-temperature NMR and UV-vis studies. FTIR data indicated the extensive propensity of these gelators to form β-sheet-like assemblies. Phase-selective gelation, even in the presence of salts in the aqueous layer, could be achieved – both by thermal processing as well as by bath-sonication at room temperature. The ability to achieve phase-selective gelation by sonication at ambient conditions opens new avenues for spill-control applications. Entrapment of tetracycline and its papain-assisted release was demonstrated to exemplify the potential utility of these gels in drug-delivery applications.
我们报告了一系列 N 保护丙
氨酸的波拉形式同二元酰胺,它们在多种溶剂中表现出高效的热可逆凝胶化。这些溶剂在
水浴溶解时也能凝胶化。芳香分子通过酰胺键(而不是
氨基甲酸酯键)与丙
氨酸的 N 端结合的凝胶剂总体上表现出较好的凝胶特性。这些酰胺凝胶剂还能使侵蚀性氢键溶剂(如小链醇和醇
水混合物)刚性化。手性纯样品的原子力显微镜显示出纳米纤维的螺旋性。变温核磁共振和紫外可见光研究评估了分子间氢键和 π 堆积对这些凝胶剂自组装的贡献。傅立叶变换红外光谱数据表明,这些凝胶剂具有形成 β 片状组装体的广泛倾向。即使在
水层中存在盐分的情况下,也能通过热处理和室温下的
水浴溶解实现相选择性凝胶化。在环境条件下通过超声处理实现相选择凝胶化的能力为溢出控制应用开辟了新的途径。
四环素的包埋及其
木瓜蛋白酶辅助释放试验证明了这些凝胶在药物输送应用中的潜在效用。