Department of Chemistry, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy.
Department of Chemistry, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy; Istituto per i Sistemi Biologici (ISB-CNR), Sede Secondaria di Roma-Meccanismi di Reazione, Dipartimento di Chimica, Università degli Studi di Roma "Sapienza", Italy.
J Colloid Interface Sci. 2022 Oct;623:723-734. doi: 10.1016/j.jcis.2022.05.025. Epub 2022 May 10.
Self-assembling molecular structures responding to light stimulus are appealing for applications as sensing and drug delivery. Supramolecular nanotubes have a relevant potential in nanotechnology as they can be used to encapsulate different loads like drugs, biological macromolecules, and nanomaterials. In addition, they are suitable elements for novel supracolloidal materials. Structural responses of supramolecular nanotubes to non-invasive stimuli are very much desired to enable controlled release of the encapsulated guests and to provide these recently developed new materials with an external trigger. Here, we describe the formation of well-defined, single wall tubules that interconvert into twisted ribbons upon UV-light exposure in aqueous environment. The structures are provided by self-assembly of an azobenzene substituted cholic acid, a biological surfactant belonging to the family of bile acids. The azobenzene group allows for the light responsiveness of the molecular packing. Concurrently the steroidal moieties assure both chiral features and extensive hydrophobic interactions for time and temperature resistant aggregates.
The molecular packing interconversion was followed by circular dichroism. Microscopy, small angle X-ray scattering and light scattering measurements demonstrated the drastic morphological variation upon irradiation. A model of the molecular arrangement within the tubular walls was suggested based on the circular dichroism spectra simulation.
Innovatively, the molecular design reported in our work allows for encoding in the same light responsive system multiple desirable features (e.g. bio-origin, temperature resistance and chirality of the aggregates). Such combination of properties, never reported before for a single molecule, might be relevant for the realization of robust, stimuli-responsive bio-vectors.
对光刺激做出响应的自组装分子结构在传感和药物输送等应用中很有吸引力。超分子纳米管在纳米技术中有很大的应用潜力，因为它们可以用来封装不同的负载，如药物、生物大分子和纳米材料。此外，它们还是新型超胶体材料的合适元素。超分子纳米管对非侵入性刺激的结构响应非常需要，以实现封装客体的可控释放，并为这些新开发的新材料提供外部触发。在这里，我们描述了在水溶液中，通过紫外线照射，由一种取代的偶氮苯胆酸自组装形成的具有良好定义的单壁管，在暴露于紫外光后会转化为扭曲的带状物。该结构由胆酸的偶氮苯取代物自组装而成，胆酸是一种属于胆汁酸家族的生物表面活性剂。偶氮苯基团使分子堆积具有光响应性。同时，甾体部分确保了时间和温度稳定的聚集物具有手性特征和广泛的疏水性相互作用。
圆二色性跟踪分子组装的转换。显微镜、小角 X 射线散射和光散射测量表明，在照射后形态发生了剧烈变化。根据圆二色光谱模拟提出了管状壁内分子排列的模型。
创新性地，我们在工作中报告的分子设计允许在同一个光响应系统中编码多种理想的特性（例如生物起源、聚集物的温度抗性和手性）。这种特性的组合以前从未在单个分子中报道过，可能与实现稳健的、响应性生物载体有关。
