Development of Supramolecular Complex Sensor Possessing Biological Recognition Function

本研究设计了一种新型的超分子配合物传感器，用于水中离子和分子的识别。硼酸荧光离子载体/β-CyD复合物结合糖并在水中产生增加的荧光发射。为了评估结构效应，设计了三种不同的硼酸荧光离子团，其中硼酸识别位点和芘荧光团与不同长度的酯间隔基（Cn-PB）或酰胺间隔基（Cn-APB）缀合。基于荧光发射机理（PET从芘供体到三角苯基硼酸受体的抑制），C1-APB获得了最高的响应效率和选择性。为了选择性地识别Pb^2+，利用了具有伪18-冠-6结构的荚状结构，其可以稳定Pb^2+螯合物，同时减少与碱金属阳离子的相互作用。因此，该复合传感器对水中Pb^2+离子具有很高的选择性。响应机制是基于γ-CyD内的荧光离子载体的二聚化，从而导致Pb^<2+>-选择性芘二聚体发射。预期胶束溶液提供疏水微环境，其将亲脂性荧光离子载体溶解在水中并增强离子载体/金属相互作用。在低于TritonX-100的临界胶束浓度（CMC）时，POD-1/TritonX-100复合物对水中Pb^2+的荧光响应出现放大。动态光散射和暗视野显微镜分析表明，DAC-1/Triton X-100复合物在Pb^2+选择性结合的触发下形成微米级聚集体，导致荧光强度增强，荧光发射明显蓝移。这是DAC-1/Triton X-100复合传感器选择性识别水中Pb^2+的一种新的超分子功能。

In this study, novel supramolecular complex sensors for ion and molecule recognition in water have been designed. The boronic acid flouoroionophore/β-CyD complex binds sugars and produces increased fluorescence emission in Water. To evaluate the structural effect, three different boronic acid fluoroionophores in which the boronic acid recognition site and the pyrene fluorophore are conjugated with different length of ester spacer (Cn-PB) or amide spacer (Cn-APB) are designed. Based on the fluorescence emission mechanism (the suppression of PET from pyrene donor to trigonal phenylboronic acid acceptor), the highest response efficiency and selectivity obtained for C1-APB. For selective Pb^<2+> recognition, a podand structure possessing pseudo-18-crown-6 structure that can stabilize Pb^<2+> chelate complexes while reducing the interaction with alkali metal cations is utilized. Thus the podand fluoroionophore (PD-1)/γ-Cyclodextrin (γ-CyD) complex sensor exhibits markedly high selectivity for Pb^<2+> ion in water. The response mechanism is based upon the dimerization of the fluoroionophore inside the γ-CyD, thereby resulting in a Pb^<2+>-selective pyrene dimer emission. The micellar solution is expected to provide a hydrophobic microenvironment that solubilizes the lipophilic fluoroionophore in water and enhances the ionophore/metal interaction. However below the critical micelle concentration (CMC) of Triton X-100, the podand fluoroionophore (DAC-1)/Triton X-100 complex is found to exhibit sit amplified fluorescence response for Pb^<2+> in water. Dynamic light scattering and dark-field microscope analyses reveal that the DAC-1/Triton X-100 complex forms micron-size aggregates triggered by selective Pb^<2+> binding, resulting in the enhancement of fluorescence intensity with a distinct blue shift of the fluorescence emission. This is a novel supramolecular function of the DAC-1/Triton X-100 complex sensor for selective Pb^<2+> recognition in water.