| By introducing macrocyclic host molecules, the host-guest recognition shows a distinctive character among various supramolecular interactions. As a kind of typical host molecule, cyclodextrin(CD) is formed by D-pyran glucose unit by α-1, 4 glycosidic bonding end to end. α-, β- and γ-CD are common macrocyclic oligosaccharides that consists of six, seven and eight glucose units respectively. CD is widely used in many fields, it can form complex with multiple types of guest molecules in solution or solid state. Due to differences in the cavity size, each type of cyclodextrin can combine with particular molecule, including adamantane(ADA), azobenzene(AZO) and ferrocene(Fc) etc. After the recognition of the host molecule and the designed guest molecule, supramolecular amphiphiles are uaually formed which is the premise of building supramolecular assembly structure.In order to develop functional supramolecular materials, research in functional supramolecular assemblies is more and more diversified in recent years. By directional non-covalent interaction, we can link different function units together to obtain the supramolecular assemblies. It is very convenient to functionalize the assemblies with a variety of special functional building block. For example: the change of p H, light radiation, redox and temperature, according to the reversible non-covalent interactions all sorts of corresponding functions can also make a reversible debugging. Therefore, developing different stimulus-responsive functionalized supramolecular nanodevices is a very noticeable development trend in the future. In this paper, based on the construction of the supra-amphiphiles formed by host–guest recognition between cyclodextrin and the guest molecules, we further build the temperature-responsive and the redox-responsive supramolecular nano systems:1. Development of the smart temperature-responsive GPx mimic. We designed a supra-amphiphilic thermosensitive vesicle-like structure by the self-assembly of host–guest interaction between cyclodextrin(CD) and adamantine(Ad) derivatives to construct a novel artificial GPx mimic with controllable catalytic activity. When the temperature exceeded the LCST of the guest molecule, the chains became coiled thus leading to the formation of a supra-amphiphilic molecule. It further self-assembled into vesicles and the selenium catalytic centers were aggregated and exposed on the surface. The supra-amphiphilic vesicles might thus offer an outstanding model for fabricating a GPx mimic with high catalytic activity by centralizing the catalytic centers together. Whereas at 25 ℃, the host-guest complexation events occurred in aqueous solution and the PNIPAM chains had high-solubility below the LCST, meanwhile the complex became hydrophilic and the selenium catalytic centers were distributed randomly in water solution, which resulted in a relatively low catalytic efficiency. Furthermore, the catalytic activity of this smart artificial GPx mimic can be reversibly modulated by temperature.2. Construction of the redox-responsive nano capsule. Designed and synthesized ferrocene-headed guest molecule with three hydrophobic alkyl chain, and constructed the amphiphilic molecule by host-guest recognition between β-CD and ferrocene, which could be further self-assemble into vesicles structure in aqueous solution. After adding the oxidant Fe3+, ferrocene was oxidated and dissociated from the cyclodextrin’s cavity, which led to the disassembly of the assemblies. The reductant GSH was further added then and the ferrocene could be reduced, because of which host-guest recognition could happen again. At the same time, GST protein was packaged into the cavity of the vesicles. We can release GST protein through the controllable assembly and disassembly of the vesicle structure and build a redoxresponsive drug loading nano capsule successfully. |
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