Cyclodextrin-Based [c2]Daisy Chain Rotaxane Insulating Two Diarylacetylene Cores

Daisy chain architectures: from discrete molecular entities to polymer materials

Daisy chain architectures, made by the self-complementary threading of an axle covalently linked to a macrocycle, represent a particularly intriguing family of supramolecular and mechanically interlocked (macro)molecules. In this review, we discuss their recent history, their modular chemical structures, and the various synthetic strategies to access them. We also detail how their internal sliding motions can be controlled and how their integration within polymers can amplify that motions up to the macroscopic scale. This overview of the literature demonstrates that the peculiar structure and dynamics of daisy chains have already strongly influenced the research on artificial molecular machines, with the potential to be implemented from nanometric switchable devices to mechanically active soft-matter materials.

γ-Cyclodextrin-based [2]rotaxane stoppered with gold(I)-ethynyl complexation: phosphorescent sensing for nitroaromatics

A [2]rotaxane is assembled by γ-cyclodextrin (γ-CD) with threaded 1,4-diethynylbiphenyl and bulky Au(I)-phosphine stoppers. The phosphorescence of the [2]rotaxane has been observed in aerated aqueous solution and found to be quenched by nitroaromatics due to γ-CD-based co-binding, providing a sensitive approach towards explosive-sensing.

DNA-Based Daisy Chain Rotaxane Nanocomposite Hydrogels as Dual-Programmable Dynamic Scaffolds for Stem Cell Adhesion

Interlocked DNA nanostructures perform programmable movements in nanoscales such as sliding, contraction, and expansion. However, utilizing nanoscaled interlocked movements to regulate the functions of larger length scaled matrix and developing their applications has not yet been reported. Herein we describe the assembly of DNA-based daisy chain rotaxane nanostructure (DNA-DCR) composed of two hollow DNA nanostructures as macrocycles, two interlocked axles and two triangular prism-shaped DNA structures as stoppers, in which three mechanical states─fixed extended state (FES), sliding state (SS), and fixed contracted state (FCS)─are characterized by using toehold-mediated strand displacement reaction (SDR). The DNA-DCRs are further used as nanocomposites and introduced into hydrogel matrix to produce interlocked hydrogels, which shows modulable stiffness by elongating the interlocked axles to regulate the hydrogel swelling with hybridization chain reaction (HCR) treatment. Then the DCR-hydrogels are employed as dynamic biointerfaces for human mesenchymal stem cells (hMSCs) adhesion studies. First, hMSCs showed lower cell density on bare DCR-hydrogel treated with HCR-initiated swelling for stiffness decreasing. Second, the cell adhesion ligand (RGD) modified DNA-DCRs are constructed for hydrogel functionalization. DCR^(RGD) hydrogel endows the mobility of RGDs by switching the mechanical states of DNA-DCR. HMSCs showed increased cell density on DCR^SS(RGD) hydrogel than on DCR^FCS(RGD) hydrogel. Therefore, our DNA-DCR nanocomposite hydrogel exhibit dual-programmable performances including swelling adjustment and offering sliding for incorporated ligands, which can be both utilized as dynamic scaffolds for regulating the stem cell adhesion. The dual-programmable cross-scale regulation from interlocked DNA nanostructures to hydrogel matrix was achieved, demonstrating a new pathway of DNA-based materials.

Maximizing the [c2]daisy chain to lasso ratio through competitive self-templating clipping reactions

Self-templating two-component coupling reactions allowed the isolation of two threaded products with different molecular sizes: a lasso-type [1]rotaxane and a [c2]daisy chain rotaxane. Their distribution in the final reaction mixture varies as a factor of the concentration of the reactants. Through this methodology we obtained a large 84-membered cyclic multistation [2]rotaxane.