2.B.60. The Interlocked Catenane/Rotaxane/Polyrotaxane (ICRP) Family
Due to their low cytotoxicity, controllable size, and unique architecture, cyclodextrin (CD)-based polyrotaxanes and polypseudorotaxanes have been considered for functions such as drug delivery, gene delivery, and tissue engineering (Li et al. 2011). CD-based biodegradable polypseudorotaxane hydrogels have been used as injectable drug delivery systems for sustained and controlled drug release. Polyrotaxanes with drug or ligand-conjugated CDs threaded on a polymer chain with biodegradable end groups may be useful for controlled, multivalent targeting delivery. Cationic polyrotaxanes consisting of multiple oligoethylenimine-grafted CDs threaded on a block copolymer chain are attractive non-viral gene carries due to the strong DNA-binding ability, low cytotoxicity, and high gene transfection efficiency. Cytocleavable end caps have been introduced in the polyrotaxane systems in order to ensure efficient endosomal escape for intracellular trafficking of DNA (Li et al. 2011).
DNA-based machines include transporters and interlocked cyclic DNA structures acting as reconfigurable catenanes, rotaxanes, and rotors (Wang et al. 2014). Interlocked circular DNA nanostructures, e.g., catenanes or rotaxanes, have been used for these and other functions (Lu et al. 2016). Naphthalene diimides (NDIs) have applications as biological sensors, molecular switching devices such as catenanes and rotaxanes and ligand-gated ion-channels (Kobaisi et al. 2016). Photoinduced electron transfer can occur in multiporphyrinic interlocked structures (Flamigni et al. 2004), and charge transfer through switchable interlinked molecules such as catenanes and rotaxanes can also occur (Jan van der Molen and Liljeroth 2010; Yang et al. 2012). Transition metal-complexed catenanes and rotaxanes are dynamic systems that can function as molecular machines (Durot et al. 2014), and interlocked cyclic DNA structures can act as reconfigurable catenanes and rotaxanes (Wang et al. 2014). Interlocked systems, rotaxanes and catenanes, have been incorporated into nanomedicine chemical platforms (Ornelas-Megiatto et al. 2015), and used as drug transporters (Wang et al. 2014; Casas-Hinestroza et al. 2019). Rotaxanes, pseudorotaxanes, and catenanes are supramolecular complexes with potential use in nanomachinery, molecular computing, and single-molecule studies and have been used to translocate proteins across ClyA nanopores (Biesemans et al. 2015). The rotaxanes described here may be structurally related to those in TC family 2.B.32.