CONSPECTUS: Host-guest chemistry can greatly improve the selectivity of biomolecule-ligand binding on account of recognition-directed interactions. In addition, functional structures and the actuation of supramolecular assemblies in molecular systems can be controlled efficiently through various host-guest chemistry. Together, these highly selective, strong yet dynamic interactions can be exploited as an alternative methodology for applications in the field of programmable and controllable engineering of supramolecular soft materials through the reversible binding between complementary components. Many processes in living systems such as biotransformation, transportation of matter, and energy transduction begin with interfacial molecular recognition, which is greatly influenced by various external stimuli at biointerfaces. Detailed investigations about the molecular recognition at interfaces can result in a better understanding of life science, and further guide us in developing new biomaterials and medicines. In order to mimic complicated molecular-recognition systems observed in nature that adapt to changes in their environment, combining host-guest chemistry and surface science is critical for fabricating the next generation of multifunctional biointerfaces with efficient stimuli-responsiveness and good biocompatibility. In this Account, we will summarize some recent progress on multifunctional stimuli-responsive biointerfaces and biosurfaces fabricated by cyclodextrin- or cucurbituril-based host-guest chemistry and highlight their potential applications including drug delivery, bioelectrocatalysis, and reversible adsorption and resistance of peptides, proteins, and cells. In addition, these biointerfaces and biosurfaces demonstrate efficient response toward various external stimuli, such as UV light, pH, redox chemistry, and competitive guests. All of these external stimuli can aid in mimicking the biological stimuli evident in complex biological environments. We begin by reviewing the current state of stimuli-responsive supramolecular assemblies formed by host-guest interactions, discussing how to transfer host-guest chemistry from solution onto surfaces required for fabricating multifunctional biosurfaces and biointerfaces. Then, we present different stimuli-responsive biosurfaces and biointerfaces, which have been prepared through a combination of cyclodextrin- or cucurbituril-based host-guest chemistry and various surface technologies such as self-assembled monolayers or layer-by-layer assembly. Moreover, we discuss the applications of these biointerfaces and biosurfaces in the fields of drug release, reversible adsorption and release of some organic molecules, peptides, proteins, and cells, and photoswitchable bioelectrocatalysis. In addition, we summarize the merits and current limitations of these methods for fabricating multifunctional stimuli-responsive biointerfaces in a dynamic noncovalent manner. Finally, we present possible strategies for future designs of stimuli-responsive multifunctional bioin...

The novel copolymers of acrylamide (AM) with complex pseudorotaxane monomer (BAMACB) of butyl ammonium methacrylate (BAMA) and cucurbit[6]uril (CB[6]) were prepared via free‐radical polymerization in aqueous solution. The copolymers containing pseudorotaxane (PAM/BAMACB) were characterized by 1H‐NMR, FTIR, elemental analysis, TGA, and DSC. The glass transition temperature (Tg) of the copolymer PAM/BAMACB are higher than that of the copolymer of acrylamide and butyl ammonium methacrylate (PAM/BAMA) because of the enhanced rigidity and the bulky steric hindrance of BAMACB side chain in PAM/BAMACB. The molecular weights of copolymer PAM/BAMACB were obtained via static light scattering. The hydrodynamic radii of coils or aggregates were investigated by dynamic light scattering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5999–6008, 2008

Supramolecular polymers, whose building blocks are noncovalently connected, have attracted much attention over the last few decades. The noncovalent nature of these polymeric systems endows them with great potential for applications in the preparation of dynamic materials. Cucurbituril (CB)-based host-guest systems, which have strong binding affinity and good selectivity, have received extensive recent attention. Among the CB family, is unique for its ability to bind two guests in its cavity and form strong ternary complexes. Such -based host-guest systems have been widely used in the construction of supramolecular architechtures. In this Focus Review, following a brief description of the host-guest interactions in -based systems, we summarize the current state of play in the fabrication of -based supramolecular polymers, which mainly include small-molecule-based supramolecular polymers and polymer-based supramolecular polymers, as a good example of the marriage between the supramolecular chemistry of cucurbiturils and polymer science.

Staying in the pocket: A cyclometalated iridium(III) biquinoline complex targets the protein-protein interface (see picture; C yellow, N blue, Ir dark green) of the tumor necrosis factor-α (TNF-α) trimer. Molecular-modeling studies confirm the nature of this interaction. Both enantiomers of the iridium complex display comparable in vitro potency to the strongest small-molecule inhibitor of TNF-α.

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A series of tunable interpenetrating polymer network (IPN) hydrogels are designed by the orthogonal incorporation of two distinct types of reversible bonds, i.e., Schiff base bonds and metal−ligand coordination bonds. Two copolymers based on poly(N,N-dimethyl acrylamide) (PDMA) are synthesized and used as building blocks for the IPN hydrogels. The first one bears ketone pendant groups and is cross-linked by dihydrazide or bishydroxylamine compounds to form, respectively, acylhydrazone-or oxime-based dynamic covalent bond (DCB) networks. The second one bears terpyridine side groups and is cross-linked by the addition of two different transition-metal cations to obtain supramolecular networks based on metal−terpyridine bis-complexes. Several IPN hydrogels are prepared by combining these different types of reversible bonds to investigate how the two subnetworks influence each other. To this end, the influence of the cross-linker nature and of the hydrogel preparation protocol on the rheological properties of these IPNs are also studied in detail. In particular, we show that the obtained IPN hydrogels exhibit a higher modulus compared to the simple addition of the moduli of the single networks, which we attribute to the entanglements between the two networks. We then study how these IPN hydrogels can disentangle and partially relax if one of the reversible subnetworks is composed of cross-links with a shorter lifetime. Finally, pH is used as a stimulus to affect the dynamics of only one of the subnetworks, and the impact of this change on the properties of the IPNs is investigated.

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A G-quadruplex-based, label-free, switch-on fluorescence detection method has been developed for the selective detection of ATP in aqueous solution using crystal violet as a G-quadruplex-selective probe. The assay is highly simple and rapid, and does not require the use of fluorescent labeling.