ABSTRACT
Hierarchical self-assembly of building blocks over multiple length scales is ubiquitous in living organisms. Microtubules are one of the principal cellular components formed by hierarchical self-assembly of nanometer-sized tubulin heterodimers into protofilaments, which then associate to form micron-length-scale, multi-stranded tubes. This peculiar biological process is now mimicked with a fully synthetic molecule, which forms a 1:1 host-guest complex with cucurbit[7]uril as a globular building block, and then polymerizes into linear poly-pseudorotaxanes that associate laterally with each other in a self-shape-complementary manner to form a tubular structure with a length over tens of micrometers. Molecular dynamic simulations suggest that the tubular assembly consists of eight poly-pseudorotaxanes that wind together to form a 4.5â nm wide multi-stranded tubule.
Subject(s)
Microtubules/chemistry , Polymers/chemistry , Bridged-Ring Compounds/chemistry , Imidazoles/chemistry , Microscopy, Atomic Force , Microscopy, Electron, Transmission , Microtubules/metabolism , Molecular Dynamics Simulation , Rotaxanes/chemistryABSTRACT
Herein we report a facile transformation of hydroxylated cucurbit[n]uril (CB[n], n = 6 and 7) to other functionality-conjugated CB[n]s by nucleophilic substitution of the hydroxyl group with a wide range of nitriles and alcohols. The reaction proceeds efficiently via generation of a superelectrophilic carbocation on the CB framework from hydroxylated CB[n]s under superacidic conditions. One of the resulting CB[n] derivatives with reactive functionality, monocarboxylated CB[7], is efficiently conjugated to an enzyme (horseradish peroxidase, HRP) by amide coupling. This provides a CB[7]-conjugated functional biomaterial (CB[7]-HRP) that selectively detects proteins labeled with a guest, adamantylammonium (AdA), based on bioorthogonal high-affinity host-guest interactions between CB[7] and AdA. We demonstrated the potential of overcoming the limitations in preparing reactive functional CB[n] derivatives, enabling the exploration of novel bioapplications of CB[n]-based host-guest chemistry with new CB[n]-conjugated functional materials.
ABSTRACT
Some host-guest complexes of cucurbit[n]uril (CB[n]) host molecules act as supramolecular amphiphiles (SAs), which hierarchically self-assemble into various nanomaterials such as vesicles, micelles, nanorods, and nanosheets in water. The structures and functions of the nanomaterials can be controlled by supramolecular engineering of the host-guest complexes. In addition, functionalization at the periphery of CB[6] and CB[7] generates CB[n]-based molecular amphiphiles (MAs) that can also self-assemble into vesicles or micelle-like nanoparticles in water. Taking advantage of the molecular cavities of CBs and their strong guest recognition properties, the surface of the self-assembled nanomaterials can be easily decorated with various functional tags in a non-covalent manner. In this feature article, the two types (SAs and MAs) of CB-based amphiphiles, their self-assemblies and their applications for nanotherapeutics and theranostics are presented with future perspectives.
Subject(s)
Antibiotics, Antineoplastic/pharmacology , Bridged-Ring Compounds/pharmacology , Doxorubicin/pharmacology , Nanostructures/chemistry , Surface-Active Agents/pharmacology , Antibiotics, Antineoplastic/chemistry , Bridged-Ring Compounds/chemistry , Cell Proliferation/drug effects , Doxorubicin/chemistry , HeLa Cells , Humans , KB Cells , Surface-Active Agents/chemistryABSTRACT
The construction of two libraries of triazole-containing isothiazolidine 1,1-dioxides is reported utilizing either a one-pot click/aza-Michael or click/OACC esterification protocol. One core dihydroisothiazole 1,1-dioxide scaffold was prepared rapidly on multigram scale via ring-closing metathesis (RCM) and was subjected to a one-pot multicomponent click/aza-Michael protocol with an array of amines and azides for the generation of a 180-member triazole-containing isothiazolidine 1,1-dioxide library. Alternatively, three daughter scaffolds were generated via the aza-Michael of three amino alcohols, followed by a one-pot, multicomponent click/esterification protocol utilizing a ring-opening metathesis polymerization (ROMP)-derived coupling reagent, oligomeric alkyl carbodiimide (OACC) to generate a 41-member library of triazole-containing isothiazole 1,1-dioxides.