“Biowheel-Axle” Assembly of β-Cyclodextrin Fitted onto Bile Acid Units Linked by PEG Spacers through Inclusion Polymerization

Abstract

A “biowheel-axle” assembly of polyrotaxanes of β-cyclodextrin (β-CD) threaded onto bile acid moieties linked by a poly­(ethylene glycol) (PEG) spacer of tunable length was prepared through an “inclusion polymerization” approach. The bile acid-diamine derivatives were allowed to first form inclusion complexes with β-CD and then polymerized with PEG-dicarbonate, followed by end-capping with a stopper of monoamino-β-CD, resulting in “biowheels” of β-CD with PEGylated bile acids as the axle in tandem. All steps were performed without the use of catalysts. The complexation between β-CD and bile acid units of the polymer chain was confirmed by the 2D NOESY NMR technique and powder X-ray diffraction, showing 85% of bile acid units entered the cavity of β-CD. The change of PEG spacer length from 45 to 6 ethylene glycol units led to a flexible–rigid conformation transition of the polyrotaxanes, supported by the random and straight orientation of the “biowheels” shown by scanning tunneling microscopy images. The control of the conformation helps to tune the property of the polyrotaxanes. The “biowheel-axle” assembly constructed from such a natural host–guest pair may also lead to the further exploration of bio-related applications.

AIE-Active and Thermoresponsive Alternating Polyurethanes of Bile Acid and PEG for Cell Imaging

“…Bile acids are a class of endogenous steroids present in humans and other animals with excellent biocompatibility. , They can be easily introduced into the backbone of polymers after appropriate functionalization. − For example, hydrophilic PEG segments were polymerized with hydrophobic bile acid units to afford polyurethanes (PU) through the use of dicarbonate derivative of bile acids in the condensation polymerization, avoiding the use of metal catalysts . The alternating PUs containing bile acids and PEG segments in the main chain display transition from soluble to aggregated states upon heating.…”

Polypseudorotaxanes Derived from Tetraphenylethylene: Preparation and Tandem-Activated Aggregation-Induced Emission

“…XRD measurements (Figure B) are used to investigate the solid-state structures of PPR, where the characteristic diffraction peaks (2θ) of γ-CD are observed at 13.8 and 16.4, and the peaks (2θ) at 18.9 and 23.1 are assigned to the characteristic diffraction peaks of PEG segments of the polymer . The diffraction peaks of γ-CD completely disappear in PPR, in which only the low diffraction peaks of PEG are observed.…”

Recent Progress in Macromolecular Design and Synthesis of Bile Acid‐Based Polymeric Architectures

“…In addition, the same group has taken another step-up design strategy and formulated an interesting macromolecular rotaxane system with CA-diamine main chained PEG spacer polymer with threading 𝛽-CD. [58] A polymeric "biowheel-axel" assembly was fabricated by crucial complexation of molecular 𝛽-CD with macromolecular CA (Figure 4; P-5). The polymeric system was end-locked through covalent conjugation of 𝛽-CD at the two ends of the pseudo-rotaxane polymer which resulted in the formation of a stable macromolecular rotaxane.…”