Cucurbituril‐Based Supramolecular Polymers for Biomedical Applications

Abstract

Supramolecular polymers (SPs) have attracted broad interest because of their intriguing features and functions. Host–guest interactions often impart tunable physicochemical properties, reversible hierarchical organization, and stimuli‐responsiveness to SPs for diverse biomedical applications. Characterized by strong but dynamic interactions with guest molecules, cucurbit[n]uril (CB[n]) has shown great potential as an important building block of various functional polymers for biomedical applications. In this Minireview, we summarize the most recent examples regarding the design, fabrication, and biomedical applications of CB[n]‐based supramolecular polymers (CSPs), which are categorized as noncovalent and covalent CSPs according to the interactions between the CB[n] and polymer backbones. The design principles of CSPs and their unique advantages for biomedical applications, as well as the developmental trends and future perspectives of this cross‐disciplinary area are also discussed.

Macrocyclic Supramolecular Assemblies Based on Hyaluronic Acid and Their Biological Applications

“…In addition to directly assembling with host–guest complexes through multiple hydrogen bonding and electrostatic interactions, HA can also be modified with macrocyclic compounds (e.g., cyclodextrins (CDs), cucurbit­[ n ]­urils (CB­[ n ]­s)) or functional guest molecules (e.g., pyridinium, adamantane, and peptide) through amidation to form multifunctional biomacromolecules for further assembly. CDs are macrocyclic oligosaccharides linked by d -glucose through α-1,4-glycosidic bonds, and the commonly used CDs contain six, seven, and eight d -glucose units, which are named α-, β- and γ-CD, respectively. − Due to the different cavity volumes, CDs can encapsulate different kinds of size-matched guest molecules through hydrophobic interactions. − CB­[ n ]­s are formed by condensation of glycoluril with formaldehyde under the condition of acid catalysis and contain a robust skeleton, a hydrophobic cavity, and two identical ports filled with carbonyl groups. , The commonly used CB­[ n ]­s are CB[6], CB[7], and CB[8], which can not only provide potential inclusion sites for nonpolar molecules but also bind cationic guests via ion–dipole interactions with carbonyl groups. − In terms of the interaction between macrocycle host and functional guest, the association constant is important in the process of self-assembly and release, − which directly affects the time frame of drug release, such as a photocontrolled system for different association constants of trans- and cis- azobenzene with cyclodextrin and the stability of a formed polymer–polymer hydrogel system through multivalent interactions. − With the aid of specific macrocycle host–guest, hydrophobic, and electrostatic interactions, many functional guests can be integrated into supramolecular assemblies; the formed host–guest complexes not only endow the assemblies with a responsiveness to multiple stimuli (e.g., enzymes, light, electricity, magnetism) but also enhance the luminescence intensity of molecules and improve the loading of drugs. − On the other hand, the nanosupramolecular assembly formed with HA can also improve its biocompatibility, reduce drug toxicity and side effects, and enhance cell permeability and accumulation in tumors, which has extensive application value in biomedical research.…”

Pit-embellished low-valent metal active sites customize CO2photoreduction to methanol

“…Thus, we conducted density functional theory (DFT) to check the influence of low-valent W species on the electronic structure of WO 3 and WO 3− x (see Calculation details in the ESI†). 34,35 As depicted in Fig. 1a, the Bader charge distribution of the W atom adjacent to the top oxygen vacancy is 2.79 electrons (2.79 e − ) on an optimized WO 3− x surface, which is between the charge of W 6+ (2.97 e − ) in a perfect WO 3 and the charge of W 4+ (2.27 e − ) in WO 2 .…”

Catalytic Hydrophosphination of Allenes Using an Iron(II) β-Diketiminate Complex

“…Enantioselective hydrophosphinylation has also been reported. 8 In terms of hydrophosphination chemistry, Mitchell initially reported the addition of diphenylphosphine over allenes through radical addition. 9 More recently, rare-earth- and transition-metal-catalyzed methods have been developed.…”