Controlled synthesis of β-cyclodextrin-based starlike helical poly(phenyl isocyanide) and its application in chiral resolution

In an effort to expand the diversity of helical polymers exhibiting intricate structures, a strategy for the precise fabrication of β-cyclodextrin-based star polymers adorned with helical poly(phenyl isocyanide) (PPI) arms has been successfully realized through the integration of isocyanide polymerization and atom transfer radical polymerization (ATRP). An elegant β-cyclodextrin embellished with 7 Pd(II) complexes on one side and 14 bromine groups on the other side, denoted as ((Pd(II))7-CD-(Br)14), was initially synthesized. Subsequently, the (PPI)7-CD-(Br)14 was synthesized through the polymerization of the phenyl isocyanide monomer initiated with (Pd(II))7-CD-(Br)14. Finally, starlike PPI was obtained by ATRP of 1,2-diacrylyl ethane initiated via the macro-initiator of (PPI)7-CD-(Br)14. Circular dichroism measurement analysis indicated that the obtained starlike PPI exhibited a consistent helical conformation with a preferred handedness, and it was revealed that the helical structure of starlike PPI originated from the PPI backbone, rather than intermolecular aggregation in solutions. Furthermore, the starlike PPI demonstrated excellent efficacy in the chiral resolution of racemic compounds, achieving an enantiomeric excess (e.e.) of 92 % for threonine racemates when used as a chiral resolution agent.

Click Chemistry as an Efficient Toolbox for Coupling Sterically Hindered Molecular Systems to Obtain Advanced Materials for Nanomedicine

Since its conceptualization, click chemistry in all its variants has proven to be a superior synthesis protocol, compared to conventional methods, for forming new covalent bonds under mild conditions, orthogonally, and with high yields. If a term like reactive resilience could be established, click reactions would be good examples, as they perform better under increasingly challenging conditions. Particularly, highly hindered couplings that perform poorly with conventional chemistry protocols-such as those used to conjugate biomacromolecules (e.g., proteins and aptamers) or multiple drugs onto macromolecular platforms-can be more easily achieved using click chemistry principles, while also promoting high stereoselectivity in the products. In this review, three molecular platforms relevant in the field of nanomedicine are considered: polymers/copolymers, cyclodextrins, and fullerenes, whose functionalization poses a challenge due to steric hindrance, either from the intrinsic bulk behavior (as in polymers) or from the proximity of confined reactive sites, as seen in cyclodextrins and fullerenes. Their functionalization with biologically active groups (drugs or biomolecules), primarily through copper-catalyzed azide-alkyne cycloaddition (CuAAC), strain-promoted azide-alkyne cycloaddition (SPAAC), inverse electron-demand Diels-Alder (IEDDA) and thiol-ene click reactions, has led to the development of increasingly sophisticated systems with enhanced specificity, multifunctionality, bioavailability, delayed clearance, multi-targeting, selective cytotoxicity, and tracking capabilities-all essential in the field of nanomedicine.

Significance of Polymers with “Allyl” Functionality in Biomedicine: An Emerging Class of Functional Polymers

In recent years, polymer-based advanced drug delivery and tissue engineering have grown and expanded steadily. At present, most of the polymeric research has focused on improving existing polymers or developing new biomaterials with tunable properties. Polymers with free functional groups offer the diverse characteristics needed for optimal tissue regeneration and controlled drug delivery. Allyl-terminated polymers, characterized by the presence of a double bond, are a unique class of polymers. These polymers allow the insertion of a broad diversity of architectures and functionalities via different chemical reactions. In this review article, we shed light on various synthesis methodologies utilized for generating allyl-terminated polymers, macromonomers, and polymer precursors, as well as their post-synthesis modifications. In addition, the biomedical applications of these polymers reported in the literature, such as targeted and controlled drug delivery, improvement i aqueous solubility and stability of drugs, tissue engineering, and antimicrobial coatings, are summarized.

Polycyclodextrins: Synthesis, functionalization, and applications

Cyclodextrins (CDs) are cyclic oligosaccharides with unique conical structure enabling host-guest inclusion complexes. However, virgin CDs sufferfrom low solubility, lack of functional groups and its inability to strong complexation with the guests. One of the most efficient ways to improve the properties of cyclodextrins is the synthesis of polycyclodextrins. Generally, there are two types of polycyclodextrins: 1) polymers containing CD units as parts of the main backbone; and 2) polymers with CD units as side chains. These polycyclodextrins are produced (i) from direct copolymerization of virgin cyclodextrins or cyclodextrins derivatives with various monomers including isocyanates, epoxides, carboxylic acids, anhydrides, acrylates, acrylamides and fluorinated aromatic compounds, or (ii) by post-functionalization of other polymers with CDs or CD derivatives.. By selecting the proper derivatives of CDs and controlling the polymerization, polycyclodextrins with linear, hyperbranched, and crosslinked structures have been synthesized. Polycyclodextrins have found significant applications in numerous areas, as adsorbents for removal of organic pollutants, carriers in gene/drug delivery, and for preparation of supramolecular based hydrogels. The focus of this review paper is placed on the synthesis, characterization, and applications of CDs so as to highlight challenges as well as the promising features of the future ahead of material developments based on CDs.

Gold nanoparticles standing on PEG/PAMAM/thiol-functionalized nanographene oxide as aqueous catalysts

Gold nanoparticles were aptly in situ grown on PEG/PAMAM/thiol-functionalized nanographene oxide platforms for aqueous catalysis.

Natural cyclodextrins and their derivatives for polymer synthesis

A toolbox of cyclodextrin derivatives, synthetic strategies for the preparation of cyclodextrin-polymer conjugates using various polymerisation techniques and representative applications of such conjugates are discussed.