Shell-Sheddable/Core-Degradable ABA Triblock Copolymer Nanoassemblies: Synthesis via RAFT and Concurrent ATRP/RAFT Polymerization and Drug Delivery Application

Reverse Block Sequence in Self-Immolative Poly(benzyl ether)-Based Amphiphiles for Tailoring End Groups and Self-Assembly Behavior

This paper reports a modular design of self-immolative poly(benzyl ether) (PBE) amphiphiles that allows precise control over polymer chain structure, end-group placement, and degradation behavior. By tuning block sequences and exposing reactive end groups, these amphiphiles undergo efficient head-to-tail depolymerization upon external stimuli. Structural variations in the monomers enable micelle formation with end groups displayed on the surface, while the carboxylate content in the hydrophilic block influences global micelle morphology. The resulting micelles are degradable in aqueous environments and can transform into spherical structures when combined with conventional surfactants. As a proof of concept, small-molecule cargos were successfully loaded and released from the mixed micelles on demand. This design platform offers a versatile route to create functional, stimulus-responsive surfactants with tunable assembly, degradation, and controlled release capabilities.

pH-Responsive Degradable Electro-Spun Nanofibers Crosslinked via Boronic Ester Chemistry for Smart Wound Dressings

Recent advances in the treatment of chronic wounds have focused on the development of effective strategies for cutting-edge wound dressings based on nanostructured materials, particularly biocompatible poly(vinyl alcohol) (PVA)-based electro-spun (e-spun) nanofibers. However, PVA nanofibers need to be chemically crosslinked to ensure their dimensional stability in aqueous environment and their capability to encapsulate bioactive molecules. Herein, a robust approach for the fabrication of pH-degradable e-spun PVA nanofibers crosslinked with dynamic boronic ester (BE) linkages through a coupling reaction of PVA hydroxyl groups with the boronic acid groups of a phenyl diboronic acid crosslinker is reported. This comprehensive analysis reveals the importance of the mole ratio of boronic acid to hydroxyl group for the fabrication of well-defined BE-crosslinked fibrous mats with not only dimensional stability but also the ability to retain uniform fibrous form in aqueous solutions. These nanofibers degrade in both acidic and basic conditions that mimic wound environments, leading to controlled/enhanced release of encapsulated antimicrobial drug molecules. More importantly, drug-loaded BE-crosslinked fibers show excellent antimicrobial activities against both Gram-positive and Gram-negative bacteria, suggesting that this approach of exploring dynamic BE chemistry is amenable to the development of smart wound dressings with controlled/enhanced drug release.

Design, Synthesis, and Acid-Responsive Disassembly of Shell-Sheddable Block Copolymer Labeled with Benzaldehyde Acetal Junction

Smart nanoassemblies degradable through the cleavage of acid-labile linkages have attracted significant attention because of their biological relevance found in tumor tissues. Despite their high potential to achieve controlled/enhanced drug release, a systematic understanding of structural factors that affect their pH sensitivity remains challenging, particulary in the consruction of effective acid-degradable shell-sheddable nanoassemblies. Herein, the authors report the synthesis and acid-responsive degradation through acid-catalyzed hydrolysis of three acetal and ketal diols and identify benzaldehyde acetal (BzAA) exhibiting optimal hydrolysis profiles in targeted pH ranges to be a suitable candidate for junction acid-labile linkage. The authors explore the synthesis and aqueous micellization of well-defined poly(ethylene glycol)-based block copolymer bearing BzAA linkage covalently attached to a polymethacrylate block for the formation of colloidally-stable nanoassemblies with BzAA groups at core/corona interfaces. Promisingly, the investigation on acid-catalyzed hydrolysis and disassembly shows that the formed nanoassemblies meet the criteria for acid-degradable shell-sheddable nanoassemblies: slow degradation at tumoral pH = 6.5 and rapid disassembly at endo/lysosomal pH = 5.0, while colloidal stability at physiological pH = 7.4. This work guides the design principle of acid-degradable shell-sheddable nanoassemblies bearing BzAA at interfaces, thus offering the promise to address the PEG dilemma and improve endocytosis in tumor-targeting drug delivery.

Synthesis of multiple stimuli-responsive degradable block copolymers via facile carbonyl imidazole-induced postpolymerization modification

A robust approach that centers on carbonyl imidazole chemistry was used to synthesize a triple-stimuli-responsive degradable block copolymer labeled with acetal, disulfide, and o-nitrobenzyl groups exhibiting acid, reduction, and light responses.