Reduction-Triggered Transformation of Disulfide-Containing Micelles at Chemically Tunable Rates

Redox-Responsive Gene Delivery from Perfluorocarbon Nanoemulsions through Cleavable Poly(2-oxazoline) Surfactants

The clinical utility of emulsions as delivery vehicles is hindered by a dependence on passive release. Stimuli-responsive emulsions overcome this limitation but rely on external triggers or are composed of nanoparticle-stabilized droplets that preclude sizes necessary for biomedical applications. Here, we employ cleavable poly(2-oxazoline) diblock copolymer surfactants to form perfluorocarbon (PFC) nanoemulsions that release cargo upon exposure to glutathione. These surfactants allow for the first example of redox-responsive nanoemulsions in cellulo. A noncovalent fluorous tagging strategy is leveraged to solubilize a GFP plasmid inside the PFC nanoemulsions, whereupon protein expression is achieved selectively when employing a stimuli-responsive surfactant. This work contributes a methodology for non-viral gene delivery and represents a general approach to nanoemulsions that respond to endogenous stimuli.

Covalent Post-Assembly Modification: A Synthetic Multipurpose Tool in Supramolecular Chemistry

The use of covalent post-assembly modification (PAM) in supramolecular chemistry has grown significantly in recent years, to the point where PAM is now a versatile synthesis tool for tuning, modulating, and expanding the functionality of self-assembled complexes and materials. PAM underpins supramolecular template-synthesis strategies, enables modular derivatization of supramolecular assemblies, permits the covalent 'locking' of unstable structures, and can trigger controlled structural transformations between different assembled morphologies. This Review discusses key examples of PAM spanning a range of material classes, including discrete supramolecular complexes, self-assembled soft nanostructures and hierarchically ordered polymeric and framework materials. As such, we hope to highlight how PAM has continued to evolve as a creative and functional addition to the synthetic chemist's toolbox for constructing bespoke self-assembled complexes and materials.

High-Fidelity End-Functionalization of Poly(ethylene glycol) Using Stable and Potent Carbamate Linkages

Commercial PEG-amine is of unreliable quality, and conventional PEG functionalization relies on esterification and etherification steps, suffering from incomplete conversion, harsh reaction conditions, and functional-group incompatibility. To solve these challenges, we propose an efficient strategy for PEG functionalization with carbamate linkages. By fine-tuning terminal amine basicity, stable and high-fidelity PEG-amine with carbamate linkage was obtained, as seen from the clean MALDI-TOF MS pattern. The carbamate strategy was further applied to the synthesis of high-fidelity multi-functionalized PEG with varying reactive groups. Compared to with an ester linkage, amphiphilic PEG-PS block copolymers bearing carbamate junction linkage exhibits preferential self-assembly tendency into vesicles. Moreover, nanoparticles of the latter demonstrate higher drug loading efficiency, encapsulation stability against enzymatic hydrolysis, and improved in vivo retention at the tumor region.

Emerging Applications of Fluorogenic and Non-fluorogenic Bifunctional Linkers

Homo- and hetero-bifunctional linkers play vital roles in constructing a variety of functional systems, ranging from protein bioconjugates with drugs and functional agents, to surface modification of nanoparticles and living cells, and to the cyclization/dimerization of synthetic polymers and biomolecules. Conventional approaches for assaying conjugation extents typically rely on ex situ techniques, such as mass spectrometry, gel electrophoresis, and size-exclusion chromatography. If the conjugation process involving bifunctional linkers was rendered fluorogenic, then in situ monitoring, quantification, and optical tracking/visualization of relevant processes would be achieved. In this review, conventional non-fluorogenic linkers are first discussed. Then the focus is on the evolution and emerging applications of fluorogenic bifunctional linkers, which are categorized into hetero-bifunctional single-caging fluorogenic linkers, homo-bifunctional double-caging fluorogenic linkers, and hetero-bifunctional double-caging fluorogenic linkers. In addition, stimuli-cleavable bifunctional linkers designed for both conjugation and subsequent site-specific triggered release are also summarized.