Photo-controlled Hierarchical Assembly and Fusion of Coumarin-containing Polydiacetylene Vesicles

Recent Advances in Functional Polymers Containing Coumarin Chromophores

Natural and synthetic coumarin derivatives have gained increased attention in the design of functional polymers and polymer networks due to their unique optical, biological, and photochemical properties. This review provides a comprehensive overview over recent developments in macromolecular architecture and mainly covers examples from the literature published from 2004 to 2020. Along with a discussion on coumarin and its photochemical properties, we focus on polymers containing coumarin as a nonreactive moiety as well as polymer systems exploiting the dimerization and/or reversible nature of the [2πs + 2πs] cycloaddition reaction. Coumarin moieties undergo a reversible [2πs + 2πs] cycloaddition reaction upon irradiation with specific wavelengths in the UV region, which is applied to impart intrinsic healability, shape-memory, and reversible properties into polymers. In addition, coumarin chromophores are able to dimerize under the exposure to direct sunlight, which is a promising route for the synthesis and cross-linking of polymer systems under "green" and environment-friendly conditions. Along with the chemistry and design of coumarin functional polymers, we highlight various future application fields of coumarin containing polymers involving tissue engineering, drug delivery systems, soft robotics, or 4D printing applications.

Approaches for the synthesis of o-nitrobenzyl and coumarin linkers for use in photocleavable biomaterials and bioconjugates and their biomedical applications

Photocleavable biomaterials and bioconjugates are particularly interesting because light sources are easy to obtain and the responsiveness of materials is convenient to control. In recent years, various photocleavable biomaterials and bioconjugates have been synthesized for the control of payload release, regulation of biomolecule activity, 3D cell culture, and investigation of molecular mechanisms. Photocleavable linkers are crucial components of photocleavable biomaterials, which significantly influence the photoresponsive capabilities of materials. Photosensitive molecules, such as o-nitrobenzyls and coumarins, have been extensively developed as photocleavable linkers. In the present review, we provide comprehensive knowledge regarding the synthetic strategies of o-nitrobenzyl and coumarin derived linkers with various functional groups and their applications for the construction of photocleavable biomaterials and bioconjugates. Finally, the biomedical applications of o-nitrobenzyl and coumarin-based photocleavable biomaterials and bioconjugates will be summarized and discussed.

Superstructure Formation and Topological Evolution Achieved by Self-Organization of a Highly Adaptive Dynamer

The adaptive property of supramolecular building blocks facilitates noncovalent synthesis of soft materials. While it is still a challenging task, fine-tuning and precise control over topological nanostructures constructed from the self-assembly of low-molecular-weight building blocks are an important research direction to investigate the structure-property relationship. Herein, we report controlled self-assembly evolution of a low-molecular-weight building block bearing cholesterol and naphthalene-dicarboximide moieties, showing ultrasensitivity to solvent polarity. In low-polarity solvents (<4), it could form an M-type fiber-constituted organogel (supergel) with high solvent content, columnar molecular packing, and self-healing property. Highly polar solvents (>7.8) favor the formation of P-type helical nanostructures terminated by nanotoroids, having lamellar molecular packing. With a further increase in solvent polarity (up to 9.6), unilamellar and multilamellar vesicles were generated, which could undergo an aggregation-induced fusion process to form branched nanotubes tuned by the concentration. Self-attractive interactions between aggregates were found to be responsible for the formation of superstructures including helix-nanotoroid junctions as well as membrane-fused nanotubes.

Photo-triggered transformation from vesicles to branched nanotubes fabricated by a cholesterol-appended cyanostilbene

Vesicles constructed from cholesteryl cyanostilbene could transform into nanotubes upon UV light irradiation, in which the photoluminescence could be fine-tuned.