Integrated Extrinsic and Intrinsic Self-Healing of Polysiloxane Materials by Cleavable Molecular Cages Encapsulating Fluoride Ions

Self-healing ability is crucial to increasing the lifetime and reliability of materials. In this study, spatiotemporal control of the healing of a polysiloxane material is achieved using a cleavable cage compound encapsulating a fluoride ion (F- ), which triggeres the dynamic rearrangement of the siloxane (Si-O-Si) networks. A self-healing siloxane-based elastomer is prepared by cross-linking polydimethylsiloxane (PDMS) with a F- -encapsulating cage-type germoxane (Ge-O-Ge) compound. This material can self-heal repeatedly under humid conditions. The F- released by hydrolytic cleavage of the cage framework contributes to rejoining of the cut pieces by promoting the local rearrangement of the siloxane networks. The use of a molecular cage encapsulating a catalyst for dynamic bond rearrangement provides a new concept for designing self-healing polysiloxane materials based on integrated extrinsic and intrinsic mechanisms.

Assembly and Covalent Cross-Linking of an Amine-Functionalised Metal-Organic Cage

The incorporation of reactive functional groups onto the exterior of metal-organic cages (MOCs) opens up new opportunities to link their well-defined scaffolds into functional porous solids. Amine moieties offer access to a rich catalogue of covalent chemistry; however, they also tend to coordinate undesirably and interfere with MOC formation, particular in the case of Cu₂ paddlewheel-based MOCs. We demonstrate that tuning the basicity of an aniline-functionalized ligand enables the self-assembly of a soluble, amine-functionalized Cu₄L₄ lantern cage (1). Importantly, we show control over the coordinative propensity of the exterior amine of the ligand, which enables us to isolate a crystalline, two-dimensional metal-organic framework composed entirely of MOC units (2). Furthermore, we show that the nucleophilicity of the exterior amine of 1 can be accessed in solution to generate a cross-linked cage polymer (3) via imine condensation.

A Light-Controlled TLR4 Agonist and Selectable Activation of Cell Subpopulations

The spatial and temporal aspects of immune cell signaling are key parameters in defining the magnitude of an immune response. Toll-like receptors (TLRs) on innate immune cells are important in the early detection of pathogens and initiation of an immune response. Controlling the spatial and temporal signaling of TLRs would enable further study of immune synergies and assist in the development of new vaccines. Here, we show a light-based method for the spatial control of TLR4 signaling. A TLR4 agonist, pyrimido[5,4-b]indole, was protected with a cage at a position critical for receptor binding. This afforded a photocontrollable agonist that was inactive while caged, yet effected NF-κB activity in cells following UV photocontrolled deprotection. We demonstrated spatial control of NF-κB activation within a population of cells by treating all cells with the caged TLR4 agonist and constraining light exposure and consequent activation to a region of interest.