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Communication between Functional Molecules using Photocontrolled Ions

Final Report Summary - COMMOTION (Communication between Functional Molecules using Photocontrolled Ions)

Communication at the molecular level is essential in Natural systems and is elegantly achieved using chemical messengers, where different stimuli provoke the release of ions and molecules to effect change or register information. Teaching molecules to talk together is equally essential in the development of molecular networks, for example in nanoelectronics and medical diagnostics domains, as well as interfacing biological architectures. Despite many different approaches, there is currently no satisfactory strategy to permit intermolecular communication in artificial molecules and molecule-based devices. A major goal of the COMMOTION project was to determine to which extent bioinspired chemical communication can be harnessed in wholly artificial systems, as well as biomimetic architectures. A range of new photoresponsive functional molecules, chromophores and nanomaterials have been designed and synthesised, which show different light-responsive properties in terms of absorption and emission colours and quantum efficiencies for structural change and emission. In terms of chromophores, ultraphotostable dyes which are compatible with live cell imaging and photodynamic therapy application have been identified and studied to the single molecule level, as well as quantum dot sensors. Among the photoresponsive molecules, one can highlight molecular photoejectors and molecular ion detectors. In a first time, the primary act of chemical communication can be described by the release of a chemical messenger from a molecular photoejector and its subsequent arrival at the molecular detector that is signaled by, for example, a light output. Light inputs / outputs can be delivered and detected with high spatial and temporal precision allowing observation in real time of processes on timescales of less than a billionth of a second. Molecular detectors have been built using highly-efficient ion-switched fluorescent chromophores. When coupled with specific receptor sites a photoinduced electron transfer (PET) process (a primary process in photosynthesis) quenches fluorescence, which is only switched "on" when a chemical message is received. In another manifestation of PET, this process was harnessed to activate metal catalysts which hold promise for safer and convenient chemical reactions from the bench to industrial scales. Concerning photoejectors, different types of novel receptor molecules which bind ions and molecules, and can release these messengers in solution or at biological membrane surfaces upon receiving a light pulse, have been conceived. Adding light energy changes the receptor structure and in turn its capacity to bind a chemical, which is thus released. In several cases subsequently adding light of a different colour reverses the process and the chemical is taken up again. In a proof-of-principle example, the photorelease of a small molecule and its arrival at a distant molecular site was demonstrated, and hence chemical communication in a fully artificial chemical system. Notably, in the interior of small dynamic self-assembled surfactant nanospheres (around 3 nm radius) reminiscent of miniscule soap bubbles, the light-triggered transfer is shown to be more efficient than in free solution, showing the importance of comparimentalization. Different host containers for functional molecules were therefore developed, including persistent 3D-vesicle capsules of different size (from 40 nm to 10 μm diameter) and micrometric self-assembled multicomparimental hosts based on polymer capsules. These latter metastable systems, which can be imaged individually, are promising minimal cell units to disentangle biochemical pathways of internalized biomolecules in a controlled microenvironment.