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Communicating Vesicles

Periodic Reporting for period 1 - CoVes (Communicating Vesicles)

Reporting period: 2019-04-08 to 2021-04-07

The process of communication at molecular level is fundamental for the regulation of chemical and biological systems. As example, the survival of cellular entities depends on their capability to send and receive chemical messages between their interior and exterior.
Therefore, the possibility to acquire knowledge on communication phenomena using artificial systems leads to understanding and developing complex information processing networks. Inspired by the regulation of chemical signal given by transmembrane receptors, “CoVes” allows to build a system made of synthetic vesicles equipped with a series of receptors able to respond to reversible chemical stimuli, so that the vesicles can react in a specific and targeted way to different molecular signals. The investigation of dynamic covalent reactions in a biocompatible environment together with the development of signalling processes is studied. The optimisation and development of a series of reversible reactions based on thiol addition to a Michael acceptor showed that the vesicles induce a template effect, which can be exploited to selectively form a desired product in the lipid bilayer. The quantitative assessment of this phenomenon provides useful guidelines for the design of molecular components for exploiting and design dynamic reversible covalent systems within lipid bilayers.
Moreover, the findings on reactivity of dynamic systems at the membrane interface is used to develop an artificial signalling system. A clear insight is provided on the functioning of a reversible system within a lipid bilayer and how it can be employed in the generation of a chemical signal or in the transport of specific molecules.
The implementation and optimisation of these systems took longer than expected and the two years project resulted not sufficient to implement the communication between different vesicles. However, the control gained on reversible process at the lipid bilayer interface furnishes promising initial results to extend and develop the adopted approach.
The work developed during the project analysed and investigated multiple aspects related to the main goal, which is the development of synthetic vesicles equipped with reversible transmembrane receptors able to respond to reversible chemical stimuli and translate it into a signalling process, with the ultimate goal to implement communication within different vesicles.
Despite the initial design for the receptors was not implemented due to instability of the planned molecule, we adapted our strategy in order to obtain a lipophilic Michael acceptor able to be inserted in the bilayer and reversibly react with a series of thiols.
We were able to investigate how vesicle lipid bilayers can be employed as templates to modulate the product distribution in a dynamic covalent library of Michael adducts formed by mixing a Michael acceptor with thiols. The equilibrium constants for formation of the Michael adducts are similar for all of the thiols used, however the effect of the vesicles on the library composition is attributed to the differential partitioning of the thiols between the lipid bilayer and the aqueous solution (Article 1).
This investigation has led to a successful development of a signalling system based on the reversible adduct formation in the lipid bilayer. In this case, the knowledge on the reactivity of the Michael acceptor towards different thiols allowed to control the selective activation of an enzyme contained in the inner vesicles, hence the generation of a related fluorescence signal. The detailed description of the observed effect, together with a quantitative assessment allowed to control a selective turn on and off of an enzymatic process within the vesicles (Article 2).
The optimised system can be used as a starting point to interface vesicles equipped with different acceptors which represent a fundamental knowledge for further interesting investigations.

Publications:
[1] C. Bravin, C.A. Hunter, “Template effects of vesicles in dynamic covalent chemistry”, Chem. Sci., 2020, 11, 9122-9125
[2] C. Bravin, Nol Duindam, C.A. Hunter “Signalling in vesicles mediated by dynamic covalent chemistry” in preparation.

Conferences:
[1] Carlo Bravin “Supramolecular cages as differential sensors for dicarboxylate anions: guest length sensing using principal component analysis of ESI-MS and 1H-NMR raw data”. “ISMSC / ISACS 2019, Lecce (IT), June 02-06, 2019. Best poster prize awarded by JACS.
[2] Carlo Bravin “Template effects of vesicles in dynamic covalent chemistry”. “ISMSC / ISACS 2020, Online event, August 24th, 2020.

Invited seminars:
[1] “Functional dynamic systems: a journey from supramolecular cages to vesicles” as seminar at the University of Bologna (IT) - Department of Chemistry - Online event, July 14th, 2020.

Public outreach:
[1] “My research journey from supramolecular cages to vesicles” - Natural Science Society Talk as a Research associate of Selwyn College, Cambridge (UK). Online event, October 29th, 2020.
1. Development of reversible thiol Michael acceptors interacting within lipid bilayers
2. Analysis and characterisation of reversible processes at the lipid bilayer interface
3. Assessment of the role of vesicles in reversible process and how they can modulate the formation of selected reaction product.
4. Implementation of the optimised reversible system to develop a signalling process in the vesicles interior with possible biomedical application and drug delivery.
These results show the development of an innovative approach to reversible process at the lipid bilayer interface which can be used to control signalling process in vesicles.
Activation of Vesicles