Emergence of Compartments Formed from Unconventional Surfactants In

University of Groningen Emergence of Compartments Formed from Unconventional Surfactants in Dynamic Combinatorial Libraries Bartolec, Boris; Leonetti, Giulia; Li, Jianwei; Smit, Wietse; Altay, Meniz; Monreal Santiago, Guillermo; Yan, Yichen; Otto, Sijbren Published in: Langmuir DOI: 10.1021/acs.langmuir.8b03662 IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2019 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Bartolec, B., Leonetti, G., Li, J., Smit, W., Altay, M., Monreal Santiago, G., ... Otto, S. (2019). Emergence of Compartments Formed from Unconventional Surfactants in Dynamic Combinatorial Libraries. Langmuir, 35(17), 5787-5792. https://doi.org/10.1021/acs.langmuir.8b03662 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 07-09-2019 This is an open access article published under a Creative Commons Non-Commercial No Derivative Works (CC-BY-NC-ND) Attribution License, which permits copying and redistribution of the article, and creation of adaptations, all for non-commercial purposes. Article Cite This: Langmuir 2019, 35, 5787−5792 pubs.acs.org/Langmuir Emergence of Compartments Formed from Unconventional Surfactants in Dynamic Combinatorial Libraries † Boris Bartolec, Giulia Leonetti, Jianwei Li, Wietse Smit, Meniz Altay, Guillermo Monreal Santiago, Yichen Yan, and Sijbren Otto* Centre for Systems Chemistry, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands *S Supporting Information ABSTRACT: Assembly processes can drive the selection of self- assembling molecules in dynamic combinatorial libraries, yielding self- synthesizing materials. We now show how such selection in a dynamic combinatorial library made from an amphiphilic building block which, by itself, assembles into micelles, can yield membranous aggregates ranging from vesicles to sponge phases. These aggregates are made from a mixture of unconventional surfactant molecules, showing the power of dynamic combinatorial selection approaches for the discovery of new, not readily predictable, self-assembly motifs. ■ INTRODUCTION that, in principle, enables selectively populating the most stable Self-assembly is a powerful concept to access nano-sized assembling systems. In the context of the origin of life and the − structures that are organized with up to atomic resolution.1 3 de novo synthesis of life, the idea of obtaining self-synthesizing Traditionally, access to such structures involved two separate compartments (i.e., discrete supramolecular structures able to keep the molecules contained within them mobile) is of steps in which the design and synthesis of the self-assembling − particular significance.27 32 Among different possible mem- molecule are followed by the assembly process in a separate 33,34 second step. In many cases, the different conditions required branous structures, vesicles are particularly appealing, for synthesis and assembly preclude their integration into a given their widespread occurrence in currently known life forms. Yet access to self-synthesizing vesicles has not single process. However, with the advent of dynamic covalent 4−6 progressed beyond proof of principle, targeting conventional chemistry, different chemistries are now available, which 23 can be operated under conditions compatible with those double-chain surfactants. We now report the formation of a − ff required for assembly, allowing a systems chemistry3,7 10 series of di erent membranous architectures, including vesicles, by a mixture of nonconventional surfactants that are approach to self-assembly where the synthesis of the selected from a small DCL formed from a simple amphiphilic assembling molecules and their self-assembly become inter- fi building block. These results demonstrate that the concept of Downloaded via UNIV GRONINGEN on August 16, 2019 at 08:22:17 (UTC). twined. Speci cally, assembly processes occurring in dynamic 11−14 self-synthesizing compartments extends well beyond canonical combinatorial libraries (DCLs) allow access to what we 15 surfactant architectures. termed “self-synthesizing materials”. The idea is that upon formation of reversible covalent bonds between different See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles. ■ RESULTS AND DISCUSSION building blocks, a diverse set of different potentially self- assembling molecules is formed, which continuously inter- We reasoned that it should be possible to discover new vesicle convert by exchanging building blocks (Figure 1a). Library forming surfactants in DCLs made from amphiphilic building blocks. Given that bilayer architectures are normally more members that self-assemble are stabilized by the noncovalent ffi interactions involved in the assembly process and the e cient in shielding their hydrophobic interior from water equilibrium shifts to amplify the assembling molecules at the than micelles, we expected that combinatorial selection experiments would preferentially lead to vesicles, even if the expense of the other library members. This approach has ff allowed access to a variety of self-assembled structures, building block by itself would assemble into a di erent including fibers15 and sheets16,17 (for these morphologies, morphology. In order to test these hypotheses, we designed the process of self-assembly-driven self-synthesis is often building block 1 which contains a hydrophobic aromatic core 18−22 functionalized with two thiol groups, which can be oxidized to autocatalytic, enabling access to self-replicators), micelles, fi and vesicles.23 The dynamic combinatorial approach to self- form a DCL of macrocyclic disul des (Figure 1b). It also synthesizing materials complements polymerization-induced features a hydrophilic tetraethylene glycol chain that enables − self-assembly,24 26 in that, in the former, the assembling molecules are formed through reversible covalent bonds, Received: November 1, 2018 whereas the latter typically involve kinetically controlled Revised: February 3, 2019 polymerization reactions. Reversibility ensures proofreading Published: April 3, 2019 © 2019 American Chemical Society 5787 DOI: 10.1021/acs.langmuir.8b03662 Langmuir 2019, 35, 5787−5792 Langmuir Article Figure 1. (a) Concept of self-synthesizing materials: self-assembly of one of the oligomers within a DCL shifts the equilibrium in the direction of the very molecule that self-assembles. (b) Amphiphilic dithiol building block 1 self-assembles into micelles or, upon oxidation, gives rise to a set of interconverting disulfide macrocycles. (c) Structures of building blocks 2−5. water solubility and renders the overall building block structure amphiphilic. DCLs were prepared by dissolving building block 1 in borate buffer (50 mM, pH 8.5) in the presence or absence of agitation and allowing the thiols to oxidize by exposing them to oxygen from the air. Agitation was conducted using a magnetic stir bar in order to facilitate a growth-breakage mechanism analogous to that observed previously for self-synthesizing fibers.15 Analysis by dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed the presence of micelles in solutions of 1 prior to oxidation of the building block (vide infra). The disulfide macrocycles formed upon oxidation can exchange building blocks through the reaction with residual thiolate anion.35 The composition of the DCLs was analyzed by ultra performance liquid chromatography (UPLC)−mass spectrometry (MS), which uses conditions under which the aggregates fall apart into the molecules from which they are constituted. In contrast to control compound 2, equipped only Figure 2. UPLC−MS analysis of a stirred DCL made from 1.0 mM ff with a carboxylate group, which forms a small DCL dominated building block 2 or 1 in aqueous borate bu er (50 mM, pH 8.5). 15 Composition of the oxidized libraries made from (a) building block 2 by cyclic trimers and tetramers (Figure 2a), the DCL made after 7 days; (b) building block 1 after 30 days; and (c) latter DCL from building block 1 consists of a much larger range of after 3 months. Assignments in blue are tentative (low signal-to-noise oligomers (Figure 2b; for a nonagitated control, see Figure ratio in the mass spectra precluded direct assignment). S1). Thus, a plethora of molecules is available with different amphiphilic properties that can potentially form supra- chromatogram eluting at around 5 min most likely contains a molecular assemblies. It took several months at room collection of high-molecular-weight species.36 The difference in temperature before the final composition of the library was product distribution between the DCLs made from building reached (Figure 2c; for the full time-dependent

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