The effect of solvent choice on the gelation and final hydrogel properties of Fmoc–diphenylalanine

Raeburn, Jaclyn; Mendoza-Cuenca, Cristina; Cattoz, Beatrice; Little, Marc A.; Terry, Ann E.; Cardoso, Andre Zamith; Griffiths, Peter Charles; Adams, Dave J.

doi:10.1039/c4sm02256d

Cited by 144 publications

(160 citation statements)

References 34 publications

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“…This phase-separation event implies that how the process is carried out will likely determine the outcome of the self-assembly and the gel properties. Again, for related gelators, we have shown that the choice of organic solvent in which the gelator is initially dissolved affects the outcome, 77 which is unsurprising as the solubility of the gelator will be different in each solvent, and different mixing rates of the solvents with water among other variables. Elsewhere, it has been stated that fresh solutions of the gelator in an organic solvent are always prepared to ensure complete dissolution of the LMWG, 73 but this is never actually proven as far as we can see.…”

Section: Process Of Assemblymentioning

confidence: 99%

Low-Molecular-Weight Gels: The State of the Art

Draper

Adams

2017

Chem

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536

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Low-molecular-weight gels are currently a hugely important class of materials that are attracting significant interest. These gels are formed when small molecules self-assemble into one-dimensional structures that entangle and cross-link to form a network that is capable of immobilizing the solvent. Here, we critically discuss the current state of the art and highlight two key areas where we believe there is significant untapped potential. The first is the observation that the properties of the gels are highly process dependent, which means that it is possible to access materials with very different properties from a single gelator. Second, using multiple gelators offers the opportunity to prepare materials with a high degree of information content and with a wider range of properties. We aim to spark thought and discussion on these aspects. INTRODUCTIONLow-molecular-weight gels (LMWGs), or supramolecular gels, are a fascinating and useful class of material. The gels arise from the self-assembly of small molecules into long, anisotropic structures, most commonly fibers. [1][2][3][4][5] At a sufficiently high concentration, these fibers entangle or otherwise form cross-links, leading to the network that is able to immobilize the solvent through surface tension and capillary forces. 1,2 These gels differ from permanently covalently cross-linked polymer gels because the cross-linking can be reversed by the input of energy, for example, by heating. 6 LMWGs have been around for many years but are receiving considerable current interest. 4 They are also used in industrial products, 7 although this seems rarely discussed in the academic literature.In addition to the industrial applications, many recent advances and uses are being described. [8][9][10][11][12] The specific self-assembly leading to gel formation can be exploited. For example, the fiber formation is a result of molecular stacking, meaning that the self-assembly leads to aggregates that can be suitable for optoelectronic applications. 13,14 The ready reversibility of gelation can be exploited, for example, to release cells from gels on demand in a manner that does not lead to cell death. 15 Ready gel formation by a simple trigger can also be used to allow easy and efficient gel loading. [16][17][18] Unsurprisingly, therefore, there is significant interest in these materials ( Figure 1). This is a fascinating area and in many ways holds attention because of the difficulties in probing and understanding the gels. The gels arise from assembly across many length scales, and understanding all of these is difficult. At the molecular level, the molecules must interact in a manner that leads to the formation of suitable aggregates that can eventually entangle. Thus, one-dimensional growth must be favored. From this perspective, it is very frustrating that it is often extremely difficult to predict whether a molecule will form a gel or not; indeed, gelation has been described as an empirical science. 4 Structurally similar small molecules can exhibitThe Bigger Pict...

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Section: Process Of Assemblymentioning

confidence: 99%

Low-Molecular-Weight Gels: The State of the Art

Draper

Adams

2017

Chem

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536

469

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“…A very illustrative example corresponds to the self-assembly of diphenylalanine (FF), as a minimal sequence to form peptide nanostructures, which organizes forming peptide nanotubes stabilized by a combination of hydrogen bonding and repeated phenyl stacking interactions. [12][13][14] In contrast, Fmoc-FF forms peptide fibrils 15 and very stable hydrogels 9,16,17 that were thought to arise from the stacking between Fmoc groups and between phenyl groups. The remarkable importance of stacking interactions induced by the Fmoc group at the N-terminus was also illustrated using a series of dipeptides and amino acids, 18 such aromatic moiety acting as a consistent facilitator of gelation in comparison to other simple hydrophobic groups, such as tert-butoxycarbonyl.…”

Section: Introductionmentioning

confidence: 99%

“…It should be noted that the presence of gelatinous rounded aggregates is supported by the role played by aromatic end groups as facilitators of gelation. 9,[16][17][18] Accordingly, the majority of the peptide molecules located at the central region of such gelatinous structures could migrate through diffusion towards the external region, allowing the development of the hollow microstructure after solubilization or precipitation of the remaining peptide molecules.…”

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confidence: 99%

Hierarchical self-assembly of di-, tri- and tetraphenylalanine peptides capped with two fluorenyl functionalities: from polymorphs to dendrites

et al. 2016

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Homopeptides with 2, 3 and 4 phenylalanine (Phe) residues and capped with fluorenylmethoxycarbonyl and fluorenylmethyl ester at the N-and C-terminus, respectively, have been synthesized to examine their self-assembly capabilities.Depending on the conditions, the di-and triphenylalanine derivatives self-organize into a wide variety of stable polymorphic structures, which have been characterized: stacked braids, doughnuts-like, bundled arrays of nanotubes, corkscrew-like and spherulitic microstructures. These highly aromatic Phe-based peptides also form incipient branched dendritic microstructures, even though they are highly unstable, making their manipulation very difficult. In opposition, the tetraphenylalanine derivative spontaneously self-assemble into stable dendritic microarchitectures made of branches growing from nucleated primary frameworks. The fractal dimension of these microstructures is 1.70, which evidences self-similarity and two-dimensional diffusion controlled growth. DFT calculations at the M06L/6-31G(d) level have been carried out on model -sheets since it is the most elementary building block of Phe-based peptide polymorphs. Results indicate that the antiparallel -sheet is more stable than the parallel one, the difference between them growing with the number of Phe residues. Thus, the cooperative effects associated with the antiparallel disposition become more favorable when the number of Phe residues increases from 2 to 4, while those of the parallel disposition remained practically constant.3

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“…the ability to reform after application of high shear. [9][10][11] This ability for recovery after high shear is particularly relevant for injectable gels sheared through a needle as following injection the gel would be required to revert back to its original state. Indeed the self-healing properties of LMWGs is uncommon 12 when compared to the reported self-healing of polymer hydrogels.…”

Section: Introductionmentioning

confidence: 99%

Developing a self-healing supramolecular nucleoside hydrogel

et al. 2016

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A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. Low molecular weight gelator hydrogels provide a viable alternative to traditional polymer based drug delivery platforms, owing to their tunable stability and in most cases inherent biocompatibility. Here we report the first self-healing nucleoside hydrogel using N4-octanoyl-2ʹ-deoxycytidine (0.5 % w/v) for drug delivery. The hydrogel's cross-linked nanofibrillar structure, was characterised using oscillatory rheology and confirmed using SEM and TEM imaging . The potential of this gel for drug delivery was explored in vitro using fluorescently labelled tracers. Cell viability assays were conducted using pancreatic cell lines which tolerated the gels well; whilst no adverse effects on the viability or proliferation of cells were observed for fibroblast cell lines.

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The effect of solvent choice on the gelation and final hydrogel properties of Fmoc–diphenylalanine

Cited by 144 publications

References 34 publications

Low-Molecular-Weight Gels: The State of the Art

Low-Molecular-Weight Gels: The State of the Art

Hierarchical self-assembly of di-, tri- and tetraphenylalanine peptides capped with two fluorenyl functionalities: from polymorphs to dendrites

Developing a self-healing supramolecular nucleoside hydrogel

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