Tuneable mechanical properties in low molecular weight gels

Chen, Lin; Raeburn, Jaclyn; Sutton, Sam; Spiller, David G.; Williams, James H.; Sharp, James S.; Griffiths, Peter Charles; Heenan, Richard K.; King, Stephen M.; Paul, Alison; Furzeland, Steve; Atkins, Derek; Adams, Dave J.

doi:10.1039/c1sm05827d

Cited by 85 publications

(133 citation statements)

References 37 publications

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“…This clarifies over a period of minutes as the gel forms. Elsewhere, for a related gelator, we have linked this process to the initial formation of micrometersized spherical droplets, 74 which then decrease in concentration as the self-assembled fibers are formed. We have no evidence that the spherical objects are directly transformed to the fibers, although it has been suggested that fibers nucleate at the surface of the spheres for Fmoc-diphenylalanine.…”

Section: Process Of Assemblymentioning

confidence: 99%

“…This agrees with our work on other systems gelled by this approach and seems to arise from a nucleation and growth process. 74 The gels formed by addition of calcium salts to a solution of 2NapFF at high pH show significant aligned domains, whereas a more typical cross-linked network is found for the acid-triggered sample. Hence, we can link the rheological properties to the network.…”

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confidence: 94%

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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%

mentioning

confidence: 94%

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

Draper

Adams

2017

Chem

Self Cite

536

469

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“…They also reported that the increase in turbidity correlated with a phase separation event forming a dispersion of spheres in solution and that the dispersion was unstable, with a fibrous network being formed at the expense of the spheres. 24 Orbach et al also monitored, by spectroscopic analysis, the formation of the Fmoc-amino acid hydrogels through a transition from a turbid solution to a transparent network. 25 In accordance with previous data of Chen et al, the hypothesis emerged that restructuring of the matter occurred, from multiple irregular aggregates possessing dimensions in the range of the visible wavelength into highly ordered structures, causing the optical characteristics of the solution to change.…”

Section: Please Do Not Adjust Marginsmentioning

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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“…A phenylalanine dipeptide formed organogels when it was firstly dissolved in 1,1,1,3,3,3-hexafluoropropanol and then diluted with poor solvent (26). Fmocprotected dipeptides formed hydrogels when first dissolved in DMSO and then diluted with water (27). In both cases, a highly polar solvent had to be used to dissolve the peptide.…”

Section: Solubility and Gel Formation Abilitymentioning

confidence: 99%