Rigid, Self‐Assembled Hydrogel Composed of a Modified Aromatic Dipeptide

Mahler, A.; Reches, Meital; Rechter, Meirav; Cohen, Smadar; Gazit, Ehud

doi:10.1002/adma.200501765

Cited by 760 publications

(812 citation statements)

References 51 publications

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“…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. Mixing of DMSO and water is an exothermic process, which leads to the mixture heating slightly.…”

Section: Process Of Assemblymentioning

confidence: 99%

“…Gels form down to a concentration as low as 1 mg/mL, with more turbid gels forming at 10 mg/mL (the highest concentration tested). As for other related gelators, 73 this method of self-assembly proceeds by the addition of water immediately resulting in a highly turbid solution. This clarifies over a period of minutes as the gel forms.…”

Section: Process Of Assemblymentioning

confidence: 99%

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

Draper

Adams

2017

Chem

536

469

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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%

Section: Process Of Assemblymentioning

confidence: 99%

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

Draper

Adams

2017

Chem

536

469

View full text Add to dashboard Cite

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“…According to earlier experimental and theoretical studies these mechanical properties are related to their molecular structure [10,12]. The exceptional mechanical properties of amyloids make them good candidates for a wide range of potential technological applications, and specifically as new bionanomaterials utilizing them as nanowires [13][14][15][16], gels [17][18][19][20][21], scaffolds and biotemplates [13,[22][23][24][25][26][27], liquid crystals [28], adhesives [29] and biofilm materials [30]. These applications often imply the functionalization of the amyloid fibrils with the introduction of additional elements, including enzymes, metal ions, fluorophores, biotin or cytochromes.…”

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confidence: 99%

Failure of Aβ(1-40) amyloid fibrils under tensile loading

Paparcone

Buehler

2011

Biomaterials

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Amyloid fibrils and plaques are detected in the brain tissue of patients affected by Alzheimer's disease, but have also been found as part of normal physiological processes such as bacterial adhesion. Due to their highly organized structures, amyloid proteins have also been used for the development of novel nanomaterials, for a variety of applications including biomaterials for tissue engineering, nanolectronics, or optical devices. Past research on amyloid fibrils resulted in advances in identifying their mechanical properties, revealing a remarkable stiffness. However, the failure mechanism under tensile loading has not been elucidated yet, despite its importance for the understanding of key mechanical properties of amyloid fibrils and plaques as well as the growth and aggregation of amyloids into long fibers and plaques. Here we report a molecular level analysis of failure of amyloids under uniaxial tensile loading. Our molecular modeling results demonstrate that amyloid fibrils are extremely stiff with a Young's modulus in the range of 18-30 GPa, in good agreement with previous experimental and computational findings. The most important contribution of our study is our finding that amyloid fibrils fail at relatively small strains of 2.5% to 4%, and at stress levels in the range of 1.02 to 0.64 GPa, in good agreement with experimental findings. Notably, we find that the strength properties of amyloid fibrils are extremely length dependent, and that longer amyloid fibrils show drastically smaller failure strains and failure stresses. As a result, longer fibrils in excess of hundreds of nanometers to micrometers have a greatly enhanced propensity towards spontaneous fragmentation and failure. We use a combination of simulation results and simple theoretical models to define critical fibril lengths where distinct failure mechanisms dominate.

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“…1,2 A recent expansion in the number of LMWG systems reported has led to a rapid growth in reports of characterisation and applications of a particular class of this type of molecule, namely aromatic conjugated dipeptide LMWG. [3][4][5][6][7][8] These systems typically consist of a hydrophobic, often aromatic, dipeptide sequences conjugated to Fmoc (9-fluorenylmethoxycarbonyl) 9,10 or naphthalene 3,4 ; further conjugations have also been reported. 11,12 Through the use of an environmental cue, 13 such as an enzymatic trigger, 14 temperature, 15,16 or light 12 some of these conjugates selfassemble into anisotropic fibrils that can eventually cause hydrogelation through the immobilisation of water by the fibrillar network.…”

Section: Introductionmentioning

confidence: 99%

Structural determinants in a library of low molecular weight gelators

et al. 2015

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ARTICLELow molecular weight hydrogels are formed by molecules that form a matrix that immobilises water to form a self-supporting gel. Such gels have uses as biomaterials such as molecular scaffolds and structures for tissue engineering. One class of low molecular weight gelators (LMWG), naphthalene-conjugated dipeptides, has been shown to form hydrogels via selfassembly following a controlled drop in pH. A library of naphthalene-dipeptides has been generated previously although the relationship between the precursor sequence and the resulting self-assembled structures remained unclear. Here, we have investigated the structural details of a set of dipeptide sequences containing alanine (A) and valine (V) conjugated to naphthalene groups substituted with a Br, CN or H at the 6-position. Electron microscopy, circular dichroism and X-ray fibre diffraction shows that these LMWG may be structurally classified by their composition: the molecular packing is determined by the class of conjugate, whilst the chirality of the self-assemblies can be attributed to the dipeptide sequence. This provides insights into the relationship between the precursor sequence and the macromolecular and molecular structures of the fibres that make up the resulting hydrogels. IntroductionThe formation of hydrogels from low molecular weight gelators (LMWG) is a useful route to the production of materials for a wide range of applications. 1, 2 A recent expansion in the number of LMWG systems reported has led to a rapid growth in reports of characterisation and applications of a particular class of this type of molecule, namely aromatic conjugated dipeptide LMWG. 3-8 These systems typically consist of a hydrophobic, often aromatic, dipeptide sequences conjugated to Fmoc (9-fluorenylmethoxycarbonyl) 9, 10 or naphthalene 3, 4 ; further conjugations have also been reported. 11,12 Through the use of an environmental cue, 13 such as an enzymatic trigger, 14 temperature, 15,16 or light 12 some of these conjugates selfassemble into anisotropic fibrils that can eventually cause hydrogelation through the immobilisation of water by the fibrillar network. There are now a large number of systems reported in the literature. 17 It is apparent from previous work that two LMWG molecules that differ only by a single amino acid can give rise to hydrogels with dramatically different rheological and phase properties. 3,4,10,18 However, the structural basis for these differences in material properties is not understood.The short-range molecular architecture of some LMWG systems has been studied. For example, the chirality of assembled naphthalene conjugated dipeptides has been reported to correlate to the D-or L-enantiomer of the incorporated amino acids with left-and right-handed assemblies being formed respectively. 3 Other reports have indicated that proteinaceous additives induce changes to the chiral organisation of the self-assembled hydrogelating molecules. 19 In addition to the plethora of molecular hydrogels with varying material properties available, the...

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Rigid, Self‐Assembled Hydrogel Composed of a Modified Aromatic Dipeptide

Cited by 760 publications

References 51 publications

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

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

Failure of Aβ(1-40) amyloid fibrils under tensile loading

Structural determinants in a library of low molecular weight gelators

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