Relationship between molecular structure, gelation behaviour and gel properties of Fmoc-dipeptides

Adams, Dave J.; Mullen, Leanne; Berta, M.; Chen, Lin; Frith, William J.

doi:10.1039/b921863g

Cited by 194 publications

(223 citation statements)

References 53 publications

(89 reference statements)

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“…To form the gels, we exploited the hydrolysis of glucono-d-lactone (GdL) to gluconic acid (Fig. 2b) 13,15,16 . The hydrolysis allows a slow, uniform pH change in the system.…”

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confidence: 99%

Chemically programmed self-sorting of gelator networks

et al. 2013

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Controlling the order and spatial distribution of self-assembly in multicomponent supramolecular systems could underpin exciting new functional materials, but it is extremely challenging. When a solution of different components self-assembles, the molecules can either coassemble, or self-sort, where a preference for like-like intermolecular interactions results in coexisting, homomolecular assemblies. A challenge is to produce generic and controlled 'one-pot' fabrication methods to form separate ordered assemblies from 'cocktails' of two or more self-assembling species, which might have relatively similar molecular structures and chemistry. Self-sorting in supramolecular gel phases is hence rare. Here we report the first example of the pH-controlled self-sorting of gelators to form self-assembled networks in water. Uniquely, the order of assembly can be predefined. The assembly of each component is preprogrammed by the pK a of the gelator. This pH-programming method will enable higher level, complex structures to be formed that cannot be accessed by simple thermal gelation.

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“…To form the gels, we exploited the hydrolysis of glucono-d-lactone (GdL) to gluconic acid (Fig. 2b) 13,15,16 . The hydrolysis allows a slow, uniform pH change in the system.…”

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confidence: 99%

Chemically programmed self-sorting of gelator networks

et al. 2013

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Section: Introductionmentioning

confidence: 99%

“…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%

“…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.…”

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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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“…The addition of glucono-d-lactone has been largely employed in the last 5 years to control the morphology of the fibres obtained by modifying the pH medium at local scale. [6][7][8][9] Extensive studies on the early stages of the formation of physical gels are crucial to underpin the main structural criteria that later defines both the mechanical properties [10] and responsive nature of the obtained self-assembled materials. The mechanism of self-assembly of a pH-sensitive low molecular weight hydrogelator (LMWG) has proved the crucial importance of the control of the pH turning at the local scale to generate monodisperse well-defined fibers.…”

Section: Introductionmentioning

confidence: 99%

Microfluidic Assisted Self‐Assembly of pH‐Sensitive Low‐Molecular Weight Hydrogelators Close to the Minimum Gelation Concentration

Hermida‐Merino¹,

Trebbin²,

Foerster

et al. 2015

Macromolecular Symposia

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Hermida-Merino, D., Trebbin, M., Foerster, S., Rodriguez-Llansola, F., & Portale, G. (2015). Microfluidic assisted self-assembly of pH-sensitive low-molecular weight hydrogelators close to the minimum gelation concentration. Macromolecular Symposia, 358(1), 59-66. DOI: 10.1002/masy.201500032 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf 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. Summary: The fibrillation and subsequent gelation of low molecular hydrogelators is usually triggered by external stimuli. Generally, strong acids are employed to trigger the self-assembly mechanism in pH-responsive supramolecular systems. However, the generation and design of novel stable gels with performing mechanical properties is a challenging task as a result of the uneven self-assembled networks formed. Here, we report the study of the self-assembly process of a low molecular weight hydrogelator (LMWG) in the proximity of its minimum gelation concentration (MGC ¼ 0.3 mg/ml). At such high dilution, the generation of homogeneous gels with good mechanical properties by turning pH by strong acids is a demanding task as a result of the lack of monodisperse 1D self-assembled rod-like aggregates. A microfluidic device is employed here to gradually and homogeneously change the pH. We show that self-assembly of LMWG in welldefined structures can be enhanced by using the diffusive mixing occurring in the microfluidic reactor channel. For very short mixing times, aggregates with 2 nm cross-section are found in the region adjacent to the focused LMWG solution ...

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Relationship between molecular structure, gelation behaviour and gel properties of Fmoc-dipeptides

Cited by 194 publications

References 53 publications

Chemically programmed self-sorting of gelator networks

Chemically programmed self-sorting of gelator networks

Structural determinants in a library of low molecular weight gelators

Microfluidic Assisted Self‐Assembly of pH‐Sensitive Low‐Molecular Weight Hydrogelators Close to the Minimum Gelation Concentration

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