Insights into low molecular mass organic gelators: a focus on drug delivery and tissue engineering applications

Skilling, Kathryn J.; Citossi, Francesca; Bradshaw, Tracey D.; Ashford, Marianne; Kellam, Barrie; Marlow, Maria

doi:10.1039/c3sm52244j

Cited by 330 publications

(255 citation statements)

References 200 publications

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“…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).…”

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confidence: 99%

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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confidence: 99%

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

Draper

Adams

2017

Chem

536

469

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“…A polymer gelator was synthesised that was envisaged to possess the capability to form hydrogen bonds between adjacent poly(amino acid) backbone chains, 36 and form hydrophobic interactions between adjacent, grafted, alkyl chains, 37 to facilitate organogel formation. Initially, poly(O-benzyl-l-serine) 20 was synthesised by the ROP of O-benzyl-l-serine NCA, using benzylamine as the initiator, before the benzyl ether protecting group was cleaved from the polymer to yield PS (Scheme 1), as confirmed by 1 H NMR spectroscopy (Fig.…”

Section: Resultsmentioning

confidence: 99%

A vegetable oil-based organogel for use in pH-mediated drug delivery

et al. 2015

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“…This could be powerful in personalised medicine, with an individual's stem cells being 45 studied in this way in order to determine optimal ways of intervening in their regeneration to treat a variety of pathologies. Although gels have been quite widely been explored for drug delivery, 28 this is not the case for solution phase supramolecular 50 polymers. In a recent paper, Dankers, Albertazzi and coworkers reported the potential of PEGylated 1,3,5-benzenetricarboxamide for intracellular delivery.…”

Section: Supramolecular Biomaterialsmentioning

confidence: 99%

“…Indeed, an excellent review of early work in this area using gels has been published. 28 In particular, it is well established that selfassembled materials can be of great utility in controlling drug 15 delivery processes (actively or passively) and enabling the growth and regeneration of cellular tissue (ex vivo or in vivo). This has led to eye-catching work in which supramolecular materials have been used (for example) in vivo to regenerate vision or spinal cord function by enabling the repair of damaged 20 nerve tissue.…”

Section: Supramolecular Biomaterialsmentioning

confidence: 99%