Journal article
The interplay of aggregation, fibrillization and gelation of an unexpected low molecular weight gelator: glycylalanylglycine in ethanol/water
Soft matter, v 12(28), pp 6096-6110
01 Jan 2016
PMID: 27363780
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
Hydrogels formed by polypeptides could be much-favored tools for drug delivery because their main ingredients are generally biodegradable. However, the gelation of peptides in aqueous solution generally requires a minimal length of the peptide as well as distinct sequences of hydrophilic and hydrophobic residues. The aggregation of short peptides like tripeptides, which are relatively cheap and offer a high degree of biodegradability, are generally thought to require a high hydrophobicity of their residues. We found that contrary to this expectation cationic glycylalanylglycine in 55 mol% ethanol/45 mol% water forms a gel below a melting temperature of ca. 36 degrees C. A pure hydrogel state can be obtained after allowing the ethanol component to evaporate. The gel phase consists of crystalline fibrils of several 100 mm, which form a sample-spanning network. Rheological data reveal a soft elastic solid gel. We investigated the kinetics of the various processes that lead to the final gel state of the ternary mixture by a unique combination of UV circular dichroism, infrared, vibrational circular dichroism (VCD) and rheological measurements. A mathematical analysis of our data show that gelation is preceded by the formation of peptide beta-sheet like tapes or ribbons, which give rise to a significant enhancement of the amide I' VCD signal, and the subsequent formation of rather thick and long fibrils. The VCD signals indicate that the tapes exhibit a right-handed helicity at temperatures above 16 degrees C and a left-handed helicity below. The tapes'/ribbons' helicity change occurs at a temperature where the UVCD data reflect a relatively long nucleation process. The kinetics of gel formation probed by the storage and loss moduli are composed of a fast process that follows tape/ribbon/fibril formation and is clearly identifiable in a movie that shows the gelation process and a slow process that causes an additional gel stabilization. The rheological data indicate that left-handed fibrils observed at low temperatures form a more solid-like structure than their right-handed counterparts formed at higher temperatures. Taken together our data reveal GAG as an unexpected gelator, the formation of which is underlied by a set of distinguishable kinetic processes.
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Details
- Title
- The interplay of aggregation, fibrillization and gelation of an unexpected low molecular weight gelator: glycylalanylglycine in ethanol/water
- Creators
- Stefanie Farrell - Drexel UniversityDavid DiGuiseppi - Drexel UniversityNicolas Alvarez - Drexel UniversityReinhard Schweitzer-Stenner - Drexel University
- Publication Details
- Soft matter, v 12(28), pp 6096-6110
- Publisher
- Royal Soc Chemistry
- Number of pages
- 15
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Biochemistry and Molecular Biology; [Retired Faculty]; Chemical and Biological Engineering
- Web of Science ID
- WOS:000379570700012
- Scopus ID
- 2-s2.0-84978636790
- Other Identifier
- 991019167832004721
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InCites Highlights
Data related to this publication, from InCites Benchmarking & Analytics tool:
- Web of Science research areas
- Chemistry, Physical
- Materials Science, Multidisciplinary
- Physics, Multidisciplinary
- Polymer Science