Special Issue "Gels from the Self-Assembling of Peptide-Based Compounds"

A special issue of Gels (ISSN 2310-2861).

Deadline for manuscript submissions: closed (31 December 2018).

Special Issue Editor

Guest Editor
Prof. Dr. Jordi Puiggalí Website E-Mail
Universitat Politécnica de Catalunya, Barcelona, Spain
Interests: structure of synthetic polymers; development of biodegradable polymers; study of nanocomposites; polymer physics; polymer crystallization

Special Issue Information

Dear Colleagues,

A great number of applications are, nowadays, derived from the self-assembly of peptide-based materials. Basically, peptides have peculiar features derived from the presence of amide groups able to establish strong intermolecular hydrogen-bonding interactions and side-chain groups able to render a highly variable functionality.

The self-assembling of low molecular weight peptides can lead to new hydrogels, which can be considered as protein-mimetic materials. Therefore, specific characteristics such as responsiveness, functionality and structural versatility can be expected, opening an immense field of cutting-edge applications. The low molecular weight of peptides gives rise to interesting characteristics as an easy synthesis and purification together with a high capacity to tune the final properties of materials. Nevertheless, it is still difficult to achieve the great efficiency of proteins since these have followed a process of natural selection during the evolution of the species.

This Special Issue of Gels aims to discuss, collect and offer recent highlights and advances on gels derived from the self-assembling of peptides. To this end, the progress on the development of self-assembling peptide compounds, the study of their structural organization, the evaluation of the responsiveness under different external stimuli (i.e., pH, temperature, concentration, intermolecular non-covalent interactions) and the study of applications in biomedicine, catalysis and materials science are some of the specific topics that should be considered.

Prof. Dr. Jordi Puiggalí
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Gels is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Self-assembling
  • Peptides
  • Amino acids
  • Protein-mimetic materials
  • Functional groups
  • Supramolecular hydrogels
  • Nanomedicine
  • Catalysis
  • Materials science
  • Responsiveness

Published Papers (7 papers)

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Research

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Open AccessFeature PaperArticle
Low Molecular Weight Gelators Based on Functionalized l-Dopa Promote Organogels Formation
Gels 2019, 5(2), 27; https://doi.org/10.3390/gels5020027 - 14 May 2019
Abstract
We prepared the small pseudopeptide Lau-l-Dopa(OBn)2-d-Oxd-OBn (Lau = lauric acid; l-Dopa = l-3,4-dihydroxyphenylalanine; d-Oxd = (4R,5S)-4-methyl-5-carboxyl-oxazolidin-2-one; Bn = benzyl) through a number of coupling reactions between lauric acid, protected l [...] Read more.
We prepared the small pseudopeptide Lau-l-Dopa(OBn)2-d-Oxd-OBn (Lau = lauric acid; l-Dopa = l-3,4-dihydroxyphenylalanine; d-Oxd = (4R,5S)-4-methyl-5-carboxyl-oxazolidin-2-one; Bn = benzyl) through a number of coupling reactions between lauric acid, protected l-Dopa and d-Oxd with an excellent overall yield. The ability of the product to form supramolecular organogels has been tested with different organic solvents of increasing polarity and compared with the results obtained with the small pseudopeptide Fmoc-l-Dopa(OBn)2-d-Oxd-OBn. The mechanical and rheological properties of the organogels demonstrated solvent-dependent properties, with a storage modulus of 82 kPa for the ethanol organogel. Finally, to have a preliminary test of the organogels’ ability to adsorb pollutants, we treated a sample of the ethanol organogel with an aqueous solution of Rhodamine B (RhB) for 24 h. The water solution slowly lost its pink color, which became trapped in the organogel. Full article
(This article belongs to the Special Issue Gels from the Self-Assembling of Peptide-Based Compounds)
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Open AccessArticle
Supramolecular Tripeptide Hydrogel Assembly with 5-Fluorouracil
Gels 2019, 5(1), 5; https://doi.org/10.3390/gels5010005 - 26 Jan 2019
Cited by 1
Abstract
In this work, we present Thioflavin T fluorescence, transmission electron microscopy (TEM), circular dichroism (CD), Fourier-transformed infrared (FT-IR), and oscillatory rheometry studies applied to an antineoplastic drug, 5-fluorouracil (5-FU), embedded in a heterochiral tripeptide hydrogel to obtain a drug delivery supramolecular system. The [...] Read more.
In this work, we present Thioflavin T fluorescence, transmission electron microscopy (TEM), circular dichroism (CD), Fourier-transformed infrared (FT-IR), and oscillatory rheometry studies applied to an antineoplastic drug, 5-fluorouracil (5-FU), embedded in a heterochiral tripeptide hydrogel to obtain a drug delivery supramolecular system. The release of 5-fluorouracil was monitored over time by reverse-phase high-performance liquid chromatography (HPLC) and its interaction with the tripeptide assemblies was probed by all-atom molecular dynamics simulations. Full article
(This article belongs to the Special Issue Gels from the Self-Assembling of Peptide-Based Compounds)
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Open AccessArticle
Assembly of Conducting Polymer and Biohydrogel for the Release and Real-Time Monitoring of Vitamin K3
Gels 2018, 4(4), 86; https://doi.org/10.3390/gels4040086 - 28 Nov 2018
Abstract
In this work, we report the design and fabrication of a dual-function integrated system to monitor, in real time, the release of previously loaded 2-methyl-1,4-naphthoquinone (MeNQ), also named vitamin K3. The newly developed system consists of poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles, which were embedded into [...] Read more.
In this work, we report the design and fabrication of a dual-function integrated system to monitor, in real time, the release of previously loaded 2-methyl-1,4-naphthoquinone (MeNQ), also named vitamin K3. The newly developed system consists of poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles, which were embedded into a poly-γ-glutamic acid (γ-PGA) biohydrogel during the gelling reaction between the biopolymer chains and the cross-linker, cystamine. After this, agglomerates of PEDOT nanoparticles homogeneously dispersed inside the biohydrogel were used as polymerization nuclei for the in situ anodic synthesis of poly(hydroxymethyl-3,4-ethylenedioxythiophene) in aqueous solution. After characterization of the resulting flexible electrode composites, their ability to load and release MeNQ was proven and monitored. Specifically, loaded MeNQ molecules, which organized in shells around PEDOT nanoparticles agglomerates when the drug was simply added to the initial gelling solution, were progressively released to a physiological medium. The latter process was successfully monitored using an electrode composite through differential pulse voltammetry. The fabrication of electroactive flexible biohydrogels for real-time release monitoring opens new opportunities for theranostic therapeutic approaches. Full article
(This article belongs to the Special Issue Gels from the Self-Assembling of Peptide-Based Compounds)
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Open AccessFeature PaperArticle
Development of a 3D Co-Culture System as a Cancer Model Using a Self-Assembling Peptide Scaffold
Gels 2018, 4(3), 65; https://doi.org/10.3390/gels4030065 - 02 Aug 2018
Abstract
Cancer research has traditionally relied on two-dimensional (2D) cell culture, focusing mainly on cancer cells and their abnormal genetics. However, over the past decade, tumors have been accepted as complex tissues rather than a homogenous mass of proliferating cells. Consequently, cancer cells’ behavior [...] Read more.
Cancer research has traditionally relied on two-dimensional (2D) cell culture, focusing mainly on cancer cells and their abnormal genetics. However, over the past decade, tumors have been accepted as complex tissues rather than a homogenous mass of proliferating cells. Consequently, cancer cells’ behavior can only be deciphered considering the contribution of the cells existing in the tumor stroma as well as its complex microenvironment. Since the tumor microenvironment plays a critical role in tumorigenesis, it is widely accepted that culturing cells in three-dimensional (3D) scaffolds, which mimic the extracellular matrix, represents a more realistic scenario. In the present work, an in vitro 3D co-culture system based on the self-assembling peptide scaffold RAD16-I (SAPS RAD16-I) was developed as a cancer model. For that, PANC-1 cells were injected into a RAD16-I peptide scaffold containing fibroblasts, resulting in a 3D system where cancer cells were localized in a defined area within a stromal cells matrix. With this system, we were able to study the effect of three well-known pharmaceutical drugs (Gemcitabine, 5-Fluorouracil (5-FU), and 4-Methylumbelliferone (4-MU)) in a 3D context in terms of cell proliferation and survival. Moreover, we have demonstrated that the anti-cancer effect of the tested compounds can be qualitatively and quantitatively evaluated on the developed 3D co-culture system. Experimental results showed that Gemcitabine and 5-FU prevented PANC-1 cell proliferation but had a high cytotoxic effect on fibroblasts as well. 4-MU had a subtle effect on PANC-1 cells but caused high cell death on fibroblasts. Full article
(This article belongs to the Special Issue Gels from the Self-Assembling of Peptide-Based Compounds)
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Open AccessArticle
Ultrashort Self-Assembling Peptide Hydrogel for the Treatment of Fungal Infections
Gels 2018, 4(2), 48; https://doi.org/10.3390/gels4020048 - 22 May 2018
Cited by 1
Abstract
The threat of antimicrobial resistance to society is compounded by a relative lack of new clinically effective licensed therapies reaching patients over the past three decades. This has been particularly problematic within antifungal drug development, leading to a rise in fungal infection rates [...] Read more.
The threat of antimicrobial resistance to society is compounded by a relative lack of new clinically effective licensed therapies reaching patients over the past three decades. This has been particularly problematic within antifungal drug development, leading to a rise in fungal infection rates and associated mortality. This paper highlights the potential of an ultrashort peptide, (naphthalene-2-ly)-acetyl-diphenylalanine-dilysine-OH (NapFFKK-OH), encompassing hydrogel-forming and antifungal properties within a single peptide motif, thus overcoming formulation (e.g., solubility, drug loading) issues associated with many currently employed highly hydrophobic antifungals. A range of fungal susceptibility (colony counts) and cell cytotoxicity (MTS cell viability, LIVE/DEAD staining® with fluorescent microscopy, haemolysis) assays were employed. Scanning electron microscopy confirmed the nanofibrous architecture of our self-assembling peptide, existing as a hydrogel at concentrations of 1% w/v and above. Broad-spectrum activity was demonstrated against a range of fungi clinically relevant to infection (Aspergillus niger, Candida glabrata, Candida albicans, Candida parapsilosis and Candida dubliniensis) with greater than 4 log10 CFU/mL reduction at concentrations of 0.5% w/v and above. We hypothesise antifungal activity is due to targeting of anionic components present within fungal cell membranes resulting in membrane disruption and cell lysis. NapFFKK-OH demonstrated reduced toxicity against mammalian cells (NCTC 929, ARPE-19) suggesting increased selectivity for fungal cells. However, further studies relating to safety for systemic administration is required, given the challenges toxicity has presented in the wider context of antimicrobial peptide drug development. Overall this study highlights the promise of NapFFKK-OH hydrogels, particularly as a topical formulation for the treatment of fungal infections relating to the skin and eyes, or as a hydrogel coating for the prevention of biomaterial related infection. Full article
(This article belongs to the Special Issue Gels from the Self-Assembling of Peptide-Based Compounds)
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Review

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Open AccessFeature PaperReview
Peptide Self-Assembly into Hydrogels for Biomedical Applications Related to Hydroxyapatite
Gels 2019, 5(1), 14; https://doi.org/10.3390/gels5010014 - 06 Mar 2019
Cited by 3
Abstract
Amphiphilic peptides can be self-assembled by establishing physical cross-links involving hydrogen bonds and electrostatic interactions with divalent ions. The derived hydrogels have promising properties due to their biocompatibility, reversibility, trigger capability, and tunability. Peptide hydrogels can mimic the extracellular matrix and favor the [...] Read more.
Amphiphilic peptides can be self-assembled by establishing physical cross-links involving hydrogen bonds and electrostatic interactions with divalent ions. The derived hydrogels have promising properties due to their biocompatibility, reversibility, trigger capability, and tunability. Peptide hydrogels can mimic the extracellular matrix and favor the growth of hydroxyapatite (HAp) as well as its encapsulation. Newly designed materials offer great perspectives for applications in the regeneration of hard tissues such as bones, teeth, and cartilage. Furthermore, development of drug delivery systems based on HAp and peptide self-assembly is attracting attention. Full article
(This article belongs to the Special Issue Gels from the Self-Assembling of Peptide-Based Compounds)
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Open AccessReview
Calcium-Dependent RTX Domains in the Development of Protein Hydrogels
Gels 2019, 5(1), 10; https://doi.org/10.3390/gels5010010 - 25 Feb 2019
Abstract
The RTX domains found in some pathogenic proteins encode repetitive peptide sequences that reversibly bind calcium and fold into the unique the β-roll secondary structure. Several of these domains have been studied in isolation, yielding key insights into their structure/function relationships. These domains [...] Read more.
The RTX domains found in some pathogenic proteins encode repetitive peptide sequences that reversibly bind calcium and fold into the unique the β-roll secondary structure. Several of these domains have been studied in isolation, yielding key insights into their structure/function relationships. These domains are increasingly being used in protein engineering applications, where the calcium-induced control over structure can be exploited to gain new functions. Here we review recent advances in the use of RTX domains in the creation of calcium responsive biomaterials. Full article
(This article belongs to the Special Issue Gels from the Self-Assembling of Peptide-Based Compounds)
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