Special Issue "Perspectives of Cyclodextrins"

A special issue of Biomolecules (ISSN 2218-273X). This special issue belongs to the section "Natural and Bio-inspired Molecules".

Deadline for manuscript submissions: 15 March 2020.

Special Issue Editor

Dr. Susana Santos Braga
E-Mail Website
Guest Editor
Department of Chemistry, University of Aveiro, Aveiro, Portugal
Interests: Solid-solid reactions by mechanochemistry; Cyclodextrin inclusion compounds, Solubilisation of active pharmaceutical ingredients (APIs), Local therapeutic systems for osteosarcoma and osteoporosis, Antioxidant flavonoids and their Ru(II) complexes, Natural and metallo-organic compounds for cytotoxic and biocidal activities; Innovative medicines for leishmaniasis based on inorganic complexes and cyclodextrins

Special Issue Information

Dear Colleagues,

Cyclodextrins, since their first report in 1891 by Villiers, have already witnessed the turning of two centuries. In the 20th century, these molecules conquered many applications in varied areas such as pharmaceuticals, food, nutrition, cosmetics, crop science, catalysis and analytical chemistry. Now, in the 21st century, CDs are growing even further. A new generation of cyclodextrin scientists is pushing the boundaries of their applications to new and exciting fields. Some CDs are finding applications in medicine, not just as excipients but as novel medicines; the natural sustainability of CDs makes them ideal for bioremediation solutions and their unique host–guest chemistry allows them to be used in the retrieval of noble metals from waste slurry or to remediate water effluent from all sorts of contaminants. Progress in the field of materials science places cyclodextrins in a wide range of novel materials with boundless applications. This Special Issue will create a forum for the presentation of the most relevant progress made by the millennial generation of cyclodextrins, looking at the innovations of the last 19 years and projecting research into the future.

The international cyclodextrin scientific community is invited to present review articles addressing the innovative aspects of CDs in the 21st century, or alternatively, to present strongly original research papers reporting breakthrough applications of CDs.

I will be looking forward to reading your contributions.

Dr. Susana Santos Braga
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. Biomolecules is an international peer-reviewed open access monthly 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 1200 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

  • Host-guest chemistry
  • Data processing and curing
  • Healthcare applications
  • Nutraceutical applications
  • Sustainability

Published Papers (5 papers)

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Research

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Open AccessArticle
Physicochemical Characterization and Antioxidant Activity Evaluation of Idebenone/Hydroxypropyl-β-Cyclodextrin Inclusion Complex
Biomolecules 2019, 9(10), 531; https://doi.org/10.3390/biom9100531 - 25 Sep 2019
Abstract
Idebenone (IDE) is an antioxidant drug active at the level of the central nervous system (CNS), whose poor water solubility limits its clinical application. An IDE/2-hydroxypropyl-β-cyclodextrin (IDE/HP-β-CD) inclusion complex was investigated by combining experimental methods and theoretical approaches. Furthermore, [...] Read more.
Idebenone (IDE) is an antioxidant drug active at the level of the central nervous system (CNS), whose poor water solubility limits its clinical application. An IDE/2-hydroxypropyl-β-cyclodextrin (IDE/HP-β-CD) inclusion complex was investigated by combining experimental methods and theoretical approaches. Furthermore, biological in vitro/ex vivo assays were performed. Phase solubility studies showed an AL type diagram, suggesting the presence of a 1:1 complex with high solubility. Scanning electron microscopy (SEM) allowed us to detect the morphological changes upon complexation. The intermolecular interactions stabilizing the inclusion complex were experimentally characterized by exploring the complementarity of Fourier-transform infrared spectroscopy in attenuated total reflectance geometry (FTIR-ATR) with mid-infrared light, Fourier-transform near-infrared (FT-NIR) spectroscopy, and Raman spectroscopy. From the temperature evolution of the O–H stretching band of the complex, the average enthalpy ΔHHB of the hydrogen bond scheme upon inclusion was obtained. Two-dimensional (2D) rotating frame Overhauser effect spectroscopy (ROESY) analysis and computational studies involving molecular modeling and molecular dynamics (MD) simulation demonstrated the inclusion of the quinone ring of IDE inside the CD ring. In vitro/ex vivo studies evidenced that complexation produces a protective effect of IDE against the H2O2-induced damage on human glioblastoma astrocytoma (U373) cells and increases IDE permeation through the excised bovine nasal mucosa. Full article
(This article belongs to the Special Issue Perspectives of Cyclodextrins)
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Open AccessArticle
Pharmacokinetic Properties of Fluorescently Labelled Hydroxypropyl-Beta-Cyclodextrin
Biomolecules 2019, 9(10), 509; https://doi.org/10.3390/biom9100509 - 20 Sep 2019
Abstract
2-Hydroxypropyl-beta-cyclodextrin (HPBCD) is utilized in the formulation of pharmaceutical products and recently orphan designation was granted for the treatment of Niemann–Pick disease, type C. The exact mechanism of HPBCD action and side effects are not completely explained. We used fluorescently labelled hydroxypropyl-beta-cyclodextrin (FITC-HPBCD) [...] Read more.
2-Hydroxypropyl-beta-cyclodextrin (HPBCD) is utilized in the formulation of pharmaceutical products and recently orphan designation was granted for the treatment of Niemann–Pick disease, type C. The exact mechanism of HPBCD action and side effects are not completely explained. We used fluorescently labelled hydroxypropyl-beta-cyclodextrin (FITC-HPBCD) to study its pharmacokinetic parameters in mice and compare with native HPBCD data. We found that FITC-HPBCD has fast distribution and elimination, similar to HPBCD. Interestingly animals could be divided into two groups, where the pharmacokinetic parameters followed or did not follow the two-compartment, first-order kinetic model. Tissue distribution studies revealed, that a significant amount of FITC-HPBCD could be detected in kidneys after 60 min treatment, due to its renal excretion. Ex vivo fluorescent imaging showed that fluorescence could be measured in lung, liver, brain and spleen after 30 min of treatment. To model the interaction and cellular distribution of FITC-HPBCD in the wall of blood vessels, we treated human umbilical vein endothelial cells (HUVECs) with FITC-HPBCD and demonstrated for the first time that this compound could be detected in the cytoplasm in small vesicles after 30 min of treatment. FITC-HPBCD has similar pharmacokinetic to HPBCD and can provide new information to the detailed mechanism of action of HPBCD. Full article
(This article belongs to the Special Issue Perspectives of Cyclodextrins)
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Open AccessArticle
Interactions of Mycotoxin Alternariol with Cyclodextrins and Its Removal from Aqueous Solution by Beta-Cyclodextrin Bead Polymer
Biomolecules 2019, 9(9), 428; https://doi.org/10.3390/biom9090428 - 30 Aug 2019
Abstract
Alternariol is an Alternaria mycotoxin that appears in fruits, tomatoes, oilseeds, and corresponding products. Chronic exposure to it can induce carcinogenic and xenoestrogenic effects. Cyclodextrins (CDs) are ring-shaped molecules built up by glucose units, which form host–guest type complexes with some mycotoxins. Furthermore, [...] Read more.
Alternariol is an Alternaria mycotoxin that appears in fruits, tomatoes, oilseeds, and corresponding products. Chronic exposure to it can induce carcinogenic and xenoestrogenic effects. Cyclodextrins (CDs) are ring-shaped molecules built up by glucose units, which form host–guest type complexes with some mycotoxins. Furthermore, insoluble CD polymers seem suitable for the extraction/removal of mycotoxins from aqueous solutions. In this study, the interactions of alternariol with β- and γ-CDs were tested by employing fluorescence spectroscopic and modeling studies. Moreover, the removal of alternariol from aqueous solutions by insoluble β-CD bead polymer (BBP) was examined. Our major observations/conclusions are the following: (1) CDs strongly increased the fluorescence of alternariol, the strongest enhancement was induced by the native γ-CD at pH 7.4. (2) Alternariol formed the most stable complexes with the native γ-CD (logK = 3.2) and the quaternary ammonium derivatives (logK = 3.4–3.6) at acidic/physiological pH and at pH 10.0, respectively. (3) BBP effectively removed alternariol from aqueous solution. (4) The alternariol-binding ability of β-CD polymers was significantly higher than was expected based on their β-CD content. (5) CD technology seems a promising tool to improve the fluorescence detection of alternariol and/or to develop new mycotoxin binders to decrease alternariol exposure. Full article
(This article belongs to the Special Issue Perspectives of Cyclodextrins)
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Open AccessArticle
Cyclodextrins Can Entrap Zearalenone-14-Glucoside: Interaction of the Masked Mycotoxin with Cyclodextrins and Cyclodextrin Bead Polymer
Biomolecules 2019, 9(8), 354; https://doi.org/10.3390/biom9080354 - 09 Aug 2019
Cited by 1
Abstract
Zearalenone (ZEN) is a Fusarium-derived xenoestrogenic mycotoxin. In plants, zearalenone-14-O-β-d-glucoside (Z14G) is the major conjugated metabolite of ZEN, and is a masked mycotoxin. Masked mycotoxins are plant-modified derivatives, which are not routinely screened in food and feed samples. [...] Read more.
Zearalenone (ZEN) is a Fusarium-derived xenoestrogenic mycotoxin. In plants, zearalenone-14-O-β-d-glucoside (Z14G) is the major conjugated metabolite of ZEN, and is a masked mycotoxin. Masked mycotoxins are plant-modified derivatives, which are not routinely screened in food and feed samples. Cyclodextrins (CDs) are cyclic oligosaccharides built up from D-glucopyranose units. CDs can form stable host–guest type complexes with lipophilic molecules (e.g., with some mycotoxins). In this study, the interaction of Z14G with native and chemically modified β- and γ-CDs was examined employing fluorescence spectroscopy and molecular modeling. Furthermore, the removal of Z14G from aqueous solution by insoluble β-CD bead polymer (BBP) was also tested. Our results demonstrate that Z14G forms the most stable complexes with γ-CDs under acidic and neutral conditions (K ≈ 103 L/mol). Among the CDs tested, randomly methylated γ-CD induced the highest increase in the fluorescence of Z14G (7.1-fold) and formed the most stable complexes with the mycotoxin (K = 2 × 103 L/mol). Furthermore, BBP considerably reduced the Z14G content of aqueous solution. Based on these observations, CD technology seems a promising tool to improve the fluorescence analytical detection of Z14G and to discover new mycotoxin binders which can also remove masked mycotoxins (e.g., Z14G). Full article
(This article belongs to the Special Issue Perspectives of Cyclodextrins)
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Review

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Open AccessFeature PaperReview
Nanoscale Restructuring of Polymer Materials to Produce Single Polymer Composites and Miscible Blends
Biomolecules 2019, 9(6), 240; https://doi.org/10.3390/biom9060240 - 19 Jun 2019
Abstract
I summarize work conducted in our laboratories over the past 30 years using small host molecules to restructure polymer materials at the nanometer level. Certain small molecules, such as the cyclic starches cyclodextrins (CDs) and urea (U) can form non-covalent crystalline inclusion compounds [...] Read more.
I summarize work conducted in our laboratories over the past 30 years using small host molecules to restructure polymer materials at the nanometer level. Certain small molecules, such as the cyclic starches cyclodextrins (CDs) and urea (U) can form non-covalent crystalline inclusion compounds (ICs) with a range of guest molecules, including many polymers. In polymer-CD- and -U-ICs, guest polymer chains reside in narrow channels created by the host molecule crystals, where they are separated and highly extended. When the host crystalline lattice is carefully removed, the guest polymer chains coalesce into a bulk sample with an organization that is distinct from that normally produced from its melt or from solution. Amorphous regions of such coalesced polymer samples have a greater density, likely with less chain entanglement and more chain alignment. As a consequence, after cooling from their melts, coalesced amorphous polymers show glass-transition temperatures (Tgs) that are elevated above those of samples prepared from their solutions or melts. Upon cooling from their melts, coalesced samples of crystallizable polymers show dramatically-increased abilities to crystallize more rapidly and much closer to their melting temperatures (Tms). These unique behaviors of polymers coalesced from their CD- and U-ICs are unexpectedly resistant to extended annealing above their Tgs and Tms. Taking advantage of this behavior permits us to create polymer materials with unique and improved properties. Among these are amorphous polymers with elevated Tgs and semi-crystalline polymers with finer more uniform morphologies. Improved mechanical properties can be achieved through self-nucleation with small amounts of the same polymer made rapidly crystallizable through coalescence from its CD- or U-IC. This can lead to single polymer composites with as-received polymer matrices and self-nucleated reinforcements. Through simultaneous formation and subsequent coalescence from their common CD–ICs, stable well-mixed blends can be achieved between any two or more polymers, despite their inherent immiscibilities. Such coalesced and well-mixed blends are also resistant to phase segregation when heated for extensive periods well above their Tgs and Tms. Full article
(This article belongs to the Special Issue Perspectives of Cyclodextrins)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Type:  article
Tentative title: Inclusion of hydroxycinnamic acids in methylated cyclodextrins: effects on guest thermal stability and the nature of host-guest interactions.
Authors: Mino R Caira, Susan A Bourne, Lee E Hunt
Affiliations: Centre for Supramolecular Chemistry Research, Department of Chemistry, University of Cape Town, South Africa
Abstract: There is considerable interest in the use of cyclodextrins (CDs) to stabilise bioactive compounds derived from natural sources for potential medicinal and cosmeceutical applications. Hydroxycinnamic acids (HCAs) and their derivatives are significant in this context as they possess a broad spectrum of activities including e.g. antioxidant, antitumor, anti-inflammatory and other beneficial biological effects. Here we report the results of a study aimed at determining the effects on the thermal stabilities of the HCAs as a result of their encapsulation by the CDs and establishing the nature of the host-guest interactions. Following the isolation of eight distinct complexes, they were characterized by thermal analysis and X-ray diffraction methods. Full structural analyses revealed a variety of guest complexation modes ranging from full inclusion within the CD host cavities to unusual instances of complete guest exclusion. Occurrences of guest disorder and crystal isostructurality also featured in this series of complexes.   

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