Explaining cyclodextrin–mycotoxin interactions using a ‘natural’ force field

Cyclodextrin-Based Displacement Strategy of Sterigmatocystin from Serum Albumin as a Novel Approach for Acute Poisoning Detoxification

This study demonstrates that sterigmatocystin (STC) interacts non-covalently with various cyclodextrins (CDs), showing the highest binding affinity for sugammadex (a γ-CD derivative) and γ-CD, and an almost order of magnitude lower affinity for β-CD. This difference in affinity was studied using molecular modelling and fluorescence spectroscopy, which demonstrated a better insertion of STC into larger CDs. In parallel, we showed that STC binds to human serum albumin (HSA) (a blood protein known for its role as a transporter of small molecules) with an almost two order of magnitude lower affinity compared to sugammadex and γ-CD. Competitive fluorescence experiments clearly demonstrated an efficient displacement of STC from the STC-HSA complex by cyclodextrins. These results are a proof-of-concept that CDs can be used to complex STC and related mycotoxins. Similarly, as sugammadex extracts neuromuscular relaxants (e.g., rocuronium and vecuronium) from blood and blocks their bioactivity, it could also be used as first aid upon acute intoxication to encapsulate a larger part of the STC mycotoxin from serum albumin.

Supramolecular Complexes of Plant Neurotoxin Veratridine with Cyclodextrins and Their Antidote-like Effect on Neuro-2a Cell Viability

Veratridine (VTD) is a plant neurotoxin that acts by blocking the voltage-gated sodium channels (VGSC) of cell membranes. Symptoms of VTD intoxication include intense nausea, hypotension, arrhythmia, and loss of consciousness. The treatment for the intoxication is mainly focused on treating the symptoms, meaning there is no specific antidote against VTD. In this pursuit, we were interested in studying the molecular interactions of VTD with cyclodextrins (CDs). CDs are supramolecular macrocycles with the ability to form host–guest inclusion complexes (ICs) inside their hydrophobic cavity. Since VTD is a lipid-soluble alkaloid, we hypothesized that it could form stable inclusion complexes with different types of CDs, resulting in changes to its physicochemical properties. In this investigation, we studied the interaction of VTD with β-CD, γ-CD and sulfobutyl ether β-CD (SBCD) by isothermal titration calorimetry (ITC) and nuclear magnetic resonance (NMR) spectroscopy. Docking and molecular dynamics studies confirmed the most stable configuration for the inclusion complexes. Finally, with an interest in understanding the effects of the VTD/CD molecular interactions, we performed cell-based assays (CBAs) on Neuro-2a cells. Our findings reveal that the use of different amounts of CDs has an antidote-like concentration-dependent effect on the cells, significantly increasing cell viability and thus opening opportunities for novel research on applications of CDs and VTD.

Testing the extraction of 12 mycotoxins from aqueous solutions by insoluble beta-cyclodextrin bead polymer

Mycotoxins are toxic metabolites of filamentous fungi; they are common contaminants in numerous foods and beverages. Cyclodextrins are ring-shaped oligosaccharides, which can form host-guest type complexes with certain mycotoxins. Insoluble beta-cyclodextrin bead polymer (BBP) extracted successfully some mycotoxins (e.g., alternariol and zearalenone) from aqueous solutions, including beverages. Therefore, in this study, we aimed to examine the ability of BBP to remove other 12 mycotoxins (including aflatoxin B1, aflatoxin M1, citrinin, dihydrocitrinone, cyclopiazonic acid, deoxynivalenol, ochratoxin A, patulin, sterigmatocystin, zearalanone, α-zearalanol, and β-zearalanol) from different buffers (pH 3.0, 5.0, and 7.0). Our results showed that BBP can effectively extract citrinin, dihydrocitrinone, sterigmatocystin, zearalanone, α-zearalanol, and β-zearalanol at each pH tested. However, for the removal of ochratoxin A, BBP was far the most effective at pH 3.0. Based on these observations, BBP may be a suitable mycotoxin binder to extract certain mycotoxins from aqueous solutions for decontamination and/or for analytical purposes.

Heparanase-driven sequential released nanoparticles for ferroptosis and tumor microenvironment modulations synergism in breast cancer therapy

The normal chemotherapy only induces the intracellular apoptosis pathway to promote primary tumor cells death, while not inhibit tumor metastasis. Herein, we proposed a kind of heparanase (HPSE)-driven sequential released nanoparticles, which modified with β-cyclodextrin (β-CD) grafted heparin (NLC/H(D + F + S) NPs) co-loading with doxorubicin (DOX), ferrocene (Fc), and TGF-β receptor inhibitor (SB431542). NLC/H(D + F + S) NPs successfully inhibited breast cancer metastasis by intracellular and extracellular hybrid mechanism. DOX and Fc loaded in NLC/H(D + F + S) NPs effectively enhanced intracellular ROS level to activate ferroptosis pathway, the enhanced ROS also induced the apoptosis pathway and decreased MMP-9 expression to synergize with ferroptosis for tumor therapy. In extracellular site, SB431542 was sequentially released by HPSE-driven, which blocked tumor metastasis by modulating tumor microenvironment, decreasing TAFs activation, and reducing the secretion of TGF-β. In addition, anti-tumor immune response induced by ferroptosis further strengthened the effect of tumor therapy. Finally, under the help of intracellular and extracellular mechanisms launched by NLC/H(D + F + S) NPs, the satisfactory anti-tumor metastasis effect was obtained in the in vivo anti-tumor assays. Therefore, NLC/H(D + F + S) NPs was a novel dosage regimen for breast cancer therapy through intracellular and extracellular mechanisms, in which ferroptosis induced by ROS played an important role.

Surface-imprinted β-cyclodextrin-functionalized carbon nitride nanosheets for fluorometric determination of sterigmatomycin

β-Cyclodextrin-functionalized carbon nitride nanosheets were modified with a molecularly imprinted polymer to obtain a fluorescent probe of type MIP@β-CD/CNNS which is shown to enable fluorometric determination of sterigmatocystin (STG). The material was characterized by transmission electron microscopy, infrared spectra, powder X-ray diffraction, X-ray photoelectron spectroscopy, and by absorption and emission spectra. The modified CNNSs have a good fluorescence quantum yield (13%), high sorption capacity for STG (86 mg·g^-1), fast adsorption rate (25 min), and superior adsorption selectivity (with an imprint factor 2.56). When used as an optical probe for STG, the CNNSs act as the chromophore, while β-CD and MIP act as the recognition groups. The blue fluorescence of MIP@β-CD/CNNS (with excitation/emission maxima at 368/432 nm) is quenched by STG. Fluorescence drops linearly in the 0.15 to 3.1 μM STG concentration range. The lower detection limit is 74 nM. The method was successfully applied to the determination of STG in spiked wheat extract. Conceivably, this detection scheme based on a combination of β-CD inclusion and molecular imprinting may be extended to the detection of various other organic compounds. Graphical abstractSchematic representation of the preparation of surface-imprinted β-cyclodextrin-functionalized carbon nitride nanosheets. These are used, along with a molecularly imprinted polymer, for fluorometric determination of sterigmatomycin.

Cyclodextrins Can Entrap Zearalenone-14-Glucoside: Interaction of the Masked Mycotoxin with Cyclodextrins and Cyclodextrin Bead Polymer

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).

Interaction of Dihydrocitrinone with Native and Chemically Modified Cyclodextrins

Citrinin (CIT) is a nephrotoxic mycotoxin produced by Aspergillus, Penicillium, and Monascus genera. It appears as a contaminant in grains, fruits, and spices. After oral exposure to CIT, its major urinary metabolite, dihydrocitrinone (DHC) is formed, which can be detected in human urine and blood samples. Cyclodextrins (CDs) are ring-shaped molecules built up from glucose units. CDs can form host-guest type complexes with several compounds, including mycotoxins. In this study, the complex formation of DHC with native and chemically modified beta- and gamma-cyclodextrins was tested at a wide pH range, employing steady-state fluorescence spectroscopic and modeling studies. The weakly acidic environment favors the formation of DHC-CD complexes. Among the CDs tested, the quaternary-ammonium-γ-cyclodextrin (QAGCD) formed the most stable complexes with DHC. However, the quaternary-ammonium-β-cyclodextrin (QABCD) induced the strongest enhancement in the fluorescence signal of DHC. Our results show that some of the chemically modified CDs are able to form stable complexes with DHC (logK = 3.2–3.4) and the complex formation can produce even a 20-fold increase in the fluorescence signal of DHC. Considering the above-listed observations, CD technology may be a promising tool to increase the sensitivity of the fluorescence detection of DHC.

Cyclodextrins in Food Technology and Human Nutrition: Benefits and Limitations

Cyclodextrins are tasteless, odorless, nondigestible, noncaloric, noncariogenic saccharides, which reduce the digestion of carbohydrates and lipids. They have low glycemic index and decrease the glycemic index of the food. They are either non- or only partly digestible by the enzymes of the human gastrointestinal (GI) tract and fermented by the gut microflora. Based on these properties, cyclodextrins are dietary fibers useful for controlling the body weight and blood lipid profile. They are prebiotics, improve the intestinal microflora by selective proliferation of bifidobacteria. These antiobesity and anti-diabetic effects make them bioactive food supplements and nutraceuticals. In this review, these features are evaluated for α-, β- and γ-cyclodextrins, which are the cyclodextrin variants approved by authorities for food applications. The mechanisms behind these effects are reviewed together with the applications as solubilizers, stabilizers of dietary lipids, such as unsaturated fatty acids, phytosterols, vitamins, flavonoids, carotenoids and other nutraceuticals. The recent applications of cyclodextrins for reducing unwanted components, such as trans-fats, allergens, mycotoxins, acrylamides, bitter compounds, as well as in smart active packaging of foods are also overviewed.

Fabrication of modular multifunctional delivery for antitumor drugs based on host-guest recognition

Herein, learning from the idea of the modular concept widely used in ship building, as a design approach that assembles some subdivided smaller modules to a specific ship, a new modular multifunctional drug delivery (MMDD) with excellent biocompatibility was directly prepared by a flexible host-guest interaction between pH-sensitive benzimidazole-graft-dextran (Dex-BM) and pre-synthesized multifunctional cyclodextrins. In this drug system, pH-sensitive Dex-BM acted as the main case and pre-synthesized multifunctional cyclodextrins were the changeable modules. To verify the feasibility of MMDD in cancer chemotherapy, doxorubicin (DOX) was used as a model drug. In vitro drug release experiments indicated that the drug released around 80% from DOX-loaded MMDD at pH 5.3, while approximately 40% of DOX released under the condition of pH 7.4. Moreover, the targeting antitumor activity of DOX-loaded MMDD was investigated in HeLa and HepG2 cells using MTT assays, confocal laser scanning microscopy and flow cytometer, which indicated that the targeted DOX-loaded MMDD provided an efficient drug delivery platform for inhibition of different cancer cells. Meantime, the incorporation of different functional modules into one system was also investigated, simultaneously exhibiting targeting and imaging property. These features suggest that this modular multifunctional drug delivery system can efficiently enhance the inhibition of cellular proliferation in vitro, and according to the needs in clinical treatment, some targeting and imaging molecules can be chosen.

Complexation of the mycotoxin zearalenone with β-cyclodextrin: Study of the interaction and first promising applications

This work reports the study of the interactions between native and substituted β-cyclodextrins and zearalenone and its derivatives α- and β-zearelonol. The data obtained by fluorescence and NMR experiments suggested that zearalenone, α- and β-zearalenol and cyclodextrins give rise to host-guest complexation, with the inclusion of the phenolic moiety inside the cyclodextrin cavity. The high stability of these complexes induces a high fluorescence enhancement upon complexation. These results have been successfully applied to the spectrofluorimetric determination of zearalenone in maize raw samples, without any chromatographic separation.

Sorption of ochratoxin A from aqueous solutions using β-cyclodextrin-polyurethane polymer

The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions was examined by batch rebinding assays. The results from the aqueous binding studies were fit to two parameter models to gain insight into the interaction of ochratoxin A with the nanosponge material. The ochratoxin A sorption data fit well to the heterogeneous Freundlich isotherm model. The polymer was less effective at binding ochratoxin A in high pH buffer (9.5) under conditions where ochratoxin A exists predominantly in the dianionic state. Batch rebinding assays in red wine indicate the polymer is able to remove significant levels of ochratoxin A from spiked solutions between 1–10 μg·L⁻¹. These results suggest cyclodextrin nanosponge materials are suitable to reduce levels of ochratoxin A from spiked aqueous solutions and red wine samples.

Investigation of solvent effect and cyclodextrins on fluorescence properties of ochratoxin A

Fluorescence properties of ochratoxin A (OTA) solutions depend on the pH, solvent polarity and can be influenced by the presence of cyclodextrins (CDs). In this work, the effect of b-cyclodextrin (b-CD) and heptakis-2,6-dimethyl-o-b-cyclodextrin (ome-CD), on fluorescence properties of OTA in aqueous solutions has been investigated by means of steady-state fluorescence at different pHs (range 2-10). Binding constants of OTA/CDs inclusion complexes have been determined by applying by non-linear regression analysis. A 1:1 stoichiometry of OTA/CDs complexes has been observed at all tested pHs. The use of ome-CD generally resulted in the greatest fluorescence intensity. The effects of solvent and pH on the positions of lambdamax (excitation) and lambdamax (emission) of OTA was determined. Correlations between the excitation and emission wavelength of OTA (monoanion and dianionic forms) and the solvent parameters were analysed with Lippert-Mataga plots. Results show that the peak position is affected mainly by specific and non-specific types of interactions between the solvent and solute. The fluorescence quenching of OTA by chloroform (aprotic) and water (protic) were studied in methanol as solvent at room temperature. The quenching was found to be appreciable and a non-linear curve with downward curvature was obtained in the Stern-Volmer (SV) plot for the water in the concentration range studied. The quenching efficiency is related to hydrogen bond-donating capacity of the quencher molecule. It was inferred that non-linearity can be attributed to fractional accessibility of fluorophore to quencher. The quenching constant was calculated from the modified SV equation.

Detection of aflatoxin M1 in human breast milk and raw cow's milk in Istanbul, Turkey

This survey was undertaken to determine the extent of aflatoxin M1 (AFM1) contamination in human breast milk and raw cow's milk in Istanbul, Turkey. Samples of human and raw cow's milk were collected randomly and analyzed for AFM1 using an enzyme-linked immunosorbent assay and high-performance liquid chromatography with fluorescence detection in which the samples were cleaned up with immunoaffinity columns. In this study, AFM, was detected in 8 (13.1%) of 61 human breast milk samples examined (mean +/- SD level, 5.68 +/- 0.62 ng/liter; range, 5.10 to 6.90 ng/liter) and 20 (33.3%) of 60 raw cow's milk samples examined (range, 5.40 to 300.20 ng/liter). Five (8.3%) of the positive raw cow's milk samples had AFM1 levels (153.52 +/- 100.60 ng/liter; range, 61.20 to 300.20 ng/liter) that were higher than the maximum tolerance limit (0.05 ppb) stipulated by regulations in Turkey and some other countries.

Mycotoxin detection plays "cops and robbers": cyclodextrin chemosensors as specialized police?

As in a cops and robbers play we discover new mycotoxins and metabolites everyday and we are forced to develop new molecules quickly as chemo- or biosensors or to modify existing molecules able to recognize these new hazardous compounds. This will result in an enormous cost saving to agro-food industry through the prevention and reduction of product recalls and reduced treatment costs. Here we present a brief review of the rapid methods used to detect mycotoxins, considering usefulness and limits. Then we propose a new fast, efficient and cheap methodology, based on a combination of computer chemistry aided design and fluorescence, that can help to drive synthesis in a more efficient way.

Cyclodextrins as selectors for mycotoxin recognition

This review deals with the applications of cyclodextrins as selectors for mycotoxin recognition. Complexation by cyclodextrins via formation of inclusion (host-guest) complexes induces significant changes in the physical and chemical properties of mycotoxins as guest molecules, effects that can be used in a variety of analytical techniques. Changes in chromatographic and electrophoretic properties and their applications to set up new separation methods are covered. Among these changes, a significant effect is the enhancement of the mycotoxin fluorescence upon inclusion, a phenomenon which provides a simple and convenient method to significantly increase the sensitivity of fluorescence-based trace analysis. The practical application of this phenomenon to set up new analytical methods is described. Studies on the mechanism of inclusion complex formation are also reported.

Use of cyclodextrins as modifiers of fluorescence in the detection of mycotoxins

Cyclodextrins, cyclic oligosaccharides composed of amylose subunits, are known to interact with mycotoxins. The interactions may be useful to analytical chemists by altering the properties of the mycotoxin of interest, namely the chromatographic properties, electrophoretic properties, fluorescence, or absorption of these fungal metabolites. Practical applications of these effects have been the incorporation of cyclodextrins into high-performance liquid chromatography and capillary electrophoresis methods for mycotoxin detection. Specific mycotoxins include those with a native fluorescence such as the aflatoxins, ochratoxin A (OTA) and zearalenone (ZEN) as well as those that can be rendered fluorescent through derivatization, such as T-2 toxin. The literature describing the applications of cyclodextrins in mycotoxin analysis is reviewed and an attempt to extend the use of cyclodextrins to the detection of labelled T-2 toxin is presented. Twenty cyclodextrins were evaluated for their ability to enhance the fluorescence emission of T-2 toxin derivatized with pyrene-1-carbonyl cyanide (T2-Pyr). This evaluation revealed that heptakis (2,6-di-O-methyl)-beta-cyclodextrin (DIMEB), in particular, enhanced T2-Pyr fluorescence. DIMEB was used as a buffer modifier in a capillary electrophoresis-laser-induced fluorescence (CE-LIF) method for detecting T-2 in maize. Because of the effects that certain cyclodextrins have, especially under aqueous conditions, they may make useful additives for a variety of mycotoxin analytical methods.