Toward a More Accurate Structural Determination of High Molecular Weight Polyrotaxanes Based on Cyclodextrins by MALDI−TOF MS

Analysis of High-Molecular-Weight Polyrotaxanes by MALDI-TOF-MS Using 3-Aminoquinoline-Based Ionic Liquid Matrix

Polyrotaxane (PR) is a necklace-like supramolecule composed of cyclic components, such as cyclodextrin (CD), and a threading polymer capped with bulky end groups. PR exhibits peculiar mechanical properties attributed to the intermolecular cross-links with CD. Various CD molecules threaded on a linear PEG chain are often modified with chemical groups to add specific physicochemical properties. In general, the stoichiometry between CD and the PEG chain is a significant parameter that defines the unique physical properties of CD-based polyrotaxane (CD-PR). To date, mass spectrometry (MS) has been applied to investigate the molecular distribution of CD-PR, modifications of CD, and the threaded ratio of CD. However, only molecular weights (MWs) up to several 10s of kDa can be subjected to such analysis, whereas the MW of CD-PR used as industrial materials is much greater. Herein, we applied two ionic liquid matrices composed of 3-aminoquinoline and a high mass detector to analyze PRs using MALDI-TOF-MS. High to very high MW PRs in the range of 90-700 kDa were successfully analyzed using this method. The threaded ratio of CD was estimated from a single MW of CD, PEG, and PR. The ratios obtained were consistent with that obtained using ¹H NMR. Furthermore, a single-stranded form of PR in γ-cyclodextrin threaded PR (γCD-PR) was clearly distinguished from a double-stranded form, which is only possible in γCD -PR because of its large host cavity.

Versatile cyclodextrin nanotube synthesis with functional anchors for efficient ion channel formation: design, characterization and ion conductance

Biomimetic ion channels with different materials have been extensively designed to study the dynamics in a confined medium. These channels allow the development of several applications, such as ultra-fast sequencing and biomarker detection. When considering their synthesis, the use of cheap, non-cytotoxic and readily available materials is an increasing priority. Cyclodextrins, in supramolecular architectures, are widely utilized for pharmaceutical and biotechnological applications. Recent work has shown that short nanotubes (NTs) based on alpha-cyclodextrin (α-CD) assemble transient ion channels into membranes without cytotoxicity. In this study, we probe the influence of new cyclodextrin NT structural parameters and chemical modifications on channel formation, stability and electrical conductance. We report the successful synthesis of β- and γ-cyclodextrin nanotubes (β-CDNTs and γ-CDNTs), as evidenced by mass-spectrometry and high-resolution transmission electron microscopy. CDNTs were characterized by their length, diameter and number of CDs. Two hydrophobic groups, silylated or vinylated, were attached along the γ-CDNTs, improving the insertion time into the membrane. All NTs synthesized form spontaneous biomimetic ion channels. The hydrophobic NTs exhibit higher stability in membranes. Electrophysiological measurements show that ion transport is the main contribution of NT conductance and that the ion energy penalty for the entry into these NTs is similar to that of biological channels.

Biomimetic ion channels formation by emulsion based on chemically modified cyclodextrin nanotubes

We present short cyclodextrin nanotubes that form ion channels in lipid bilayers.

Linear polymers of β and γ cyclodextrins with a polyglutamic acid backbone as carriers for doxorubicin

Cyclodextrins have been used to encapsulate drugs improving their stability and efficiently regulating their release. Polymeric nanoparticles containing cyclodextrins are currently undergoing clinical trials as nanotherapeutics. In this context, we have synthesized new linear polymers based on polyglutamic acid with pendant β- or γ-cyclodextrins, using a high yield reaction route. The new polymers with an average number of about 17 cyclodextrin cavities were characterized (NMR, MALDI-MS, DLS) and tested as carriers of doxorubicin in human tumor cells. They can include doxorubicin, and the inclusion complexes show antiproliferative activity in human tumor cells.

Interactions between shape-persistent macromolecules as probed by AFM

Water-soluble shape-persistent cyclodextrin (CD) polymers with amino-functionalized end groups were prepared starting from diacetylene-modified cyclodextrin monomers by a combined Glaser coupling/click chemistry approach. Structural perfection of the neutral CD polymers and inclusion complex formation with ditopic and monotopic guest molecules were proven by MALDI-TOF and UV-vis measurements. Small-angle neutron and X-ray (SANS/SAXS) scattering experiments confirm the stiffness of the polymer chains with an apparent contour length of about 130 Å. Surface modification of planar silicon wafers as well as AFM tips was realized by covalent bound formation between the terminal amino groups of the CD polymer and a reactive isothiocyanate-silane monolayer. Atomic force measurements of CD polymer decorated surfaces show enhanced supramolecular interaction energies which can be attributed to multiple inclusion complexes based on the rigidity of the polymer backbone and the regular configuration of the CD moieties. Depending on the geometrical configuration of attachment anisotropic adhesion characteristics of the polymer system can be distinguished between a peeling and a shearing mechanism.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

Investigation of 5-(3-Trifluoromethylbenzylidene)thiazolidine-2,4-dione as a Matrix for Analyses of Biogenic Monoamine Transmitters Using MALDI-MS

In order to discover new matrices suitable for the analyses of low molecular-weight compounds using positive-ion mode matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (MS), 5-(3-trifluoromethylbenzylidene)thiazolidine-2,4-dione (3-CF3-BTD) was synthesized, and its effectiveness was compared with that when commercially available α-cyano-4-hydroxycinnamic acid was used. 3-CF3-BTD was sufficiently sensitive to analyze neurotransmitters, i.e., dopamine, serotonin, histamine, and epinephrine, in amounts of several picomoles. Similar to vacuum MALDI experiments, atmospheric-pressure MALDI-MS measurements using 3-CF3-BTD as a matrix also detected dopamine.

Aminocyclodextrin Oligomers as Protective Agents of Protein Aggregation

Over 30 different amyloid proteins and a number of corresponding protein-misfolding diseases have been identified. Among these is Alzheimer's disease, the most common neurodegenerative disorder. The treatment of these diseases is still a goal to reach and many molecules have been studied in this context. Among these, the cyclodextrins have shown interesting potential as agents against protein aggregation (antiaggregants). On the basis of this interest, we investigated the effect on protein aggregation of some oligomers of β-cyclodextrins. In particular, it was found that amino oligomers show good inhibition of β-amyloid aggregation in the micromolar concentration range. The presence of both a multicavity system and amino groups seems to be essential for preventing protein aggregation.

Synthesis of 2-hydroxypropyl-β-cyclodextrin/pluronic-based polyrotaxanes via heterogeneous reaction as potential Niemann-Pick type C therapeutics

Five polyrotaxanes were synthesized by threading 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) onto a variety of α,ω-ditriethylenediamino-N-carbamoyl-poly-(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic) triblock copolymers using a two-pot strategy under heterogeneous, nonaqueous conditions. The threaded HP-β-CD units were retained on the pseudopolyrotaxane precursors by end-capping the branched diamine termini with sodium 2,4,6-trinitrobenzene sulfonate. Inclusion of the Pluronic copolymers within the HP-β-CD cavities was more favorable in nonpolar solvents, such as diethyl ether and n-hexane, both of which gave better coverage ratios than polar solvents. (1)H NMR and MALDI-TOF were used to estimate the average molecular weights of the purified polyrotaxane products. A globular morphology of aggregated polyrotaxanes was observed by tapping-mode AFM imaging of dried samples. Treatment of Niemann-Pick C (NPC) type 2-deficient fibroblasts with the polyrotaxane derivatives produced substantial reductions in sterol accumulation, as seen by diminished filipin staining in these cells, suggesting that Pluronic-based polyrotaxanes may be promising vehicles for delivery of HP-β-CD to cells with abnormal cholesterol accumulation.

Further Insight into the Detailed Characterization of a Polydisperse Cyclodextrin-Based Polyrotaxane Sample by Electrospray Ionization Mass Spectrometry

An easy and fast approach based on electrospray mass spectrometry (ESI-MS) was developed to provide a detailed characterization of a mixture containing polydisperse cyclodextrin-based polyrotaxane (CD-based PR). Here, method gave access to usual data such the weight-average molecular weight, the number-average molecular weight and the polydispersity index, but also to more specific features as the average number of CDs threaded and the average threading degree. Moreover, the nature and the average number of groups grafted per CD, such as sulfate or silyl groups, can be accurately determinate. This ESI-MS approach advantageously complements the widely used NMR and SEC methods and, thereby, constituting a milestone in the actual MS bottleneck regarding the analysis of polydisperse supramolecular assemblies.