Host–guest complexations of local anaesthetics by cucurbit[7]uril in aqueous solution

Wyman, Ian; Macartney, Donal H.

doi:10.1039/b915694a

Cited by 93 publications

(85 citation statements)

References 75 publications

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“…Cucurbit [7]uril (CB7, Figure 1) is a water-soluble macrocycle that has been investigated extensively in biological applications including drug delivery, [29][30][31][32][33] interactions with enzymes, 34,35 plasma membrane protein fishing, 36 and label-free enzyme assays. [22][23][24][25] The repeating glycoluril units produce a barrel-shaped container that has a hydrophobic cavity and negatively charged portals.…”

Section: Resultsmentioning

confidence: 99%

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

et al. 2011

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An analytical method has been developed for the continuous monitoring of protease activity on unlabelled peptides in real time by fluorescence spectroscopy. The assay is enabled by a reporter pair comprising the macrocycle cucurbit [7]uril (CB7) and the fluorescent dye acridine orange (AO). CB7 functions by selectively recognizing N-terminal phenylalanine residues as they are produced during the enzymatic cleavage of enkephalintype peptides by the metalloendopeptidase thermolysin. The substrate peptides (e.g., ThrGly-Ala-Phe-Met-NH2) bind to CB7 with moderately high affinity (K ca. 10 4 M -1 ), while their cleavage products (e.g., Phe-Met-NH2) bind very tightly (K > 10 6 M -1 ). AO signals the reaction upon its selective displacement from the macrocycle by the high affinity product of proteolysis. The resulting supramolecular tandem enzyme assay effectively measures the kinetics of thermolysin, including the accurate determination of sequence specificity (Ser and Gly instead of Ala), stereospecificity (DAla instead of LAla), endo-versus exopeptidase activity (indicated by differences in absolute fluorescence response), and sensitivity to terminal charges (-CONH2 versus -COOH). The capability of the tandem assay to measure protease inhibition constants was demonstrated on phosphoramidon as a known inhibitor to afford an inhibition constant of (17.8 ± 0.4) nM. This robust and label-free approach to the study of protease activity and inhibition should be transferable to other endo-and exopeptidases that afford products with N-terminal aromatic amino acids.2

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Section: Resultsmentioning

confidence: 99%

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

et al. 2011

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“…At present, it has been shown that calabadion 1, like his ancestor CB [7], forms stable hostguest complexes with local anesthetics in aqueous solution in vitro. 37,45 If these findings are relevant in vivo, a second application of the calabadions may relate to treatment of local anesthetic-induced toxicity. In light of the application explored in current study, it is important to investigate in a future study whether systemic local anesthetic administration or systemic distribution may result in reparalysis after calabadion 1-induced reversal of neuromuscular block.…”

Section: Discussionmentioning

confidence: 99%

Calabadion

et al. 2013

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Introduction:To evaluate whether calabadion 1, an acyclic member of the Cucurbit[n]uril family of molecular containers, reverses benzylisoquinoline and steroidal neuromuscular-blocking agent effects. Methods: A total of 60 rats were anesthetized, tracheotomized, and instrumented with IV and arterial catheters. Rocuronium (3.5 mg/kg) or cisatracurium (0.6 mg/kg) was administered and neuromuscular transmission quantified by acceleromyography. Calabadion 1 at 30, 60, and 90 mg/kg (for rocuronium) or 90, 120, and 150 mg/kg (for cisatracurium), or neostigmine/glycopyrrolate at 0.06/0.012 mg/ kg were administered at maximum twitch depression, and renal calabadion 1 elimination was determined by using a 1 H NMR assay. The authors also measured heart rate, arterial blood gas parameters, and arterial blood pressure. Results: After the administration of rocuronium, resumption of spontaneous breathing and recovery of train-of-four ratio to 0.9 were accelerated from 12.3 ± 1.1 and 16.2 ± 3.3 min with placebo to 4.6 ± 1.8 min with neostigmine/glycopyrrolate to 15 ± 8 and 84 ± 33 s with calabadion 1 (90 mg/kg), respectively. After the administration of cisatracurium, recovery of breathing and train-of-four ratio of 0.9 were accelerated from 8.7 ± 2.8 and 9.9 ± 1.7 min with placebo to 2.8 ± 0.8 and 7.6 ± 2

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“…For instances, it has been found that the stability constants of CB [7] complexes with local anesthetics are 2−3 orders of magnitude greater than those of β-cyclodextrin complexes. 34 Nau and co-workers have also shown that the solubility of CB [7] formulation is 1 order of magnitude larger than that of β-cyclodextrin-based formulation. 40,41 Therefore, CB [7] is supposed to act as a potential pharmaceutical excipient to improve the solubility and physical stability of drugs.…”

Section: ■ Introductionmentioning

confidence: 99%

The Delivery of Triamterene by Cucurbit[7]uril: Synthesis, Structures and Pharmacokinetics Study

Chen

Jiang

et al. 2013

Mol. Pharmaceutics

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In recent years, cucurbit [7]uril (CB [7]) has attracted great attention in drug delivery. Though the effect of CB [7] in enhancing the solubility of water insoluble drugs has been validated, the underlying mechanism remains poorly understood, particularly at a molecular level. This study is designed to evaluate a CB [7]-based pharmaceutical formulation to improve solubility and bioavailability of triamterene (a mild potassium-sparing diuretic). Two polymorphs of triamterene@CB [7] were obtained, and their crystal structures were determined by single crystal X-ray diffraction. The CB [7] molecule forms a stable host−guest complex with triamterene (K a = 1.69 ± 0.34 × 10 4 M −1 ) in aqueous solution (pH = 1.0). The results of dissolution study demonstrate that the apparent solubility value of triamterene@CB [7] complex in 0.1 M HCl is 1.6 times as large as that of triamterene, while free triamterene was released from triamterene@CB [7] complex in phosphate buffer of pH 6.8. Pharmacokinetic studies in rats reveal that the AUC 0−∞ value of triamterene@CB [7] complex increases 2.8-fold compared with that of free triamterene, and t 1/2 is prolonged from 1.42 to 2.61 h (P < 0.05) after oral administration. The increased solubility and oral bioavailability are attributed to the formation of a hydrophilic capsule composed of two CB [7] molecules, in which two insoluble triamterene molecules are encapsulated. These results demonstrate that triamterene@CB [7] complex is a stable and effective pharmaceutical formulation. KEYWORDS: cucurbit [7]uril, triamterene, crystal structure, solubility, pharmacokinetics ■ INTRODUCTIONPoor aqueous solubility is a major bottleneck in drug discovery and drug development: more than 40% of drug candidates are poorly water-soluble, and poor aqueous solubility is the main factor to restrict the bioavailability of drugs.1,2 Various approaches have been investigated to improve solubility of drugs, including cocrystal, 3,4 salts, 5 prodrugs, 6 solid dispersion, 7 macrocyclic hosts (e.g., cyclodextrins, cucurbiturils), 8,9 etc. Triamterene, 2,4,7-triamino-6-phenylpteridine (Scheme 1) is a mild potassium-sparing diuretic used either alone or in combination with potassium-wasting diuretics such as hydrochlorothiazide.10,11 It displays low oral bioavailability, and there exists wide intersubject variation because of its poor aqueous solubility (45 mg/L). 12,13 Though triamterene contains three primary amine groups, various methods to obtain soluble salts failed, probably due to its weak basicity. 12 To date, only a few formulations have been proposed to improve the solubility of triamterene, including cyclodextrins 14,15 and solid dispersions. 16,17 However, parenteral administration of β-cyclodextrin results in renal toxicity, 18 and solid dispersions are often physically unstable upon storage at elevated temperature and humidity, 19 and neither of the two triamterene formulations has been applied for clinical therapy. Therefore, the development of new pharmaceutical formulation of triam...

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Host–guest complexations of local anaesthetics by cucurbit[7]uril in aqueous solution

Cited by 93 publications

References 75 publications

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

Calabadion

The Delivery of Triamterene by Cucurbit[7]uril: Synthesis, Structures and Pharmacokinetics Study

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