Effect of cucurbit[n]urils on tropicamide and potential application in ocular drug delivery

The supramolecular interactions of the ocular drug tropicamide (TR) with cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) were investigated in aqueous solutions by using 1 H NMR, ESI-MS and UV-vis spectroscopic techniques. The results indicate a 1:1 binding stoichiometry of TR with CB7 and CB8. The b...

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Bibliographic Details
Published in:Supramolecular chemistry 2011-09, Vol.23 (9), p.650-656
Main Authors: Saleh, Na'il, Meetani, Mohammed A., Al-Kaabi, Leena, Ghosh, Indrajit, Nau, Werner M.
Format: Article
Language:English
Subjects:
cucurbiturils
drug ionisation
host-guest complexes
shifts
tropicamide
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Summary:The supramolecular interactions of the ocular drug tropicamide (TR) with cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) were investigated in aqueous solutions by using 1 H NMR, ESI-MS and UV-vis spectroscopic techniques. The results indicate a 1:1 binding stoichiometry of TR with CB7 and CB8. The binding constants of TR in its protonated form were higher (e.g. K = 4 × 10 6  M − 1 with CB8) than in its neutral form (e.g. K = 1.4 × 10 4  M − 1 with CB8), which led to a complexation-induced increase in its pK a value of ca. 0.5 and 2 units with CB7 and CB8, respectively. In the presence of about 1% (w/v) CB8, the ionisation degree of 0.1% (w/v) TR was increased from 2% to 62% at neutral pH. The increase in the pK a value and thus stabilisation of the protonated TR species at neutral pH is discussed in the context of supramolecular drug delivery of ophthalmologic drugs.
ISSN:1061-0278
1029-0478
DOI:10.1080/10610278.2011.593631