Effect of cucurbit[n]urils on tropicamide and potential application in ocular drug delivery |
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| Authors: | Na'il Saleh Mohammed A Meetani Leena Al-Kaabi Indrajit Ghosh |
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| Institution: | 1. Department of Chemistry , College of Science, UAE University , P.O. Box 17551, Al-Ain , United Arab Emirates n.saleh@uaeu.ac.ae;3. Department of Chemistry , College of Science, UAE University , P.O. Box 17551, Al-Ain , United Arab Emirates;4. School of Engineering and Science, Jacobs University Bremen , Campus Ring 1, D-28759 , Bremen , Germany |
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| Abstract: | The supramolecular interactions of the ocular drug tropicamide (TR) with cucurbit7]uril (CB7) and cucurbit8]uril (CB8) were investigated in aqueous solutions by using 1H 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 × 106 M? 1 with CB8) than in its neutral form (e.g. K = 1.4 × 104 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. |
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| Keywords: | cucurbiturils tropicamide drug ionisation pK a shifts host–guest complexes |
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