Fluorescence enhancement and pKa shift of a rho kinase inhibitor by a synthetic receptor
Autor: | Ruibing Wang, Hang Yin, Chunming Wang, Linmin Chen, Simon Ming-Yuen Lee, Binrui Yang, David Bardelang |
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Rok vydání: | 2017 |
Předmět: |
Aqueous solution
010405 organic chemistry Chemistry Stereochemistry Electrospray ionization Organic Chemistry Isothermal titration calorimetry 010402 general chemistry 01 natural sciences Biochemistry Fluorescence 0104 chemical sciences Rho kinase inhibitor Bathochromic shift Proton NMR Titration Physical and Theoretical Chemistry Nuclear chemistry |
Zdroj: | Organic & Biomolecular Chemistry. 15:4336-4343 |
ISSN: | 1477-0539 1477-0520 |
Popis: | Fasudil (FSD), a selective rho kinase (ROCK) inhibitor, was found to form 1 : 1 host–guest inclusion complexes with a synthetic macrocyclic receptor, cucurbit[7]uril (CB[7]), in aqueous solutions, as evidenced by 1H NMR, photoluminescence and UV-visible spectroscopic titrations, isothermal titration calorimetry (ITC) titration, and electrospray ionization (ESI) mass spectrometry, as well as density functional theory (DFT) molecular modeling. Upon encapsulation, whereas the UV-vis absorbance of FSD experienced a moderate decrease and bathochromic shift, the fluorescence intensity of FSD at 354 nm was dramatically enhanced for up to 69-fold at neutral pH, which could potentially be applied in fluorescent tracking of the drug delivery and release. More interestingly, the binding affinity (Ka = (4.28 ± 0.21) × 106 M−1), of FSD–CB[7] complexes under acidic conditions (pH = 2.0), is approximately three orders of magnitude higher than that (2.2∼6.6 × 103 M−1) under neutral pH conditions (pH = 7.0). Accordingly, UV-visible spectroscopic titration of the free and complexed FSD under various pH conditions has demonstrated that the encapsulation of FSD by CB[7] shifted the pKa of the isoquinoline-N upward from 3.05 to 5.96 (ΔpKa of 2.91). The significantly higher binding affinity of the complexes under acidic conditions may be applied in developing the “enteric” formulation of FSD. Furthermore, our in vitro study of the bioactivity of FSD in the absence and presence of CB[7] on a neural cell line, SH-SY5Y, showed that the complexation preserved the drug's pro-neurite efficacy. Thus this discovery may lead to a fluorescence-trackable, orally administered enteric formulation of rho kinase inhibitors that are stable under gastric conditions, without compromising bioactivity of the drugs. |
Databáze: | OpenAIRE |
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