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Stoichiometry and thermodynamics of gemcitabine and cucurbituril Q7 supramolecular complexes in high acidic aqueous solution.

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Title: Stoichiometry and thermodynamics of gemcitabine and cucurbituril Q7 supramolecular complexes in high acidic aqueous solution.
Authors: Buczkowski, Adam1 adam.buczkowski@chemia.uni.lodz.pl, Palecz, Bartlomiej1, Schroeder, Grzegorz2
Source: Journal of Molecular Structure. Feb2019, Vol. 1178, p554-563. 10p.
Subjects: Stoichiometry, Thermodynamics, Cucurbituril, Supramolecular electrochemistry, Aqueous solutions
Abstract: Abstract Cucurbiturils are a relatively new class of nanocarriers which show low toxicity and make it easier for ligand molecules to cross through the cellular membrane. These macrocyclic compounds can bind cationic centers of ligand molecules with high affinity. This ability is complementary to binding properties of other families of modern nanocarriers (like liposomes, cyclodextrins, and dendrimers). Isothermal titration calorimetry and mass spectrometry results show that cucurbituril molecule (Q7) binds to gemcitabine (Gem) cation forming thermodynamically stable supramolecular complexes in an aqueous high acidic solution of hydrochloric acid with pH = 1.7, despite that at this pH value some of carbonyl groups of cucurbituril portals are protonated (p K a ≈ 3) in aqueous solution. In solutions containing a molar excess of gemcitabine in relation to cucurbituril, complexes with a stoichiometry 1:1 are formed, while a molar excess of cucurbituril towards gemcitabine results in the formation of complexes with stoichiometry 1:2 (LQ 2). The formation of these complexes with different stoichiometries has been confirmed, examining aqueous solutions of cucurbituril (Q7) and gemcitabine (Gem) by ESI mass spectrometry. In calorimetric measurements, it has been shown that the process of binding cucurbituril Q7 with gemcitabine has an exothermal character (Δ H < 0) and is accompanied by a favorable change in entropy (Δ S > 0). Graphical abstract Image 1 Highlights • ITC and ESI MS measurements were performed in an aqueous solution at pH < 2. • Protonation of some of CB carbonyl groups doesn't unable the cationic guest binding. • Binding has exothermal enthalpy and a favorable change in entropy. • LQ is formed in solution with a molar excess of gemcitabine to cucurbituril. • To form LQ 2 a molar excess of cucurbituril towards gemcitabine is necessary. [ABSTRACT FROM AUTHOR]
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Abstract:Abstract Cucurbiturils are a relatively new class of nanocarriers which show low toxicity and make it easier for ligand molecules to cross through the cellular membrane. These macrocyclic compounds can bind cationic centers of ligand molecules with high affinity. This ability is complementary to binding properties of other families of modern nanocarriers (like liposomes, cyclodextrins, and dendrimers). Isothermal titration calorimetry and mass spectrometry results show that cucurbituril molecule (Q7) binds to gemcitabine (Gem) cation forming thermodynamically stable supramolecular complexes in an aqueous high acidic solution of hydrochloric acid with pH = 1.7, despite that at this pH value some of carbonyl groups of cucurbituril portals are protonated (p K a ≈ 3) in aqueous solution. In solutions containing a molar excess of gemcitabine in relation to cucurbituril, complexes with a stoichiometry 1:1 are formed, while a molar excess of cucurbituril towards gemcitabine results in the formation of complexes with stoichiometry 1:2 (LQ 2). The formation of these complexes with different stoichiometries has been confirmed, examining aqueous solutions of cucurbituril (Q7) and gemcitabine (Gem) by ESI mass spectrometry. In calorimetric measurements, it has been shown that the process of binding cucurbituril Q7 with gemcitabine has an exothermal character (Δ H < 0) and is accompanied by a favorable change in entropy (Δ S > 0). Graphical abstract Image 1 Highlights • ITC and ESI MS measurements were performed in an aqueous solution at pH < 2. • Protonation of some of CB carbonyl groups doesn't unable the cationic guest binding. • Binding has exothermal enthalpy and a favorable change in entropy. • LQ is formed in solution with a molar excess of gemcitabine to cucurbituril. • To form LQ 2 a molar excess of cucurbituril towards gemcitabine is necessary. [ABSTRACT FROM AUTHOR]
ISSN:00222860
DOI:10.1016/j.molstruc.2018.10.077