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Published on: March 18, 2020
Kinetics of Antimicrobial Drug Ion Transfer at a Water/Oil Interface Studied by Nanopipet Voltammetry
Surendra Raj Puri1, Jiyeon Kim1
1Department of Chemistry , The University of Rhode Island , Kingston , Rhode Island 02881 , United States.
Abstract:
Effective delivery and accumulation of antimicrobial agents into the microbial organism is essential for the treatment of bacterial infections. Transports of hydrophilic drug molecules, however, encounter a robust barrier of hydrophobic double membrane cell envelope, thus, leading to drug-resistance in Gram-negative bacteria. Accordingly, a deeper understanding about a transit of charged molecules through a bacterial membrane is needed to remediate the antibacterial resistance. Herein, we apply a steady-state voltammetry using nanopipet-supported interfaces between two immiscible electrolyte solutions (ITIES) to quantitatively study transport-kinetics of antimicrobial drug ions (quinolones and sulfonamides) at a water/oil interface. Importantly, ITIES can mimic a cellular membrane system, thus, being employed as insightful surrogates for the kinetic study of drug entry through bacterial cytoplasmic membranes. This approach enables us to voltammetrically and amperometrically detect redox-inactive drug ions as pristine under physiological conditions. Considerably slow kinetics of drug-ion transports are successfully measured by nanopipet voltammetry and theoretically analyzed. This analysis reveals that the drug-ion transport is ∼3 orders of magnitude slower than tetrabutylammonium ion transport. In addition, the extreme hydrophilicity of drug ions in comparison to ClO4- is quantitatively assessed from half-wave potentials of obtained voltammograms. The high hydrophilicity exclusively attributed to localized negative charges on carboxylate or amide group of deprotonated quinolone or sulfonamide, respectively, may play a dominant role in sluggish kinetics due to the increase in energy barriers upon interfacial ion transfer. Notably, this study using nanopipet voltammetry provides physicochemical insights on the correlation between structural properties of pristine drug ions and their transfer kinetics at a water/oil interface in lieu of biological membranes.
Insights
This study uses nanopipet voltammetry to measure how antimicrobial drug ions cross simulated cell membranes. Findings reveal slow transport kinetics due to drug ion hydrophilicity, offering insights into bacterial drug resistance.
Area of Science:
- Electrochemistry
- Biophysical Chemistry
- Materials Science
Background:
- Antimicrobial drug delivery faces challenges due to Gram-negative bacteria's double membrane.
- Understanding charged molecule transport across membranes is crucial for overcoming drug resistance.
- Existing methods lack quantitative insights into drug ion transfer kinetics.
Purpose of the Study:
- To quantitatively investigate the transport kinetics of antimicrobial drug ions across a model membrane system.
- To explore the correlation between drug ion structure and their interfacial transfer rates.
- To provide a novel electrochemical approach for studying drug-membrane interactions.
Main Methods:
- Utilized steady-state voltammetry with nanopipet-supported interfaces between two immiscible electrolyte solutions (ITIES).
- Mimicked cellular membrane systems to study drug ion transit at a water/oil interface.
- Voltammetrically and amperometrically detected redox-inactive drug ions under physiological conditions.
Main Results:
- Successfully measured and theoretically analyzed the slow kinetics of antimicrobial drug ion transport.
- Drug ion transport was found to be approximately 3 orders of magnitude slower than tetrabutylammonium ion transport.
- Quantified extreme hydrophilicity of drug ions, linked to localized negative charges, contributing to increased energy barriers.
Conclusions:
- Nanopipet voltammetry offers a powerful tool to study drug ion transfer kinetics at interfaces, mimicking biological membranes.
- The study provides physicochemical insights into how drug ion structure influences transfer rates, impacting antimicrobial efficacy.
- Findings contribute to understanding and potentially remediating antimicrobial resistance by elucidating drug entry mechanisms.
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