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Direct Optofluidic Measurement of the Lipid Permeability of Fluoroquinolones

View Article: PubMed Central - PubMed

ABSTRACT

Quantifying drug permeability across lipid membranes is crucial for drug development. In addition, reduced membrane permeability is a leading cause of antibiotic resistance in bacteria, and hence there is a need for new technologies that can quantify antibiotic transport across biological membranes. We recently developed an optofluidic assay that directly determines the permeability coefficient of autofluorescent drug molecules across lipid membranes. Using ultraviolet fluorescence microscopy, we directly track drug accumulation in giant lipid vesicles as they traverse a microfluidic device while exposed to the drug. Importantly, our measurement does not require the knowledge of the octanol partition coefficient of the drug – we directly determine the permeability coefficient for the specific drug-lipid system. In this work, we report measurements on a range of fluoroquinolone antibiotics and find that their pH dependent lipid permeability can span over two orders of magnitude. We describe various technical improvements for our assay, and provide a new graphical user interface for data analysis to make the technology easier to use for the wider community.

No MeSH data available.


Comparison of the permeability coefficients (P) for the four fluoroquinolones studied as a function of pH.The error bars (s.e.) are smaller than the symbol size. The permeability coefficient values for norfloxacin at pH 5 and 7 are taken from Ref. 4. For all the molecules, the permeability increases as we increase the pH from 5 to 7. We find large differences in the absolute values of the permeability coefficients between the drugs; the permeability of enrofloxacin is approximately two orders of magnitude greater than that of norfloxacin, across the pH range studied. Norfloxacin has the lowest permeability of the drugs studied, while enrofloxacin has the highest.
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f3: Comparison of the permeability coefficients (P) for the four fluoroquinolones studied as a function of pH.The error bars (s.e.) are smaller than the symbol size. The permeability coefficient values for norfloxacin at pH 5 and 7 are taken from Ref. 4. For all the molecules, the permeability increases as we increase the pH from 5 to 7. We find large differences in the absolute values of the permeability coefficients between the drugs; the permeability of enrofloxacin is approximately two orders of magnitude greater than that of norfloxacin, across the pH range studied. Norfloxacin has the lowest permeability of the drugs studied, while enrofloxacin has the highest.

Mentions: For all three drugs, we observed an increase in permeability coefficients as we increased the pH from 5 to 7. The permeability coefficients are provided in Table 1, and depicted visually in Fig. 3. Histograms of the permeability coefficients (from all the experiments performed) are provided in Fig. 2 and in further detail in Supplementary Figure S7. In our earlier work we had measured the permeability of norfloxacin at pH 5 and 7; for completeness, we measured norfloxacin permeability at pH 6 as well (Supplementary Information Figure S3). At pH 5, the molecules are predominantly positively charged, whereas the proportion of zwitterionic/uncharged molecules is higher at pH 6 and 7. This explains the pH dependence of the permeability coefficients, since charged moieties are less lipophilic as they do not easily dissolve in the hydrocarbon core of the lipid bilayer.


Direct Optofluidic Measurement of the Lipid Permeability of Fluoroquinolones
Comparison of the permeability coefficients (P) for the four fluoroquinolones studied as a function of pH.The error bars (s.e.) are smaller than the symbol size. The permeability coefficient values for norfloxacin at pH 5 and 7 are taken from Ref. 4. For all the molecules, the permeability increases as we increase the pH from 5 to 7. We find large differences in the absolute values of the permeability coefficients between the drugs; the permeability of enrofloxacin is approximately two orders of magnitude greater than that of norfloxacin, across the pH range studied. Norfloxacin has the lowest permeability of the drugs studied, while enrofloxacin has the highest.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015079&req=5

f3: Comparison of the permeability coefficients (P) for the four fluoroquinolones studied as a function of pH.The error bars (s.e.) are smaller than the symbol size. The permeability coefficient values for norfloxacin at pH 5 and 7 are taken from Ref. 4. For all the molecules, the permeability increases as we increase the pH from 5 to 7. We find large differences in the absolute values of the permeability coefficients between the drugs; the permeability of enrofloxacin is approximately two orders of magnitude greater than that of norfloxacin, across the pH range studied. Norfloxacin has the lowest permeability of the drugs studied, while enrofloxacin has the highest.
Mentions: For all three drugs, we observed an increase in permeability coefficients as we increased the pH from 5 to 7. The permeability coefficients are provided in Table 1, and depicted visually in Fig. 3. Histograms of the permeability coefficients (from all the experiments performed) are provided in Fig. 2 and in further detail in Supplementary Figure S7. In our earlier work we had measured the permeability of norfloxacin at pH 5 and 7; for completeness, we measured norfloxacin permeability at pH 6 as well (Supplementary Information Figure S3). At pH 5, the molecules are predominantly positively charged, whereas the proportion of zwitterionic/uncharged molecules is higher at pH 6 and 7. This explains the pH dependence of the permeability coefficients, since charged moieties are less lipophilic as they do not easily dissolve in the hydrocarbon core of the lipid bilayer.

View Article: PubMed Central - PubMed

ABSTRACT

Quantifying drug permeability across lipid membranes is crucial for drug development. In addition, reduced membrane permeability is a leading cause of antibiotic resistance in bacteria, and hence there is a need for new technologies that can quantify antibiotic transport across biological membranes. We recently developed an optofluidic assay that directly determines the permeability coefficient of autofluorescent drug molecules across lipid membranes. Using ultraviolet fluorescence microscopy, we directly track drug accumulation in giant lipid vesicles as they traverse a microfluidic device while exposed to the drug. Importantly, our measurement does not require the knowledge of the octanol partition coefficient of the drug – we directly determine the permeability coefficient for the specific drug-lipid system. In this work, we report measurements on a range of fluoroquinolone antibiotics and find that their pH dependent lipid permeability can span over two orders of magnitude. We describe various technical improvements for our assay, and provide a new graphical user interface for data analysis to make the technology easier to use for the wider community.

No MeSH data available.