Potentiometric assessment of Gram-negative bacterial permeabilization of tobramycin

The construction and electrochemical response characteristics of beta-cyclodextrin-based sensor for determination of the amino glycosidic antibiotic, tobramycin, is described. The membrane incorporates carboxylated poly (vinyl chloride) as matrix polymer, tetrakis-fluorophenyl borate as fixed anionic site and nitrophenyloctylether as plasticizer. The uptake of aminoglycosidic drug was applied to determine permeability changes in the Gram-negative bacteria Escherichia coli as test organism and ethylenediamine tetraacetic acid as model permeabilizer. The sensor shows linear response over concentration range of 10(-2) to 10(-5)M tobramycin with cationic slope of mV per concentration decade and accuracy of 99.8+/-2.14%. The proposed method was successfully applied to the determination of tobramycin uptake, by 100 microl E. coli suspension in presence of up to 10 microg ml(-1) of EDTA solution, with average recovery of 99.3+/-2.77%. The obtained results were compared reasonably well with the data obtained using the compendial fluorimetric assay. The proposed potentiometric assay serves as a convenient method in analyzing and quantifying the effects of permeabilizers on Gram-negative bacteria upon treatment with tobramycin.