Influence of physicochemical properties of fluoroquinolones on encapsulation efficiency in liposomes

Three fluoroquinolones, ciprofloxacin, norfloxacin and a newly synthesized compound (CNV-8912), were encapsulated in liposomes of DPPC at pH 7.40 and encapsulation efficiency was determined by two methods: spectrophotometry of isopropanol-lysed vesicles and HPLC. These methods are compared with a view to the reproducibility and sensitivity of each technique. Physicochemical properties such as octanol-buffer coefficients and pKs were determined in order to interpret the encapsulation efficiency values in terms of affinity for lipid environments and microspeciation at pH 7.40.