Determination by fluorimetric titration of the ionization constants of ciprofloxacin in solution and in the presence of liposomes.
A fluorescence titration method was applied for the determination of pKa of ciprofloxacin (CPX) in solution. Values of 6.18 +/- 0.05 and 8.76 +/- 0.03 were obtained for pKa1 and pKa2, respectively. The method was used to determine the ionization constants in the presence of liposomes of dipalmitoylphosphatidylcholine (DPPC) and DPPC with 10 mol% of dipalmitoylphosphatidylglycerol. A dependence on the surface charge of liposomes was found which supported the existence of a basic electrostatic interaction between CPX and the phospholipid bilayer. Both pK values for the N-4 butyl-piperazinyl derivative (BCPX) of the parent compound were also determined in solution and in the presence of liposomes. The competition of both drugs for the same binding site as 1-anilino-8-naphtalene sulfonate demonstrate that the interaction is governed by electrostatic forces.
Vázquez
J L
JL
Laboratori V de Fisicoquímica, Facultat de Farmàcia, Barcelona, Spain.
Berlanga
M
M
Merino
S
S
Domènech
O
O
Viñas
M
M
Montero
M T
MT
Hernández-Borrell
J
J
D000890:Anti-Infective Agents / Q000737:chemistry; D002939:Ciprofloxacin / Q000031:analogs & derivatives / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008081:Liposomes; D010777:Photochemistry; D012996:Solutions; D013050:Spectrometry, Fluorescence; D055672:Static Electricity
D000890:Anti-Infective Agents; D008081:Liposomes; D012996:Solutions; D002939:Ciprofloxacin