Fluorometric study of fluoxetine DNA binding

Fluoxetine (FLX), a selective serotonin reuptake inhibitor (SSRI), is commonly prescribed to treat depression. The interaction between FLX antidepressant and calf thymus DNA (ctDNA) was investigated under simulated physiological conditions (Tris–HCl buffer at pH 7.4) using methylene blue [3,7-bis(dimethylamino) pheno-thrazin-5-ium chloride] (MB) dye as a probe using fluorescence spectroscopy. A strong fluorescence quenching reaction of DNA to FLX was observed. The corresponding numbers of binding sites (n) and binding constants (Kf) of DNA with FLX at 281, 310 and 318 K were calculated 2.1 × 105, 6.7 × 105 and 9.7 × 105 respectively. It can be concluded that FLX molecules could interact with ctDNA via outside, non-intercalative, binding as evidenced by quenching study with I−, ionic strength with NaCl and competitive investigation with MB. Thermodynamic parameters, enthalpy (ΔH) and entropy (ΔS) changes were calculated according to Van’t Hoff equation, which indicated that reaction is entropically driven. Furthermore, the interaction of FLX with poly A–T and poly C–G were carried out in order to comprehend the binding location of drug to DNA.