Box–Behnken Design-Based Development and Validation of a Reverse-Phase HPLC Analytical Method for the Estimation of Paclitaxel in Cationic Liposomes

Stability-indicating reverse-phase HPLC analytical method for the quantification of Paclitaxel (PTX) in the bulk and cationic liposomes was developed. The optimized method was validated according to the ICH Q2 (R1) guidelines by following a 2-level–4-factor interaction Box–Behnken design using Design-Expert^® software. The responses measured at 228 nm were retention time (Rt), peak area, tailing factor (Tf_10%), and the number of theoretical plates (NTP). PTX was eluted best using the Luna^® C₁₈ LC Column along with a mobile phase of methanol and 25 mM ammonium acetate buffer (pH 6) 75:25 v/v mixture at 25 ± 2 °C temperature. The currently developed method was linear in the 2.5–100 µg/mL range with a detection limit of 0.062 µg/mL and a quantification limit of 0.188 µg/mL. The optimized method was utilized to evaluate the stability of PTX in different stress conditions by performing forced degradation studies. The results from the degradation study stipulated that on exposure to various stressors, namely acid, alkali, oxidative, thermal, and UV light, the PTX did not show considerable degradation except alkali exposure. Further, the method was successfully used for the quantification of PTX in cationic liposomes. The particle size, zeta potential, and polydispersity index of the PTX-loaded liposomes were 219.25 ± 7.566 nm, 57.15 ± 12.374 mV, and 0.807 ± 0.1958 respectively. The percent of drug entrapped was quantified and was found to be 59 ± 1.414%.