Optimization of Atorvastatin calcium-loaded niosomes for solubility enhancement using central composite design and response surface methodology

Atorvastatin calcium is a BCS class II drug characterized by low solubility and high permeability. This study aims to enhance its solubility through niosomal formulation. The solubility of this drug is more desirable through formulating as a niosomal vesicles. Further optimization is done using a central composite design to select a desired Atorvastatin calcium niosomal formulation. Atorvastatin calcium-loaded niosomes were formulated using ether injection technique. The study employed a 3-factor, 3-level central composite design combined with response surface methodology (CCD-RSM) for optimizing formulation parameters, utilizing Stat-Ease Design Expert® 13 software. Particle size and Zeta potential were analyzed using Zeta sizer (Malvern). Niosomes were evaluated for their entrapment efficacy, in-vitro drug release properties including their stability performance. The independent variables—surfactant, cholesterol concentration, and stabilizer amount—affected Zeta potential, entrapment efficacy, and niosome particle size. Zeta potential ranged from −17.3 to −38.6 mV, ensuring electrostatic stability. Particle size varied from 358.3 to 1224 nm, while entrapment efficacy ranged from 32.6% to 93.1%. Atomic force microscopy confirmed a spherical shape with an average height of 875.8 nm and diameter of 181.81 nm. The optimized model showed significant predictability (p < 0.0001) with satisfactory regression coefficients for particle size (R² = 0.9345), zeta potential (R² = 0.8135), and entrapment efficiency (R² = 0.8560). Drug release followed zero-order kinetics with R² = 0.9892. Optimized formulation, particle size was found to be 812.364 nm, zeta potential −23.631 mV, and %EE 80.247. Cholesterol influences particle size of the formulation, and it has been observed that the stabilizer exhibited minimal impact on the particle size. All the formulated niosomes exhibited an optimal %entrapment efficacy, which shows higher drug loading. Atorvastatin calcium niosomes enhanced drug solubility, as demonstrated by a cumulative drug release of 60.15% over 8 h, compared to 19.5% from pure drug.