Formulation and Evaluation of Nanostructured Lipid Carriers for Enhanced Drug Solubility and Bioavailability

The present study was undertaken to develop and optimize CTZ-loaded nanostructured lipid carriers (CTZ-NLCs) using a Quality by Design (QbD) approach for improved drug delivery. Initially, Preformulation studies were performed to evaluate the solubility of CTZ in various solid lipids, liquid lipids, surfactants, and co-surfactants. Based on the solubility results, suitable formulation components were selected. The NLCs were developed using selected lipid, surfactant, and homogenization conditions. A Box–Behnken Design (BBD) was employed to investigate the effects of three independent variables, namely lipid concentration (A), surfactant concentration (B), and homogenizer speed (C), on drug content (Y1), entrapment efficiency (Y2), and drug release (Y3). The quadratic models obtained for all three responses were found to be statistically significant. The optimized formulation F9 was selected based on the desirability criteria and evaluated for physicochemical characteristics and drug release. FTIR analysis of F9 showed characteristic absorption bands at 3322.75 cm⁻¹ (O–H), 2972.73 cm⁻¹ (aliphatic C–H), 1720–1740 cm⁻¹ (C=O), 1585.20 cm⁻¹ (C=C), 1381.75 cm⁻¹ (C–H bending), 1032.69 cm⁻¹ (C–O), and 879.38 cm⁻¹ (C–H out-of-plane bending), which were within the reported ranges. The absence of major peak shifts or disappearance indicated compatibility between CTZ and the selected excipients. In-vitro drug release was performed using the dialysis membrane method in phosphate buffer pH 6.8 for 6 h. Overall, the study demonstrated that the QbD-based approach was effective for systematic optimization of CTZ-NLCs, and the optimized F9 formulation showed satisfactory physicochemical characteristics and controlled drug release, indicating its potential as a promising lipid-based drug delivery system.