Title : Application of quality by design for pulmonary liposomes: Preliminary study to nano in-microparticle
Abstract:
Introduction: Pulmonary surfactants in liposomes production became relevant components due to their compatibility with the pulmonary environment. However, the understanding of critical process parameters (CPP) needs to be elucidated. Thus, Quality by Design (QbD) combined with a Box–Behnken design enables systematic identification and optimization of CPP. This study evaluated Dioleoyl-α-lecithin (DOPC) and L-α-Phosphatidylcholine (DPPC) as pulmonary surfactants in liposome composition, assessing surfactant ratio, extrusion cycles, and hydration medium towards nano-in-microparticle pulmonary delivery.
Methods: The Box–Behnken experimental design was developed to optimize the liposome synthesis process. A total of 15 experiments were generated using Minitab® software to evaluate independent variables and their effects on analytical responses. Three factors were assessed at three levels: the ratio of DOPC:DPPC was fixed at a total concentration of 30 mg/mL (70:30, 50:50, and 30:70), the hydration medium (purified water, phosphate buffer pH 6.8 or 7.2), and the number of extrusion cycles (10, 20, and 30). Extrusion was performed through polycarbonate membranes with decreasing pore sizes (0.4, 0.2, and 0.1 μm). Hydrodynamic size, polydispersity index, and zeta potential were measured using a NanoZS® instrument. A QbD study was conducted to identify critical factors affecting liposome properties.
Results: The Box–Behnken modeling revealed that formulation and process variables significantly influenced liposomal physicochemical properties. Additionally, quadratic models were statistically significant by ANOVA, confirming adequacy for data description and prediction. The liposomes showed hydrodynamic diameters of 114.0 ± 3.73 to 189.2 ± 0.14 nm, PdI of 0.041 ± 0.017 to 0.227 ± 0.051, and low-magnitude negative zeta potentials (−12.0 ± 0.51 to−27.5 ± 1.81 mV). Response surface analysis indicated surfactant ratio as the main factor, with hydration medium and number of cycles showing secondary effects. Moreover, the multi-response optimization using desirability functions, guided by literature-based targets, yielded a composite desirability of 0.9460. This value indicates a high overall fulfillment of all criteria, reflecting trade-offs among size, PdI, and zeta potential. The optimized conditions corresponded to liposomes with a size (~100 nm) and PdI (< 0.1), consistent with requirements for pulmonary delivery.
Conclusion: Based on the Box–Behnken methodology, liposomes with a promising size (~100 nm) and PdI (< 0.1) were obtained. The QbD study identified a 70:30 DOPC:DPPC ratio, using phosphate buffer pH 6.8 as a hydration medium, and 15 extrusion cycles as optimal, supporting their potential for pulmonary delivery and nano-in-microparticle systems.
