Preparation and characterization of catalase-loaded solid lipid nanoparticles based on soybean phosphatidylcholine.

High-purity soybean phosphatidylcholine (SPC) (94%) were prepared using macroporous resin adsorption chromatography previously. Catalase is a food enzyme for promoting health and protecting against many age-related disease. Solid lipid nanoparticles (SLN) are safe immobilizing systems for efficient protein transportation to biomembranes while avoiding adverse degradation of protein. This study was aimed at developing and characterizing catalase-loaded SLN using SPC as solubilizers and stabilizing agents, to protect catalase from proteolysis. Catalase-loaded SLN were prepared by the double emulsification method and solvent evaporation techniques, using acetone-methylene chloride (1:1, v/v) as an organic solvent, SPC-tripalmitin as oil phase and Poloxamer 188 as a surfactant. The optimized SLN were prepared using an SPC:tripalmitin ratio of 5% (w/w), 20 s plus 30 s sonication, 20 g L⁻¹ Poloxamer 188 and 1:2 (v/v) of oily phase:outer aqueous phase ratio. The mean particle size of SLN was 296.0 ± 7.0 nm, polydispersity index range and zeta potential were 0.322-0.354 and -36.4 ± 0.6, respectively, and encapsulation efficiency reached its maximum of 77.9 ± 1.56%. Catalase, which was found to distribute between the solid lipid and inner aqueous phase, was gradually released from SLN up to 20% within 20 h. Catalase-loaded SLN had stably retained 30% of H₂O₂-degrading activity for at least 24 h in a proteolytic environment, while free catalase lost its activity within 1 h. Catalase can indeed be loaded in tripalmitin-based SLN using SPC as solubilizers and stabilizing agents, which protected it against proteolysis, suggesting the potential application of SPC in delivery and protection of functional food enzyme.