Lipid-Coated, pH-Sensitive Magnesium Phosphate Particles for Intracellular Protein Delivery

To develop cationic lipid-coated magnesium phosphate nanoparticles (LPP) for intracellular catalase (CAT) delivery.

Magnesium phosphate nanoparticles (MgP NP) were prepared by micro-emulsion precipitation and mixed with catalase-loaded cationic liposomes (DOTAP/cholesterol) to yield LPP formulation of catalase (LPP-CAT). The size and ζ-potential of LPP-CAT were measured by dynamic light scattering. The pH-sensitivity of LPP-CAT was determined by monitoring their degradation of hydrogen peroxide (H₂O₂) and their morphologies under transmission electron microscopy (TEM) at pH 7.4 and 5.5. The ability of LPP-CAT to protect MCF-7 cells against hydrogen peroxide was measured by MTS assay. ROS levels in EA.hy926 cells were measured after treatment with LPP-CAT.

LPP-CAT were successfully prepared and carried an average diameter of <300 nm and ζ -potential of about +40 mV. At pH 5.5, LPP-CAT degraded H₂O₂ almost 4-fold as fast as pH 7.4 and displayed drastic morphological changes of an osmotic explosion. LPP-CAT protected MCF-7 cells from lethal level of exogenous H₂O₂ and significantly lowered the ROS levels in EA.hy926 cells. A lipid with a pH-sensitive conformational switch (flipid) further enhanced the protein delivery of LPP-CAT.

LPP represents a promising nano-system for intracellular protein delivery.