Preparation and characterization of phospholipid stabilized nanoemulsions in small-scale

Abstract

Phospholipids have been used to prepare liposomes. The use of phospholipids to stabilize nanoemulsions may cause spontaneous formation of liposomes. The main objective of this study is to develop a method to prepare phospholipid stabilized nanoemulsions in small scale (< 1 mL) and to minimize the formation of liposomes.\n\nA combination of hand extrusion and detergent removal methods was used in this study. Extrusion through polycarbonate membranes was performed in two steps, firstly using membranes of 400 nm followed by 200 nm membranes as the second step. Sodium cholate was used as a detergent to solubilize the formed liposomes which was later removed via dialysis. Nanoemulsions were characterized by measuring their particle size, polydispersity index and zeta-potential using Photon Correlation Spectroscopy and Cryo-TEM pictures. The stability of nanoemulsion stored under refrigeration was also studied.\n\nFifty-one extrusion cycles through polycarbonate membrane of 400 nm pore size followed by one-hundred fifty-three cycles through polycarbonate membrane of 200 nm produced nanoemulsions having particle size below 200 nm (diameter). The nanoemulsions were found to be homogenous as depicted by polydispersity index (PDI) value below 0.1. Similarly, the zeta-potential was measured to be above -30 mV which is sufficient to keep nanoemulsions stable for as long as 7 months when stored under refrigeration. The Cryo-TEM pictures revealed 30 mM to be an optimum concentration of sodium cholate to prepare homogenous nanoemulsions with negligible proportion of liposomes.\n\nIt was concluded that this method could be established as a small scale method of preparing nanoemulsions which will not only reduce the cost of preparation but also the disposal cost of toxic chemicals used for functionalizing nanoemulsions for scientific research.