Physicochemical properties of structured phosphatidylcholine in drug carrier lipid emulsions for drug delivery systems

Drug carrier emulsions were prepared with structured phosphatidylcholine (PC-LM) which has both a long hydrocarbon chain and a medium hydrocarbon chain, and the characteristics of PC-LM as an emulsifier were investigated by measuring the creaming ratio, the surface tension of the emulsion system, and the mean particle size and zeta potential of the oil droplets in emulsions. The emulsion prepared with PC-LM as an emulsifier kept the condition and the ratio of separation was lower than those with purified egg yolk lecithin (PEL). The mean particle size of the emulsion prepared with PC-LM was smaller than that with PEL when using only sonication, approximately 250 nm. When using a high-pressure homogenizer after sonication, the mean emulsion size with PC-LM was also smaller than with PEL, approximately 150 nm. The surface tension of the various emulsions and the zeta potential of the emulsion droplets were measured to investigate the stability of the systems. In emulsions with PC-LM or PEL, the surface tension as an index of stability increased as the pressure of the homogenizer increased. Moreover, the zeta potential of the emulsion droplets prepared with PC-LM also increased with an increase in pressure of the homogenizer. As a result, it was found that the drug carrier emulsion prepared with PC-LM had significant advantages in terms of stability and mean diameter. We considered it could be used for the preparations of nanoparticle dispersion systems in drug delivery systems.