Physical characterisation of drug encapsulated soybean oil nano-emulsions

Abstract

Lecithin based soybean oil emulsions, similar to Intralipid®, were used to successfully encapsulate drugs having a range of hydrophobicity and acid-base characteristics. The drugs studied were phenanthrene, diazepam, histamine and chloroquine and these were compared with previous studies involving halofantrine. The drug encapsulated emulsions were tested for pH, stability, particle size, zeta potential and morphology (cryo electron microscopy). Encapsulation of any drug was found to decrease the stability of the emulsion, increase the particle size, decrease the (negative) zeta potential and in some cases, resulted in distortions to the particles. Specifically, close to the isoelectric point, gross distortions were observed involving large, elongated, worm like structures for the drugs halofantrine and histamine. The short term stability of all drug encapsulated emulsions were good, however all showed some signs of instability with time, probably due to a concomitant pH drift to low pH values, resulting in a decreased zeta potential and loss of stability. Neither hydrophobicity nor the acid-base nature of the encapsulated drug was found to have a strong influence on the stability, particle size or zeta potential profile of the emulsion.

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