Effects of surfactant mixture ratio and concentration on nanoemulsion physical stability

Abstract

Keywords: Nanoemulsions; Tween 20^®; Transcutol^®; Physical stability; Ostwald ripening rate

Objective: The aim of this study is to study the effects of surfactant mixture (smix) ratio and concentration on physical properties and physical stabilities of nanoemulsions.

Methods: Oil-in-water nanoemulsions were prepared by high-pressure homogenization method. Caprylic/capric triglycerides was used as oil phase. Surfactant mixtures between Tween 20^® and Transcutol^® were varied with different ratios and concentrations. Nanoemulsions were characterized for physical appearances, particle size and size distribution. Their physical stabilities were tested using centrifugation, heating-cooling cycle, and Ostwald ripening rate after storage at room temperature.

Results: The mean particle sizes of nanoemulsions were in the range of 88.3 to 227.2 nm with narrow size distribution (polydispersity index of 0.086-0.197). Smaller particle sizes were obtained with an increase in smix concentration. However, high Tween 20^®, Transcutol^®, or total smix concentration showed high Ostwald ripening rate and resulted in instable nanoemulsions when stored in accelerated conditions. F1 formulation containing the least amount of surfactant and only Tween 20^® presented the lowest Ostwald ripening rate of 3.70 × 10^-2 nm³/h and was the most stable nanoemulsion.

Conclusion: Smix ratio and smix concentration showed influences on nanoemulsion physical properties and especially stabilities. Therefore, further works need to be done in order to develop more stable nanoemulsions.