Impact of process parameters in the generation of novel aspirin nanoemulsions – Comparative studies between ultrasound cavitation and microfluidizer

► Efficiencies of microfluidizer and ultrasound were compared to generate nanoemulsions. ► Both methods produced Aspirin nanoemulsions ranging from 150 to 170nm. ► Emulsion droplet size was independent of operating pressure and number of passes. ► Sonicated emulsion strongly depends on the pre-homogenization and drug loading. ► Ultrasound was found to be 18 times more energy-efficient than microfluidizer. In the present investigation, the operating efficiency of a bench-top air-driven microfluidizer has been compared to that of a bench-top high power ultrasound horn in the production of pharmaceutical grade nanoemulsions using aspirin as a model drug. The influence of important process variables as well as the pre-homogenization and drug loading on the resultant mean droplet diameter and size distribution of emulsion droplets was studied in an oil-in-water nanoemulsion incorporated with a model drug aspirin. Results obtained show that both the emulsification methods were capable of producing very fine nanoemulsions containing aspirin with the minimum droplet size ranging from 150 to 170nm. In case of using the microfluidizer, it has been observed that the size of the emulsion droplets obtained was almost independent of the applied microfluidization pressure (200–600bar) and the number of passes (up to 10 passes) while the pre-homogenization and drug loading had a marginal effect in increasing the droplet size. Whereas, in the case of ultrasound emulsification, the droplet size was generally decreased with an increase in sonication amplitude (50–70%) and period of sonication but the resultant emulsion was found to be dependent on the pre-homogenization and drug loading. The STEM microscopic observations illustrated that the optimized formulations obtained using ultrasound cavitation technique are comparable to microfluidized emulsions. These comparative results demonstrated that ultrasound cavitation is a relatively energy-efficient yet promising method of pharmaceutical nanoemulsions as compared to microfluidizer although the means used to generate the nanoemulsions are different.