Development of ascorbyl palmitate nanocrystals applying the nanosuspension technology

Ascorbyl palmitate (AP) is an antioxidant used in both cosmetics and food industry. Owing to its poor solubility and instability caused by oxidation having been observed in several colloidal systems, the aim of this study was to investigate the feasibility of applying the nanosuspension technology by high-pressure homogenization (HPH) (DissoCubes® technology) to enhance the chemical stability of AP, followed by lyophilization. Sodium dodecyl sulfate (SDS) and Tween 80 were chosen as emulsifying agents to stabilize the developed AP nanosuspensions. After 3 months of storage at three different temperatures (4 °C, 25 °C and 40 °C), the photon correlation spectroscopy (PCS) analysis of AP nanosuspensions revealed that the mean particle size of those stabilized with SDS significantly increased compared to those stabilized with Tween 80. The results observed from both atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed AP nanocrystals of cubic-like shape. The percentage of AP remaining in nanosuspensions stabilized with Tween 80 was higher than 90% after 3 months storage at 4 °C, 25 °C and 40 °C. To increase the chemical stability of AP nanosuspensions, a drug powder was prepared by lyophilization. The effect of the presence of cryoprotectant trehalose on the physical stability was evaluated at different concentrations. After redispersing the lyophilized product, the mean size of AP nanosuspensions without trehalose was significantly higher compared with the system with trehalose. After 3 months of storage at 25 °C the mean size of lyophilized AP nanosuspensions remained constant. X-ray diffraction revealed the crystalline character of AP nanocrystals after HPH and lyophilization.