Development of solid lipid nanoparticles containing astaxanthin from shrimp shell extract for skin delivery

Abstract

The objective of this study was to develop solid lipid nanoparticles (SLNs) containing astaxanthin from shrimp shell extract for skin delivery. The suitable condition for hydrolysis the shrimp shell crude extract was examined. The effect of extract and components in the formulation to SLNs formation, which were prepared by microemulsion technique, and its stability was investigated. The studies of release and skin permeation of free astaxanthin from SLNs were also carried out. This study indicated that the suitable condition for hydrolysis the shrimp shell crude extract was 0.03 N NaOH. The hydrolyzed extract was composed of free astaxanthin at 21.66%w/w and showed the highest DPPH scavenging activity (0.7297 μmole/mL) in comparison to standard astaxanthin and apocarotenal. Factors affecting the particle size of blank-SLNs prepared by microemulsion method were types and quantities of formulation ingredients. Increasing the concentration of solid lipid, surfactant, and co-surfactant resulted in the augmentation of particle size. The SLNs generated from glycerylmonostearate (GMS) as solid lipid gave a bigger size than Dynasan®118. The use of solid surfactants (Myrj®52 and Brij®S721) also provided the larger particle size than the use of liquid surfactants (Tween®80 and Cremophor®RH40). Fourteen formulations of blank-SLNs, which passed the physical stability study at room temperature for 1 month, were selected for loading astaxanthin from hydrolyzed extract at a concentration of 25 mg/mL. The results indicated that those formulations were in nanometer size range and the entrapment efficiencies of free astaxanthin were in the range of 46-91%. Powder X-ray diffraction study revealed that solid lipids lost their crystallinity after SLNs preparation and tended to be in more amorphous form when compared to the physical mixture. ASX-SLNs formulations prepared using Tween®80 and Cremophor®RH40 demonstrated the better capacity to entrap free astaxanthin than the use of Myrj®52. After 3 months of storage at room temperature and protected from light, the physical and chemical stability of ASX-SLNs formulations was superior to the control solution. The entrapment efficiency of free astaxanthin in each formulation gradually decreased with the increase in crystallinity index. In vitro release study showed sustained release profiles of free astaxanthin from SLNs and was well fitted to the Higuchi equation. The in vitro permeation study using newborn abdominal pig skin revealed that SLNs could significantly enhance the skin penetration of free astaxanthin as compared with the control solution.