Prodigiosin development and its entrapped topical microstructured sunscreen for laser and UV radiation protection and antioxidant activity

Purpose: To develop prodigiosin (PG) cream for laser and ultraviolet radiation (UV) protection. Methods: The cream containing PG (PG-C) was prepared and characterized. In vivo skin irritation was evaluated on Wistar rats by shaving the animals and applying the calculated amount on the animal skin daily for 3 days, while occlusivity was carried out in vitro. Trans-epithelial water loss and melanin contents were evaluated in rats and antioxidant studies of PG were done using DPPH (0.1 mM) and ABTS (7 mM) protocols. In vitro drug release was conducted using dissolution tester and paddles. Furthermore, laser obscuration and sun protective factor (SPF) were screened. Results: The PG-C appeared pinkish with pH of 6.63 ± 0.21, viscosity of 2957 ± 2 Pa·s and spreadability of 36.85 g · cm/sec. There was no skin irritation during the 14-day treatment. Transmission electron microscope (TEM) and scanning electron microscopy (SEM) revealed the sizes of PG and PG-C to be 50 nm. The IC50 of PG was 28.74 ± 0.89 μg/mL (DPPH) and 11.9 ± 0.75 μg/mL (ABTS), while the average IC50 for PG-C was 21.33 ± 1.91 μg/mL (DPPH) and 24.0 ± 0.82 μg/mL (ABTS) with ascorbic acid at 43.89 ± 1.41 μg/mL. The PG-cream was able to block the laser and UV light. The PG release at 4 h from cream was 2 – 10 %. The loss of water content from human skin was minimal, while melanin content was not affected. Conclusion: This study has shown that PG-C offered protection against laser and UV light and demonstrates the presence of remarkable antioxidants.