Formulation and characterization of a cooling sunscreen incorporated with chitosan-encapsulated spirulina

Exposure to ultraviolet radiation can disrupt the normal balance of skin, leading to increased oxidative damage and accelerated photoaging (aging associated with light) and increased risk of developing skin cancer. To address these issues, it has become increasingly important to develop more effective, stable, and protective photoprotective products. The use of traditional sunscreens provides an adequate barrier against UV rays but they are known to cause skin irritation, be unstable when exposed to heat and moisture, and reduced acceptability by consumers. Spirulina contains phycocyanin and various natural antioxidants, presents strong photoprotective and anti-inflammatory potential; however, its poor stability and low penetration hinder direct incorporation into formulations. This paper deals with the encapsulation of Spirulina extract by the ionic gelation technique, using chitosan nanoparticles to provide higher stability, better retention of antioxidants, and sustained release. These nanoparticles are combined into an optimized oil-in-water cooling sunscreen cream containing both mineral and chemical UV filters, such as ZnO, TiO₂, Avobenzone, and Octocrylene, with soothing agents like Panthenol and Menthol.
The developed sunscreens were tested for their physicochemical properties, SPF values, antioxidant activity, stability, rheology, spreadability, and microbiological safety. This study is expected to highlight the fact that chitosan-encapsulated Spirulina can act as an excellent natural SPF booster and antioxidant, improving photoprotection along with enhanced skin comfort and reduced irritation. This proposed formulation should be capable of offering a multifunctional, stable, cosmetically acceptable cooling sunscreen with broad-spectrum UV protection in addition to therapeutic benefits.