Chitosan Nanoformulations of Mycosporine-like Amino Acid (MAA)-Rich Extracts from Mazzaella laminarioides Effectively Protect Human Keratinocytes Against UVA Radiation Damage

Abstract

Mycosporine-like amino acids (MAAs) are secondary metabolites of interest for the development of natural sunscreens, owing to their antioxidant activity and ultraviolet radiation (UVR)-absorbing properties. MAA-rich aqueous extracts obtained from the Chilean red alga Mazzaella laminarioides (locally known as luga cuchara) were analyzed by HPLC and loaded into chitosan nanoparticles (CSNPs), with an encapsulation efficiency of 90.1%. The resulting CS nanoformulations (CSNFs) were characterized by FTIR spectroscopy, DLS and TEM microscopy, confirming the presence of nanoparticles with a core diameter of 94 ± 11 nm and FTIR absorption bands accounting for CS functional groups. Pre-treatment of HaCaT keratinocytes with CSNFs conferred complete protection against low-to-moderate UVA doses (5, 10, 15, and 30 J/cm2). Remarkably, cells still retained a protection efficacy of 64.7% under lethal UVA exposure (60 J/cm2), with gene expression evidence suggesting the activation of a compensatory stress response to photo-oxidative damage. CSNFs were also capable of restoring cell viability in post-treatment experiments at UVA doses of 30 J/cm2 (100% cell viability) and 60 J/cm2 (~43% cell viability). This is the first demonstration that nanoencapsulation of an MAA-rich algal extract yields superior UVA photoprotection in human keratinocytes compared with non-encapsulated MAA-based formulations, contributing to the effort of developing eco-friendly sunscreens.