Phycocyanin- and Polydopamine-Conjugated Titania Nanoparticles for UV Protection

With the increasing incidence of skin cancers each year, there is growing concern regarding ultraviolet (UV) radiation protection. However, titanium dioxide (TiO2), as a commonly used physical sunscreen agent, has certain photocatalytic activity, which can generate a large amount of reactive oxygen species (ROS), thus posing potential skin toxicity risks. Incorporating organic molecules with free radical scavenging ability to modify TiO2 can effectively improve the UV protection performance. In this study, the PC–PDA@TiO2 composite nanoparticles were successfully prepared by coupling the biomolecules phycocyanin (PC) and polydopamine (PDA) to the surface of TiO2 nanoparticles using a simple spontaneous oxidation polymerization method. Characterization methods including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analyses demonstrated that the PC–PDA@TiO2 composite nanoparticles uniformly coated with a PC–PDA composite nanolayer have been successfully prepared. The UV–vis diffuse reflectance spectroscopy results and electron spin resonance (ESR) tests showed that the PC–PDA composite nanolayer significantly increased the UV absorption capacity of the composite nanoparticles and reduced the concentration of free radicals through the synergistic effect of PC and PDA. Furthermore, in vitro toxicity assessment and in vivo UV protection efficiency tests showed no significant cytotoxicity and high UV protection efficiency of the PC–PDA@TiO2 composite nanoparticles. These findings suggest that the biomacromolecule PC shows great promise as a safer material for sunscreen products to enhance their efficacy.