Objectives: Design of photocatalytic antibacterial indoor coatings Design of skin UV-protecting agents Transcutaneous administration of nanoparticles for direct delivery to the region of interest, i.e. pathologically modified areas of the tissue Design of agents for optical diagnostics and therapy at cell and tissue levels Optical characterization of exosomes Outline: Introduction Gypsum-titania fiber nanocomposites for indoor antimicrobial coatings Titania nanoparticles for skin protection against UV light Nanoparticle delivery Design of gold nanoagents for optical imaging and therapy Heating of gold nanoparticles Upconversion nanoluminophores for deep-tissue imaging Cell-derived vesicles: optical characterization Conclusion