Summary - the development of new nano-biotechnologies is a promising and ever demanding research field. In particular, the possibility to use the organic chemistry tools to build molecules sensitive to a wide range of external stimuli, responsible of a switching between their two isomers, represents an interesting area of investigation with suitable applications in novel nano-technologies. The use of photochromic molecular switches in applications ranging from drug delivery to the probing of biochemical parameters, passing through their uses in material science, in polymer and carbon nano materials realms, constitute the main research subject of my PhD course. In this manuscript I’ll report in Chapter 3 investigations upon Spiropyrans molecular switches in their metal complexations attitude for the Visible light regulated delivery of pharmaceutical active compounds. Chapter 4 will be dedicated to the study I conducted on hybrid mesostructures prepared combining Azobenzenes molecules and Graphene Oxide in order to apply these modified materials in the biological context. Chapter 5 will be instead dedicated to the study of photochromic Oxazines and Oxazolidines in their modifications with fluorophores to have ratiometric Temperature and pH sensing tools and in their use as switchable blocks in photo-modulable polymers.