Phase transitions in materials formed by surfactants and polymers are determined by physicochemical parameters that can be considered external stimuli. This project will focus on new formulations for in situ-forming long-acting drug delivery systems (LADDS). These systems will be designed to transition from injectable fluid solutions to highly viscous systems with solubilising capacity, such as liquid crystals, water-in-water emulsions and wormlike micelles, under conditions that mimic in vivo environments (dilution, pH, temperature and biomolecule concentration). A comprehensive physicochemical, structural and rheological characterisation of a wide variety of formulations will be carried out. In addition, nanomaterials with photothermal and magnetic responses, as well as functional organic nanoparticles, will be integrated to enable greater control over rheological properties and drug release.