We report a water-soluble hybrid nanosystem that combines luminescence LaVO4:Eu3+ (LEu) nanoparticles with a photoswitchable and bioactive diamine phosphine oxide (DP) shell for light-activated medical treatment. While existing photopharmacological agents often face challenges with water solubility and real-time tracking, our design integrates imaging and photoswitchable therapeutic functions in a single platform. The synthesized hybrids were thoroughly characterized by a wide set of experimental techniques, including NMR, Raman, XRD, and optical spectroscopy. Remarkably, the hybrid maintains strong Eu3+ emission (5D0–7F2 transition at 613 nm), which is affected by laser irradiation. Biological studies revealed a three-fold enhancement in butyrylcholinesterase inhibition efficiency (20 %–60 %) after laser irradiation, surpassing the performance of free DP (two-fold enhancement under the same conditions). In vivo evaluation using Daphnia magna demonstrated excellent biocompatibility and selective accumulation in the digestive system, with clearly distinguishable Eu3+ luminescence against tissue autofluorescence. This work advances photopharmacology by providing a robust strategy for developing image-guided, light-responsive therapies with high precision and efficacy.