Photodynamic therapy (PDT) is a medical treatment based on the optical excitation of a drug, called photosensitizer. When photosensitizers are exposed to light of specific wavelength, they can produce reactive species, such as singlet oxygen, capable of killing cells close to the irradiated site, such as cancer cells. Hybrid nanomaterials, comprising metallic nanoparticles and polymeric components, are investigated for their potential in biomedical applications due to their ability to simultaneously allow detection for diagnosis and therapy (theranostic). Thanks to the multi functionality assured by the nanoparticle plasmonic properties and therapeutic activity of the drug nanotransporters, the encapsulation of gold nanoparticles (AuNPs) wrapped by biocompatible polymers has become an attractive way to test photodynamic therapy, with the great advantage of preventing effects of aggregation under biological conditions. This dissertation focuses on the stabilization and photodynamic activity of a hybrid nanomaterial composed of AuNPs synthesized in water by laser ablation. The copolymer Pluronic F-127 was used as a polymeric component to stabilize the nanoparticles. The production of singlet oxygen by the photosensitizers chlorin e6 and methylene blue was studied in the absence and presence of AuNPs using 1,3 diphenylisobenzofuran (DPBF) as a molecular probe. The specific reaction of DPBF with singlet oxygen modifies its absorption spectrum in the visible range and allows to obtain rates of cytotoxic species production. Samples were irradiated with a LED emitting 650 nm radiation and the absorption spectra were monitored as a function of time during irradiation. Rates of photosensitizers degradation and quantum yields of singlet oxygen production were obtained in different cases.