n this doctoral thesis, biodegradable microspheres and nano-spheres of PLGA have been developed for the sustained release of VEGF angiogenic factor and GDNF nerotrophic factor for its application in Parkinson's disease and Alzheimer's disease. The synergistic effect of VEGF and GDNF released from these micro and nanospheres has led to improved rotational behaviour of the injured animals as well as to better protection and neuronal regeneration, and nanospheres loaded with VEGF were administered in a murine model of Alzheimer's disease (transgenic mouse APP/Ps1). After 3 months of treatment, an improvement was obtained in the cognitive deficit characteristic of these mice. An increase in angiogenesis and cerebral neurogenesis was also observed along with a decrease in B-amyloid plaques, so we can conclude that the administration of nerotrophic and angiogenic factors encapsulated in micro and nanospheres of PLGA could be an alternative for the treatment of neurodegenerative diseases.