Intranasally delivered NPs formed by DNA coding for glial cell line-derived neurotrophic factor (GDNF) complexed with polyethylene glycol (substituted with lysine residues) showed peak expression in the rat striatum a week after administration and neuroprotective action in a rat model of Parkinson’s disease (PD) [16]. The gene discussed is GDNF; the disease is Parkinson disease.