In addition, macrophages transfected with glial cell line-derived neurotrophic factor (GDNF) can migrate to the brain after systemic administration and almost completely restore motor function in PD mice.203 The drug-loaded nanoparticles can be coated by macrophage plasma membranes204 or neutrophil-macrophage hybrid membranes,205 which facilitates crossing the BBB for treating GBM. The gene discussed is GDNF; the disease is Parkinson disease.