Nanocarriers have demonstrated the ability to transport GDNF across the BBB [83]; however, there is still a gap in the development of NPs that are capable of increasing the efficiency of GDNF uptake, delivery across the BBB, and site-specific targeting to realize the full potential of GDNF-conjugated NPs in the treatment of early stage PD. The gene discussed is GDNF; the disease is Parkinson disease.