Early research, and with rodents, but very interesting.

Researchers have developed a new, non-invasive and non-toxic genetic therapeutic technique to restore dopaminergic neuron function in rats suffering from Parkinson’s disease. The technique, which makes use of magnetic-resonance-image-guided ultrasound and brain-penetrating nanoparticles, reverses neurodegeneration thanks to expression of the neurotrophic growth factor GDNF in motor-neuron pathways. A singe injection of the nanoparticles continues to act for at least 10 weeks.

Brain-penetrating nanoparticles restore neuron function - nanotechweb.org

http://pubs.acs.org/doi/abs/10.1021/...nolett.7b00616