A method and system that is directed to the local delivery of growth factors to the mammalian CNS to treat CNS disorders associated with neuronal death and/or dysfunction is described.

This disclosure is directed to mixed micelle compositions for administration of e.g., therapeutic agents or imaging agents to a subject.

Nanoclusters comprising inorganic nanocrystals and a biodegradable polymer are disclosed. The inorganic nanocrystals have a mean particle size of 1 to 500 nm. The inorganic nanocrystals are contained within a core of the nanoclusters, on the surface of the nanoclusters, contained within a core of the nanoclusters, dispersed throughout the nanoclusters, or a combination thereof. The biodegradable polymer allows the inorganic nanocrystals to be excreted renally over a period of time. The nanoclusters can be used for medical imaging or other biomedical applications.