1. Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA.
2. Department of Experimental Medical Science, Neuronano Research Center, Lund University, BMC F10, 221 84 Lund, Sweden.
3. Department of Cell Biology, Duke University, Durham, NC 27710, USA.
4. Center for Neuroengineering, Duke University, Durham, NC 27710, USA.
5. Department of Biomedical Engineering, Duke University, Durham, NC 27710, USA.