In the strictest sense, nanorobots are still conceptual: the Oxford English Dictionary definition of nanorobots (nanobots) is hypothetical very small (nanoscale) self-propelled machines, especially ones that have some degree of autonomy and can reproduce. While this definition that includes autonomy and reproducibility is one for the farther future, in reality there are a number of nanoscale inorganic objects that have already been in use in the body for some time in a variety of medical applications. So far, the activity scope of these nano-objects has been pathology resolution, but the same kinds of techniques and characterization of the underlying biological processes could be explored for enhancement purposes.
The most developed area of nanomedicine is nanoparticle drug delivery (designed particles that disgorge cargo in cellular destinations per simple onboard logic instructions) and other therapeutic techniques, followed by nano-diagnostics, and nano-imaging (like quantum dot imaging) (Boysen 2014). Some of the more recent interesting applications are nanosponge waste soak-up and biomimetic detoxification (Hu 2013), optogenetics (controlling the brain with light) (Klapoetke 2014), and neural dust brain sensors that might be able to read whole sections of brain activity externally (Seo 2013). The current status of the development of neural nanomedicine is well covered in the scientific literature (Provenzale 2010, Kateb 2013, Schulz 2009, Mavroidis 2014, and Boehm 2013).
Thinking in the longer-term, Robert Freitas has designed several classes of medical nanorobots such as respirocytes, clottocytes, vasculoids, and microbivores that could perform a variety of biophysical clean-up, maintenance, and augmentation functions in the body (Freitas 2003). One example of neural nanorobotic clean-up is autonomous diamondoid “defuscin” class nanodevices. These are conceptual nanodevices designed to eliminate the residual lipofuscin waste granules in lysosomes (the ‘trash compactor’ of the cell) that the body cannot fully digest.
Boehm, F. (2013). Nanomedical Device and Systems Design: Challenges, Possibilities, Visions. New York, NY: CRC Press, especially Chapter 17: Nanomedicine in Regenerative Biosystems, Human Augmentation, and Longevity, 654-722.
Boysen, E. (2014). Nanotechnology in Medicine – Nanomedicine. UnderstandingNano.com. Retrieved from http://www.understandingnano.com/medicine.html.
Freitas, R., Jr. (2003). Nanomedicine, Vol. IIA: Biocompatibility. Austin, TX: Landes Bioscience.
Kateb, B. & Heiss, J.D. (Eds). (2013). The Textbook of Nanoneuroscience and Nanoneurosurgery. New York, NY: CRC Press.
Klapoetke, N.C., Murata, Y., Kim, S.S., Pulver, S.R., Birdsey-Benson, A., et al. (2014). Independent Optical Excitation of Distinct Neural Populations. Nature Methods, 11, 338–346.
Mavroidis, C. (2014). Nano-Robotics in Medical Applications: From Science Fiction to Reality, Northeastern University. Retrieved from http://www.albany.edu/selforganization/presentations/2-mavroidis.pdf.
Provenzale, J.M. & Mohs, A.M. (2010). Nanotechnology in Neurology: Current Status and Future Possibilities. US Neurology, 6(1), 12-17.
Seo, D., Carmena, J.M., Rabaey, J.M., Alon, E., Maharbiz, M.M. (2013). Neural Dust: An Ultrasonic, Low Power Solution for Chronic Brain-Machine Interfaces. arXiv, 1307.2196 [q-bio.NC]. Retrieved from http://arxiv.org/abs/1307.2196.
Schulz, M.J., Shanov, V.N., Yun, Y. (Eds.). (2009). Nanomedicine Design of Particles, Sensors, Motors, Implants, Robots, and Devices. New York, NY: Artech House.