MAGNETIC nanoparticles targeted to nerve cell membranes can be used to remotely control cellular activity and even the simple reflex behaviours of nematode worms, according to research by a team of biophysicists at the University of Buffalo. The new method, which is described in the journal Nature Nanotechnology, could be very useful for investigating how cells interact in neuronal networks, and may eventually lead to new therapies for cancer and diabetes.
Heng Huang and her colleagues synthesized manganese-iron nanoparticles, each just 6 millionths of a millimeter in diameter, and coated with the bacterial protein straptavidin attached to a fluorescent molecule called DyLight549. Strepdavidin binds another molecule, much like a key fits into a lock, enabling specified cells to be targeted, while DyLight549 acts like a molecular thermometer, whose fluoresence intensity changes with temperature.
BRAIN implants containing microelectrodes are used widely in the laboratory and clinic, both to stimulate nerve cells and to record their activity. Researchers routinely implant electrode arrays into the brains of rodents to investigate the neuronal activity associated with spatial navigation, or into monkeys’ brains to gain a better understanding of the mechanisms of motor control. As a result, we now have brain-computer interfaces that can help paralysed patients to communicate or control a prosthetic limb. Electrode arrays can also be used to assess vegetative patients, and to treat conditions such as Parkinson’s Disease and depression.
In most instances, keeping the electrodes in place for long periods of time is crucial. But this is difficult, for a number of reasons. In experiments involving freely moving rats, for example, the animal’s movements can cause the electrodes to be displaced, and when they do stay in place, the electrodes become gradually become ensheathed with glial cells, causing the signal to deteriorate with time. The devices have to be re-adjusted regularly, and their decoding algorithms recalibrated, to maintain the signal strength. Implants containing movable electrodes can potentially overcome these problems. The latest such device (described in a new paper in the journal Frontiers in Neuroengineering) is the most advanced yet. It uses microelectromechanical systems (MEMS) to move the electrodes up and down, and can record stably for up to 6 months.