Measuring the activity that happens inside a cell in a living organism can be done today. However, the methods used to gain access to the inside of the cells are relatively crude and destructive. Often accessing the inside of the cells using today's methods kills the cell within only a few hours, if the cells survive the initial insertion of probes.

Scientists at Stanford University have developed a new nanoscale probe they have dubbed the "stealth probe" which can monitor the inner workings of a cell without causing damage to the cell. The probe can be used to capture the signals used by cells to communicate with each other and to monitor the so called "digestive rumblings" of the cells as they react to medications for up to a week.

The breakthrough came when the researchers developed a nanoscale probe that mimics the natural gateways within a cell that allows materials in and out of the cellular membrane according to one of the researchers , Nick Melosh. The team believes that with some modifications, their stealth probe could be used to insert medications directly inside the cells of the human body.

Another possible use would be in interfacing a new generation of prosthetic limbs with muscles that would allow direct control of the prosthesis just as the muscles controlled the natural limb. For instance, the muscles of the chest could be connected to an artificial arm using the probes.

The team used metal-coated silicon probes about 600nm long to develop their stealth probe. The tricky part of the design according to the researchers was developing a hydrophobic band that could be applied to the probe tip that was only a few nanometers thick.

Melosh said, "Getting that hydrophobic band just a few nanometers in thickness was an incredible technical challenge." The hydrophobic band was a very important part of designing a functional probe and getting the probe to be able to transfer materials in and out of the cell.

The probe is an artificial version of the transmembrane protein gateways that naturally occur inside cells. Melosh said, "What we have done is make an inorganic version of one of those membrane proteins, which sits in the membrane without disrupting it. Now we can envision using it for doing our own gate keeping." 

The next step in the research is to demonstrate a functional probe in living cells. The team is currently working with human red blood cells, cervical cancer cells, and ovary cells from a specific hamster species.

"Ideally, what you'd like to be able to do is have an access port through the cell membrane that you can put things in or take things out, measure electrical currents … basically full control," said Melosh. "That's really what we've shown – this is a platform upon which you can start building those kinds of devices."