University of Chicago researchers have discovered that human endothelial cells eat nanowires, opening up a plethora of possibilities for the development of bioelectrical devices that work at the single-cell level. The discovery raises the exciting prospect of being able to monitor communication between organelles inside cells and enable physicians to deliver drugs inside cells.
The research team, led by Bozhi Tian, discovered that silicon nanowires are consumed by cells in a process called phagocytosis – just as immune system phagocytes consume, kill and digest bacteria. The team was able to observe the activity using a combination of electron microscopy and a new imaging technique – scatter-enhanced phase contrast (SEPC) – designed to show the movement of the nanowires into the cells. The imaging technique uses dark field imaging to show the nanowires and phase contrast imaging for observing the cell.
The researchers showed that the outer membrane of the cells fold inwards to create a pocket and take in the nanowires; enveloping them in membrane-lined bubbles. The nanowires are then transported close to the cell nucleus, often at high speed. Movement of up to 99.4 nanometers per second was recorded by the team.
Interestingly, the process occurred in endothelial cells that line the blood vessels. Endothelial cells form a barrier that is difficult to penetrate with drugs. By using nanowires, it is possible that drugs could be taken inside cells and delivered in tiny quantities. The team also suggests the nanowires could be used to electrically stimulate certain parts of cells with precision, for example, stimulating mitochondria from within a cell. Potentially, optogenetics could be incorporated, allowing light to be introduced inside cells to stimulate cellular activity.
The exact process of how the cells take in the nanowires needed to be studied before any potential applications could be developed. Now that the process has been documented, potential applications can now be seriously considered.
While the team was able to observe the activity in endothelial cells, not all cells have the phagocytosis mechanism. The team was able to show that smooth muscle cells behaved in a similar way, although the process did not work in neuron and cardiac cells. The researchers suggest that at some point it may be possible to make some surface moderations to allow nanowires to be incorporated into other cell types.