Our bodies have a wide variety of methods for guiding particular cells, enzymes, and molecules to specific structures inside them. White blood cells can find their way to the site of an infection, while scar-forming cells migrate to the site of a wound. However finding ways of guiding artificial materials within the body has proven to be more difficult.
In our previous post on nanotechnology, we looked at nano-sized robots being able to attach themselves to cancerous cells to deliver a payload of chemicals to kill them.
Now a team of researchers at MIT has demonstrated a new target-finding mechanism. The new system allows microscopic devices to autonomously find their way to areas of a cell surface, for example, just by detecting an increase in surface friction in places where more cell receptors are concentrated.
Cells have a way of locating areas that have a specific kind of chemical signature – a process called chemotaxis – which is the method used by white blood cells, for example, to locate regions where pathogens are attacking body cells.
The system, developed by MIT, without guidance, samples areas on a surface and migrates towards those where friction is greater, which also corresponds to areas where receptors are concentrated.
The system uses a pair of linked particles with magnetic properties. In the presence of a magnetic field, the paired particles begin to tumble across a surface, with first one particle and then the other making contact, thus creating an effect of walking across the surface.
So far, the work has been carried out on a model cell surface, on a functionalised microscope slide. According to MIT team member Alexander-Katz, the effect should also work similarly with living cells. The team’s goal now is to demonstrate the ability of these microscopic walkers to find their way towards concentrations of receptors in actual living tissue.
The method could potentially have a variety of applications. For example, it could be developed as a method of locating tumour cells within the body by identifying their surface texture, perhaps in combination with other characteristics.
Such magnetic micro-walkers could be unleashed to locate areas of interest on various kinds of surfaces, based solely on differences in friction. The particles naturally migrate toward high-friction regions, where they could then be induced to interact with a surface by active molecules attached to them.
The next step is to test the approach in more complex settings. The initial work was done with flat surfaces. The team now aims to conduct studies in complex settings to make sure the process works effectively in situations that more closely resemble a real cellular environment.
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