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Vesicles could help locate tumours or track medication

A new system for monitoring drugs and disease in the body using vibrating organic molecules is under development at Nottingham University.

Researchers are hoping to create a medical imaging system that can track the progress of disease, drug molecules or stem cells with tiny self-assembling structures that give off audio signals when exposed to an electric field.

These molecules, known as vesicles, act as beacons that can be detected with specialised microphones, allowing doctors to locate tumours or check that stem cells or drugs are reaching the desired part of the body.

‘You can functionalise these vesicles with molecules that will target, for example, cancers,’ principal investigator Dr Melissa Mather told The Engineer. ‘You can inject these into the body and they will migrate to the areas of disease.’

The vesicles can also be attached to drug molecules or stem cells, which doctors hope could be used to treat numerous conditions, such as cancer, Parkinson’s disease, diabetes and spinal injuries.

‘Often, for stem cell therapies, doctors inject a large population into the body but for some reason they disperse, or there aren’t enough for a therapeutic dose, and it’s very difficult to determine what’s happened,’ said Mather.

The researchers plan to create vesicles called liposomes, which are made from phospholipid fat cells found in biological cell membranes and already used to deliver drugs into the body.

To create the electric field, the team plans to experiment with MRI equipment and more portable surface electrodes, such as those used to take ECG readings.

When the liposomes collect in high-enough concentrations, the sound signals can then be picked up using a hydrophone (a microphone for use in water).

Liposomes are formed from smaller molecules that self-assemble into a bowl or bubble-like structure in water because one side of each molecule is attracted to water (hydrophilic) and the other is repelled by it (hydrophobic).

Because of the way the molecules are asymmetrically arranged, the liposome has an electric charge. In the presence of an electric field, the structure bends back and forth to produce a sound wave, much like a speaker cone.

To develop a working imaging system, the researchers plan to investigate ways to enhance the audio effect by increasing the asymmetry of the structure and so producing a bigger vibration that is easier to detect.

They may also need to develop a custom hydrophone, because the models currently used for detecting sound waves in the sea are unlikely to be sensitive enough.

The research is funded by a £733,000 grant from the EPSRC and also involves academics from Queensland University in Australia. The researchers hope to have an experimental prototype ready by 2016.


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