Miniature devices could deliver drugs directly to tumours

It is currently possible for nano-particulate drugs to be guided to a site in the body by encapsulating magnets into such delivery devices.

Sheffield University’s Dr Stephen Ebbens explained to The Engineer that drug delivery using magnetic fields requires either magnets to be located near the targeted site by implanting, which is invasive, or by applying the field externally, which involves a visit to hospital.

‘A drug-delivery system that can find its own way to the targeted site can potentially be administered as a conventional drug, without any additional intervention required,’ said Ebbens, who is leading Sheffield’s contribution to the EPSRC-funded project that involves Cornell University and the University of Wisconsin Madison in the US, in addition to Oxford University.

This, in turn, would lead to cost savings as there would be a reduced need for instrumentation, staff and patient visits to hospital.

However, the success of the system will depend on its ability to propel its way through the myriad of liquid environments encountered in the body on the way to the drug-delivery site.

For this reason, the team is designing a device that can change its shape according to its environment.

Ebbens proposes a self-assembling, shape-changing delivery system made from hydrogels.

In these water-permeable polymeric gels, the degree of interaction between the individual long molecules can be modulated by the presence of a particular chemical. 

‘As the interaction between chains becomes more attractive, a bulk reduction in size occurs, while making the chains repel causes the bulk material to expand,’ explained Ebbens, who is working in conjunction with Dr Jon Howse at Sheffield.

‘The ultimate goal is to use a material that can respond to a protein or other biological marker produced by a tumour. The device would then follow these biological “breadcrumbs” to reach the tumour.’

On reaching the tumour site, the device would be triggered to release drugs when it detects the concentration of a signalling molecule to be above a critical value.

‘The signalling chemical will ideally be a unique marker for the therapeutic delivery site,’ said Ebbens. ‘The first approach we are investigating is based on materials that change size in response to the signal. This size change could be used to release drug cargo from the surface of the delivery device, for example, by opening up pores or causing the physical detachment of other carriers, such as vesicles.’

Ebbens stressed that his research, which began in September 2011 and has received £896,741 worth of funding, is currently being performed at a fundamental level.

However, if successful, it has the potential to tap into the global market for nano-particulate drug delivery, which is predicted to reach $2,650m (£1,653m) by 2015.