A polymer that combines drug-eluting and self-cleansing agents could reduce the risk of bacterial infection through urinary catheters, say researchers at Queen’s University Belfast, UK.

The material, derived from esters of acrylic and methacrylic acid, is melt-extruded in a confidential multilayer extrusion mechanism to produce a catheter surface that continuously delivers antimicrobial agents over prolonged periods, minimising bacterial colonisation.

‘Although medical device technology has made significant advancements, the inherent problems associated with implanted urinary devices and the significant role microbial biofilms play in device-related infection are now widely recognised as major disadvantages of an otherwise highly effective treatment strategy’, says Dr Gavin Andrews, who is leading the project at the University’s School of Pharmacy.

Andrews believes that his team’s concept is unique as the material has been designed to respond intelligently in vivo to minimise the likelihood of microbial biofilm formation and encrustation on the device surface. ‘It has been shown that thermally-liable drugs can be processed using melt extrusion due to significant low residence time inside the extruder barrel’, he explains.

Although, the researchers say this is highly likely to prevent patients from developing infections, the Belfast team have designed a patent pending self-cleansing technology into the material that will initiate should this prevention mechanism fail.

‘This approach involves the production of self-shedding layers manufactured from pH-erodible polymers’, says Andrews. ‘During the process of infection, urea is broken down by urease-producing bacteria. This produces ammonia that elevates urinary pH. We are using this trigger to cause surface-shedding of the material.’

The shedded material would be passed out with the urine so there is no issue with break down of materials.

The team have now developed model laboratory materials representing clinically relevant devices.

Second skin

Andrews assessed the anti-biofilm of his efficacy by comparing antimicrobial-free and loaded films using microtitre susceptibility testing. The resistance of the engineered biomaterials to microbial adherence, which is the initial stage in medical device associated infection, and the formation of antibiotic-resistant microbial biofilm were measured using a disease control biofilm reactor.

Andrew Lewis at Biocompatibles UK, a medical technology company based in Farnham, believes that the work is a good example of materials innovation in the growing area of drug-device combination products.

‘The approach undertaken by Queen’s University Belfast seems sound, as they are moving beyond just the drug component by adding some stimulus-sensitive property to allow the catheter to respond to a potential infection.

‘However, there has been a great deal of research in this area and even some of the most antifouling surfaces have come unstuck in the presence of biofilms.’

He adds, ‘Moreover, there is an additional commercial tension, as these urinary products are considered relatively cheap commodities and the market dynamics may not bear the higher asking price that could be necessary for such complex combination products. That being said, a step-change in clinical performance may change the market perspective.’

Andrews says the team are in confidential talks with medical device companies to take the work further.