Biomaterials test could prevent medical trauma

A new way of testing biomaterials that could help to avoid a repeat of the vaginal mesh scandal has been developed by researchers at Sheffield University.

PP mesh material before and after being tested using the new Sheffield method (Image: Sheffield University)

Researchers led by Dr Nicholas Farr from the University’s Department of Materials Science and Engineering have developed an oxidative stress test that can form the basis of an early-warning system to identify biomaterials that are not suitable for clinical use inside the human body. The team’s findings have been published in RSC Advances.

Compared to current methods, the new approach is claimed to be better at simulating deployment environments and identify cracks and surface degradation in biomaterials.

The test subjects biomaterials to oxidation and mechanical stresses, which would be experienced inside a patient, and can give biomaterials producers a better understanding of how their materials will perform over time in clinical use and any issues that are likely to occur should they be used as a medical treatment.

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The researchers developed their procedure by evaluating a type of surgical mesh made of polypropylene (PP mesh), which has been used to treat pelvic organ prolapse and stress urinary incontinence, a condition that affects 50 per cent of postmenopausal women. The use of PP mesh has caused life-changing complications in thousands of women and led to medical negligence lawsuits.

According to the University, manufacturers assert that PP material is inert and non-degradable, but an increasing body of evidence reveals PP meshes are subject to oxidative damage, which is supported by explanted material from patients suffering with clinical complications showing evidence of fibre cracking and oxidation.

The new testing method developed by the Sheffield researchers could form the basis of an early-warning system against these types of failures as it can detect inappropriate material at the nanoscale.

In a statement, Dr Nicholas Farr, EPSRC Doctoral Research Fellow at Sheffield University, said: “The process starts with subjecting the material to conditions which mimic the natural processes of oxidation and mechanical stress experienced within the human body.

“This is followed by analysis using novel material characterisation techniques to evaluate the nanoscale surface of the material.

PP mesh inside the bioreactor that is used in the test – this is how the new method enables the researchers to put the material under the same pressure and conditions it would experience inside the human body (Image: Sheffield University)

“It is envisioned that the process outlined has the potential to form the basis of an “early warning” analysis system which possesses the ability to identify materials which are not suitable for clinical deployment within the human body.

“My hope is that this research can not only aid the development of new implantable materials but also help to update the regulatory standards which govern medical device production.”

Investigation

Using this new technique, the Sheffield researchers have been able to further investigate why the PP mesh was not suitable for use in the pelvic floor.

The researchers found that the stress loaded onto the PP mesh while inside the body is likely to have caused polymer oxidation and chemical reactions in the materials – this oxidation and these reactions are likely to have changed the material’s molecular structure, causing the material to crack and the release of etched oxidised insoluble particles initiating an inflammatory response in the body.

Emeritus Professor Sheila MacNeil, who has worked with NHS Consultant Professor Chris Chapple to develop alternative safer materials for use in the pelvic floor, said:“The polypropylene material used to provide support in the pelvic floor is very strong but has produced severe complications in many women.

“In this study we looked to see how the material performed under simulated stress conditions.

“We stretched the material repeatedly for three days, subjected it to mild oxidative stress and then we used the very sensitive test to reveal tiny fissures and cracks in the surface of the material. Our extensive study has shown this material does not cope well under pressure.”