A different drum
A thin, transparent membrane produced from silk fibres could provide a novel but simple solution to a problem that affects millions of people.
Up to 330 million people worldwide suffer chronic eardrum perforation as a result of infection, leading to hearing loss.
In Australia, one in six people suffer hearing impairment according to the Ear Science Institute Australia (ESIA).
The usual treatment for chronic eardrum perforations is a major procedure, requiring a full anaesthetic and surgery, taking a graft of muscle membrane or cartilage from the patient’s body and transplanting it to their eardrum. While most of these grafts can seal the perforation after surgery and reduce the chance of infection, the procedure cannot restore hearing or assist optimum regeneration of ear drum.
An alternative being developed by researchers at the Institute of Frontier Materials (IFM) and ESIA, as part of an ARC Linkage project, involves using fine silk membranes to replace damaged ear drums. Dr Rangam Rajkhowa and Dr Ben Allardyce are using the natural properties of silk fibres to produce an artificial eardrum which could be implanted in a simple outpatient procedure.
"The material needs a number of properties to be successful as a potential eardrum replacement," said Dr Rajkhowa. "It needs to be thin and able to vibrate like the natural eardrum, biocompatible, strong enough to resist inner ear pressure, to biodegrade when ear drum is regenerated, and easy to shape and manipulate during surgery."
The researchers process silk fibres obtained from various silk species, dissolve it in solution after purification and cast the solution into a thin (30-90 micrometres) transparent membrane. They are assessing different silk fibres sourced from India and China and looking at different formats e.g. solid sheets, perforated sheets, fibre reinforced or a mat of silk to optimise the biomechanical properties and produce a range of ear drums to suit patients with different conditions.
When inserted into the ear, the membrane acts as a bio-scaffold, allowing cells to grow on and into it. Eventually the silk dissolves and leaves behind the new cells.
Researchers at ESIA have begun experiments to try and grow human eardrum cells on the membrane. In experiments where silk membranes have been implanted in the perforated ears of rats and guinea pigs, cells are starting to grow back much faster and more regularly on silk compared to other materials and there are no signs of any adverse effects after six months of study.
The team at IFM and ESIA has recently received a NHMRC development grant and ESIA hopes to start conducting clinical trials in humans in 2014.