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Implantable hearing aidA new implantable hearing aid is under clinical study at the University of Tübingen, Germany. A sound receiver is implanted in the wall of the ear canal, the battery and processor are subcutaneouly implanted behind the ear and an electro-mechanical transducer is implanted in the mastoid and laser-welded to the incus bone of the middle ear. The different elements of the hearing aid are housed in titanium capsules. The battery is rechargeable and the hearing aid external elements are expected to last for up to 5 years. All 5 patients receiving the hearing aid have so far esxperienced improved hearing of 20-60%. The US company Symphonix Devices, has also developed hearing aids that use internally-implanted sound processors, with or without externally-implanted processors to boost reception of higher-frequency sounds. New orthopaedic implantsMedical software may be quite important for the success of new orthopaedic implants, and will certainly be vital for the type of customised implant created by CAD-stereolithography that is being investigated for certain uses such as maxillofacial and spinal surgery. The US company Integrated Surgical Systems, that has also developed the ROBODOC surgcial assistant, is undertaking a number of joint-development agreements to tailor its software to specific manufacturers’ hip implants. The latest agreement was recently announced with Zimmer, adding to those in place with Johnson & Johnson, Aesculap, DePuy, Howmedica, PLUS Endoprosthetik and Biomet. Biomaterials include living cellsThe biomaterials of the future may well include living cells. Biomaterials technology may also be useful in organ replacement. Short-term extracorporeal devices to maintain liver function are already well-developed in USA and under development in the EU. Artificial pancreases have also bee manufactured and studied in small-scale clinical work. One avenue of cell research that may by-pass biomaterials altogether is direct transplant of cells. Some degree of success has already been achieved with use of fetal brain cells to aid Parkinson’s disease patients. A trial of direct injection of pancreas islet and stem cells, under cover of anti-rejection drugs and anti-interleukin-2-receptor antibodies, is being carried out at the Diabetic Research Institute of the University of Miami USA, with the hope that the problems of immune rejection of donor cells will be avoided. Bioerodible depot injection polymersDespite many years of work, reliable long-term medication with protein drugs has had only patchy success. Part of the problem lies with biochemical and physical changes, including polymerisation and degradation, which larger proteins can undergo. A model protein, bovine somatotropin, still requires daily injections and the difficulties of devising adequate long-term delivery (as well as the regualtory issues) have driven most companies away from commercialising this product for animals. The global leader in commercialising solid-state and polymer-based delivery systems, Alza Corporation (Palo Alto California) has now developed bioerodible depot injection polymers that will allow delivery of proteins for up to 28 days. The first targets will be human use but it will be interesting to see if this developments leads to a resurgence of interest in bovine and porcine somatotropin for milk and meat production.
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