Zukunftsfähige medizinische Implantate

Functionalized Middle Ear Prostheses
Funktionalisierte Mittelohrprothesen
Dr. Nina Ehlert, Tammo Lüßenhop, Olga Kufelt, Rebecca Lensing, Daniela Hesse, Nils
Prenzler, Dr. Martin Stieve, Prof. Thomas Lenarz, Muhammad Badar, Prof. Peter P. Müller,
Laura Doniga-Crivat, Dr. Silke Besdo, Prof. Peter Wriggers, Prof. Peter Behrens
The aim of this project is the development of optimized middle ear implants, on the one hand
by employing novel biomaterials to support the healing process after replacement of the
ossicular chain and on the other hand by simulation techniques to achieve optimal
functionality.
As base for the functionalization of middle ear implants we chose prostheses made of
Bioverit® II, a glass mica ceramic, and coated them with a nanoporous silica layer.
Nanoporous materials are currently being investigated for possible applications as
biomaterials. In several investigations we were able to show that nanoporous silica is
basically biocompatible and has even a positive effect in the middle ear. [1-3]. Nevertheless
modern biomaterials need to exhibit more specific biological functions. Therefore, we
modified nanoporous silica and, for comparison, amorphous silica coatings with BMP2 (bone
morphogenetic protein 2), a signalling protein which induces differentiation of bone-forming
cells. The aim of this strategy was a stronger fixation of the prosthesis by establishing a
connection between the prosthesis and the residual stapes bone. We have tested the
biochemical and biological activity of BMP2 attached to the surface of nanoporous and plain
amorphous silica. Additionally we made first in vivo experiments in a rabbit model.
Furthermore the nanoporous silica layer can be employed as a drug delivery system. We
made investigations with the antibiotic ciprofloxacin which is known to be effective against
bacteria like Pseudomonas, which cause typical infections in the middle ear. Further
functionalizations were developed to achieve a controlled release rate and to reduce the
initial burst effect often observed [4]. The materials exhibit a good antibacterial efficacy
against luminescent bacteria in vitro and in a rabbit and in a mouse model in vivo. Another
approach to fight against chronic inflammations in the middle ear is the development of an
antibacterial coating based on polymers.
During the next period the main focus will be on the implant-tissue interactions and the
healing process in the region of the ear drum as well as the addition of a cushioning element.
The aim is the development of a collagen-composite scaffold which is supposed to act as a
cushioning element between the ear drum and the prosthesis. Furthermore a combination
with nanoporous silca nanoparticles in order to realize a drug delivery of antiproliferativa is
possible. Simulation techniques support the development of the composite scaffold in order
to optimize its shape and sound transmission behaviour.
[1] C. Turck, G. Brandes, I. Krueger, P. Behrens, T. Lenarz, M. Stieve, Acta Oto-Laryngology 127, 8
(2007) 801-808.
[2] J.C. Vogt, G. Brandes, I. Krueger, P. Behrens, I. Nolte, T. Lenarz, M. Stieve, J. Mater. Sc.: Mater.
Med. 19, 7 (2008) 2629-2636.
[3] J.C. Vogt, G. Brandes, N. Ehlert, P. Behrens, I. Nolte, P.P. Mueller, T. Lenarz, M. Stieve, J.
Biomater. Appl. 24, 2 (2009) 175-191.
[4] N. Ehlert, M. Badar, A. Christel, S.J. Lohmeier, T. Luessenhop, M. Stieve, T. Lenarz, P.P. Mueller,
P. Behrens, J. Mater. Chem., 2011, DOI: 10.1039/C0JM01487G.
TP D1 Dr. rer. nat. Nina Ehlert