Development of an silicone - based implant material for accommodable intraocular lenses (IOL)
Goal of the project is to provide an implant material together with a micro injection molding process for the development of an accommodable intraocular lens. Key properties of the material are high softness, flexibility, transparency, biocompatibility, and dimensional stability. Such a material is currently commercially not available.
The polydimethyl-methyl-phenyl-siloxane-block copolymers were synthesized for increasing the refractive indices of polysiloxanes. For applications as an a-IOL, the refractive index of the polysiloxanes must be equivalent to that of a young human eye lens. The polysiloxane molecular weight is controlled by the ratio of the cyclic siloxane to the endblocker APTMDS. The transparency of the PSU elastomers is examined by the transmittance measurement of films between 200 and 750 nm. Transmittance values at 750 nm (upper end of the visible spectrum) are plotted against the PDMS molecular weight, and > 90% of the transmittance is observed until a molecular weight of 23,000 g·mol−1. Mechanical properties of the PSU elastomers are investigated using stress-strain tests. For evaluating mechanical stability, mechanical hysteresis is measured by repeatedly stretching the specimens to 5% and 100% elongation. Hysteresis considerably decreases with the increase in the PDMS molecular weight. In vitro cytotoxicity of some selected PSU elastomers is evaluated using an MTS cell viability assay. The methods described herein permit the synthesis of a soft, transparent, and noncytotoxic PSU elastomer with a refractive index approximately equal to that of a young human eye lens.
/ Riehle, N., Thude, S., Athanasopulu, K., Kandelbauer, A., Tovar, G., Lorenz, G. /
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financial support & acknowledgement
The authors would like to thank the Federal Ministry of Education and Research (BMBF) for funding this work under grant number 13FH032I3. Financial support by the Deutsche Forschungsgemeinschaft (DFG, Gepris project 253160297) is gratefully acknowledged. The authors further like to express their thanks to Priska Kolb and Paul Schuler from the University of Tübingen for performing 1HNMR and 29SiNMR measurements. Thanks are also due to CSC Jäkle Chemie GmbH & Co. KG for their supply of H12MDI. The authors would like to thank Herbert Thelen and André Lemme from Biotronik for performing ethylene oxide sterilization of the PSU samples and Lada Kitaeva (Reutlingen University) for her support with stress-strain and hysteresis measurements.