Hermetic and biocompatible encapsulants for retinal prostheses

POLY 369

Carmen Scholz, cscholz@chemistry.uah.edu1, Willy Vayaboury1, Robyn Sweitzer1, Doug Shire2, and Joseph Rizzo3. (1) Department of Chemistry, University of Alabama in Huntsville, John Wright Drive, MSB, Huntsville, AL 35899, (2) Cornell University, Ithaca, NY, (3) The Boston Retinal Implant Project, Harvard Medical School, Boston, MA 02103
Age-related macular degeneration and retinitis pigmentosa are both blindness-causing, incurable diseases, characterized by a progressive photoreceptor-loss with the neuronal retina remaining intact. Thus, retinal prostheses could restore some degree of vision by electrically stimulating intact ganglia, following an electrode stimulation pattern transcribed from an electronically captured image. After implantation into the subretinal space, retinal prostheses (microfabricated PI flexcircuits) must be (i) hermetically sealed guaranteeing long-term electrical function and (ii) biocompatible, ideally without any tissue response. Diamond-like carbon (by pulsed laser ablation and vacuum arc vapor deposition) and amorphous aluminum oxide (by argon ion beam sputtering) were investigated as hermetic sealants. Block copolymers of PEG and poly(amino acids), poly(Lys), poly(Asp), poly(Glu) were synthesized by using amino-terminated PEG as macroinitiator for the anionic ring-opening polymerization of N-carboxyanhydrides of the respective amino acids. Subsequent thiolation of the poly(amino acid) block provides multiple anchoring groups for the block copolymer. Results on materials synthesis, characterization, deposition, biocompatibility and histology will be presented.