In this project the Hector Fellows Manfred Kappes, Karl Leo, Martin Wegener and Eberhart Zrenner worked together with the HFA Postdocs Dr. Wadood Haq (Eberhard Karls Univer­sity, Tübin­gen) and Dr. Franz Selzer (TU Dresden). They devel­oped new micro electrodes based on high tech materi­als to improve the spatial and tempo­ral resolu­tion of neuronal stimu­la­tions. These high efficient electrodes shall be used for retinal implants and shall enhance the eye-sight of blind people.

World­wide millions of people suffer from blind­ness due to degen­er­a­tion of the light sensi­tive photore­cep­tor cells of the retina. To date there are no thera­pies avail­able to cure this progres­sive disease. However, promis­ing results for restora­tion of vision have been achieved in clini­cal trials with electronic retinal implants [Zrenner et al., 2013]. Blind patients with hered­i­tary retinal degen­er­a­tion were enabled to experi­ence some visual sensa­tions again: they local­ized objects of daily life; some of them could even identify large letters.

This inter­dis­ci­pli­nary project aims at optimiz­ing the inter­face of electrode mater­ial and neuron in order to improve tempo­ral and spatial resolu­tion of retinal implants by bring­ing together experts in the field of ophthal­mol­ogy and retinal implants, of novel electrode materi­als as well as of the synthe­sis and struc­tur­ing of such materi­als. The challenge on the one hand is the limited choice of electrode materi­als that are bio-compat­i­ble and on the other hand the high density of differ­ent neurons to be stimu­lated.
This optimiza­tion process will iterate through the loop of three steps:

1. Exper­tise in fabri­ca­tion of highly efficient electrodes (Prof. Leo & Dr. Selzer): To improve the spatial resolu­tion of the implant, the devel­op­ment of micro electrodes is planned.These electrodes will ideally allow the address­ing of single or few retinal cells by electri­cal stimulation.

2. Fabri­ca­tion of conduc­tive 3D microstruc­tures (Prof. Kappes & Prof. Wegener): Not only the size, but also the topol­ogy and the electric conduc­tiv­ity of electrodes have impact on the excita­tion of differ­ent functional cell types of the retina as well as on selec­tiv­ity and safety. Electrode arrays are being devel­oped that are suffi­ciently conduc­tive and that can be struc­tured into three-dimen­sional archi­tec­tures by using laser lithography.

3. Exper­tise of ophthal­mol­ogy and retinal implants (Prof. Zrenner & Dr. Haq): The efficiency and safety of the devel­oped electrodes for neuronal stimu­la­tion will be inves­ti­gated and evalu­ated in the ex-vivo retina of mouse models for retinal degeneration.

The inter­ac­tive feedback between the partners will allow contin­u­ous improve­ment of the electrodes. The final milestone of the project is to incor­po­rate the optimized electrodes in an implant (demon­stra­tor) for improved retinal stimulation.

Refer­ences:

[Zrenner et al., 2013] "Fight­ing Blind­ness with Micro­elec­tron­ics", Eberhart Zrenner, Science Trans­la­tional Medicine 2013, Vol. 5, Issue 210, pp. 210ps16, DOI: 10.1126/scitranslmed.3007399