The utilisation of naturally occurring protein nanomachines will be used as the basis for a technology that may restore vision and thereby benefit millions of people worldwide that are suffering from retinal degenerative diseases. This project will seek to develop a novel artificial retina, built around the photosensitive protein, bacteriorhodopsin, which represents the utmost example of a “bottom-up” approach and the ideal design of modern nanotechnology.
This project combines a highly sophisticated nanomachine derived and optimized through natural evolution, with current state of the art in microfabricated electronic circuitry and sensors. The result is a device that is directly powered by incident light, does not require any external power supplies or bulky hardware, and offers the potential for far greater visual resolution than competing electrode-based technologies.
The development of a high-resolution integrated microsensor array that combines optical, electrical, and electrochemical pixels will constitute a key element of the project work. The array will be used to probe the function of ordered arrays of bacteriorhodopsin through a direct optical investigation of the active (light absorbing) state while recording the charge redistribution and subsequent translocation of protons. The proton translocation couples downstream to stimulate the remaining nerve cells in the retina to give a perception of sight.
Such functional verification has yet to be reported and will generate additional insight into protein behaviour as well as facilitating the development and optimization of implantable devices using bacteriorhodopsin as the photo-transducing element.
The aim of this proposal is to develop a high-resolution integrated microsensor array for rapid evaluation of biomolecular retinal implant prototypes based on photosensitive proteins. The array will consist of combined optical, electrical and electrochemical pixels that will measure the proton pumping action of bacteriorhodopsin (BR). A multiple sensor configuration will provide a direct optical investigation into the active (light absorbing) state of the protein while recording the charge redistribution and subsequent translocation of protons. Such functional verification has yet to be reported in scientific literature and would generate additional insight into protein behaviour as well as facilitating the development of implants using BR as the photo-transducing element.
The sensors will be derived from micro- and nanotechnology and consists of photodiodes that mimicking the function of the biological retina. Each photodiode will be associated with an ion sensitive field effect transistor (ISFET) which records the ionic current originating from the proton translocation, and a platinum electrode detecting the amperometric signal originating from the charge displacement of the BR molecule. These three sensors form a collective single "pixel" in the microarray, which will vary in size from approx. 25 to 50 micrometers square. The retina implant will be incorporated on the microsensor array and consist of BR that is connected in series through a layer-by-layer deposition process. This will amplify the light induced ionic signal to a level that should depolarise intact bipolar cells in the retina in order to restore vision.
This proposal builds on results obtained on a pre-project linked with a Leiv Eiriksson mobility award in which the photoactive and inactive state of BR films could be discriminated by CMOS photopixels without the use of any focusing lenses.