IIT: first artificial organic retina successfully implanted in animal models
It works like a last-generation photovoltaic panel and can substantially restore visual function in case of blindness due to degenerative diseases of photoreceptors, including Retinitis Pigmentosa. This new artificial retina, the first ever built with carbon polymers, was developed by the researchers of the Italian Institute of Technology (IIT), who have submitted their results for publication to the international journal Nature Materials.
During the trial, some prototypes of the new organic retina were implanted into a sample of blind rats, carriers of a spontaneous genetic mutation in one of the genes implied in human Retinitis Pigmentosa. The implanted artificial retina can restore the pupillary reflex, electrical and metabolic responses to light stimuli in the cortex, the capacity of spatial discrimination (visual acuity) and light-guided animal orientation in the environment. This important recovery has remained stable for over 10 months after implant, without causing any inflammation to retina tissues nor degradation of prosthesis materials.
“This approach – said Fabio Benfenati, Director of the Centre of Synaptic Neuroscience (NSYN) in Genoa – is an important alternative to the methods we have used so far to restore neuron photoreceptive capacity. As compared to the two models of artificial retina currently available which are based on silicon technology, our prototype has a number of advantages including marked tolerability, long duration and full autonomy of functioning, with no need for an external power source. These ‘structural’ advantages are accompanied by restored visual function and not only in terms of light sensitivity, but also in terms of visual acuity and metabolic activity of visual cortex”.
In particular, the prosthesis is made of a double layer of organic polymers which are alternatively semiconductors and conductors stratified on a basis of fibroin, a protein that makes silk in nature. This device is able to convert light stimuli into an electric activation of retina neurons spared by degeneration, by mimicking the process assigned to cones and rods present in the healthy retina. “The use of this semiconductor organic material was crucial to address a number of issues – said Guglielmo Lanzani, Director of the ITT Centre for Nanoscience and Technology (CNST) in Milan. – Being organic, this material is soft, light and flexible, provides an excellent biocompatibility also avoiding complications to surrounding tissues, thus ensuring long-term functioning. Moreover, organic polymers can transmit electronic and ionic impulses without dispersing too much heat, which could cause additional damage to a retina which is already experiencing a degenerative process”.
Today, a new artificial retina is being tested in pigs that have eyes similar to those of humans in terms of size and microscopic structure. The aim is to start testing in men as soon as 2018, initially testing patients who are blind due to degenerative photoreceptor diseases, such as Retinitis Pigmentosa.