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Development of fully dissolvable devices and application as implanted neuroprostheses

Periodic Reporting for period 1 - Edible Neuroprosthetics (Development of fully dissolvable devices and application as implanted neuroprostheses)

Reporting period: 2016-04-01 to 2018-03-31

Neuroprosthetics aims at the development and intimate integration of artificial devices with the neural tissue, in order to restore impaired or lost human functions, such as sensory and motor behaviours (1,2). One of the main issues in Neuroprosthetics is represented by the materials used in electronic devices, such as metal and silicon, that are quite different from those exploited in biology by nature (3). Due to their structural kinship to biological building blocks and their ability to support electronic as well as ionic transport, carbon-based materials like conjugated polymers became attractive candidates for the translation between the electron-based world of electronics and the ion- and molecular-based world of biology. Their key enabling features, such as being biocompatible, biodegradable, soft and conformable, combined with their conductivity make them suitable for the design of devices with similar functionality as traditional electronics. Nevertheless, the main limiting factor of these materials is their natural biodegradability, which limits the device lifetime in the biological environment up to few months. As a consequence, the research effort in organic bio-electronics is now focused on evaluating new fabrication and encapsulation strategies to obtain highly biocompatible implants with an extended lifetime. On the contrary, transient bio-electronics is an emerging field exploiting standard inorganic electronic devices capable of disappearing in the body in a controlled manner, with a time-scale ranging from days to months or years (4,5). Transient devices could find application as implantable diagnostic or therapeutic tools in order to avoid long-term side effects and eliminate the need for retrieval. Edible Neuroprosthetics aims at diverting the paradigm in organic bio-electronics by exploiting the transient concept. Effectively, it benefits from the natural feature of conductive polymers to disappear in the body, in order to create highly compatible and transient prosthetic devices. In summary, Edible Neuroprosthetics exploits soft organic polymers as material of choice for the development of innovative implantable and dissolvable prosthetic devices.

[1] Zrenner, E. Sci Transl Med (2013).
[2] Borton, D. et al. Sci Transl Med (2013).
[3] Lanzani, G. Nature Materials (2014).
[4] Hwang, S.-W. et al. Science (2012).
[5] Hwang, S.-W. et al. Nano letters (2015).
During the project, I designed, fabricated and characterized a transient electrode array prototype for neural recordings entirely based on biocompatible polymers. The characterization includes electrochemical properties and recording performance of the device, as well as biocompatibility and degradability evaluation of the materials used.
Full absorbability of the device is currently under investigation. A series of neural probes were fabricated and implanted in mice brains (visual cortex area) to assess the materials durability in-vivo. Several time-points (1, 3, 6, 9 and 12 months) have been established for the implant analysis in order to have a better comprehension of the degradation process within the biological environment and the response of the biological environment itself to the insertion of the selected materials.
Results on the advancements of this project have been presented as poster and oral contributions at the following international conferences:
- International Conference on Organic Electronics 2017, Saint Petersbourg (RUS) 4th-8th June 2017 (poster)
- Materials Research Society Fall Meeting 2017, Boston (MA, USA) November 26th-December 1st 2017 (oral)
- Gordon Research Conference Neuroelectronic Interfaces, Galveston (TX, USA) 25th-30th March 2018 (poster)
The Edible Neuroprosthetics project is thought to tackle an extremely challenging research issue. Its originality relies on the use of soft organic materials (instead of silicon and metals) as building blocks for neuroprosthetic devices, an approach that is still at its infancy in this field. The fact that the devices are conceived to be literally demolished and digested by cells in the host represents the most innovative aspect in countertrend with respect to the majority of research projects in this area. By exploring highly performing organic materials and deposition processes compatible with flexible substrates, I contributed to pen a new field of research.
The scientific advancement provided by the project will have a major impact on the entire Neuroprosthetic field, by paving the way for a new set of implants characterized by the transient presence in the body. This will have a major impact in term of tolerability, avoiding the need for surgical retrieval, and greatly reducing their invasiveness. Overall, this concept will make the field of Neuroprosthetics much more attractive and helpful for medical application.
Degradable electrode array