"Introduction: The acquisition of neural signals from the brain cortex has always been of high relevance in the field of neuroscience in order to analyze and interpret brain processes as well as individuate neurological diseases and disorders . Nowadays, the design of a neural interface conformable with the brain tissue is one of the major challenges, since the inadequate conformability might lead to inaccurate signal recording and potential misdiagnosis .
Methodology: In this research, we design and produce a soft neural interface composed of polyacrylamide hydrogel loaded with plasmonic silver nanocubes to provide the system with good electrical properties. The hydrogel nanocomposites are surrounded by a template of two layers of silicon-based materials (i.e. polydimethylsiloxane and soft skin adhesive) as supporting elements for guaranteeing a tight and stable neural-hydrogel contact, while allowing a stable recording from specific locations of the brain cortex.
Results: The morphological, chemical, electrical, and mechanical properties of the platform are evaluated. The hydrogel nanocomposites show superior conductivity properties, while mimicking the brain tissue mechanical characteristics. Furthermore, in vitro biological tests performed by seeding neural progenitor cells reveal the biocompatibility of the hydrogel-based system as well as neural differentiation and proliferation. In vivo experiments on a mouse model demonstrate that the hydrogel nanocomposite-based neural interface permits the efficient recording of neural signals with augmented amplitude. Additionally, chronic neuroinflammation tests reveal no adverse response towards the proposed platform.
Conclusions: The biocompatible conductive hydrogel nanocomposite-based device is a promising candidate as neural interface for brain signal acquisition without provoking neuroinflammation. The potential exploitation of the proposed conductive hydrogel platform in electronic devices for Electrophysiological Recording of Electrocorticographic or Electroencephalography Recording will be investigated in the near future.
This study was supported by the First TEAM grant number POIR.04.04.00-00-5ED7/18-00, which is conducted within the framework of the First TEAM programme of the Foundation for Polish Science (FNP) and co-financed by the European Union under the European Regional development Fund.
 Nam, J. et al., ACS Nano 14, 664−675, (2020).
 Rinoldi, C. et al., Biomacromolecules 22, 3084-3098, (2021)."