Biology subjects

Airaghi Leccardi, M. J.

Publications and source records attributed to Airaghi Leccardi, M. J..

4 recordsLinked to original sources

bioRxiv2022

Conformable neural interface based on off-stoichiometry thiol-ene-epoxy thermosets

Off-stoichiometry thiol-ene-epoxy (OSTE+) thermosets have recently gained attention for the rapid prototyping of microfluidic chips because they show low permeability to gases and little absorption of dissolved molecules, they allow direct low-temperature dry bonding without surface treatments, they have a low Youngs modulus, and they can be manufactured via UV polymerisation. The compatibility with standard clean-room processes and the outstanding mechanical properties make OSTE+ an excellent candidate as a novel material for neural implants. Here we exploit OSTE+ to manufacture a conformable multilayer micro-electrocorticography array with 16 platinum electrodes coated with platinum black. The mechanical properties allow device conformability to curved surfaces such as the brain. The low permeability and strong adhesion between layers improve the stability of the device. Acute experiments in mice show the multimodal capacity of the array to record and stimulate the neural tissue by smoothly conforming to the mouse cortex. Devices are not cytotoxic, and immunohistochemistry stainings reveal only modest foreign body reaction after two and six weeks of implantation. This work introduces OSTE+ as a promising material in the field of implantable neural interfaces.

bioengineering↗

bioRxiv2022

Three-dimensional multilayer concentric bipolar electrodes enhance the selectivity of optic nerve stimulation

ObjectiveIntraneural nerve interfaces often operate in a monopolar configuration with a common and distant ground electrode. This configuration leads to a wide spreading of the electric field. Therefore, this approach is suboptimal for intraneural nerve interfaces when selective stimulation is required. ApproachWe designed a multilayer electrode array embedding three-dimensional concentric bipolar electrodes. First, we validated the higher stimulation selectivity of this new electrode array compared to classical monopolar stimulation using simulations. Next, we compared them in-vivo by intraneural stimulation of the rabbit optic nerve and recording evoked potentials in the primary visual cortex. Main resultsSimulations showed that three-dimensional concentric bipolar electrodes provide a high localisation of the electric field in the tissue so that electrodes are electrically independent even for high electrode density. Experiments in-vivo highlighted that this configuration leads to evoked responses with lower amplitude and more localised cortical patterns due to the fewer fibres activated by the electric stimulus in the nerve. SignificanceHighly focused electric stimulation is crucial to achieving high selectivity in fibre activation. The multilayer array embedding three-dimensional concentric bipolar electrodes improves selectivity in optic nerve stimulation. This approach is suitable for other neural applications, including bioelectronic medicine.

bioengineering↗

bioRxiv2020

Tailored polymeric, photovoltaic, and near-infrared-responsive neuroprosthesis

Organic materials, such as conjugated polymers, are attractive building blocks for bioelectronic interfaces. In particular, organic semiconductors showed excellent performances in light-mediated excitation and silencing of neuronal cells and tissues. However, the main challenges of these organic photovoltaic interfaces compared to inorganic prostheses are the limited stability of conjugated polymers in the aqueous environment and the exploitation of materials only responsive in the visible spectrum. In this report, we show a new photovoltaic organic interface tailored for neuronal stimulation in the near-infrared spectrum. Also, we adjusted the organic materials by chemical modification in order to improve the stability in aqueous environment and to modulate the photoelectrical stimulation efficiency. As proof of principle, we tested this interface for retinal stimulation. Our results provide an efficient, reliable, and stable implant applicable for neural stimulation.

bioengineering↗

bioRxiv2019

Photovoltaic stimulation efficiently evokes network-mediated activity of retinal ganglion cells

ObjectivePhotovoltaic retinal prostheses theoretically offer the possibility of standalone high-resolution electrical stimulation of the retina. However, in artificial vision, achieving locally selective epiretinal stimulation is particularly challenging, on the grounds of axonal activation and electrical cell coupling.\n\nApproachHere we show that electrical and photovoltaic stimulation of dystrophic retinal circuits with capacitive-like pulses leads to a greater efficiency for indirect network-mediated activation of retinal ganglion cells. In addition, a biophysical model of the inner retina stimulation is proposed to investigate the waveform and duration commitments in the genesis of indirect activity of retinal ganglion cells.\n\nMain resultsBoth in-vitro and in-silico approaches suggest that the application of long voltage pulses or gradual voltage changes are more effective to sustainably activate the inner excitatory and inhibitory layers of the retina, thus leading to a reproducible indirect response. The involvement of the inhibitory feedback from amacrine cells in the forming of indirect patterns represents a novel biological tool to locally cluster the response of the retinal ganglion cells.\n\nSignificanceThese results demonstrate that recruiting inner retina cells with epiretinal stimulation enables not only to bypass axonal stimulation but also to obtain a more focal activation thanks to the natural lateral inhibition. In this perspective, the use of capacitive-like waveforms generated by photovoltaic prostheses may allow improving the neural response resolution while standing high-frequency stimulation.

neuroscience↗