All-polymeric transient neural probe for prolonged in-vivo electrophysiological recordings

Laura Ferlauto,Paola Vagni,Adele Fanelli,Elodie Geneviève Zollinger,Katia Monsorno,Rosa Chiara Paolicelli,Diego Ghezzi

doi:10.1016/j.biomaterials.2021.120889

Laura Ferlauto, Paola Vagni + Show 5 more

Open Access

https://doi.org/10.1016/j.biomaterials.2021.120889

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Abstract

Transient bioelectronics has grown fast, opening possibilities never thought before. In medicine, transient implantable devices are interesting because they could eliminate the risks related to surgical retrieval and reduce the chronic foreign body reaction. Despite recent progress in this area, the potential of transient bioelectronics is still limited by their short functional lifetime owed to the fast dissolution rate of degradable metals, which is typically a few days or weeks. Here we report that a switch from degradable metals to an entirely polymer-based approach allows for a slower degradation process and a longer lifetime of the transient probe, thus opening new possibilities for transient medical devices. As a proof-of-concept, we fabricated all-polymeric transient neural probes that can monitor brain activity in mice for a few months, rather than a few days or weeks. Also, we extensively evaluated the foreign body reaction around the implant during the probe degradation. This kind of devices might pave the way for several applications in neuroprosthetics.

Highlights

Building devices able to disappear in the surrounding environment after a programmed lifetime, leaving minimal and harmless traces after their disposal, is a fascinating idea for the development of green elec tronics to preserve the environment by reducing waste production and recycling processes [1,2,3,4,5]
We fabricated transient neural probes (TNPs) based on PCL as substrate and encapsulation layers, and PEDOT:PSS doped with ethylene glycol (EG) as a conductive element, by using soft lithographic techniques
Impedance spectroscopy (IS) showed remarkable performances of all-polymeric TNPs based on PEDOT:PSS:EG, characterised by low impedance magnitude (Fig. 1f) and low impedance phase angle (Fig. 1g) over a wide range of frequency, which makes them appropriate for the recording of both low- and high-frequency neuronal signals, such as Local field po tentials (LFPs) and neural spiking activities respectively

Summary

Introduction

Building devices able to disappear in the surrounding environment after a programmed lifetime, leaving minimal and harmless traces after their disposal, is a fascinating idea for the development of green elec tronics to preserve the environment by reducing waste production and recycling processes [1,2,3,4,5]. While several biodegrad able natural or synthetic polymers, such as cellulose [1], silk [15] and poly(lactic-co-glycolic acid) [16,17], are often used as substrate and encapsulation materials, so far the choice for the functional elements has always landed on transient inorganic materials These materials, such as magnesium, zinc, molybdenum, or iron, dissolve within minutes, hours, or maximum days, once in contact with body fluids [11,18]. This short functional window still limits the list of potential medical applications for transient devices

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