pHEMA Encapsulated PEDOT-PSS-CNT Microsphere Microelectrodes for Recording Single Unit Activity in the Brain

Abstract

The long-term reliability of neural interfaces and stability of high-quality recordings are still unsolved issues in neuroscience research. High surface area PEDOT-PSS-CNT composites are able to greatly improve the performance of recording and stimulation for traditional intracortical metal microelectrodes by decreasing their impedance and increasing their charge transfer capability. This enhancement significantly reduces the size of the implantable device though preserving excellent electrical performances. On the other hand, the presence of nanomaterials often rises concerns regarding possible health hazards, especially when considering a clinical application of the devices. For this reason, we decided to explore the problem from a new perspective by designing and testing an innovative device based on nanostructured microspheres grown on a thin tether, integrating PEDOT-PSS-CNT nanocomposites with a soft synthetic permanent biocompatible hydrogel. The pHEMA hydrogel preserves the electrochemical performance and high quality recording ability of PEDOT-PSS-CNT coated devices, reduces the mechanical mismatch between soft brain tissue and stiff devices and also avoids direct contact between the neural tissue and the nanocomposite, by acting as a biocompatible protective barrier against potential nanomaterial detachment. Moreover, the spherical shape of the electrode together with the surface area increase provided by the nanocomposite deposited on it, maximize the electrical contact and may improve recording stability over time. These results have a good potential to contribute to fulfill the grand challenge of obtaining stable neural interfaces for long-term applications.

Glassy carbon MEMS for novel origami-styled 3D integrated intracortical and epicortical neural probes

“…The experimentally verified charge injection limit (Qinj) is 7.2 mC cm −2 . These results are comparable to previously reported CTCs and charge injection limit of PEDOT-PSS-CNT coated nanostructured gold microelectrodes [54,55]. An example of CVs of PEDOT-PSS-CNT coated GC microelectrodes with two different electrochemical windows (EWs) is shown in supporting figure S2 of the supplementary information.…”

“…The addition of a 30 µm thick polyimide layer (that appears dark in appearance in PEDOT-PSS-CNT composite was successfully polymerized on the 30 µm diameter microelectrodes with very high localized precision, as can be seen from a representative picture of a PEDOT-PSS-CNT coated GC microelectrodes ( figure 5(b)). A High-resolution SEM image of the PEDOT-PSS-CNT layer shown in figure 5(c) demonstrates a very porous morphology from which emerges a fine nanoscale CNT scaffold structure, similar to what was reported in a previous study on flat and spherical Au electrode surfaces [53,54]. As expected, after the deposition of the PEDOT-PSS-CNT composite, there was a significant reduction in the impedance (nearly three orders of magnitude at 1 kHz) of the electrodes (figure 6(a)), from 555.1 ± 128.1 kΩ to 3.6 ± 1.2 kΩ at 1 kHz.…”

Incorporation of Silicon Carbide and Diamond‐Like Carbon as Adhesion Promoters Improves In Vitro and In Vivo Stability of Thin‐Film Glassy Carbon Electrocorticography Arrays

“…The two-electrode method is suitable for measuring impedance from microelectrodes due to the large difference in impedance relative to the reference and the small current passing through the circuit. [35] During the EIS measurements, a sine wave (10 mV RMS amplitude) is imposed onto the open circuit potential while varying the frequency from 1 to 10 5 Hz. EIS is carried out using a potentiostat/galvanostat (Reference 600, Gamry Instruments, USA).…”

The rise of flexible electronics in neuroscience, from materials selection to in vitro and in vivo applications

“…Nano-coating is also playing a relevant role in reducing the immune reaction in long-term implants, as demonstrated by some smart encapsulation mechanisms (e.g. hydrogel-based layer) [78]. In fact, if properly functionalized, nanostructures can be exploited as slow releasing system to delivery anti-inflammatory agents [79] or even serve as scaffold for the grow of autologous cells, thus creating cell-implant hybrids to solve foreign body problem [80].…”