Limits...
Resistive and reactive changes to the impedance of intracortical microelectrodes can be mitigated with polyethylene glycol under acute in vitro and in vivo settings.

Sommakia S, Gaire J, Rickus JL, Otto KJ - Front Neuroeng (2014)

Bottom Line: We show that exposure to a model protein solution in vitro and acute implantation result in both resistive and capacitive changes to electrode impedance, rather than purely resistive changes.We also show that applying 4000 MW polyethylene glycol (PEG) prevents impedance increases in vitro, and reduces the percent change in impedance in vivo following implantation.Our results highlight the importance of considering the contributions of non-cellular components to the decline in neural microelectrode performance, and present a proof of concept for using a simple dip-coated PEG film to modulate changes in microelectrode impedance.

View Article: PubMed Central - PubMed

Affiliation: Weldon School of Biomedical Engineering, Purdue University West Lafayette, IN, USA ; Physiological Sensing Facility at the Bindley Bioscience Center and Birck Nanotechnology Center, Purdue University West Lafayette, IN, USA.

ABSTRACT
The reactive response of brain tissue to implantable intracortical microelectrodes is thought to negatively affect their recordable signal quality and impedance, resulting in unreliable longitudinal performance. The relationship between the progression of the reactive tissue into a glial scar and the decline in device performance is unclear. We show that exposure to a model protein solution in vitro and acute implantation result in both resistive and capacitive changes to electrode impedance, rather than purely resistive changes. We also show that applying 4000 MW polyethylene glycol (PEG) prevents impedance increases in vitro, and reduces the percent change in impedance in vivo following implantation. Our results highlight the importance of considering the contributions of non-cellular components to the decline in neural microelectrode performance, and present a proof of concept for using a simple dip-coated PEG film to modulate changes in microelectrode impedance.

No MeSH data available.


Related in: MedlinePlus

Changes in electrode impedance following immersion in BSA, without and with PEG treatment. (A) Resistance of electrodes immersed in BSA with no PEG treatment exhibits significant increases compared to control at all observed frequencies, notably an increase in resistance of 30.7% compared to control at 1 kHz. Electrodes treated with PEG prior to immersion in BSA exhibit no significant changes in resistance compared to control. (B) Reactance of electrodes immersed in BSA with no PEG treatment exhibit significant increases at frequencies greater than 50 Hz, with the highest increase observed at 10 kHz. PEG treatment prior to immersion in BSA resulted in minor, but significant decreases at frequencies greater than 50 Hz. (C) Changes in total impedance closely match changes in reactance. Error bars represent the standard error of the means. Single asterisks (*) respresent p < 0.05, double asterisks (**) represent p < 0.001, triple asterisks (***) represent p < 0.0001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4120760&req=5

Figure 3: Changes in electrode impedance following immersion in BSA, without and with PEG treatment. (A) Resistance of electrodes immersed in BSA with no PEG treatment exhibits significant increases compared to control at all observed frequencies, notably an increase in resistance of 30.7% compared to control at 1 kHz. Electrodes treated with PEG prior to immersion in BSA exhibit no significant changes in resistance compared to control. (B) Reactance of electrodes immersed in BSA with no PEG treatment exhibit significant increases at frequencies greater than 50 Hz, with the highest increase observed at 10 kHz. PEG treatment prior to immersion in BSA resulted in minor, but significant decreases at frequencies greater than 50 Hz. (C) Changes in total impedance closely match changes in reactance. Error bars represent the standard error of the means. Single asterisks (*) respresent p < 0.05, double asterisks (**) represent p < 0.001, triple asterisks (***) represent p < 0.0001.

Mentions: Figure 3A shows percent changes in the real component of the impedance, i.e., resistance, relative to the control at four frequency values across the spectrum. Electrodes immersed in BSA without PEG pretreatment exhibited statistically significant increases in the resistance compared to the uncoated control at examined frequencies. The highest resistance increase relative to control was in the middle of the frequency spectrum, specifically at 1 kHz, with a 30.7% increase in resistance. At 50 Hz, the increase in resistance for the BSA coated electrodes without PEG pretreatment was 14.5%, at 100 Hz, the resistance increase was 23.9%, and 10 kHz, the resistance increase was 17%. The electrodes pretreated with PEG prior to BSA immersion, on the other hand, did not exhibit any significant differences in resistance compared to the uncoated controls at all examined frequencies.


Resistive and reactive changes to the impedance of intracortical microelectrodes can be mitigated with polyethylene glycol under acute in vitro and in vivo settings.

Sommakia S, Gaire J, Rickus JL, Otto KJ - Front Neuroeng (2014)

Changes in electrode impedance following immersion in BSA, without and with PEG treatment. (A) Resistance of electrodes immersed in BSA with no PEG treatment exhibits significant increases compared to control at all observed frequencies, notably an increase in resistance of 30.7% compared to control at 1 kHz. Electrodes treated with PEG prior to immersion in BSA exhibit no significant changes in resistance compared to control. (B) Reactance of electrodes immersed in BSA with no PEG treatment exhibit significant increases at frequencies greater than 50 Hz, with the highest increase observed at 10 kHz. PEG treatment prior to immersion in BSA resulted in minor, but significant decreases at frequencies greater than 50 Hz. (C) Changes in total impedance closely match changes in reactance. Error bars represent the standard error of the means. Single asterisks (*) respresent p < 0.05, double asterisks (**) represent p < 0.001, triple asterisks (***) represent p < 0.0001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4120760&req=5

Figure 3: Changes in electrode impedance following immersion in BSA, without and with PEG treatment. (A) Resistance of electrodes immersed in BSA with no PEG treatment exhibits significant increases compared to control at all observed frequencies, notably an increase in resistance of 30.7% compared to control at 1 kHz. Electrodes treated with PEG prior to immersion in BSA exhibit no significant changes in resistance compared to control. (B) Reactance of electrodes immersed in BSA with no PEG treatment exhibit significant increases at frequencies greater than 50 Hz, with the highest increase observed at 10 kHz. PEG treatment prior to immersion in BSA resulted in minor, but significant decreases at frequencies greater than 50 Hz. (C) Changes in total impedance closely match changes in reactance. Error bars represent the standard error of the means. Single asterisks (*) respresent p < 0.05, double asterisks (**) represent p < 0.001, triple asterisks (***) represent p < 0.0001.
Mentions: Figure 3A shows percent changes in the real component of the impedance, i.e., resistance, relative to the control at four frequency values across the spectrum. Electrodes immersed in BSA without PEG pretreatment exhibited statistically significant increases in the resistance compared to the uncoated control at examined frequencies. The highest resistance increase relative to control was in the middle of the frequency spectrum, specifically at 1 kHz, with a 30.7% increase in resistance. At 50 Hz, the increase in resistance for the BSA coated electrodes without PEG pretreatment was 14.5%, at 100 Hz, the resistance increase was 23.9%, and 10 kHz, the resistance increase was 17%. The electrodes pretreated with PEG prior to BSA immersion, on the other hand, did not exhibit any significant differences in resistance compared to the uncoated controls at all examined frequencies.

Bottom Line: We show that exposure to a model protein solution in vitro and acute implantation result in both resistive and capacitive changes to electrode impedance, rather than purely resistive changes.We also show that applying 4000 MW polyethylene glycol (PEG) prevents impedance increases in vitro, and reduces the percent change in impedance in vivo following implantation.Our results highlight the importance of considering the contributions of non-cellular components to the decline in neural microelectrode performance, and present a proof of concept for using a simple dip-coated PEG film to modulate changes in microelectrode impedance.

View Article: PubMed Central - PubMed

Affiliation: Weldon School of Biomedical Engineering, Purdue University West Lafayette, IN, USA ; Physiological Sensing Facility at the Bindley Bioscience Center and Birck Nanotechnology Center, Purdue University West Lafayette, IN, USA.

ABSTRACT
The reactive response of brain tissue to implantable intracortical microelectrodes is thought to negatively affect their recordable signal quality and impedance, resulting in unreliable longitudinal performance. The relationship between the progression of the reactive tissue into a glial scar and the decline in device performance is unclear. We show that exposure to a model protein solution in vitro and acute implantation result in both resistive and capacitive changes to electrode impedance, rather than purely resistive changes. We also show that applying 4000 MW polyethylene glycol (PEG) prevents impedance increases in vitro, and reduces the percent change in impedance in vivo following implantation. Our results highlight the importance of considering the contributions of non-cellular components to the decline in neural microelectrode performance, and present a proof of concept for using a simple dip-coated PEG film to modulate changes in microelectrode impedance.

No MeSH data available.


Related in: MedlinePlus