Impact of Protein Fouling on the Charge Injection Capacity, Impedance, and Effective Electrode Area of Platinum Electrodes for Bionic Devices

Abstract

The impact of protein fouling on platinum electrodes was assessed by electrochemical methods. Protein fouling affected the electrode potential and charge transfer through the electrode-solution interface. Adsorbed proteins partially blocked the electrode, with no charge passing through blocked regions. The electrochemical theory and methodology for investigating partially blocked electrodes is fully presented, applied to protein adsorption, and the implications for bionics applications are discussed. The partially blocked electrode had a reduced admittance, and increased impedance and polarization resistance consistent with a smaller effective electrode area. The charge storage capacity and charge injection capacity decreased after protein adsorption. The effective electrode area was assessed by impedance and cyclic voltammetry. The diffusion profile towards the partially blocked electrode was mixed between linear and radial diffusion.

Comparison of the In Vitro and In Vivo Electrochemical Performance of Bionic Electrodes

“…The impedance at low frequencies was seen to decrease with electrode activation and admittance. This frequency was previously shown to strongly correlate with electrode area, thermal noise, and signal-to-noise ratio [26,35]. Reporting of in vitro impedance at low frequencies would therefore be a far better predictor of in vivo performance.…”

“…No Faradaic process was present at this potential, so the equivalent circuit was valid for in vitro and in vivo measurements. Changes to electrode potential do not affect the solution resistance, but will change the admittance value by ~10-20% [35]; however, this is significantly smaller than the order of magnitude change seen from electrode activation (Table S2).…”

“…When judging the utility of the in vitro voltammetric analysis of electrodes as a model for in vivo performance, the solution composition is of critical importance. Similar ionic concentration and composition, low oxygen tension, and similar pH and organic composition are required [21,[32][33][34][35]. While saline or similar buffered electrolyte solutions offer reasonable, simple-to-use testing conditions, trace components in vivo may affect the voltammetric response.…”

“…The similarity of the initial and explanted electrode resistivity also indicates that any protein fouling has a minimal impact on impedance. The effects of protein fouling on electrodes in vitro were studied previously [35]. When an electrode was placed into a protein containing solution with a similar composition to perilymph, it partially blocked the electrode, resulting in impedance at 12 Hz increasing by ~20-30 kΩ and admittance decreasing slightly.…”

Electrochemical Determination of Kynurenine Pathway Metabolites—Challenges and Perspectives

“…Protein removal Protein adsorption blocks the electrode surface, reducing its effective area and impacting charge transfer across the electrode-solution interface [97]. Protein fouling on platinum electrode [97], GCE [98], and gold electrode [99] has been reported. The problem can arise during the analysis of protein-rich samples like serum or measurements using implantable electrodes.…”