Nanostructured Interfaces for Enhanced H2O2 Measurement for Improved Biosensor Performance

MADRID RE; GUISEPPI-ELIE, A.

Workshop; Electrochemistry at Nano-interfaces Faraday Discussion; 2018

Electrified nanostructured interfaces present interesting new opportunities and pose fundamental challenges for diagnostic biosensors. Enzyme-based diagnostic biosensors that consume hydrogen peroxide (H2O2) hold a special place because of the importance of the oxidoreductases and peroxidases in biosensor development and application [1]. One approach to enhanced performance of enzyme-based diagnostic biosensors is to microlithographically fabricate or emboss microelectrodes and microelectrode arrays with critical length scales of less than 25 µm [2]. A second approach is to create nano-scaled topographic features on macroelectrodes. This work describes combining nanostructured topographic features on previously developed microfabricated Microdisc Electrode Arrays (MDEA 5037-Pt; ABTECH Scientific, Inc.) that comprised two electrochemical cells-on-a-chip [3]. Nanostructured redox mediator layers of iron-nickel hexacyanoferrate were deposited using a potentiostatic electrochemical deposition and nickel hexacyanoferrate layers [4, 5] were deposited using a potentiodynamic electrochemical deposition onto the working electrodes of MDEA 5037-Pt (37 microelectrodes; =50 µm) [6]. To allow for a direct comparison, non-mediating layers of nanostructured platinum were similarly deposited on the working electrodes of MDEA 5037-Pt. Platinum black was electrodeposited by chronocoulometry (platinization) at varying electrodeposition charge densities (1, 5, 10, 50 mC/cm2) to yield MDEA 5037-Pt|Pt and platinum nanofeatures were created by under-potential deposition of platinum to yield MDEA 5037-Pt|Ptupd. Devices were characterized by SEM, TEM and AFM. The amperometric response of the devices, each modified with different layers, was studied using step potential chronoamperometry in ferrocene monocarboxylic acid (FcCOOH), by amperometry at 0.6 V DC using a dual channel wireless potentiostat [7] at two different concentration ranges of H2O2 (1-10 µM and 10-100 µM) and by electrochemical impedance spectroscopy (EIS). Transient chronoamperometric response in 0.8mM FcCOOH favored MDEA-like over MDE-like behavior while steady state current increased from 48 (±3) to 58 (±3) nA (21%) following platinization and approached a temporal profile between that of theoretical MDE and MDEA. MDEA 5037-Pt|Pt sensitivity to hydrogen peroxide increased steadily from 0.184 nA/µM (un-platinized) to 0.516 nA/µM (platinized to 50 mC/cm2) (p < 0.0003). Nanostructured modification of microfabricated electrochemical device interfaces with redox mediators and nanocatalysts offer potential for significant improvement in biosensor performance.