“Smart” sensing interface for the improvement of electrochemical immunosensor based on enzyme-Fenton reaction triggered destruction of Fe3+ cross-linked alginate hydrogel

Abstract

In this work, a “smart” electrochemical sensing interface was designed for the improvement of electrochemical immunosensor based on enzyme-Fenton reaction triggered destruction of Fe3+ cross-linked alginate (Fe3+-alginate) hydrogel. The electrode was covered with multi-walled carbon nanotubes to improve its conductivity. Then Fe3+-alginate hydrogel with “smart’ response to Fenton reaction was generated in situ on electrode to construct the electrochemical sensing interface. The immunoreaction was implemented separately in tubes using silica oxide-glucose oxidase nanocomposites as immunoprobes to realize high efficiency of glucose oxidation and H2O2 generation. When the electrode was immersed in the supernate of enzyme reaction mixture, Fenton reaction was triggered by H2O2, in which realized the transition from Fe3+ to Fe2+. In this case, Fe3+-alginate hydrogel will be destroyed due to the consumption of Fe3+, leading to significantly decrease of the interface resistance. The concentration of targets can be quantitatively determined by measuring the current response of the electrochemical interface in [Fe(CN)6]3−/4−. Under optimal conditions, neuron-specific enolase (NSE) was quantitatively detected with wide linear range from 1 pg mL-1 to 100 ng mL−1, a low detection limit of 0.447 pg mL−1 and ultra-high sensitivity of −27.51 μA (log10 CNSE)-1.