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

In this work, a “smart” electrochemical sensing interface was designed for the improvement of electrochemical immunosensor based on enzyme-Fenton reaction triggered destruction of Fe 3+ cross-linked alginate (Fe 3+ -alginate) hydrogel. The electrode was covered with multi-walled carbon nanotubes to improve its conductivity. Then Fe 3+ -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 H 2 O 2 generation. When the electrode was immersed in the supernate of enzyme reaction mixture, Fenton reaction was triggered by H 2 O 2 , in which realized the transition from Fe 3+ to Fe 2+ . In this case, Fe 3+ -alginate hydrogel will be destroyed due to the consumption of Fe 3+ , 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 (log 10 C NSE ) -1 .