Local removal of oxygen for NAD(P)+ detection in aerated solutions

Abstract

The mediated electrochemical reduction of NAD(P) + in aerated solution was investigated and exploited for NAD(P)H regeneration in view of biosensing application. Oxygen was locally removed from the electrode surface with an electrochemical oxygen filter made of platinum grids positioned close to the oxygen sensitive reactions. The working electrode was a bucky paper functionalized with [Cp*Rh(bpy)Cl] + by diazonium electrografting. The local oxygen removal was first evaluated, before to be applied to deoxygenation for NAD + and NADP + reduction. A porous silica gel layer encapsulating D-sorbitol dehydrogenase was finally deposited on the top of the modified bucky paper and the resulting bioelectrode was found sensitive to the presence of D-fructose.

Electroanalytical metal sensor with built-in oxygen filter

“…However, approaching more negative potential value may cause hydrogen formation at the electrode surface that can probably affect the SCP measurement. Thus, we have opted for a safe reduction potential of Efilter = -0.40 V for oxygen removal, which agrees with previous reports [18,19]. Under this condition, a waiting time of 40-50 s is necessary to reach an adequate current of -1.5 µA.…”

“…The second setup aims at eliminating the oxygen at the vicinity of the mercury electrode. This electrochemical system comprises: two superposed disk-shaped platinum grids [18,19] as the working electrode (WE2 in Fig. 1), a platinum rod as the auxiliary electrode and a Ag/AgCl (in KCl 3M) reference electrode (Dri-Ref5).…”

“…However, this procedure provokes a significant loss of the detection level since the measurable peak is inversely proportional to the stripping current. A novel solution of removing the oxygen by an electrochemical oxygen filter for the purpose of omitting the nitrogen purging step has been introduced recently [18,19]. This approach provided a rapid and reliable way of locally removing the oxygen near the sensor surface.…”

“…The application of a given potential at the platinum grid induces the oxygen reduction locally, in the vicinity of the sensor. This approach was successfully studied on the model analyte, paraquat [19] and detection of NAD(P) + in a biosensing application [18].…”

Improved Productivity of NAD+ Reduction under Forced Convection in Aerated Solutions

“…This approach is based on the use of an additional porous electrode, placed in front of the working electrode, to which a negative potential is applied in order to electrochemically reduce oxygen before it can reach the working electrode surface. This idea was firstly investigated with a porous platinum electrode (platinum mesh) [26] that was applied for the detection of NAD(P) + in the absence of convection [27] . Electrochemical removal of oxygen was also shown for an electrochemical hydrazine sensor, in which an 80 % reduction in oxygen response was observed using interdigitated platinum microelectrode array [28] .…”