Biosensors amperometric response

FIGURE 2.5 (a) Amperometric response of CNT modified screen-printed biosensor for methyl parathion in 0.1 M PBS containing 0.1 M NaCl (pH 7.4) at applied potential of 0.50 V and (b) die relative inhibition of CNT AChE/CHO biosensor as a function of methyl parathion concentration (adapted from [40]). 

MWNTs favored the detection of insecticide from 1.5 to 80 nM with a detection limit of InM at an inhibition of 10% (Fig. 2.7). Bucur et al. [58] employed two kinds of AChE, wild type Drosophila melanogaster and a mutant E69W, for the pesticide detection using flow injection analysis. Mutant AChE showed lower detection limit (1 X 10-7 M) than the wild type (1 X 10 6 M) for omethoate. An amperometric FIA biosensor was reported by immobilizing OPH on aminopropyl control pore glass beads [27], The amperometric response of the biosensor was linear up to 120 and 140 pM for paraoxon and methyl-parathion, respectively, with a detection limit of 20 nM (for both the pesticides). Neufeld et al. [59] reported a sensitive, rapid, small, and inexpensive amperometric microflow injection electrochemical biosensor for the identification and quantification of dimethyl 2,2 -dichlorovinyl phosphate (DDVP) on the spot. The electrochemical cell was made up of a screen-printed electrode covered with an enzymatic membrane and combined with a flow cell and computer-controlled potentiostat. Potassium hexacyanoferrate (III) was used as mediator to generate very sharp, rapid, and reproducible electric signals. Other reports on pesticide biosensors could be found in review [17],... 

The incorporation of CNTs into OP biosensors may improve the amperometric response and the reversibility of the mediator used in the... 

The biosensor was used for the analysis of gluconic acid in honey samples. No matrix effect was observed and, therefore, the determination was carried out by interpolation of the corresponding amperometric responses into an appropriate calibration graph. 

Figure 2. Effect of glucose oxidase concentration on the amperometric response to 20 mM glucose for biosensors prepared with different amounts of enzyme mixed with 25 il of AQ 1%. The AQ-glucose oxidase films were dried at 50°C during 30 min in an oven.

Figure 32 shows the amperometric response of the biosensor in the presence of different hydrogen peroxide concentration. As shown a well defined response was observed after hydrogen peroxide addition. The values of KM, 0.96 mM for hemoglobin and 1.37 mM for catalase indicates the immobilized biomolecules into nickel oxide nanoparticles retained their native activity. 

FIGURE 2.5 (a) Amperometric response of CNT modified screen-printed biosensor f methyl parathion... 

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