Redox mediated whole cell biosensors

Redox Mediated Whole Cell Biosensors for Toxicity Assessment and Environmental Protection... 

Redox mediated whole cell biosensors for toxicity assessment... 

There are practical difficulties in producing redox mediated whole cell biosensors that are reproducible within and between batches [53]. Models such as the one here can provide insights into the influence of various physical factors on the sensor outputs. Perturbations such as those described by the function if/ may be used to describe both stimulation and inhibition of these biosensors which are of importance in rapid toxicity assessment. 

Fig. 7.5. Schematic representation of some of the redox mediator processes at a whole cell biosensor. Lipohilic mediators may be reduced at redox active sites in the plasma membrane or at sites within the cytoplasm or both processes may occur—depending on the cell type and the mediator. Lipophobic mediators can only be reduced at sites on the outside edge of the plasma membrane. The oxidized form of the mediator. O, may be present in excess, but much of the reduced form. R, may need to diffuse between packed cells (dotted arrows) or through the cytoplasm (squiggly arrows). The subscripts aq, cyt, elec, and surf represent mediator in the aqueous phase, within the cytoplasm, at the electrode surface, and at the plasma membrane-aqueous interface, respectively.

A significant advance in whole-cell biosensor technology accompanied the development by Rawson et al, [372] of a mediated electrochemical sensor employing a layer of blue-green algae (cyanobacteria). These authors demonstrated that a low molecular mass redox-active mediator, such as Fe(CN)ft or benzoquinone, could accept electrons from the photosynthetic energy chain of a cyanobacterium and relay them, via diffusion, to an electrode. The sensor proved capable of detecting aqueous herbicides on the basis of their inhi-... 

Bennetto HP, Box J, Delaney GM, Mason JR, Roller SD, Stirling JL, Thurston CF (1987) Redox-mediated electrochemistry of whole microorganisms from fuel cells to biosensors. Oxford Scientific Publishers, Oxford, p 291... 

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