Biosensors whole-cell

LUMINESCENCE WHOLE-CELL BIOSENSOR ANALYZER FOR WATER TOXICITY ASSESSMENT... 

In conclusion, a review of the application of whole-cell biosensors for early warning systems [60] showed that electrochemical biosensors are well suited for on-site use in the monitoring of general toxicity as well as hydrocarbons and heavy metals. 

Currently, a large spectrum of microbial biosensors have been developed that enable the monitoring of pollutants by measuring light, fluorescence, colour or electric current and electrochemical signal [60]. A recent study [19] shows that whole-cell biosensors based on the detection of changes in gene... 

Bentley, A. Atkinson, A. Jezek, J. Rawson, D.M. Whole cell biosensors - electrochemical and optical approaches to ecotoxicity testing. Toxicol, in Vitro 2001, 15, 469-475. 

L. Bousse, Whole cell biosensors, Sens. Actuators B Chem., 34(1-3) (1996) 270-275. 

Nivens, D.E. McKnight, T.E. Moser, S.A. Osbourn, S.J. Simpson, M.F. Sayler, G.S., Bioluminescent bioreporter integrated circuits Potentially small, rugged and inexpensive whole-cell biosensors for remote environmental monitoring J. Appl. Microbiol. 2004, 96, 33-46. 

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

Redox mediated whole cell biosensors for toxicity assessment... 

Whole cell biosensors are those devices that incorporate biological cells rather than cellular components such as enzymes, membrane fragments or spheroplasts. The biological material may be in the form of tissue slices or organelles [7-9] but the emphasis of this work is on the use of isolated cell cultures (bacteria, micoalgae, microfungi, invertebrate or mammalian cell cultures, etc.) or the use of consortia of cell populations (e.g., activated sludge). The number and variety of natural cell types is truly enor-... 

Cellular biosensors have been widely described [11-55]. In many cases, the cells have been used in a manner analogous to that of enzyme based devices simply because they contain substantial quantities of particular enzymes. There are, of course, advantages to this approach since the enzymes do not have to be isolated and so may be cheaper but also more active and more stable than the purified components. However, the reproducibility, speed of response and selectivity of the cell based devices will, in general, be less favorable than their enzyme based counterparts. This is because of the relatively large physical size of the cells, the presence of membranes that hinder diffusion and the presence of enzymes other than the one(s) of particular interest. Nevertheless, a range of approaches has been adopted to improve the selectivity and other characteristics of whole cell biosensor devices. These were reviewed by Racek [11] and include ... 

Whole cell biosensors may be divided into two groups depending on whether or not it is necessary for the cellular membranes to be intact. If the cells are being used simply as a source of one or more bound enzymes then the integrity of the cellular membranes may be of little import whereas if the enzymes are not bound within the cells then the contiguity of the cellular membranes is of vital importance. The status of the cell membranes is of particular importance when it is necessary that the cells be alive (i.e., potentially or actually capable of cell division, etc.). This requirement imposes additional difficulties on the fabrication of devices. However, biosensors that contain intact whole cells have the potential to act as convenient surrogates for traditional applications of biological cells and systems. At the forefront are those applications... 

WHOLE CELL BIOSENSORS FOR ESTIMATION OF BIOCHEMICAL OXYGEN DEMAND... 

With respect to whole cell biosensors utilising dissolved oxygen probes, Liang et al. reported a four-layer model to describe the signals from an oxygen probe used to transduce the respiratory activity of mouse leukaemia tumour cells [13]. This work was carried out with a view to using the biosensor to study the dynamic responses to various drugs. Finite difference methods were used to solve the material balances between the inner... 

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.

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. 

Surfactants Amperometric whole cell biosensor using Pseudomonas and Achromobacter 25 mg L-1 21... 

LAS Amperometric whole cell biosensor using Trichosporun 0.2 mg L-1 22... 

A green fluorescent protein-based Pseudomonas fluorescens strain biosensor was constructed and characterized for its potential to measure benzene, toluene, ethylbenzene, and related compounds in aqueous solutions. The biosensor is based on a plasmid carrying the toluene-benzene transcriptional activator (Stiner and Halverson, 2002). Another microbial whole-cell biosensor, using Escherichia coli with the promoter luciferase luxAB gene, was developed for the determination of water-dissolved linear alkanes by luminescence (Sticher et al., 1997). The biosensor has been used to detect the bioavailable concentration of alkanes in heating oil-contaminated ground-water samples. 

In comparison to equivalent optical detection methods using whole cell biosensors for water toxicity detection, these results proved to be more sensitive and produce faster response time. Concentrations as low as 1% of ethanol and 1.6 ppm of phenol could be detected in less than 10 min of exposure to the toxic chemical, whilst a recent study [11] which utilized bioluminescent E.coli sensor cells, detected 0.4 M (2.35%) ethanol after 220 min. An additional study [1] based on fluorescent reporter system (GFP), enabled detection of 6% ethanol and 295 ppm phenol after more than one hour. Cha et al [12] used optical detection methods of fluorescent GFP proteins, detected 1 g of phenol per liter (1,000 ppm) and 2% ethanol after 6 hours. Other studies [13] could not be directly compared due to different material used however their time scale for chemicals identification is hours. 

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