Cross-reactive sensor analysis

E. coli as well as Salmonella enterica bind to mannose. This limitation may be overcome using cross-reactive sensor analysis [56]. Thus, the binding to a variety of different analytes is checked in parallel. By comparison with known data, the detection and determination of single or multiple pathogens, even within complex mixtures, should be possible in the near future. The underlying principle is the basis for the olfactory sense in most animals. 

There are also some potentially useful agent-sensing technologies that do not rely on biological sensors. These new devices may offer more rapid analysis and simpler, continuous measurement. One kind of new sensor is the electronic (or artificial) nose. An array of semiselective, cross-reactive sensors produces a response pattern characteristic of a chemical (Gardner and Bartlett, 1999 Albert and Walt, 2000). The patterns are preprogrammed mathematically so that upon exposure, the patterns are matched to the chemicals sensed. There are two main groups of electronic noses ... 

CoPc chemiresistors has been used as a cross-reactive sensor array to discriminate among 12 different volatile analytes using linear discriminant analysis of the array current response. Due to the linear response of the sensors, it was possible to distinguish different analytes regardless of the concentration over the linear range of the sensor array, provided that the array response was normalized to one of the sensors (ZnPc) [56]. 

The field has advanced a lot in the last decade and now several examples of luminescence based cross-reactive sensor arrays have been reported in the literature, for the analysis of both gaseous and liquid phases. Furthermore, the development of consumer electronics has allowed the possibility of using these devices, originally conceived for different applications, to develop optical based sensor arrays. In this chapter we will review the progress of the luminescence based cross reactive sensor arrays reported in this first decade of the new century. 

An example of a CILA using optical fibers has been described by Wang et al. [114] for the analysis of 6-mercaptopurine (6-MP). The template, 6-MP, was oxidized to a strong fluorescent compound by H202 in alkaline solution. Upon optimization of the H202 and NaOH concentrations and of the assay temperature, the sensor showed a linear response in the 1.0 x 10 s to 6.0 x 10 6 g mL-1 range with a detection limit of 3.0 x 10-9 g mL-1. Cross reactivity to metal ions, amino acids, and carbohydrates was tested and the sensor was applied to the analysis of 6-MP in spiked serum. 

Hapten monolayer electrode sensor assembly was used to detect triazine in a flow injection analysis mode. The interaction of the electrode with different antibody concentrations resulted in the formation of an antibody-antigen (Ab-Ag) complex which insulated the electrode towards the [Fe(CN)6] /Fe(CN)6] " redox probe and diis in turn resulted in no charge transfer. The extent of insulation depends on the antibody concentration and the time of exposure to the antibody solution. The decrease in amperometric response of the antigenic monolayer to corresponding antibody solution for a fixed time produces a quantitative measurement of the antibody concentration. Typical responses obtained for cyanazine-hapten monolayer electrode to different antibody concentrations is shown in Figure 4. The lowest detection limit achieved for cyanazine sensor was 4.0 pg/ml at a response time of few minutes and a less-than 2% cross-reactivity to atrazine, simazine and other metabolites. 

---