New Trends in Biosensors for Water Monitoring

Intensive industrialisation and farming associated to domestic uses of a growing number of chemicals have led to the release of many toxic compounds in the environment, causing an important pollution of aquatic ecosystems. In Europe, the Water Framework Directive WFD 2000/60/EC lays down the monitoring of a large number of substances, the so-called “priority substances”, with the objective of restoring a good chemical and ecological status of all water bodies by 2015 (Allan et al., 2006). To implement effective monitoring and treatment programs, complementary analytical methods are required: low cost and high throughput screening methods for semi-quantitative determination of families of compounds and/or prediction of their harmful biological effects (overall toxicity, genotoxicity, estrogenicity), conventional methods based on chromatographic separation techniques (LC/MS, LC/MS/MS, GC/MS or ICP-MS), which are more time consuming, costful and require trained operators. These methods do not provide informations on water toxicity but allow the rescan of positive samples for more accurate analytes identification (Rodriguez-Mozaz et al., 2007). Biological techniques, such as bioassays and biosensors, constitute the first category of methods. Many works in the past have been focused on the development of bioassays and have led to the commercialization of bacterial bioassays and immunoassays (Allan et al., 2006; Farre et al., 2005). In recent years, biosensors have received particular attention owing to their high sensitivity, low cost and possible easy adaptation for on-line measurements (Barcelo & Hansen, 2009). A biosensor is an electronic device used to transform a biological interaction into an electrical signal. This device is based on the direct spatial coupling of the immobilised biologically active element, the so-called “bioreceptor”, with a transducer that acts as detector and electronic amplifier. Different types of bioreceptors (enzymes, receptors, antibodies, DNA or microorganisms) combined with electrochemical, optical or mechanical transduction have been used for the elaboration of biosensors in view of water monitoring applications (Badihi-Mossberg et al., 2007; Rogers, 2006). To answer to the ever increasing requirements of water monitoring legislation, not only in terms of amount and reliability of informations provided, but also in terms of rapidity of response, selectivity, sensitivity and cost, tremendous efforts have been devoted in the last few years to improve the different elements contributing to the overall response of the biosensors, i.e. bioreceptor, transducer