ABSTRACT
Massive use of herbicides in agriculture over the last few decades has become a serious environmental problem. The residual concentration of these compounds frequently exceeds the maximum admissible concentration in drinking water for human consumption and is a real environmental risk for the aquatic ecosystem. Herbicides inhibiting photosynthesis via targeting photosystem II function still represent the basic means of weed control. A multibiosensor was constructed for detecting herbicides using as biosensing elements photosynthetic preparations coupled to an optical fluorescence transduction system (Giardi et al. EU patent EP1134585, 01830148.1-2204); this paper is about its application in the detection of herbicide subclasses in river water. Photosynthetic material was immobilized on a silicio septum inside a series of flow cells, close to diodes so as to activate photosystem II (PSII) fluorescence. The principle of the detection was based on the factthat herbicides selectively modify PSII fluorescence activity. The multibiosensor has the original feature of being able to distinguish the subclasses of the photosynthetic herbicides by using specific immobilized biomediators isolated from mutated organisms. This setup resulted in a reusable, portable multibiosensor for the detection of herbicide subclasses with a half-life of 54 h for spinach thylakoids and limit of detection of 3 x 10(-9) M for herbicides present in river water.
Subject(s)
Herbicides/analysis , Herbicides/chemistry , Photosystem II Protein Complex/drug effects , Soil Pollutants/analysis , Biosensing Techniques , Environmental Monitoring/methods , Mutation , Optics and Photonics , Photosynthesis/drug effects , Photosystem II Protein Complex/genetics , Photosystem II Protein Complex/physiology , Sensitivity and SpecificityABSTRACT
Isolated photosynthetic materials have a relatively short active lifetime that limits their effective use. To circumvent this limitation, various immobilization techniques have been designed to improve their stability both under storage and working conditions. The immobilization methods are identified either as chemical or physical methods. In this chapter, two immobilization methods frequently used are described; a physical method based on the entrapment of photosynthetic materials in photo-crosslinkable poly(vinylalcohol) polymer bearing styrylpyridinium groups (PVA-SbQ) and a chemical method where the photosynthetic materials are immobilized by co-reticulation in an albumin-glutaraldehyde crosslinked matrix (BSA-Glu). Different immobilization procedures in relation with various photosynthetic materials are mentioned.
