Bioreporter pseudomonas fluorescens HK44 immobilized in a silica matrix

The bioluminescent bioreporter Pseudomonas fluorescens HK44, the whole cell bacterial biosensor that responds to naphthalene and its metabolites via the production of visible light, was immobilized into a silica matrix by the sol-gel technique. The bioluminescence intensities were measured in the maximum of the bioluminescence band at X = 500 nm. The immobilized cells (>105 cells per g silica matrix) produced light after induction by salicylate (cone. > 10 g/l), naphthalene and aminobenzoic acid. The bioluminescence intensities induced by 2,3-dihydroxynaphthalene 3-hydroxybenzoic acid and 4-hydroxybenzoic acid were comparable to a negative control. The cells in the silica layers on glass slides produced light in response to the presence of an inductor at least 8 months after immobilization, and >50 induction cycles. The results showed that these test slides could be used as assays for the multiple determination of water pollution

Hybrid coatings as transducers in optical biosensors

Sensitive coatings are described for a novel enzyme-based optical sensor for in-situ continuous monitoring of reactants, such as glucose, in biotechnological production processes. Glucose oxidase, incorporated into suitable coating materials that are applied on lenses or optical fibers, is used to catalyze oxidization of glucose to gluconic acid in the presence of oxygen. The presence and consumption of oxygen is determined by measuring the fluorescence signal of incorporated metal organic ruthenium complexes, which is quenched by oxygen. Inorganic-organic hybrid polymers, synthesized via sol-gel processing, were used as coating material. Due to the hybrid character of the coating, good adhesion is achieved on both glass and polymer surfaces. Good compatibility is also given with enzymes and ruthenium complexes. The sensitive optical coating was built up as double-layer and single-layer structures. The double layer comprised a primary coating containing the oxygen-sensitive ruthenium complex, and a secondary coating containing the enzyme. The single layer comprised a single coating containing both the ruthenium complex and the enzyme

Optical fibre biosensors for oxygen and glucose monitoring

An optical fibre biosensor that uses an oxygen sensitive coating; Ruthenium complex [Dichlorotris(1,10-phenantroline)-ruthenium(II) hydrate], incorporated into an adhesive inorganic-organic hybrid polymer coating (ORMOCER®) is described. The Ruthenium/ ORMOCER® layer is used with optical fibres to form an extrinsic or intrinsic sensor. It can be applied to a microscope slide or lens to be interrogated by optical fibres, or form a cladding layer for an evanescent field optical fibre sensor. The Ruthenium complex is caused to fluoresce by a high brightness blue LED at 470 nm and the excitation light at 600nm is detected by a photomultiplier tube used as a photon counter, to measure fluorescence lifetime. The fluorescence is quenched by oxygen depletion within the layer, which can be linked to glucose by incorporation of suitable enzymes. The detection threshold is 0.7mg(O2)/litre, and the sensitivity is 70 ns/mg per litre