Luminescence-based fibre-optic probes

New fibre-optic probes with both high selectivity and sensitivity have been designed in our group, based on light-emitting reactions (LER). Chemiluminescence reactions involving luminol and requiring hydrogen peroxide are particularly interesting, as they can be enzymatically catalysed by peroxidase, as well as bioluminescence reactions catalysed by luciferases either from the firefly or from marine bacteria, which provide a light emission correlated to the concentration of ATP or NAD(P)H, respectively. Co-immobilization of other enzymes like dehydrogenases used as auxuliary enzymes enabled the performance of the probe to be extended to other target molecules. In parallel, in the presence of suitable substrates, dehydrogenases activities can be monitored using the bacterial bienzyme system. The design of a reagentless probe has been investigated using the combination, in a multifunction sensing layer, of covalent immobilization technique for enzymes associated with loose embedding for co-reactants. Flavin mononucleotide can be trapped in a polyvinyl alcohol matrix, allowing about 35–40 consecutive accurate measurements to be performed. Promising results have also been obtained by connecting such probes to flow-injection-analysis manifolds for the monitoring of biotechnological processes. The potential of chemiluminescence and bioluminescence is especially attractive, since no light source or monochromator is required and since their sensitivity, selectivity and polyvalence appear particularly promising for extended development.